# Sticky  What solution do folks use for the dreaded BFD hum?



## Mitch G

I'm a big believer in standing on the shoulders of giants. 
In this case that means I would like to know what solution folks use for addressing The Hum.

Right now I'm using a cheater plug, but I would like to solve the problem the right way. I saw the links to Jensen and Ebtech stuff, but Jensen has a bunch of different products, and the Ebtech links are qualified with words like "possible."

So, what are you audio giants using to address The Hum?

Thanks,


Mitch


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## lcaillo

The right way is to convert the balanced connections on the BFD to unbalanced that are required by most AV systems using a transformer. You can get them at radio shack for about $14. Using the cheater plug is OK for testing and may never cause a problem, but why not do it right?


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## Guest

this worked great for me, whisper quiet. The cheater plug was definitely louder. It also got a good review at secrets. 

http://www.dcispec.com/


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## fibreKid

I use a cleanbox II.

http://www.musiciansfriend.com/prod...assive-Hum-Eliminator?sku=180634&src=3SOSWXXA


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## azjimmy

I use the ART CleanBoxII

http://www.audiomidi.com/CleanBox-II-P4657.aspx

Worked like a charm.​


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## azjimmy

Great minds think alike:nerd:​


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## Hakka

I've never heard of this problem before, my BFD doesn't hum, then again im in Australia on 240v, not sure if that has anything to do with it or not.

I've had a look at the links posted in this thread, could one of those be used to eliminate the ground loop caused by a laptop on mains power? 


Harry.


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## brucek

> could one of those be used to eliminate the ground loop caused by a laptop on mains power?


Most likely, if it's in the audio chain.




> I would like to know what solution folks use for addressing The Hum


In the BFD GUIDE, under the first section "Connecting The BFD", it discusses the solutions to this problem, including several of the products already mentioned. Some use transformers, some differential amps - take your pick... The DC1 that stitz mentioned seems to be a good price and get good reviews. I've never tried it myself.

You want to stay away from inexpensive devices for this application, since their low frequency response are quite poor. The Radio Shack product is particularily bad in this regard.

brucek


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## Mitch G

Just so people don't think I'm a complete idiot, I did see the suggestions in the BFD guide, but there appear to be a hundred Jensen products and the other products are listed in the guide as "possible solutions."
Hence, I wanted to hear some first hand accounts of what people are using.



Mitch


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## Dundas

Has anyone tried the HumX? Not having to insert something in the signal path would be prefered.
http://www.ebtechaudio.com/humxdes.html


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## Josuah

The cheapest solution I found, which also worked the best/easiest, was to buy XLR ground-lift adapters. I think they were $7/each (one per channel as necessary, not all channels since I still want the ground level between my processor and amp to be equal) from Sweetwater.


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## brucek

> was to buy XLR ground-lift adapters


Most people use RCA unbalanced though..... Can't lift that ground


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## tdamocles

brucek said:


> Most people use RCA unbalanced though..... Can't lift that ground


I see that sweetwater has a plethora of adapters and couplers that might work if a ground lift works. Could you attach a rca(f)/xlr(m) adapter to a xlr(f)/xlr(m) ground lift coupler into the BFD and use the 1/4" jack/rca(f) as the output to the sub woofer? It would be a cheaper option compared to a transformer/humx? if it works...... Will the amount of different attachments screw with the signal?


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## brucek

> Could you attach a rca(f)/xlr(m) adapter to a xlr(f)/xlr(m) ground lift coupler into the BFD and use the 1/4" jack/rca(f) as the output to the sub woofer?


Well, you always have to remember a basic rule in electronics, that no signal can flow in an open ended circuit. You need to create a loop for current to flow. In an unbalanced interface, there is only a single unbalanced line that requires a return path, and that's the ground. You can't break that path - no amount of adapters can break that rule. The shield in a balanced circuit isn't a return path, so you are allowed to lift it. Not the case with a single ended circuit.

I suspect the Hum-X to be ineffective. You really need a device that is placed in the audio circuit itself, such as the DC1...


brucek


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## tdamocles

brucek said:


> Well, you always have to remember a basic rule in electronics, that no signal can flow in an open ended circuit. You need to create a loop for current to flow. In an unbalanced interface, there is only a single unbalanced line that requires a return path, and that's the ground. You can't break that path - no amount of adapters can break that rule. The shield in a balanced circuit isn't a return path, so you are allowed to lift it. Not the case with a single ended circuit.
> 
> I suspect the Hum-X to be ineffective. You really need a device that is placed in the audio circuit itself, such as the DC1...
> 
> 
> brucek


Got it!


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## Dundas

brucek said:


> I suspect the Hum-X to be ineffective. You really need a device that is placed in the audio circuit itself, such as the DC1...
> 
> 
> brucek


Gotta question your quick assumption there Bruce given that we all know that lifting the power line groung with a cheater solves the problem it's just that it is not a good thing to do from a safety standpoint. If the HumX device is able to do what it says: "Hum X filters out unwanted voltage and current in the ground line that cause ground loop hum while simultaneously maintaining a solid, safe ground" then it would seem to me to be the best solution. Anyways I have one on order so I'll let you know in a week or so.


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## brucek

> Gotta question your quick assumption there Bruce given that we all know that lifting the power line groung with a cheater solves the problem


Yeah sorry, I answered quick because I have concerns over these devices. I have no doubt it likely does the job. But we all know there is no way to eliminate that ground loop hum at the plug/receptacle without lifting the safety wire or inserting components into its path.

Those components have to be able to support the entire 120volt AC current to ground in the event of a failure in your equipment. They must support that current until the breaker trips. This requires quite high wattage components. Do they fit into that little device? Does the device have UL certification? If so, where are the specification sheets on their site. All I read is advertising hyperbole.

I'm more comfortable recommending line-level components.

brucek


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## Guest

Hmmm, I thought as Dundas did not having to insert something in the signal path would be preferable, and so have been using the HumX with great success, but...after reading bruceks' comments may need to rethink this.

Any thoughts on the suggested converting BHD balanced out to unbalanced RCA?

RG


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## brucek

> Any thoughts on the suggested converting BHD balanced out to unbalanced RCA?


Can you explain what you mean? The BFD has both balanced and unbalanced capability on the output already. If you have a hum, you could try the DC1 that was mentioned..

Again, I have no experience with the HumX, so I was just asking questions about its safety. I couldn't find any testing reports or specs on the site or otherwise....

brucek


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## Mitch G

I was reading some other stuff about ground loop hums and one suggestion was to ground your cable TV service to the same place as the power ground.

My humming is clearly related to my cable TV because once I disconnect the cable TV, the hum goes away. My cable TV service is grounded outside where it enters the house. But, that ground is not the same as used for power. 

So, I was considering adding a coax grounding block where the cable enters the house and then running ground wire to the water pipe where my power ground is. My coax entry and my circuit breaker box are basically colocated. So, it's not as if I'm running the ground wire any further than the power ground wire. 

If I understand the root cause of ground loop hums, this seems like it will remove the voltage potential that is causing the hum. But, I would like to hear from the experts before I pull the trigger on this. 


Mitch


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## brucek

> If I understand the root cause of ground loop hums, this seems like it will remove the voltage potential that is causing the hum.


In some cases it will. It never hurts to ground the cable at the service panel. Any difference in potential on the safety grounds at your equipment can cause a hum.

Even though the safety ground is a cold conductor, it can and usually does, develop a small potential, through mutual inductance, wire resistance and various other reasons that can be quite different at each receptacle in your house. 

When you plug a power amp into one receptacle and a preamp into another receptacle, the metal cases of these two units can have a small potential difference in their safety grounds which means that this equipment's metal cases are at a slightly different potential. When you connect a single ended (RCA) cable between these two devices, a small AC current can flow in the shield because of the potential difference. This unwanted signal is in the signal loop circuit and can cause a hum. An interconnect circuit has a loop path (completed circuit) that flows through the centre conductor of the interconnect cable and back on the shield. If there is an AC signal on the shield flowing because of the ground difference potential, you'll hear a hum. Breaking the safety ground of one of the two devices removes the potential and the path for the unwanted signal flow...

Exactly the same situation can occur, except usually worse, when you introduce a new ground into the system from cable TV or a satellite. Their ground on the shield may possess a different potential than the ground in your system and current will flow in all the interconnects. Usually by centralizing and bonding all external grounds to the common house ground you're at least giving yourself the best chance of reducing this problem.

With cable, sometimes it's necessary to use an isolator device like this one. They usually work - not by magic, but by using an RF balun or similar device. They are quite safe, albeit a bit expensive.

brucek


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## lcaillo

Mitch G said:


> I was reading some other stuff about ground loop hums and one suggestion was to ground your cable TV service to the same place as the power ground.


Not only is it advisable, it is a violation of electrical codes anywhere in the US to not ground the cable to the a.c. service ground. You should have a ground block at the entry point connected tot he same ground rod that your electrical service is grounded to, not a water pipe. This will likely improve your problem.

You don't have to do it yourself. Your cable provider is REQUIRED to do it. If they refuse contact your county inspector's office or state professional certification board and let them know that they are not properly grounding their installations. You'll get action.


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## Guest

brucek said:


> Can you explain what you mean? The BFD has both balanced and unbalanced capability on the output already. If you have a hum, you could try the DC1 that was mentioned..
> 
> brucek


I was referring to lcaillo's post, the second in this thread, where he suggests this to be the proper way to cure the problem, apparently with some type of adapters or cables of adaptive nature. This would seem preferable to line source measures that utilize filters or whatever. Would this cure the problem? Apparently lcaillo believes so. Any drawbacks to this? Anyone else tried this approach?

Regarding the HumX, I agree without some data how are we to evaluate the product. Upon recieving the product, which does not include any additional data, I was left wondering if I had in fact just purchased the worlds most expensive cheater plug! :dunno: 

RG


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## Sonnie

Robert_Gibran said:


> I was left wondering if I had in fact just purchased the worlds most expensive cheater plug! :dunno:


We need to call out the manufacturer on it if we find this to be true.


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## Darren

No hum on mine. Using phono connectors.


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## lcaillo

brucek said:


> Can you explain what you mean? The BFD has both balanced and unbalanced capability on the output already.
> brucek


The BFD manual states that the outputs are balanced and recommends using balanced devices. The BFD is no different from any other balanced device, in that you can ground one side and use it with unbalanced devices, halving the impedance. While this may work fine in some systems, others will have problems with it. The only certain way to avoid ground loops due to kludged unbalanced connections is to use a balancing transformer or an active device designed to modify the output configuration. Transformers are the logical choice for low frequencies like we use with subs.


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## brucek

> I was referring to lcaillo's post, the second in this thread, where he suggests this to be the proper way to cure the problem, apparently with some type of adapters or cables of adaptive nature. This would seem preferable to line source measures that utilize filters or whatever. Would this cure the problem? Apparently lcaillo believes so. Any drawbacks to this? Anyone else tried this approach?


Robert,

I'm don't see where lcaillo's post refers to adapters or cables. He said the proper way to eliminate the problem is with a transformer - and he's correct. I backed this up in my post where I suggested any of the in-line solutions suggested in the Guide would work by using transformers or differential amps. You do have to be careful to not purchase a transformer that is so cheap that it suffers a poor low frequency response.

Either the DCI-ALHI or the Ebtech Hum Eliminator would be fine. Personally, I like Jensen transformers. Some people just make their own with Jensen transformers or they purchase them in a box like this or this.
Jensen supplies this type of proper spec sheet. Why can't the others? I suppose that's why Jensen products are so **** expensive.
 MarkerTek for $120.....or mono  MarkerTek for $95............... 

brucek

EDIT: I should be mentioning the Jensen isolator for subs which has better low frequency response.


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## Dundas

Bruce,
The HumX patent application appears to be number 20040264712 which can be seen at:
http://appft1.uspto.gov/netahtml/PTO/srchnum.html

In addition to the BFD I also have a hum problem with an HDMI connection between my Panasonic projector and Denon receiver. I have not seen any signal path solutions for HDMI.


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## lcaillo

Dundas said:


> Bruce,
> The HumX patent application appears to be number 20040264712 which can be seen at:
> http://appft1.uspto.gov/netahtml/PTO/srchnum.html
> 
> In addition to the BFD I also have a hum problem with an HDMI connection between my Panasonic projector and Denon receiver. I have not seen any signal path solutions for HDMI.


The HDMI connection is just one of the ground paths that exist in your system. Look for a solution elsewhere by improving the ground at some point or isolating one. Chances are that the problem is something else and breaking that connection is just one of several that relieves the problem.


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## brucek

> Upon recieving the product, which does not include any additional data, I was left wondering if I had in fact just purchased the worlds most expensive cheater plug!





> The HumX patent application appears to be number 20040264712 which can be seen at:


The patent documentation shows the device to be exactly as I indicated before. It uses the standard method of inserting (parallel back to back diodes) in series with the safety ground. Using the fact that the flow of current that causes hum is usually quite low, it is easy to see that if you place a device in series that inhibits that flow until a small breakdown voltage is reached, then no current will flow and the hum problem is solved. 

A single diode has a breakdown of 0.7volts and two would have a breakdown of 1.4volts, etc. You need two sets in parallel with opposing polorization, since this is required to pass AC current.

This is the standard principle used in marine galvanic isolators to block AC and DC currents from reaching a boat connected to shore power. It eliminates corrosion of the boat hull etc.

Anyway, this is great as long as those diodes are rated to pass a steady state current long enough to trip a breaker on the hot line. A 120voltAC dead short can pass enormous current. It can easily be a few hundred amps depending on your service. The breaker should trip fairly quick. It must trip before those diodes blow. Most high current diodes are the variety that require bolting to a heat sink to achieve their rating. But then, they must pass that current for long periods of times. The diodes in the HumX only need to pass that current long enough to trip a 15 or 20 amp breaker. Hopefully the diodes that are jammed into that little device are spec'd to achieve that. I'd feel confident if it had a UL or CSA sticker on it. Either way, the HumX is sure better than a cheater plug.

You also have to realize that if the BFD is connected to a device that has a safety ground, then the shields of the interconnects will pass the current in the event of a BFD failure and trip the breaker. In fact, that's long been a trick to eliminate ground loops and its resultant hum. Choose a central device that everything is connected to (such as a processor), and then cheat every other device except the processor. The theory being that the interconnects will provide the path to safety ground through the one device that is safe. This is a horrible idea though, since some unsuspecting person may have the interconnects pulled off and a fault may occur and electrocute them. Don't use this method.

The best and safest method is to plug in the three prong plug to the wall and if there is a hum, solve it at the line level.........

brucek


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## Ayreonaut

I'm going to buy an isolation transformer for this purpose very soon.

Is the Ebtech Hum Eliminator significantly better than the Art Cleanbox II?


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## brucek

I haven't any experience with these two products, but the specs they publish show the low frequency response of the Art CleanBoxll to be better. That's important for a sub application.

The HUM Eliminator shows down 0.5dB @ 20Hz. We don't know what the 10Hz value is.
The ART shows 0.5dB @ 10Hz. 

These transformer based hum devices generally would use an "input" type transformer. This is evidenced in the ART spec with it's large insertion loss with low input impedance loads. This would mean it is a good idea to install it very close to the load amplifier. Probably a good idea anyway, because since it allows balanced or unbalanced connections. I would run a long balanced interconnect from the BFD to the ART box and then a very short RCA unbalanced interconnect to the power amplifier (unless your amp is balanced input - then use that)...........

brucek


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## Ayreonaut

I have a balanced interconnect from the BFD to a Carvin amp. No problem there.
The noise is in the connection between the Denon receiver and the BFD. 
I should install the Cleanbox close to the receiver, right?


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## brucek

> The noise is in the connection between the Denon receiver and the BFD.
> I should install the Cleanbox close to the receiver, right?


Well, since you'll be running balanced from the cleanbox to the BFD, and unbalanced from the receiver to the cleanbox, you would think that the distance from the receiver to the cleanbox should be shortest, but I don't feel that it would be best here.

My reasoning being that the output impedance of the cleanbox demands that the output cables be the shorter ones, although the worst that will happen with long lines after the cleanbox is that it will act as a low pass filter and lower transient response.

Either way, your BFD must be located close to the reciever, no?

brucek


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## brucek

Actually, after rethinking this, I would definitely place the Cleanbox close to the BFD and run the longer unbalanced lines to the cleanbox from the receiver.

The cleanbox's job is reject noise. Even though the line feeding it is unbalanced, the common mode rejection will be very high since transformers tolerate the mismatched source impedance very well.
The short lines on the output of the cleanbox will offer the lowest distortion and overall insertion loss.

brucek


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## Ayreonaut

I guess it's a useful discussion for others, but silly for me to debate. 
My BFD is sitting next to my receiver, literally touching it. 
Two 18" cables will do the trick.


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## Ayreonaut

*HELP!*

HELP!

I bought the ARTcessories CleanBOX II and hooked it up. It made a terribly loud hum!

I connected my recievers subwoofer pre-out to the CleanBOX II with a cable that has an RCA jack on one end and an unbalanced 1/4" TS jack on the other. I connected the CleanBOX to the BFD with a balanced 1/4" TRS cable. I powered up the amp and it hummed very loudly. What did I do wrong?

The connections on the CleanBOX II are confusingly labeled in that one side is labeled input and the other side is labeled output, but a painted line seems to indicate that the inputs are connected, which seems not to be the case as I have tried connecting the cables all ways.

Help!


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## tdamocles

brucek said:


> Most people use RCA unbalanced though..... Can't lift that ground


How about this duo? This combined with a cheater plug?

Will this work? I've found the gfci elsewhere for about $12. $12+cost of a cheater plug could be a cheap solution to eliminate ground loop hum.... Any comments?

What I found is that the GFCI works the same as the ground(3rd prong) with one difference....If there is a ground fault, you won't know until you touch it and get a slight shock before it shuts power off. If the BFD isn't bypassed with the cheater plug a ground fault would blow a fuse or circuit immediately without touching it.


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## brucek

> I connected my recievers subwoofer pre-out to the CleanBOX II with a cable that has an RCA jack on one end and an unbalanced 1/4" TS jack on the other. I connected the CleanBOX to the BFD with a balanced 1/4" TRS cable. I powered up the amp and it hummed very loudly. What did I do wrong?
> 
> The connections on the CleanBOX II are confusingly labeled in that one side is labeled input and the other side is labeled output, but a painted line seems to indicate that the inputs are connected, which seems not to be the case as I have tried connecting the cables all ways.


This is a stereo unit, so there are two inputs and two outputs. The funny line between the two seems dumb for sure.

Anyway, since we presume this is a transformer device, you can remove the ground reference at its input and simply use the differential input.

Does the sub amp hum with just the BFD and cleanbox connected without the receiver connected?

Are you able to make your own cables?

brucek


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## Ayreonaut

Thanks for helping, Bruce.

There is no hum at all if the receiver is not connected to the input of the CleanBOX.

I don't make cables, but I could always order a custom one from a local shop if I needed to. What could be wrong wtih the way it's hooked up now?

(Maybe some bonehead bought this unit and fried it with an amplified signal and then returned it to the store. ???)

Here's what I tried and got the very loud hum.


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## brucek

The cable that goes from the receiver to the ART is an RCA to TS. It has the center pin of the RCA connected to the TIP of the TS plug, and it has the shield of the RCA connected to the SHIELD of the TS plug. This grounds one side of the input transformer in the ART.

The standard remedy for this is to float the input side of the transformer with a cable called an XLR ground lift adapter. It is a cable with XLR's on both ends with the sleeve connection lifted on one end, and so the signal goes to the transformer which is now floating without the ground loop passed through.

You can make your own single solution with an RCA connector and a TRS connector and a piece of shielded wire.

Of course we don't have a schematic of the ART, but it's a good quess...

The schematic would be like this:









Make any sense? 

brucek


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## Ayreonaut

I don't have it with me but there is a schematic on the back of the package of the CleanBOX II. On the input side, the tip and sleeve are connected to the transformer. On the output side, the tip and ring are connected to the transformer.


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## brucek

> On the input side, the tip and sleeve are connected to the transformer


Mmm, doesn't make sense to me, since it accepts balanced inputs, it would have to have the tip and ring connected to the input of the transformer and the sleeve to transformer ground.....

Take a picture of it so I can see....

brucek


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## Ayreonaut

I won't have a chance to scan it, I'm leaving for vacation tomorrow morning and I have to go home and pack tonight. But I remeber what it looks like pretty well, I was studying it very hard last night.

It looked something like this:


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## brucek

When you return you'll have to take a picture and then we'll sort it out because that makes very little sense with regard to the ability to feed a balanced signal to the device - there is no ring (-ve) connection on the input?......

brucek


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## Ayreonaut

Despite what I said, I took a "break" from packing to scan and post the CleanBOX II schemaitc. Here 'tis.


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## brucek

Oh well, call me surprised. They are only allowing unbalanced inputs when the information says, "Connections, 1/4" balanced/unbalanced jacks".... I would take that to mean the input or output would accept balanced or unbalanced.

OK fine, the input accepts unbalanced and you can use the RCA to 1/4" TS plug connected from the receiver to the ART that you used before.

On the output you can use the balanced 1/4" TRS cable except you need to lift the shield on one end. You can make your own cable or modify the one you have (if it doesn't have molded connectors). I've never seen TRS ground lift adapters - only XLR ground lift adapters..

brucek


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## Ayreonaut

I went back to Sam Ash today to get a cable that I can mod if necessary. 

While there, we hooked up my CleanBOX II to make sure it was working properly. 
We used an RCA-to-1/4"TS adapter cable for input, and a 1/4"TRS cable for ouput, just like I have at home. No problem at all.

Why am I having this problem at all? Am I haveing to lift the ground because of a problemm with my BFD? Do the other people using the CleanBOX II with the BFD have to lift the ground too?

Tonight I'll try my new cable with the ground lifted from the CleanBOX II and see if it works.


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## brucek

> We used an RCA-to-1/4"TS adapter cable for input, and a 1/4"TRS cable for ouput, just like I have at home. No problem at all.
> Why am I having this problem at all? Am I haveing to lift the ground because of a problemm with my BFD? Do the other people using the CleanBOX II with the BFD have to lift the ground too?


No, you don't have a problem with your BFD. You established that when you answered my question and said, "There is no hum at all if the receiver is not connected to the input of the CleanBOX."

This says the ground reference of the BFD and the Carver amp are close and not creating a hum producing ground loop. When you hook up the Receiver, the hum begins. This is where the potential difference exists. This problem requires we convert the unbalanced signal of the receivers output to balanced (using the ART), so that we are then able to lift the line-level ground (completely safe, as opposed to lifting an AC safety ground). 

Note, we couldn't lift the ground on a single ended unbalanced signal, since the ground shield itself is required for proper signal flow. This is the beauty of balanced signals (that the ART is supplying) - we are able to lift the line-level ground because the signal is carried on two difference signals from the transformer. Sometimes you get away without lifting the ground on a balanced signal, and sometimes not. In your case it would seem not.

Lift the shield between the ART and the BFD and you should be fine..........

brucek


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## Ayreonaut

Thanks 1,000,000 Bruce. I'll let you know what happens.


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## Ayreonaut

I'm sorry to report that lifting the ground did not help. I desoldered the ground from the sleeve in the TRS connector plugged into the CleanBOX II, and the results were unchanged. It still generated a loud hum. Wierd.

The hum I'm trying to get rid of is very low level. I can hear the hum start when I rotate the receiver volume dial up from "---" (muted) to "-70" dB. Could it simply be the noise floor of the sub pre-out of my Denon AVR-1905?

I did come up with something that reduced the level of the hum by -10dB, so that its _pratically_ inaudible at the listening positions now. 

I had the BFD input set to "-10 dBV" as instructed. But I had to set my reciever's sub pre-out to the minimum -12dB and it still clipped the input of the BFD with "The Haunting" in DTS at reference level. So I switched the BFD to the "+4 dBu" setting and was able to increase the receiver's pre-out level to -2 dB without clipping, and dial back 10dB on the amp. So now the hum is being amplified 10dB less, and its _barely_ noticable. It doesn't bother my wife at all, and I only care because I tend to obsess. :coocoo:


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## brucek

> I desoldered the ground from the sleeve in the TRS connector plugged into the CleanBOX II, and the results were unchanged. It still generated a loud hum. Wierd


Then it's not a ground loop. That's what this exercise was supposed to remove. The hum is in the signal from the receiver. No amount of gizmos will remove that unfortunately...

brucek


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## Josuah

Well, my DMC-1 and MPS-1 are both plugged into the same outlet, and if I completely decouple the grounds between the two, I have crazy noise. I found that depending on the arrangement of XLR pre-outs to amp modules, the amount of noise (and the channels, since different channels are going to different modules now) would vary. I had to decouple only some of the XLR connection grounds.

So, I didn't have a ground loop either, it would seem, based on extensive troubleshooting on my own, with AV123, and from discussions with a Furman engineer. However, I did have noise that I was able to remove by lifting the ground on selective interconnects.


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## Ayreonaut

brucek said:


> The hum is in the signal from the receiver. No amount of gizmos will remove that unfortunately


Note that I'm talking about two different hums. 

1. Without the CleanBOX II there is a very _quiet_ hum. It might be the receiver.
2. When the CleanBOX II is introduced, there is a very _loud_ hum. I don't know how this is being generated.

The quiet hum may be generated by the receiver, but I wanted to try the isolation transformer to see if it would be eliminated that way or not. Unfortunately, the isolation transformer is introducing another problem altogether and I am no closer to a definitive diagnosis of the original problem.


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## Ayreonaut

I may try the original CleanBOX instead of the CleanBOX II. 
It converts RCA inputs to XLR outputs.

Will the BFD convert an XLR input to a 1/4"TRS output?


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## brucek

> When the CleanBOX II is introduced, there is a very loud hum. I don't know how this is being generated


Makes no sense to me........



> Will the BFD convert an XLR input to a 1/4"TRS output?


Yep, both connectors are active



> I may try the original CleanBOX instead of the CleanBOX II.


I think they're the same except the Cleanbox introduces some gain with an active stage (requires plugging in an AC adapter).

brucek


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## Josuah

Inserting the CleanBox II seems to be exactly what I experienced when I completely disconnected the processor and amp grounds from each other. I had to leave ground between at least one channel, or else everything was kaka.

Have you tried rearranging which outlets your receiver and BFD plug into? Trying combinations of different outlets and same outlets might do something. It didn't do anything for me, but you might try it.

One thing I was doing before with a Yamaha RX-V1400 and Outlaw Audio 7100 and Alesis DEQ-830 was to wire the chassis together using 12awg copper and then stick the last end of the copper into the ground of an empty outlet on the same power strip used by all three components. That reduced my noise by a few dB.


----------



## Ayreonaut

I'm thrilled to report that I eliminated the receiver hum completely. 
No, I did not solve the CleanBOX II mystery. 

I messed around with the BFD filters some more. I used the old fake lowpass trick by inserting a filter at 1.00 kHz, 120/60 octaves wide, down -30 dB. This obliterated whatever noise the receiver was generating, all of which was above the subwofer band.

The CleanBOX II will go back. It never made sense to me either, Bruce.


----------



## brucek

> by inserting a filter at 1.00 kHz, 120/60 octaves wide, down -30 dB. This obliterated whatever noise the receiver was generating, all of which was above the subwofer band


Interesting that your receiver is outputting a noise around 1000Hz.

When I look at your filter (in green) I see it has almost no effect on your existing filters. That's good.
The phase (in red) only effects the crossover area by about 5 degrees, so that's good.

Too bad you had to go to so much trouble to track down the problem, but that happens sometimes.











brucek


----------



## Ayreonaut

The noise isn't centered on 1.00 kHz, it seems to be made up of many frequency components and I couldn't track them all down by ear. The broad cut was my attempt to kill all components of that noise wherever they were in one fell swoop, and it worked.

Thanks for showing me the phase too. (Note that my filter width is two octaves and it looks like you simulated for one.)


----------



## brucek

> The noise isn't centered on 1.00 kHz, it seems to be made up of many frequency components


I guess you could get creative with more than one filter and create a brick wall. We had a thread a while back where Sonnie and John created a crossover out of filters. It was quite well done. I can't find it. Either way, you say the problem is solved now with the single filter. ....



> Note that my filter width is two octaves and it looks like you simulated for one


Ahh, good catch. OK, here it is with 120/60. A bit more of an effect to your existing filters I would think. The single filter adds ~-4dB at 100Hz and about 6 degrees of phase at the 80Hz crossover area. You might want to do an REW sweep sometime to see the actual effect that this single bad boy causes....












brucek


----------



## Ayreonaut

brucek said:


> The single filter adds ~-4dB at 100Hz and about 6 degrees of phase at the 80Hz crossover area.


I used the attenuation to help shape my house curve. 
My crossover is at 60 Hz, that bit of phase shift is no big deal right? 
Should I add or subtract a foot from my receiver time delay to compensate?


----------



## brucek

> I used the attenuation to help shape my house curve


Great..good idea..



> My crossover is at 60 Hz, that bit of phase shift is no big deal right?


Agreed.



> Should I add or subtract a foot from my receiver time delay to compensate?


Neither. The foot you add to sub speaker distance (when you use a BFD) is to compensate for the full 1 msec delay the BFD offers. A change in phase as small as this filter creates around the crossover would likely have negligable effect and could only be esatablished by doing a response check and see if you have any new dips or peaks around the 60Hz area......

brucek


----------



## lovingdvd

Interesting reading. I'm trying to eliminate my hum and would like some advice please...

I have my BFD and sub plugged into the same AC outlet and I get a low hum out of the sub.

Now, I am CERTAIN that the BFD is causing the hum and not my receiver, because if I remove the BFD from the chain (go straight from my receiver to my sub with the RCA) then there is no hum.

What is the cheapest and simpliest way to resolve this issue? Is it really necessary to purchase a $40-50 part for this? I do not want to use a cheater plug for safety reasons.

This product looks pretty basic http://www.jensen-transformers.com/ci1rr.html but I'm not sure how much it runs.

Also - I read in another thread that someone connected a wire between the BFD grounding screw and a screw on their amp/pre-amp and solved the problem. I don't have that option as the sub is the only other piece of equipment near the BFD. However I was wondering if I could run a wire from the BFD grounding screw to a screw on the metal backplate on my HSU sub. Do you think that backplate is grounded? If so would this work? If there is any risk of shock or damage to the equipment trying this than I'd want to stay clear. Thanks!

Edit: Just found the pricing for the Jensen - over $100 wow, that rules that out...


----------



## lovingdvd

Also just to follow up from my post directly above - I'd like to clarify a few things please...

I have this hum even when my receiver is OFF.

If I unplug the INPUT RCA going into the BFD (from the receiver) then the hum stops. However if I take this same plug and go directly into my sub, I do NOT get any hum (even with the BFD still plugged into the same AC wall outlet as the sub).

I also notice that once in a while the hum gets a tad louder (again with the receiver and all AV components off or even unplugged0 and the first light on the output LED array of lights blinks a bit.

So it does not seem like this is an AC grounding loop. Rather the BFD is generating this hum internally. I do not remember having this issue at all once I first set this up.

The hum is quite low but enough to be audible and also enough to keep the sub woofer on all the time instead of going into its passive mode when the receiver is off.

Has my BFD gone bad? Or is all this par for the course, and this a perfect candidate to fix using the Jensen transformer or similar solution to resolve this?

Thanks!


----------



## Wayne A. Pflughaupt

> If I unplug the INPUT RCA going into the BFD (from the receiver) then the hum stops. However if I take this same plug and go directly into my sub, I do NOT get any hum (even with the BFD still plugged into the same AC wall outlet as the sub).


There ya go – that means the problem is a ground loop between the BFD and other components in your system. This is probably because you have it plugged into a different circuit on a different service leg as the rest of the system. Your best bet would be to move the BFD to where the rest of the electronics are.

If that doesn’t get it, look to your cable TV service or sat dish. The CATV service and the dish should be grounded outside to the ground stake at your electrical service. 

Regards,
Wayne


----------



## brucek

> So it does not seem like this is an AC grounding loop.


Sounds exactly like an AC grounding loop.

Re-read your post where you say:

_If I unplug the INPUT RCA going into the BFD (from the receiver) then the hum stops_

Fairly clear indication that there is a potential difference between the Receiver and the BFD. This is standard fare and can be confirmed by testing with a cheater at the BFD. Does the hum go away. yes? then you have a ground loop.

Even though the safety ground (a.k.a. third prong) is a cold conductor, it can and usually does, develop a small potential, through mutual inductance, wire resistance, etc., that can be quite different at each receptacle in your house. In addition, various other reasons (such as introducing a new ground from cable or a satellite) can cause a safety ground potential difference between chassis.

For example, when you plug a receiver into one receptacle and a BDF into another receptacle, the metal cases of these two units can have a small potential difference in their safety grounds which means that these equipment's metal cases are at a slightly different potential. Since internally the AC ground is connected to the DC ground, this potential will be on the shield of an interconnect. When you connect a single ended (RCA) cable between these two devices, a small AC current can flow in the shield because of the potential difference. This unwanted signal is in the signal loop circuit and can cause a hum. An interconnect circuit has a loop path (completed circuit) that flows through the centre conductor of the interconnect cable and back on the shield. If there is an AC signal on the shield flowing because of the ground difference potential, you'll hear a hum. Breaking the safety ground of one of the two devices removes the potential and the path for the unwanted signal flow... Breaking the safety ground is dangerous though and not recommended. (See the advantage of balanced XLR circuits where you are able to safely lift the shield and the circuit remains intact on the (+)/(-) lines?).

Anyway, the solution is to either find the ground loop (which is between your receiver and BFD) or safely use a transformer device that allows the signal to pass but breaks the shield. The device you indicated would achieve that end. Expensive though.

Again. First prove that its a ground loop with the cheater on the BFD. Then remove it and find your solution. Try unplugging you cable.

brucek


----------



## bobgpsr

Wayne A. Pflughaupt said:


> There ya go – that means the problem is a ground loop between the BFD and other components in your system. This is probably because you have it plugged into a different circuit on a different service leg as the rest of the system. Your best bet would be to move the BFD to where the rest of the electronics are.


I had the same issue and a cheater plug adapter would fix the hum (not perferred). The BFD was plugged into the same power strip as the AVR. And the sub (PCU) was on the same house circuit as the AVR. 

But I also had intermitent shield/ground connection problems with the RCA to phone plug adapters I was using to connect unbalenced connections to the BFD. My solution was to custom build RCA to XLR cables and experiment with different ground/shield connection possibilities with the XLR wiring. Problems were solved when I used just the + & - connections (leaving the shield/ground open) for the input to the BFD from the AVR. Did have to hook up both the - and the shield/ground for the run to the sub. Cheater plug no longer required and the XLR connections are very reliable. :T


----------



## lovingdvd

brucek said:


> Sounds exactly like an AC grounding loop.
> 
> Re-read your post where you say:
> 
> _If I unplug the INPUT RCA going into the BFD (from the receiver) then the hum stops_
> 
> Fairly clear indication that there is a potential difference between the Receiver and the BFD. This is standard fare and can be confirmed by testing with a cheater at the BFD. Does the hum go away. yes? then you have a ground loop.
> brucek


Thanks. Here's the part though that is most confusing... I actually unplugged my AV receiver from the wall, but the hum did not go away! So basically I have a 25 foot RCA cable that goes into the AV receiver that is disconnected from the AC. Yet when I remove that end from the BFD the hum goes away. How can this be possible ?? I actually removed the power cord from the back of the AV receiver so I know I had the right plug unplugged. If this was a grounding loop, wouldn't the AV receiver need to be plugged in? 

Also a couple side notes to consider - my cable box and dvd player all have just two prongs. Wouldn't it need 3 prongs to have the ground loop issue? Also as a test I plugged my sub and the BFD into a power string, then plugged the power strip into the same AC outlet that my equipment rack is powered by. This made no difference in the hum. I also tried plugging this into various outlets and also made no difference.


----------



## Wayne A. Pflughaupt

> But I also had intermitent shield/ground connection problems with the RCA to phone plug adapters I was using to connect unbalenced connections to the BFD. My solution was to custom build RCA to XLR cables and experiment with different ground/shield connection possibilities with the XLR wiring. Problems were solved when I used just the + & - connections (leaving the shield/ground open) for the input to the BFD from the AVR.


Hmm, surprised that would work. I guess the balanced transformers (or whatever the BFD uses for those inputs) was able to nuke it. I imagine brucek can tell us how that worked – he’s the expert on these things. :T 



> Also a couple side notes to consider - my cable box and dvd player all have just two prongs. Wouldn't it need 3 prongs to have the ground loop issue?


Not at all. Remember, the cable service (i.e., the coaxial feed coming into your system) is grounded to *earth* somewhere. So is the BFD - its ground goes back to the electrical service panel, which in turn goes to the ground stake (*earth*).

That’s also why you still get the hum with the receiver unplugged. The ground loop is still connected through the cable feed, which ties to the cable box chassis, which connects it to the shield of the RCA cable running to the BFD and sub.

Looks like what you need to do is fix that cable TV feed. It’s the problem, not the BFD. Or maybe try Bob’s XLR-to-RCA connection scheme. I’ll be happy to make those cables for you if you like – just send me the parts and supplies.

Regards,
Wayne


----------



## lovingdvd

Wayne A. Pflughaupt said:


> Hmm, surprised that would work. I guess the balanced transformers (or whatever the BFD uses for those inputs) was able to nuke it. I imagine brucek can tell us how that worked – he’s the expert on these things. :T
> 
> 
> Not at all. Remember, the cable service (i.e., the coaxial feed coming into your system) is grounded to *earth* somewhere. So is the BFD - its ground goes back to the electrical service panel, which in turn goes to the ground stake (*earth*).
> 
> That’s also why you still get the hum with the receiver unplugged. The ground loop is still connected through the cable feed, which ties to the cable box chassis, which connects it to the shield of the RCA cable running to the BFD and sub.


Great post, thanks. It makes perfect sense now.  

My cable STB is connected to the receiver via HDMI cables. As a test I'll try removing these and some other cables to narrow things down. Or actually, better yet, I'll disconnect the cable feed from the cable box...



> Looks like what you need to do is fix that cable TV feed. It’s the problem, not the BFD.


Let's say I am able to confirm it is the cable box. You mention that one option would be to "fix that cable TV feed". How could I even go about that? Doesn't seem like there would by many (any?) options since the cable line is grounded and has to connect into the STB. Unless there is some sort of cable adapter that removes the ground?

Ya know, I just thought of something... I used to run the cable feed directly into the STB. But recently I changed it so that it runs into a UPS backup with surge protection. So the cable line feeds into the coax input for that, and then back out and into the STB. I'm now wondering if that introduced this problem... As you may recall from an earlier post I don't remember having this issue earlier so it seems to have appeared recently. I will need to play with this later today to see what happens as I switch it back the old way and so forth.



> Or maybe try Bob’s XLR-to-RCA connection scheme. I’ll be happy to make those cables for you if you like – just send me the parts and supplies.
> 
> Regards,
> Wayne


Thanks for the offer Wayne! :T That is very kind. I'm surprised they don't make something like this that can be purchased off the shelf.

Can you please supply a list of supplies (preferably Radio Shack) for exactly what you need? I'm happy to pay you for your time on this too!

Thanks again!


----------



## Wayne A. Pflughaupt

> Ya know, I just thought of something... I used to run the cable feed directly into the STB. But recently I changed it so that it runs into a UPS backup with surge protection. So the cable line feeds into the coax input for that, and then back out and into the STB. I'm now wondering if that introduced this problem....


I never did trust those things... Something about sending a coaxial feed through a surge protector with all that AC power just seems wrong to me. Again, brucek is the expert on such things – maybe he can waylay my fears. 



> Thanks for the offer Wayne!
> I'm surprised they don't make something like this that can be purchased off the shelf.
> 
> Can you please supply a list of supplies (preferably Radio Shack) for exactly what you need?


If moving the cable from the surge protector doesn’t help, PM me. I’ll take a look at RadioShack, but typically their prices are outrageous. For instance, they charge $4.00 for this mediocre RCA plug. You can get *far* better connectors at Parts Express for well under $2.00 each. Of course, there are the shipping charges to consider, so you might be ahead with RS in the end. We’ll see.

Regards,
Wayne


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## brucek

> Hmm, surprised that would work. I guess the balanced transformers (or whatever the BFD uses for those inputs) was able to nuke it. I imagine brucek can tell us how that worked


Yeah, that works. It's know as pseudo-balanced. The common mode rejection ratio (CMRR) is quite comprimized compared to a proper balanced interface and offtime you won't have sufficient levels since both the (+)ve and (-)ve signals are expected to contain the signal with an associated maximum line level.

As you know the signal is fed into a differential amplifier at the receiving end (BFD). The CMRR advantage is fully realized when the two signal carrying conductors have identical impedances to ground (as in a proper balanced circuit). This will give the maximum noise rejection. 
If we unbalance this teacup and use a paired wire core coaxial interconnect where we connect the hot signal from the source of an unbalanced circuit to (+)ve and the shield at the source end to the second wire of the pair to (-)ve, while only connecting the shield at the source end, think about what has happened. The (+)ve signal at the differential amplifier sees the source impedance of the source (i.e. 100 ohms), while the (-)ve signal at the differential amplifier sees the source impedance of zero ohms from ground. You have an impedance mismatch and the CMRR goes to the dogs. The differential amplifer still works, but its comparing partner has no signal, so the output will not be quite as high as expected.

But still, there are some advantages. You've broken the ground loop by not tying the shield to the receiving end. You've realized a bit of common noise rejection even with the poor impedance match. If there is sufficient signal to drive the BFD, then you've accomplished something.



> So basically I have a 25 foot RCA cable that goes into the AV receiver that is disconnected from the AC. Yet when I remove that end from the BFD the hum goes away. How can this be possible ??


As stated in posts above, the interconnect shields are connected to the AC case of every piece of equipment. In the case of cable, it comes in on the shield as a different potential and passes through the shields and cases of every piece of equipment that is connected together with interconnects.



> Doesn't seem like there would by many (any?) options since the cable line is grounded and has to connect into the STB. Unless there is some sort of cable adapter that removes the ground?


There are cable in-line transformer gizmos to break the cable ground. Doesn't work with satellites though (they phantom DC through the coax to power the LNA at the horn). They work for cable though.



> But recently I changed it so that it runs into a UPS backup with surge protection.


Yeah, that will be the loop. Bypass it and see what happens..

brucek


----------



## lovingdvd

OK for those of you following along at home - its definitely the cable TV feed, and not the result of going through the UPS/surge protector which makes no difference.

To keep the test simple I ran the cable TV line directly into the STB. Hum was present. Disconnected it from the STB, hum disappeared.

Further, I then put a cheater plug just as a temporary test on the BFD and get no hum even with the cable TV plugged into the STB.

Based on this, do you think I would be better off with the custom built connectors Wayne can build? Or should I go with the Jensen VRD-1FF which is about $60... ? Wayne you have a PM? Thanks all!


----------



## Wayne A. Pflughaupt

> But still, there are some advantages. You've broken the ground loop by not tying the shield to the receiving end. You've realized a bit of common noise rejection even with the poor impedance match. If there is sufficient signal to drive the BFD, then you've accomplished something.


Hmm, looks like were on to something then! Don’t know why someone hasn’t tried or recommended this before (‘course, it could have been a thread I wasn’t following...)

Regards,
Wayne


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## Wayne A. Pflughaupt

> Wayne you have a PM?


Yup – click on my name (above the avatar) to access it.

Regards,
Wayne


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## bobgpsr

Wayne A. Pflughaupt said:


> Hmm, looks like were on to something then! Don’t know why someone hasn’t tried or recommended this before


Actually this type of problem has been discussed at length a couple of years ago in AVS in a thread about using pro amps with AVRs. An engineer from QSC, Bob Lee, IIRC, showed various wiring options going from unbalanced output AVRs to balanced input pro amp inputs.


----------



## lovingdvd

Wayne A. Pflughaupt said:


> Yup – click on my name (above the avatar) to access it.
> 
> Regards,
> Wayne


Sorry. I meant "You have a PM."


----------



## brucek

> Hmm, looks like were on to something then! Don’t know why someone hasn’t tried or recommended this before


Because it's fraught with potential problems. We're dealing with a wacky auto servo connection that acts as both a balanced and unbalanced interface using the same jacks. Hard to say how the 4 circuits will react (2 input / 2 output).

The RCA to XLR trick in this case hinges on not activating the pin 1 to pin 3 short, because that would connect the troublesome shield of the source device to the shield of the BFD. So the auto servo level control is not activated and so the difference signal will generally be lower.

I'd be trying to find the ground loop and eliminate it if possible.

burcek


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## lovingdvd

brucek said:


> I'd be trying to find the ground loop and eliminate it if possible.
> burcek


Thanks. As noted above I did find the source and it is the ground in the cable TV coax into the STB.

So it looks like I have two choices:

1) This product from Jensen: http://www.jensen-transformers.com/datashts/vrd1ff.pdf or one like it. Does anyone know of any other product like this I should consider?

I do not use satellite so that's not an issue. Only potential problem is that the site says there have been some reports about certain channels not coming in.

2) Take Wayne up on his offer to send him the parts/supplies and construct the special connectors. 

Which is the better route to go here folks? Advantages/disadvantages of these approaches?


----------



## lcaillo

Have you tried properly grounding the cable line?


----------



## lovingdvd

lcaillo said:


> Have you tried properly grounding the cable line?


No - I didn't realize that was something I even could do. I thought the cable company or something grounds it to earth at some point outside.

Are you saying that it is not properly grounded for sure if I am getting this hum?

How could I go about checking to see if the cable line is properly grounded and correcting it if not? Thanks.


----------



## Wayne A. Pflughaupt

Look around the back of your house for the point where the cable service enters the house. It should be where your electric meter is. You should see a so-called “grounding block” that looks like this:








The coaxial cable connects to both sides of it. Where the screw terminal is, there should be a wire that goes to the copper ground stake for your electrical service. Make sure the wire is tight and secure on both ends. Maybe even replace it to make sure the connections aren’t oxidized and corroded.

Since we’re dealing with cable TV service, a trick that often works is to use a pair of 75-300 ohm transformers, like this:








Connect the screw terminals together, and your coaxial cables on the other ends. A barrier strip is a good way to tie them together and keep the connections seperated:







 
You can do this inside the house, between the wall and the cable box. Check your channels after you’re done, though – sometimes it can affect the picture on the high-numbered channels, if I recall.

Regards,
Wayne


----------



## lovingdvd

Thanks Wayne. I don't recall seeing any such grounding block, but I will check this out.

A few quick questions please:

1) If the grounding block is there and installed properly, and the AC outlet I'm using for the BFD is grounded properly, would that mean for certain that I would not have any hum in that situation? Or is it possible for both the cable feed and the AC outlet to be grounded properly yet still get a hum?

2) Assuming the cable tv and AC outlet is grounded properly yet I still have a hum, I'm thinking it would be best to just treat this at the BFD where the connectors are. This way I do not have to worry about any interference with my cable receiption which can have its moments as it is...

3) What are the costs of the parts involved to make the custom connectors for the BFD you mentioned? I can likely create these myself if I know exactly what parts to get and have good instructions.

Thanks!!


----------



## Wayne A. Pflughaupt

> 1) If the grounding block is there and installed properly, and the AC outlet I'm using for the BFD is grounded properly, would that mean for certain that I would not have any hum in that situation? Or is it possible for both the cable feed and the AC outlet to be grounded properly yet still get a hum?


It’s still possible to get the hum. The feed could already be “infected” before it gets to your house. (Again, brucek knows more about the technicalities of ground loops that I do - I'll defer to his thoughts on this.)



> 2) Assuming the cable tv and AC outlet is grounded properly yet I still have a hum, I'm thinking it would be best to just treat this at the BFD where the connectors are. This way I do not have to worry about any interference with my cable receiption which can have its moments as it is...


It’ll only cost a few bucks to try out the dual transformer trick. You can take the parts back to Radio Shack and get a refund if it doesn’t work for you. Give it a try.



> 3) What are the costs of the parts involved to make the custom connectors for the BFD you mentioned? I can likely create these myself if I know exactly what parts to get and have good instructions.


 From Parts Express, $1.70 for a Neutrik RCA, $2.45 for a 1/4” TRS plug (or $2.33 for an XLR), $0.60/ft. for the cable. Plus shipping. Do you have a soldering iron?

Regards,
Wayne


----------



## brucek

> Since we’re dealing with cable TV service, a trick that often works is to use a pair of 75-300 ohm transformers


Yeah, the problem there is two-fold. Many of these baluns pass the ground through on one side. You have to get the kind that uses no ground pass-thru. It needs to be checked with a meter. The other problem is the bandwidth. Many of these baluns only pass TV signals and don't pass the CATV full bandwidth. 

The best solution would be to use a in-line transformer on the CATV cable that passed at least 1GHz and those are expensive, so the capacitive solution is the next best so as to block the DC current, yet pass the bandwidth for CATV AC signals.

Here's a ISO-MAX VRD-1FF Cable TV Ground Isolator ground break solution that you would put at the STB as the cable enters. It should do the trick I would think. A bit expensive, but that's what it takes...



> 1) If the grounding block is there and installed properly, and the AC outlet I'm using for the BFD is grounded properly, would that mean for certain that I would not have any hum in that situation? Or is it possible for both the cable feed and the AC outlet to be grounded properly yet still get a hum?


Correct. The further you are away from the point of grounding, the more difference potential can build across the long distance (distance adds impedance).



> 2) Assuming the cable tv and AC outlet is grounded properly yet I still have a hum, I'm thinking it would be best to just treat this at the BFD where the connectors are. This way I do not have to worry about any interference with my cable receiption which can have its moments as it is...


Or treat the cable as I mention above.....



> 3) What are the costs of the parts involved to make the custom connectors for the BFD you mentioned? I can likely create these myself if I know exactly what parts to get and have good instructions.


At the CATV frequencies, it's best to buy off the shelf.
Even if you attack it at the audio level (i.e. transformers after or before the BFD), it has to be done to pass the low frequency signal of a sub without attenuation. A transformer that can pass 10Hz would be the Jensen variety you mentioned earlier. Pricy though..

brucek


----------



## lovingdvd

Wayne A. Pflughaupt said:


> From Parts Express, $1.70 for a Neutrik RCA, $2.45 for a 1/4” TRS plug (or $2.33 for an XLR), $0.60/ft. for the cable. Plus shipping. Do you have a soldering iron?


Yes, I have a soldering iron and most of the basics (electrical tape etc).



brucek said:


> At the CATV frequencies, it's best to buy off the shelf.
> Even if you attack it at the audio level (i.e. transformers after or before the BFD), it has to be done to pass the low frequency signal of a sub without attenuation. A transformer that can pass 10Hz would be the Jensen variety you mentioned earlier. Pricy though..


Would this apply to the approach Wayne is talking about with the custom cable, and I'd have to worry about whether the sub frequencies were getting mucked with? Or is the custom cable/connector approach just a matter of isolating the ground that doesn't really make any changes to the frequencies itself (my understanding)?

Thanks!


----------



## brucek

> Would this apply to the approach Wayne is talking about with the custom cable, and I'd have to worry about whether the sub frequencies were getting mucked with? Or is the custom cable/connector approach just a matter of isolating the ground that doesn't really make any changes to the frequencies itself (my understanding)?


The latter statement is correct, but realize the cable approach isn't guaranteed to work in all cases. Most people would rough that sort of idea up first and if it worked in their case, then they'd spend some money and make it nice....

brucek


----------



## lovingdvd

brucek said:


> The latter statement is correct, but realize the cable approach isn't guaranteed to work in all cases. Most people would rough that sort of idea up first and if it worked in their case, then they'd spend some money and make it nice....
> 
> brucek


Here's a quick update... I check outside and there is a grounding block that is grounded into a cooper pipe. Looks like the telephone is also tied into this pipe. The cooper pipe runs inside the house and into the electrical panel. So it sounds like the cable is grounded properly.

As far as solutions go - I did find a cable isolator similar to the Jensen except it is only $10 and rated up to 1000Mhz instead of 1300Mhz like the Jensen. 

However I'd much prefer to try with the custom cable / adapter approach as I don't like the idea of inserting anything before the STB. The only issue the ground loop is causing is with the BFD.

So Wayne if you'd be so kind as perhaps to provide some detailed instructions I'd like to give this a try first. If that doesn't work then I'll go to the Jensen or similar isolation transformer for insertion at the STB. Thanks!


----------



## brucek

> However I'd much prefer to try with the custom cable / adapter approach as I don't like the idea of inserting anything before the STB. The only issue the ground loop is causing is with the BFD.


If you still use any analog cable channels, I suspect there's a few hum bars in the video. The digital channels wouldn't give a hoot..... 

brucek


----------



## lovingdvd

brucek said:


> If you still use any analog cable channels, I suspect there's a few hum bars in the video. The digital channels wouldn't give a hoot.....
> 
> brucek


Nope, no analog whatsoever. 

Wayne - as a side note it sounds like your plan is to create a cable that goes directly from the BFD to the sub input. However if possible I'd prefer to make just an adapter piece that I can plug my existing cable into. This would provide more flexibility in the future if I move components around (not locked into a specific cable length).


----------



## brucek

> as a side note it sounds like your plan is to create a cable that goes directly from the BFD to the sub input


Is the ground loop not between the BFD and the source equipment? Why are you not trying this cable mod between the receiver and the BFD? This a unbalanced to balanced modification....

brucek


----------



## lovingdvd

brucek said:


> Is the ground loop not between the BFD and the source equipment? Why are you not trying this cable mod between the receiver and the BFD? This a unbalanced to balanced modification....
> 
> brucek


Good point I was thinking about this the wrong way because I was picturing modding the connecting between the BFD and the sub. When it really needs to be between the BFD and the receiver...

Which brings up a very important point. My RCA cable run from the receiver to the BFD is 25 feet and under permanently installed carpet. No way for me to switch that out. So I'll definitely need some sort of coupler/adapter that I can plug into the end of this cable (currently at the BFD) and then plug that into the BFD (replacing the connection between the receiver and BFD is not an option).


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## Wayne A. Pflughaupt

lovingdvd said:


> Wayne - as a side note it sounds like your plan is to create a cable that goes directly from the BFD to the sub input.


What brucek said – you want this between the receiver and BFD. No point doing it from the BFd’s output – that won’t help.



> My RCA cable run from the receiver to the BFD is 25 feet and under permanently installed carpet. No way for me to switch that out. So I'll definitely need some sort of coupler/adapter that I can plug into the end of this cable


I don’t know of any decent female RCA connectors, so I’d just make a short cable with a male RCA and an XLR (or 1/ 4” TRS), and use a coupler to connect that to the cable you’re using now.



> So Wayne if you'd be so kind as perhaps to provide some detailed instructions


Basically, all you need to do is connect the RCA’s center conductor (signal +) to the XLR’s Pin 2 terminal, and the RCA’s shield (-) to the XLR’s Pin 3. Using a TRS, it would be (+) to tip, and (-) to ring. See the bottom diagram here, only the black wire would go to Pin 3. Do *not* add the jumper between Pins 1 and 3

If you need more detailed instructions, let me know.

Regards,
Wayne


----------



## lovingdvd

OK - I'm confused already! 

I'm not sure what the difference is between XLR vs. TRS and how/if it matters which to use.

Currently my RCA line from the receiver goes into a Radio Shack plug that has the 1/4" pin on one end and the RCA female on the other. Is this a XLR, TRS, or neither?

Also in my custom cable thingie what is going to serve as the female end that my existing RCA feed from the receiver will now go into?

I'm also confused about that bottom diagram you reference in that link. That link shows a XLR but when talking about using a TRS you refer to it even though it is a XLR.

I'm also confused about this custom piece of cable. It sounds like a need to by a RCA cable with a female end on one end that my existing RCA would feed into, then cut off the other end and solder that into the XLR / TRS?

If its not too much trouble can you provide the short list of Radio Shack part #s I'll need, and exactly what wires I'll be connecting to what terminal # in each part #? Think of it as a "anti-hum custom cable creation for dummies guide" 

Once I know what to get I'll pick up the parts on my way home today and give it a shot, and let you know how it works out! Thanks again!!


----------



## Wayne A. Pflughaupt

> I'm not sure what the difference is between XLR vs. TRS and how/if it matters which to use.


It doesn’t matter which you use:

*TRS (tip/ring/sleeve, aka “stereo plug”)










XLR male (input)










XLR female (output)







*​



> Currently my RCA line from the receiver goes into a Radio Shack plug that has the 1/4" pin on one end and the RCA female on the other. Is this a XLR, TRS, or neither?


That would be a TS (tip/sleeve, aka “mono plug”).



> I'm also confused about that bottom diagram you reference in that link. That link shows a XLR but when talking about using a TRS you refer to it even though it is a XLR.


When I said “or TRS” that meant a different _connector_, not a different _name_ for an XLR. Either connector can be used for a balanced input. See Pg. 19 of the BFD manual for some details.



> I'm also confused about this custom piece of cable. It sounds like a need to by a RCA cable with a female end on one end that my existing RCA would feed into, then cut off the other end and solder that into the XLR / TRS?


You could certainly do that. 



> If its not too much trouble can you provide the short list of Radio Shack part #s I'll need,


Are you going to make it from scratch, or chop one end off a re-made cable and solder on an XLR? Different parts list for each...

Regards,
Wayne


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## lovingdvd

Hi Wayne - thanks for all the great feedback.

Probably the most straight forward thing to do would be to cut off the end of the 25 foot RCA at the BFD of that comes from the receiver and change that into the gizmo stero plug.

HOWEVER - I'm not comfortable doing that for a couple reasons. Mainly because that is an impossible cable to rerun and if I mess it up I'm stuck. In addition, if I should change my set up later and no longer use the BFD then I have a stereo plug on one end of a cable that I likely need to be RCA (aka the way it was).

So.... here's what I'd like to do that is the safest approach I think and one that I'd be most comfortable with. I'd like to construct a new cable that is hard wired on one end into a 1/4" TRS that will go into the BFD input, and on the other end has a female RCA plug. This way I can put this gizmo inline without any disruption to my existing 25 foot cable.

Just doing a quick search at Radio Shack it looks like there is no RCA female cable that's just a cable, but plenty of ones that are part of a Y adapter. I assume I can just buy one of those and cut off one of the female ends with some cord to spare. Then tie that somehow into the TRS with a basic wiring configuration? Also please clarify if the 1/4" plug is supposed to be mono or stereo (TRS vs. a TS). I mention this because you say I use a TS now but it sounds like part of this plan involves going to a TRS.

Thanks again!!


----------



## lcaillo

To clarify my comments on the cable grounding...and this applies to everyone and any system...

You should verify that there is a GOOD ground on the incoming lines such as cable, sat, antenna, etc. This means measure the resistance (with the equipment disconnected) between the cable ground and the a.c. ground. If it is more than a few ohms, it may be the source of the problem and it definitely needs to be addressed from a protection point of view. I do not recommend using isolation transformers as they may introduce problems with low frequency communication needed for digital and broadband cable. They should ALWAYS be after ground points and surge suppression in the line and just before the receiving equipment if they are used.

The BFD hum problem usually comes down to one of two problems, poor or different ground paths such as on a poorly grounded cable line or simply improper matching of the balanced/unbalanced equipment. Ultimately a decent matching transformer may be needed.

I have tested the radio shack transformer, btw, and find no problem with its low frequency performance. The problem is that the combination of connectors requires a clumsy 6 inch kludge.


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## lovingdvd

*My current plan...*

OK, so after reading through this a few more times it started to sink in and actually now seems pretty simple.

Here is my current plan:

- I've decided to use a TRS instead of a XLR. The XLR actually looks a bit easier to work with. However, Radio Shack apparently does not sell a MALE XLR plug, which is need to feed the input of the BFD. Please correct me if I'm wrong.

- First I'll need a female RCA plug to accept the sub out line coming from my receiver. Radio Shack apparently doesn't sell the adapter alone. So I'm going to purchase a cable like this one http://www.radioshack.com/product/index.jsp?productId=2103367&cp (catalog # 42-2542) and cut off one of the ends leaving about 6" of cord on it to work with.

- Next I'm going to purchase this TRS 1/4" plug http://www.radioshack.com/product/index.jsp?productId=2103445&cp (catalog #274-139)

- Next per Wayne's earlier instructions I'm going to connect the RCA’s center conductor (signal +) to the tip of the TRS, and the RCA’s shield (-) to the ring of the TRS.

- Plug her in, and hope for the best!

My only remaining questions are:

1) Does the above look like a good plan (make sense)?

2) Once I cut off the RCA female part from the Radio Shack plug, will it be obvious which lead is the signal + and which is the shield - ? If not, I guess I can easily confirm this with an ohm meter.

3) Regarding the TRS plug - I've never worked with one of these. What do you do - unscrew the pin from the case to get at the solder joints? And the biggest question of them all, within the TRS solder joints are they labeled so I know which are the ring, tip and shield? If not what is the procedure with an ohm meter to determine this (I don't know when looking at the plug which is shield and which is ring - tip is fairly obvious!  )

Thanks all!


----------



## Wayne A. Pflughaupt

> Just doing a quick search at Radio Shack it looks like there is no RCA female cable that's just a cable, but plenty of ones that are part of a Y adapter. I assume I can just buy one of those and cut off one of the female ends with some cord to spare. Then tie that somehow into the TRS with a basic wiring configuration?


That’ll work. Only we’re hopefully going to solder and not “tie?” 



> Also please clarify if the 1/4" plug is supposed to be mono or stereo (TRS vs. a TS). I mention this because you say I use a TS now but it sounds like part of this plan involves going to a TRS.


Yes, we’re going to use the stereo plug instead of the mono plug you’re using now.



> However, Radio Shack apparently does not sell a MALE XLR plug, which is need to feed the input of the BFD. Please correct me if I'm wrong.


It’s doubtful that Radio Shack sells any loose XLRs. However, if you have a guitar shop somewhere in town, they probably do.



> - Next I'm going to purchase this TRS 1/4" plug http://www.radioshack.com/product/index.jsp?productId=2103445&cp (catalog #274-139)


That’ll work, although I’d prefer to see one with a metal barrel. Just don’t step on the thing!



> 2) Once I cut off the RCA female part from the Radio Shack plug, will it be obvious which lead is the signal + and which is the shield - ? If not, I guess I can easily confirm this with an ohm meter.


The shield is signal (-), the center conductor is signal (+). The shield is what’s wrapped around the center conductor. It’ll look something like this (the braided part is the shield):














> And the biggest question of them all, within the TRS solder joints are they labeled so I know which are the ring, tip and shield?


The shield is easy. The tip and ring you’ll have to check with an ohm meter.

Again, look at the picture on Pg. 19 in the BFD manual (Fig. 10).

Regards,
Wayne


----------



## lovingdvd

Thanks Wayne - yes the pic on page 19 is very helpful indeed! Looks like my local guitar shop has the male XLR so I may go that route instead.

Just one question remaining - how am I supposed to wire the shield of the RCA to the proper pin on the TRS or XLR?

I ask because my understanding now is that the shield will be a braided type of aluminum similar to that found on RG6 cable. So because it is not a wire (rather just "foil") how am I suppose to connect that to the right pin? Am I suppose to take a little wire and wrap it around the shield/foil a few times and solder it there, then connect that to the proper pin?


----------



## lovingdvd

*Success!!*

I'm happy to report that the custom adapter worked!! The hum is now gone and bass is unaffected (at least by ear - haven't rechecked with REW but not planning to).

Funny thing is that when I first turned it on it was humming pretty good. My initial thought was "not good". Then I remembered I still had the cheater plug on that I used to test for the ground loop.

When I removed the cheater plug the hum was gone. I don't know the theory about how this fix works but it seems logical that having the cheater plug in with this new cable would then "reverse" the situation and bring the hum back.

Again I want to say thanks to all those who contributed to this thread, idea and a special thanks to Wayne for offering to build the cables. I can't say I'm proud of my solder job - but hey, it works!


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## bobgpsr

*Re: Success!!*



lovingdvd said:


> but hey, it works


Just the "+" and the "-" used to feed the input of the BFD with the shield ground input to the BFD left open?  So you had the same good results in doing this that I did.


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## Wayne A. Pflughaupt

Just now seeing your new posts, Ric. For some reason my e-mail notification is spotty these days. Happy that you were able to sub an XLR for that crummy Radio Shack plug!



> Just one question remaining - how am I supposed to wire the shield of the RCA to the proper pin on the TRS or XLR?


After you unwrap the braiding, you can twist it all together, like this:















​

At that point I would cut the shield fairly short (tin it first) before soldering it to Pin 3. Since it doesn't have any protective insulation, you don't want it shorting out somewhere:







​

Regards,
Wayne


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## tbrooke

I've had my BFD for a while with no hum problem but I connected up my cable and I have the dreaded hum. The BFD is near my sub amp and actually moving it a little helps but still some hum. 

I have followed this thread and am I correct in thinking that all I have to do to solve the hum problem is make some of these XLR thingies?

It ssems with all the hum discussion on this forum an enterprising solderer would make some BFD connectors - Since no one has I guess I'll break out the soldering iron and make my own.

Tom


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## lovingdvd

The only thing I'm not particularly happy about with my custom made cable is that I didn't know how to do anything special to prevent someone from pulling on the cable and pulling the solder leads right off or having them break off (more likely).

With a smaller wire I would have just made a knot in the inside. How can I go about adding something to make it more "tug proof"?


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## Wayne A. Pflughaupt

Typically XLR’s have built-in strain relief. Some have a pair of screws 180 degrees apart at the end of the barrel that you can tighten down. Neutrik XLRs (the ones in the pictures I posted before) have a built-in collar that clamps down on the cable when you screw the barrel on.

The soldered connection is very robust – it’s not going to break free. The wires will break before the solder gives up. 

Regards,
Wayne


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## lovingdvd

Oh ok thanks Wayne, so that's what that little plastic piece does inside of the XLR. Nice!


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## RazorX

brucek said:


> Yeah, the problem there is two-fold. Many of these baluns pass the ground through on one side. You have to get the kind that uses no ground pass-thru. It needs to be checked with a meter. The other problem is the bandwidth. Many of these baluns only pass TV signals and don't pass the CATV full bandwidth.
> 
> The best solution would be to use a in-line transformer on the CATV cable that passed at least 1GHz and those are expensive, so the capacitive solution is the next best so as to block the DC current, yet pass the bandwidth for CATV AC signals.
> 
> Here's a ISO-MAX VRD-1FF Cable TV Ground Isolator ground break solution that you would put at the STB as the cable enters. It should do the trick I would think. A bit expensive, but that's what it takes...
> 
> brucek


brucek,

Can I install this where the cable feed enters the house, prior to the first splitter the feed is connected to, instead of at the STB? Doing it at the point it enters the house would correct the problem for all TV's in the house as well as for my cable modem. Would there be anything wrong with doing it this way?

I plan on adding an XBOX 360 in the near future. It will be connected to my home network and I don't want to have the same problem with the XBOX 360 causing this problem after I fix it at the STB.

Thanks,


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## brucek

> Can I install this where the cable feed enters the house, prior to the first splitter the feed is connected to, instead of at the STB?


Yeah, but be sure to install it after (downstream) from the point where the cable itself is grounded (located inside or outside the house - if at all).

brucek


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## lcaillo

If it is not grounded at or near the entry point it would be a viloation of electrical codes in the USA, and could be the source of the problem. Unfortunately, grounding problems are all too common.

http://www.hometheatershack.com/for...nce-information/7442-grounding.html#post62267


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## RazorX

Thanks for the quick response. 

I'm not familiar with Jensen Transformer products. I don't mind ordering online but I would like to grab one locally if possible so I can get the hum sorted out today if possible. Can you typically find their products at any type of local store or are they usually only available online? What kind of local store would you usually find them, it they were to be found locally?


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## lovingdvd

Wayne,

Its so strange that this thread was just resurrected after all this time - I was just getting ready to post an update to where we last left off based on some testing from last night!

As you may recall a bit earlier in this thread you helped me understand how to create one of these XLR adapters to solve my hum problem.

This worked great for several months, but recently I started getting this VERY slight hum from my subwoofer that was only noticeable when a source (such as my HD DVD player or STB) was outputting a signal AND it wsa in a silent passage. Nonetheless its been driving me crazy.

So in other words if the source was not sending a signal, such as if a HD DVD was stopped and my AVR showed not bitstream or PCM signal, then there was no slight hum. But once I hit play, during silent passages I could hear the hum - and if I hit mute on the AVR the hum would go away. And I know this is not the HD DVD player as the same thing would happen with other sources.

I rechecked all my connections and things looked fine. Eventually I became suspicious over my home made RCA female to XLR plug with the wiring change to isolate the ground loop. And that's indeed what turned out to be causing the slight hum.

I verified this by temporaily putting a cheater plug in and removing my custom adapter, connecting it instead with a standard Radio Shack female RCA to male Phono plug. Violia, no hum whatsoever.

Now I don't think that my custom XLR plug has gone bad (or at least not completely), because if I wire things direct without my XLR plug and without the cheater then it hums badly. And then if I insert my home made XLR plug then the hum stops completely - except for when the AVR is sending an active signal, in which case the hum returns. Again, with the cheater plug in and no custom XLR, I get no hum whatsoever at any time.

What do you think may be going on here? I don't think this is the typical grounding loop hum, because it only happens when there is an active source.

I really hate the idea of sticking with the cheater plug and would like to solve this once and for all. 

Any ideas what may be going on here and how it can be definitively solved without the cheater plug? Apparently my custom XLR approach was not the full solution (either that or it has gone bad, at least partially)?

Thanks!


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## RazorX

lcaillo said:


> If it is not grounded at or near the entry point it would be a viloation of electrical codes in the USA, and could be the source of the problem. Unfortunately, grounding problems are all too common.
> 
> http://www.hometheatershack.com/for...nce-information/7442-grounding.html#post62267


Great information. Thanks for the link. What should I be looking for to ensure the cable feed is properly grounded to the ground rod? I'm not sure what the ground rod looks like or where it would be located. I'm assuming it is outside the house, perhaps close to where the electric, phone, and cable lines enter the house. Is that correct? Is there any danger in grounding the cable feed to the ground rod once I find it? I'm assuming it isn't connected to the ground rod or the connections isn't good since I obviously have a ground loop causing the hum.

I'm going to see if I can get under my deck and try to fix the actual ground problem when I get back from church this morning. I know I will need to remove a section of the lattice from the lower portion of the deck but I'm not sure I will be able to get far enough under the deck to access the ground block or the grounding rod. We'll see...

BTW, I am repeatedly blown away by how much great information is available on this site and the amount of help you guys are willing to offer. It is very much appreciated. Hopefully, I will be knowledgeable enough to contribute to the helping others someday.


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## RazorX

*Update: The hum is gone and it didn't cost any $*

I just finished eliminating the hum so I thought I'd post an update on what I did to eliminate it. 

I took off a small section of the lattice where the cable ground block is located and I also had to remove a couple of the planks above to gain enough access to the ground block. To my surprise, there was a ground wire (loosely) attached to the ground block but the other end wasn't attached to anything. I attached the other end of the wire to a clamp that was already on the main power ground wire which was connected to the ground rod. I tested my system to see if I had eliminated the hum and discovered it was still there.

My next step was to use my Dremel with a soft wire brush to remove the corrosion that had built up on the ground wire from the CATV ground block and the main ground wire. I reattached the ground wire from the CATV ground block and retested. The hum was still there. That is when I noticed the screw on the ground block was loose. Next step...

I decided to clean the end of the ground wire connected to the CATV ground block and snug it up. This wasn't as easy as you would think because the deck was built in a way that one of the joists obstructed the ground block. I had to use a small 1/4" wrench to sloooooowwwwwwly loosen the ground block from the wall just so I could get to the screw that applies clamping force to the ground wire. I cleaned this end of the ground wire and snugged it down. Hum test number 3: The hum is gone. Woohoo!!! I went back out and mounted the ground plate in a new location that is easier to access and put the two planks back in place. I will need to put the lattice back at some point but I think I will tweak the sound a bit now that the hum is gone.

I'm glad I was able to get the hum problem resolved and without shelling out $ makes it even sweeter. 

I think the cable TV picture actually looks better now too but this could just be a placebo effect. One thing that was also resolved which I know isn't just in my mind is a hum in our phones that was getting worse and worse over the last year...

Thanks for all the information and tips guys. You ROCK!


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## Wayne A. Pflughaupt

Congrats on your success, Rich!

lovingdvd,

There’s nothing wrong with your cables. The clue is here:



> Now I don't think that my custom XLR plug has gone bad (or at least not completely), because if I wire things direct without my XLR plug and without the cheater then it hums badly.


This tells me that the problem is that severity of your ground loop has become worse than it was.

Reviewing a couple of pages back, I noted that you said there was a grounding block for the cable service (post #89). Looking at that post again, this looks a little fishy:



lovingdvd said:


> Here's a quick update... I check outside and there is a grounding block that is grounded into a cooper pipe. Looks like the telephone is also tied into this pipe. The cooper pipe runs inside the house and into the electrical panel. So it sounds like the cable is grounded properly.


This ground looks suspicious. There should be a *copper ground stake* somewhere for the electrical service, drove into the ground. I don’t really trust grounding to pipes.

Aside from that, in light of Rich’s success by cleaning up all the connection points of the ground connection, I’d try that first. In light of the fact that further corrosion of the ground’s connection points would make the hum increase in volume over time, I strongly suspect that this is where you’re going to find the problem to be.

Is it possible to get the wire from the ground block to the breaker panel directly?

Regards, 
Wayne


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## lovingdvd

Wayne A. Pflughaupt said:


> This ground looks suspicious. There should be a *copper ground stake* somewhere for the electrical service, drove into the ground. I don’t really trust grounding to pipes.
> 
> Aside from that, in light of Rich’s success by cleaning up all the connection points of the ground connection, I’d try that first. In light of the fact that further corrosion of the ground’s connection points would make the hum increase in volume over time, I strongly suspect that this is where you’re going to find the problem to be.


Thanks Wayne! I definitely think you are on to something here. It appears that my "ground" is not grounded at all!

Here's what I mean - I just went and took another look outside. Basically there is about a 1/4" copper pipe that is mounted along the side of the house. The pipe *is not in the ground at all!*

It actually starts about 18" off the ground and runs for about 2 feet along the side of the house where it then gets routed into the house. From the inside of the house I can see where it comes in from outside and runs inside my electric breaker panel where I assume it is connected in.

On the outside of the house there is a metal-like wire that runs from the cable TV line and attaches to the copper pipe via a basic little metal terminal block (the wire is pinched to the pipe via this block/screw). Similarly the telephone outside line has a wire that runs from the phone box to this copper pipe.

So again, the pipe runs from the electrical panel, outside the house and then stops way short of the ground, with cable tv and telephone attached to it. As I examined the pipe closer, I noticed that it is very sharp on the bottom edge as if it had been broken off.

I am not the original homeowner so who knows what went on way back when. I'm thinking that perhaps something outside the house caused the copper pipe to break off. Then again I don't see the other half coming up from the ground either, so who knows, maybe it was never put in right in the first place.

Am I correct to assume then that based on this my electric panel is not really grounded at all?? And I suppose this has implications beyond just my home theater?

Now as far as fixing this thing goes - what is my best option? I am NOT very handy at all (still a miracle I managed to make my own XLR cables  ) . And there's no way I'm cracking open the electrical panel. Sounds like I need an electrician to come out and fix things up. Do you agree? I just want to make sure that's really needed - don't want to pay their fee only to have them come out and say its grounded properly already.



> Is it possible to get the wire from the ground block to the breaker panel directly?


Not sure what you mean by this... ? I think the answer is no, because a) currently I have nothing that really runs literally to ground, and b) it doesn't look like I can get to anything in the panel without cracking it open and that's the last place I want to mess around!

Thanks again!!


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## Wayne A. Pflughaupt

Good detective work there, lovingdvd!

How does this copper pipe attach to the breaker box? Typically if it’s conduit, it’ll be with an EMT box connector (I think that’s what they call them):










But I’ve never seen copper pipe used for anything electrical.

I’m wondering, how old is your house? Does it have grounded outlets? 



> Not sure what you mean by this... ? I think the answer is no, because a) currently I have nothing that really runs literally to ground...


I meant from the cable TV ground block to the panel, but I see now there is no reason to do that. 



> ...and b) it doesn't look like I can get to anything in the panel without cracking it open and that's the last place I want to mess around!


Hmmm... Well, I guess there isn’t much more that we can do. 

Have any friends with some electrical knowledge that might be up to tackling this?

Regards,
Wayne


----------



## lovingdvd

Wayne A. Pflughaupt said:


> How does this copper pipe attach to the breaker box? Typically if it’s conduit, it’ll be with an EMT box connector (I think that’s what they call them):


Not sure - as it goes into the panel and disappears. When I open the door where the breakers are, you only see the breakers. The pipe actually runs into the panel underneath that.



> But I’ve never seen copper pipe used for anything electrical.


The best way to describe the pipe is that it is a hard flexible material. In other words its not completely rigid like a water pipe. Instead it can be bend - not easily but it can. In fact that is what they do to curve it to turn it into the house and then route it into the panel.



> I’m wondering, how old is your house? Does it have grounded outlets?


Less than 10 years old and yes all outlets are grounded. I believe my UPS battery powered backup devices I have (several) have a built in warning if you plug them into an improperly grounded circuit, and I've never seen that warning come on FWIW.



> Have any friends with some electrical knowledge that might be up to tackling this?


I'll ask around. Also I've called an electrician that does work for us. Hopefully he'll come out and take a look at it soon.

*UPDATE*: I just took a look at my neighbors house which is built by the same builder. From the outside his telephone and cable is grounded in the exact same way as me. Same copper-like "pipe", and just like mine it is NOT attached literally to (into) the ground.

Is it possible to have a properly grounded electrical panel when the other end is not literally steaked ito the ground?

I just had another thought - perhaps the electric panel is grounded by some other means, and the copper pipe leading outside the house is for the sole purpose of grounding the cable and telephone. If the panel was grounded some other way, then it would make sense that they could send this pipe out to connect other things to ground... ?

Also am I correct to assume that an electrician has the tools to be able to determine whether outlets in the house are grounded properly? If such a tool shows the ground is indeed ok, then where is my hum coming from???


----------



## Wayne A. Pflughaupt

> The best way to describe the pipe is that it is a hard flexible material. In other words its not completely rigid like a water pipe. Instead it can be bend - not easily but it can.


Wow, that sounds like the stuff they use on my water heater, between it and the wall!



> Not sure - as it [the copper pipe] goes into the panel and disappears. When I open the door where the breakers are, you only see the breakers. The pipe actually runs into the panel underneath that.


You only see breakers because there is a cover in place. Four bolts will remove it and let you see the “innards.” It’s perfectly safe to remove the cover – just don’t go sticking your hands in there!



> Is it possible to have a properly grounded electrical panel when the other end is not literally steaked ito the ground?


Not if it’s up to code.



> I just had another thought - perhaps the electric panel is grounded by some other means, and the copper pipe leading outside the house is for the sole purpose of grounding the cable and telephone. If the panel was grounded some other way, then it would make sense that they could send this pipe out to connect other things to ground... ?


That did occur to me, that the electrical ground stake is not readily available, so this was a means to provide a ground for the phone and cable TV. 

I was thinking about attaching a wire to the CATV ground and using that pipe as a conduit to get the wire to the breaker panel, where it could be connected to the proper ground. If you pull the cover on the breaker panel, it should be easy to see the ground cable connection. I’m guessing that since it’s inside, the breaker panel is flush-mounted in a wall?



> Also am I correct to assume that an electrician has the tools to be able to determine whether outlets in the house are grounded properly?


You don’t need an electrician for that. This cheap gizmo from any hardware store will tell you if your outlets are wired correctly and are properly grounded:












> If such a tool shows the ground is indeed ok, then where is my hum coming from???


The cable TV ground is not consistent with the electrical ground – i.e., the two have separate paths to ground. If that’s not the problem, then the problem is in the feed itself, and the problem is “upstream,” and it would be their responsibility to fix it. But we need to make sure your ground is proper and secure before we start throwing rocks at the cable company. 

Regards,
Wayne


----------



## lovingdvd

Thanks again Wayne. To answer your question, yes the electrical box is flush mounted to a wall.

I spoke to a friend who said that the electrical feed into the house carries a common ground, and that is what the electrical panel is likely grounded to. After seeing the neighbor's "pipe" set up the same as mine, I started thinking that perhaps the issue was not with the pipe not going into the ground.

So then I started thinking more about your messages about corrosion and Rich's recent success. As I looked closely at the catv ground wire, the lead was fairly corroded. Likewise the copper pipe itself had a layer of grim on it where the leads were clamped to it.

I took some general purpose sand paper and sanded down the leads and the pipe where the clamp connected everything. I removed the cheater plug, put my custom XLR isolation cable back in place, fired it up, and volia - no more hum!! So I believe this solves the issue - thanks so much.

One question though - if indeed things are properly grounded, should it still be necessary to use the custom XLR to isolate (lift) the ground like it does? The obvious answer is YES because I still have the hum without my custom connector - but just wondering if that is supposed to be the case.

Happy Thanksgiving everyone!


----------



## Wayne A. Pflughaupt

You should have no hum using regular XLR wiring (i.e. signal [-] to pin 1). So it looks like you’ve improved but not eliminated the ground loop.

Can’t say that I’ve ever heard of electrical service carrying a “common ground,” but then I’m not an electrician...

Regards,
Wayne


----------



## lovingdvd

UPDATE: Some interesting developments since we last left off...

I had my electrician come out. He checked all the internal wiring and said things were grounded properly. As it turns out there is a ground wire that runs from the electric panel into the foundation of the house. The copper rod on the outside is just a conduit of sorts to tie the phone and cable tv to ground.

He decided to check my outside meter box before leaving, and its a good thing he did. Open opening the box we discovered that there was a small, mist-like smoke coming from area where the two main electrical wires from the ground feed into the meter box!

There was also a brown-like reside on the inside of the panel, likely the residue from that smoke building up over time.

He wiggled something a bit and sparks shot out for a second like a sparkler! The power company came out that day to service the unit.

It turns out that one of the fiberglass-like insulator blocks had cracked and one of the leads was being slightly shorted to ground. They since repaired it and said that settlement of the house sometimes causes this and they have seen it plenty of times before. My house is about 7 years old. Its hard to know how long it had that wiring issue...

I'm not sure if this at all could have been impacting my ground loop. I'm going to try removing the custom XLR cable to see if the hum is still there since this wiring issue is now cleared up. I suspect the hum will still be present, in which case I'll just stick to the XLR (since it is perfectly silent with the custom XLR since I sanded down the copper pipe to improve the cable ground).

At any rate I am very glad to have caught that issue as it seems like a real hazard the way it was. A special THANK YOU to all of you helping here and making the point that something was amiss somewhere. Although this may not have been the source of that issue, it was the catalyst in discovering this problem and resolving it!!


----------



## Guest

So here's my twist/question on this whole situation:

Just had Directv installed with a dual tuner box. Got the hum; if I disconnect both cables going into the satellite box, the hum disappears, so I assume it's a ground loop issue. Looking outside yesterday, I don't see a separate ground wire running from the satellite dish to my cable panel in the outside wall of my house. 

So, I'm assuming this should have been grounded? Additionally, the four cables running down from the satellite feed a 4x8 multiswitch, with cables that then run from the switch into my house. I don't see any grounding blocks anywhere - are all four cables running from the satellite to the multiswitch supposed to run through grounding blocks?

Tried all of the quick fixes found in the forums to eliminate the hum. The only thing that worked was to run a 14 guage copper wire from a screw on my directv receiver to a screw on the BFD. This eliminated about 75% of the hum, but I can still hear it. Would a thicker guage wire eliminate a greater portion of the hum, or am I off base with that?

Any help would be appreciated. Thanks.


----------



## brucek

> are all four cables running from the satellite to the multiswitch supposed to run through grounding blocks?


Yes, I certainly run _my_ cables through an outside grounding block before entering the home...........



> I don't see a separate ground wire running from the satellite dish to my cable panel in the outside wall of my house.


I think it's smart to do this, but I don't know if every installation complies.



> Would a thicker guage wire eliminate a greater portion of the hum


No, ground loops are very low current. It's not a power issue at all. It only requires a small potential difference on the grounds to cause a hum. Eliminating it simply takes a lot of trial and error.

brucek


----------



## Guest

Wow, thanks for the quick reply. Just realized I spelled gauge wrong, what a tool.

As for grounding the 4 coax cables running from the satellite:

Does anyone make a 4 in 1 grounding block, or should I just use two 2 in 1 blocks? Do I ground them before or after the multiswitch? And finally, can I connect a wire from the multiswitch to the house ground directly, in lieu of grounding each of the coax cables?

As for trial and error, phew, never done so much plugging/unplugging/switch outlets in my life. Such fun.

Thanks.


----------



## Wayne A. Pflughaupt

With my Direct TV, both RF feeds go through a grounding block which is located just below the antenna. There are wires going from the grounding block to the antenna and the main electrical ground stake. Since I didn’t get a ground loop, I assume this is the correct installation method. 

I suggest making the installer come back out and do it right. If he give you any grief, complain to Direct TV. 

Regards,
Wayne


----------



## Guest

You say "both RF feeds;" I have 4 coax cables coming out of the dish, not 2. I'm not sure how this compares.

And I thought I read somewhere that daisy-chaining the ground as you described it is actually not a good idea.


----------



## brucek

> should I just use two 2 in 1 blocks?


Just use two double blocks.....



> Do I ground them before or after the multiswitch?


Mount the blocks outside before the switch. It's nice to mount the switch indoors for troubleshooting when its poor weather outside. 

I mounted my blocks outside and then ran the grounds (along with a dish ground) to a 8' rod in the ground nearby. Then that rod is bonded to the central house ground with heavy ground cable. That way, I have an outside path to ground before it ever enters the house.



> can I connect a wire from the multiswitch to the house ground directly, in lieu of grounding each of the coax cables?


Nope....

brucek


----------



## Wayne A. Pflughaupt

> You say "both RF feeds;" I have 4 coax cables coming out of the dish, not 2. I'm not sure how this compares.


Doesn’t matter how many you have - they should all be going through a ground block.



> And I thought I read somewhere that daisy-chaining the ground as you described it is actually not a good idea.


They aren't daisy-chained. If one wire from the ground block goes to the ground stake, and the other goes to the antenna, that's essentially a direct path from the antenna to the ground stake. 

Besides, that has to do with the grounds on electrical circuits (not that I buy it), not this.

Regards,
Wayne


----------



## Guest

OK, I think I've got it guys. Thanks very much for the quick help on this matter. Have a nice holiday.


----------



## allredp

Great--I thought I dodged the dreaded hum problem! 

Without too much backstory, I've been running the BFD for nearly a year between my Yammy rx-v1200 and my SVS pb12+/2. No hum, 4 filters, happy as can be.

Then I get a break financially and decide to upgrade to a Sherbourn 5 x 200 amp and the new Yammy rx-v1800 as the pre/switcher. 

Now that I'm hooked up (with the BFD between the Yammy using an XLR to RCA 18" cable and an RCA to RCA with 1/4" adapter between the BFD and the SVS) I have a hum through all the speakers and I can very much hear the hum from the BFD itself, which is back inside the equipment closet. Haven't checked to hear a hum through the SVS or not.

So, I'm at odds over why I get some hum now and not with my previous setup? 

I have the Sherbourn amp's 2 powercords going to their own 2 gang box on one side of my equipment closet, and I have the BFD, Yammy and other componenets going through a power-surge protector and connected to a seperate 2 gang box on the opposite side of the closet. 

Help! :help:


----------



## brucek

> I have the Sherbourn amp's 2 powercords going to their own 2 gang box on one side of my equipment closet, and I have the BFD, Yammy and other componenets going through a power-surge protector and connected to a seperate 2 gang box on the opposite side of the closet.


You just answered your own question...............

brucek


----------



## allredp

Hey BruceK,
Sorry to be so dense! Help me know how I answered my own question!!! 
I actually called Sherbourn to see if they knew what was causing it--he said to just get a couple "cheater" plugs, which I did, and the hum is still there... 
When I plug in and power up the BFD it has its own hum from the unit itself. When I take it out of the loop and just fire everything else up the speakers still hum--but the SVS doesn't.
Aarrgghh...
Thanks for any help!


----------



## allredp

OK, Brucek, I think I see what you mean. 

I've gone back over this thread and I see where you said that using different recepticles for the amp and pre-amp may cause this problem.

So, I'll go try that out and let you know.


----------



## brucek

> Help me know how I answered my own question!!!


OK, sorry, I've been in such a rush lately...



> he said to just get a couple "cheater" plugs, which I did, and the hum is still there...


Can you tell me where you tried the cheater plugs and the results? Did you try one on the BFD itself, and what was the effect to the sub hum?



> When I plug in and power up the BFD it has its own hum from the unit itself


By this you mean a mechanical hum from the metal case itself, and not from any speakers? This is another issue and certainty not related to the addition of an external power amplifier.



> When I take it out of the loop and just fire everything else up the speakers still hum--but the SVS doesn't.


Are you saying that if you leave the BFD in the sub circuit, that it also hums in addition to the new hum you're getting from your main speakers?



> You just answered your own question


This comment was to indicate that the nature of any properly installed ganged box is that each of the two receptacles in the box will be powered from a seperate circuit. Each circuit will be on an opposite leg of the service panel. This is a recipe for a ground loop.
As a test, unlug your entire HT except for the power amp and receiver (being used as a preamp) plus the sub and BFD. Plug these things into a single receptacle and see if the hum is there. Granted there may not be enough power to run your whole system this way, but it's a test to see if powering from a common leg will remove the hum.

brucek


----------



## allredp

Man, I've tried so many different things to no avail...

Cheater plugs, isolating everything down to the amp and avr alone, checking to see if the CableOne guys grounded their stuff outside, etc. 

I've definitely got something introduced by the amplifier or the avr. I guess my next thing is to just try the avr by itself to test that...

BTW, everytime I power down I get a sharp "snap" sound from my speakers (not very loud, but noticeable).

Do I have a faulty unit? Since I've not ever heard this noise in my setup before it stands to reason that one of the new pieces (the Sherbourn or the Yamaha) is the problem, right?

I really appreciate the help!


----------



## imbeaujp

Hello, I recently added a BFD between my Rotel processos RSP-1098 and my Rotel RB-1080 sub amp. All thoses equipments are on a Rotel RLC-1040 line conditioner. The interconects between the BFD and the amp are XLR - XLR, and RCA - 1/4 between the Processor and the BFD.

Before the insertion of the BFD in the audio line, there was absolutly NO noize, Nothing, Niet. I must admit that now, I got a little noize on the sub. I can ear what I call a 'processing' noize when I am verry close to the sub, but this not seem to be an 'electrical ground' noize.

My conclusion at this time is that the BFD is quite a nice product for features, but not a HI-FI product.

Maybe the velodyne SMS-1 has better results ?


----------



## brucek

> BTW, everytime I power down I get a sharp "snap" sound from my speakers (not very loud, but noticeable).


Not uncommon at all for power amplifiers. The manufacturer will usually attempt to design an elegant shutdown, but it all costs money. It's a bit easier for the receiver to do a proper silence shutdown since the processor and power amp is in the same chassis and can be sequenced.

Anyway, you've got the right idea, that you have to strip the system down to nothing and start to build it back up until you identify the culprit causing the loop. 



> My conclusion at this time is that the BFD is quite a nice product for features, but not a HI-FI product.


It's completely fine for a sub though. Don't be fooled into thinking a ground loop has a particular specific 'sound'.
Most people use a BFD with zero hum, buzz etc. You have a ground loop and you'll need to find it if you want your buzz to go away....

brucek


----------



## Wayne A. Pflughaupt

allredp said:


> Man, I've tried so many different things to no avail...
> 
> Cheater plugs, isolating everything down to the amp and avr alone, checking to see if the CableOne guys grounded their stuff outside, etc.


Have you disconnected the cable line from the system to see if that’s the problem?

Regards,
Wayne


----------



## Trekari

Well, if I use cheater plugs on the BFD of my system as well as on my plasma TV, I get slight hum with my cable feed connected.

If I disconnect my cable feed from the wall outlet, without cheater plugs, I get no hum.

So clearly my problem lies within my cable feed. The moment I hook or even touch the coax to the wall outlet I get hum through all of my speakers.


----------



## brucek

> The moment I hook or even touch the coax to the wall outlet I get hum through all of my speakers.


You need to check if the cable is properly grounded to your house ground. This is usually done where the cable enters the home near the service panel.


----------



## Trekari

I already have Comcast coming out today between 4-6pm as this symptom is present on all my coax jacks 

Up until I started getting serious about my home entertainment, I never understood what made my bedroom subwoofer make a crazy loud hum if I jiggled the cable the wrong way.

Now I believe that also is a 60hz hum being transmitted, as I have those devices also plugged into the coax (cable internet) in one way or another.


----------



## Trekari

A special thanks to brucek, wayne, and HClarkx for their help in my humming problems.

These links also proved to be useful in both understanding what a ground-loop actually is, as well as troubleshooting methods to resolve them.

http://www.audioholics.com/tweaks/c.../ground-loops-eliminating-system-hum-and-buzz

http://forum.ecoustics.com/bbs/messages/34579/180767.html

http://www.epanorama.net/documents/groundloop/home_solving.html

I ordered the Jensen transformer, and I'm hoping to put it where my CATV coax comes into my condo, before the splitter sends it to my 3 rooms. That would solve the problem at all ends, otherwise I will settle for getting my main entertainment system fixed.

-Jason


----------



## Wayne A. Pflughaupt

Since this is a perennial problem, I’m making this thread a sticky.

Regards,
Wayne


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## Trekari

So my Jensen transformer arrived today.

Basic rundown of the symptoms:

1) With cheater plugs not installed on my 3-prong devices, I had audible hum from subwoofers and satellites if the cable coax was connected to the TV.

2) With a cheater plug on the TV and Behringer, I still had slight hum when the coax cable was connected.

3) With cheater plugs and no cable coax, I had zero hum.

4) Without cheater plugs and the cable still disconnected, I had zero hum.

With my new MFW-15 subs, I still had a VERY slight hum if the Behringer was connected and the coax was also connected.

I installed my Jensen transformer as the first device after my coax feed enters my condo, before the splitter that connects my bedrooms/living room to the main feed.

I then went over and turned on all my audio devices, and only have an audible HISS at near-reference volume, which can easily be attributed to the noise-floor being amplified.

I HAVE NO HUM!

The Jensen Transformer worked like a pro for me.


----------



## WmAx

I do not know if this has already been posted in the thread(frankly, it's a long thread and I don't intend to read all of it), but Behringer has a new passive ground loop isolator. It also has balanced to unbalanced conversion. I have not had one to measure, so I can not comment on it's frequency response.

Behringer HD400

http://www.zzounds.com/item--BEHHD400

-Chris


----------



## Guest

I just hooked up my BFD/amp setup with my new sub and got the hum. I have a Belkin PureAV power console where my cable TV connects as well. I had my BFD connected to a separate strip, but after reading some of this thread I tried plugging it in to the Belkin and the hum is gone. I don't know where my ground loop was, but this fixed it.


----------



## myn

Mark Seaton had mentioned in another forum regarding a thread on hum: "Markertek sells their house brand of TecNec cables for very reasonable prices. If you order XLR-RCA terminated cables, they are wired correctly, and very fairly priced.."

When he says "wired correctly" I am assuming he means pins 1 and 3 bridged at the rca end?

Also within this BFD/REW guide it again mentions Markertek and this particular cable which appears to be the same one that was referenced by Mark Seaton.

Has anyone purchased this and confirmed this is indeed wired correctly (pins 1 and 3 are bridged) demoting the notorious hum?


----------



## Wayne A. Pflughaupt

Pins 1 and 3 would only occur in an XLR connection. That cable you linked is functionally the same as a regular RCA cable using a RCA to 1/4" adapter on one end.

Regards,
Wayne


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## brucek

> Has anyone purchased this and confirmed this is indeed wired correctly (pins 1 and 3 are bridged) demoting the notorious hum?


The urls you mention show a typical 1/4" TS phone plug at one end and an RCA at the other. There is no pin 1,2,3 on a 1/4" phone plug. The phone plug can be a type TS (tip/sleeve) or a TRS (tip/ring/sleeve).

In the case of a BFD, we want to use the 1/4" TS phone plug (as shown in your url). This essentially shorts the ground and the minus differential amp together, which would be equivalent to shorting pin 1 and 3 on an XLR connector.

This would be the correct connection, but would do nothing to reduce hum if you were experiencing it.

brucek


----------



## myn

brucek said:


> The urls you mention show a typical 1/4" TS phone plug at one end and an RCA at the other. There is no pin 1,2,3 on a 1/4" phone plug. The phone plug can be a type TS (tip/sleeve) or a TRS (tip/ring/sleeve).
> 
> In the case of a BFD, we want to use the 1/4" TS phone plug (as shown in your url). This essentially shorts the ground and the minus differential amp together, which would be equivalent to shorting pin 1 and 3 on an XLR connector.
> 
> This would be the correct connection, but would do nothing to reduce hum if you were experiencing it.
> 
> brucek


So the cable I linked (TS to RCA) wouldn't offer me any more value over my existing RCA cable to RCA->TS adapter?


----------



## brucek

> So the cable I linked (TS to RCA) wouldn't offer me any more value over my existing RCA cable to RCA->TS adapter?


In what regard? Do you mean noise immunity?

brucek


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## myn

brucek said:


> In what regard? Do you mean noise immunity?
> 
> brucek


Removing hum.


----------



## brucek

> Removing hum.


The only way to remove hum with a cable would be to build a cable that uses a pseudo balanced configuration.

This involves buying a 1/4" TRS plug and wiring it to an RCA connector using two conductor shielded cable as shown below.

See how the positive (+) of the RCA connects to the Tip (+) of the TRS, and the ground of the RCA connects to the Ring (-) of the TRS, and the shield of the TRS connects to the shield of the cable without a connection back to the RCA.

This removes the physical connection between the RCA device chassis and the BFD chassis, which reduces the ground loop considerably. There is still noise rejection realized from the balanced configuration in the BFD, since noise rejection basically relies on matched impedances at the two inputs of the differencial amplifier stage. The impedance of the positive differential amplifier will be that of the previous stages output impedance, while the negative differential amplifier will be at ground or zero impedance. The mismatch still offers decent noise rejection.

Note that you require two conductor shielded cable to use this configuration, and that depending on the severity of the ground loop, this may not offer enough help.









brucek


----------



## myn

Very thorough explanation. Thanks.


----------



## bobgpsr

Excellent post Bruce! One can also use a XLR connector plug instead of the 1/4" TRS phone plug to do the same thing.


----------



## myn

So the The easiest way to build this cable might be to buy an XLR to XLR or TRS to TRS cable and then remove one of the XLR or TRS ends replacing it with an RCA connector wiring the RCA connector appropriately as documented in the image above? 

This would fit the requirement around having a cable with 2 conductors with shield and you're half there having the cable already bound with either an XLR or TRS connector on one end. I am assuming there wouldn't have to be any changes made to the XLR or TRS end as the main change in wiring occurs at the RCA termination.

Correct?


----------



## brucek

Correct..........


----------



## RazorX

*Rolls HE18 Buzz Off Hum Eliminator*

I bought a Rolls HE18 "Buzz Off" hum eliminator at my local Guitar Center last week and I am very happy with the results. 

I had a pretty noticeable hum that I was chasing down and decided to try a hum eliminator. I have read of many people having good luck with the ART Cleanbox II but couldn't find any local. I was able to find one of these in stock so I decided to give it a try. It has completely eliminated the hum and the response curve is unchanged (measured with REW). I also like the fact it has standard RCA inputs/outputs in addition to the 1/4" inputs/outputs.


----------



## thsmith

I ordered the DCI product that many people seem to have good luck with here, I currently have a cheater plug I am using on the BFD.

Where does the DCI product go, between AVR and BFD or BFD and sub ?

Thanks


----------



## Wayne A. Pflughaupt

From what I see at the DCI web page, it's supposed to be connected in front of the amplifier - i.e., between BFD and sub.

Regards,
Wayne


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## thsmith

Thanks, that what I thought but wanted to make sure.


----------



## Aminbiz

When I ran my Cable/satellite coax into a power/line conditioner first before connecting it to the box it solved my problem, no more hum !


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## lcaillo

That likely means that your system is not grounded properly. The surge suppressor is just a patch for this and should not be used as a final solution.

http://www.hometheatershack.com/forums/manufacturer-vendor-reference-information/7442-grounding.html


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## Aminbiz

so what you are saying is that if the line conditioner is grounded and it eliminates the problem then this is wrong ?


----------



## lcaillo

No, I am saying that it is only a patch on the real problem. You have tied the grounds to the same potential. This is fine, but you should not rely on the ground path through the line conditioner. You should be sure that the cable and sat systems are properly gorunded to the electrical service ground, and that all of the connections are clean and tight. You could still get a ground loop with everything properly grounded, but it is far less likely. Your protection is compromised if you have a bad (or no) ground on any system coming into the home. 

Read the material that I linked to.


----------



## thsmith

I am currently using a cheater plug on the BFD until I sort out my hum problem. I ordered the DCI product which made matters worse.

Working with Dave at DCI we determined it is a SAT receiver issue and come to find out DirectTV never grounded the mast or installed grounding blocks for the cables, that has been remimeded this morning.

Anyway, Dave sent me this article. This weekend I tried the cable modiciation describe on the BFD hum forum with no difference but when I tried the one Dave sent it cust the hum in half. When I put the DCI at the sub as recommended the hum was back being louder.

Tonight I will test again with a properly grounded SAT.


----------



## jstefano

I just plugged in my new BFD and I have the dreaded "HUM" has anyone come up with any new fixes for this since 10-14-08 "Last Post"? What seems to be best? I checked my grounds they are intact.
Joe


----------



## texfrazer

jstefano said:


> I just plugged in my new BFD and I have the dreaded "HUM" has anyone come up with any new fixes for this since 10-14-08 "Last Post"? What seems to be best? I checked my grounds they are intact.
> Joe


Hi Joe,

I see that you are using DirecTV as one of your video sources. From what I have seen (and read in this forum), there is a decent probability that your satelite receiver is not properly grounded. I would check that to start with. If that is ok, then I would check your electrical ground wire to ensure that it is tight, with no corrosion.

Let us know what you find.


----------



## NEO Dan

Another alternative:
The ground goes to your AVR's chassis/phono/AM ground.


----------



## thewire

I sawed off the end of an extention cable and plugged the BFD into it without the ground. I plugged that into a surge protector. Now when I turn my level up higher past -10dB reference I do not hear the hum in the speakers.


----------



## bobgpsr

I still think the brucek's way (post #155 in this thread) is the best method. 

Do not connect the cable shield at the AVR source end. Avoid making this connection to avoid a ground loop. Connecting a cable shield every chance you get is great for stopping RF leakage but bad for audio hum caused by ground loops.


----------



## NEO Dan

bobgpsr said:


> I still think the brucek's way (post #155 in this thread) is the best method.
> 
> Do not connect the cable shield at the AVR source end. Avoid making this connection to avoid a ground loop. Connecting a cable shield every chance you get is great for stopping RF leakage but bad for audio hum caused by ground loops.


Bob,
there are lots of folks out there who've already tried the cable connection I've suggested including myself. In my experience it has always been quieter with the shield connected at both ends. Nobody that tried this cable(I sent quite a few out) has ever said that they created a ground loop or more noise with the shield connected at the source. Quite the opposite in fact, most of the people that tried it wanted to buy the cable.


----------



## Wayne A. Pflughaupt

NEO Dan said:


> Another alternative:
> The ground goes to your AVR's chassis/phono/AM ground.


Not sure how or why that would work. The phono ground lug has continuity with all RCA sleeves. IOW, it's no different than tying the shield and black together on the RCA end. Which is no different than using a plain RCA to mono 1/4" plug. Am I missing something? :scratch:

Regards,
Wayne


----------



## NEO Dan

Apparently there are lots of "quality" AVR's out there that have some difference of potential between the Chassis Ground and the Phono Ground that it makes an audible difference. 

I run my EP2500's bridged with the gains full open, and it's significantly quieter with the shield connected at both ends.


----------



## bobgpsr

The ideal solution is to never have cable shields carrying any ground current. Rather have a seperate wire "star" ground connection from all the audio equipment to a single point ground. Using "cheater" plugs is okay if you then use the cheater plug's ground lug to implement the star ground connection.

from http://en.wikipedia.org/wiki/Electrical_grounding:



> *Separating low signal ground from a noisy ground*
> In television stations, recording studios, and other installations where sound quality is critical, a special signal ground known as a "technical ground" (or "technical earth") is often installed, to prevent ground loops. This is basically the same thing as an AC power ground, but no appliance ground wires are allowed any connection to it, as they may carry electrical interference. In most cases, the studio's metal equipment racks are all joined together with heavy copper cables (or flattened copper tubing or busbars) and similar connections are made to the technical ground. Great care has to be taken that nobody places any AC-grounded appliances (heaters etc) on the racks, as a single AC ground connection to the technical ground will destroy its effectiveness. For particularly demanding applications, the main technical ground may consist of a heavy copper pipe, if necessary fitted by drilling through several concrete floors, so they can all be connected by the shortest possible path to a grounding rod in the basement.


The AC ground the article refers to is not the third wire safety ground but rather the AC neutral line which hopefully (but don't bet your life on it!) also is grounded at the mains electrical distribution box. You do not want to involve the AC neutral in any way with the low level audio technical ground. Any audio equipment that only uses a two connector power cable will need a seperate technical ground from its internal chassis or internal audio signal ground "star" connected to the audio main technical ground point.

http://en.wikipedia.org/wiki/Electrical_wiring_(United_States)


> *neutral* wire is connected to the center tap of the final step-down transformer and is identified by gray or white insulated wire, perhaps with stripes; most commonly bonded to earth for a fixed known path to stabilize the voltages only at the main service panel; many times called the grounded wire. Note that all metallic systems in a building are to be bonded to the panel; e.g., water, natural gas, HVAC piping, etc.


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## NEO Dan

bobgpsr said:


> Any audio equipment that only uses a two connector power cable will need a separate technical ground from its internal chassis or internal audio signal ground "star" connected to the audio main technical ground point.


Response from popular AVR manufacturers= :yawn:


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## brucek

NEO Dan said:


> Response from popular AVR manufacturers= :yawn:


Perhaps it's boring, but non the less a true statement.

Are you refuting the information, or do you not understand it?

brucek


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## bobgpsr

NEO Dan said:


> Response from popular AVR manufacturers= :yawn:


My Yamaha AVR has a nice big knurled screw post for connecting an earth ground and labeled for such.


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## NEO Dan

I am not an AVR manufacturer

My line of thought was that if an AVR manufacturer actually cared there would be a 3pin IEC on the AVR. 

You are aware that "star" grounding a BFD to your AVR does in fact connect your AVR chassis to Earth/AC Neutral via your homes breaker box. That is if you are wired to code.


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## bobgpsr

NEO Dan said:


> I am not an AVR manufacturer
> 
> My line of thought was that if an AVR manufacturer actually cared there would be a 3pin IEC on the AVR.
> 
> You are aware that "star" grounding a BFD to your AVR does in fact connect your AVR chassis to Earth/AC Neutral via your homes breaker box. That is if you are wired to code.


Sure no problem with that. 

The third wire safety ground does not normally carry any current -- but the best way to avoid any AC current induced hum in audio interconnects is to have only one final connection from the star point back directly to an earth ground. Ideally a completely seperate wire going to the ground rod or buried copper water pipe connection. However you can use the safety ground from a given one of the 3 wire outlet power sockets that the audio equipment uses to then ground the "starred" ground point.

Most users just try to use one common power strip for all the audio equipment that uses 3 conductor power plugs, but any equipment that only has a two prong AC power plug should have a seperate wire running from the equipment's gound connection to one of the power strip's safety ground sockets or to the metal chassis of the power strip. Don't have the RCA audio interconnect cable shields providing the only earth ground for any audio equipment (esp the two prong AC powered ones) if you are working to reduce hum pickup to a minimum.


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## Sonnie

Chris mentions the Behringer HD400... this seems like it would be worth investigating...










_This ultra-compact 2-channel hum destroyer may be small in size, but there is nothing lacking in its performance. This super-compact solution removes AC hum and noise quickly, easily and reliably. Ground loops are safely broken while the highest sonic quality is maintained. Plus, the HD400 automatically converts unbalanced signals into balanced without any signal loss. The unit carries two 1/4' TRS inputs and outputs for 2 mono or 1 stereo signal._


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## bobgpsr

Sonnie said:


> Chris mentions the Behringer HD400... this seems like it would be worth investigating...


We would need to be sure that its freq response at the low end is flat to 10 Hz or so. Allow 1 dB down at 10 Hz?


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## WaveyD4vey

i ordered the BFD yesterday and it will be arriving on thursday...i also ordered the cheater plugs for now...ive been reading through alot of this thread but still have a few questions as its still a little confusing...first of all, the way i understand it at least, there is NO other way to get rid of this other than making your own cable as some people (brucek i think) have shown in diagrams how to do...either you make your own cable or you get one of the hum or buzz eliminators...but what about buying a XLR to RCA cable? im talking about one thats an actual cable and not an adapter of any sort...theres a link below to the one im talking about...and one more thing...i have no cable feed coming into my projector...it seems like a ton of people who have the hum with the cheater plugs have this caused by their cable or sat feed...i do have cable internet coming in to this room (obviously)...could that cause the hum as well? i would assume it could...and ONE more while im at it...is it a good idea to get a hum or buzz eliminator box even if i dont get hum with the cheater plugs? 

i also must say ive been at AVSforum for a loooooong time...i really like this place alot better...a whole lot less arguing goes on over here....at least from what ive seen so far.


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## brucek

> but what about buying a XLR to RCA cable?


It would have to be modified if you required the shield to be open at the XLR end.



> could that cause the hum as well?


Yes, and is most often the culprit.



> is it a good idea to get a hum or buzz eliminator box even if i dont get hum with the cheater plugs?


Nope. In fact you may not (and most don't) experience any hum at all. I wouldn't use the cheater until I found out if I had hum.



> a whole lot less arguing goes on over here


It's against the rules. 

brucek


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## WaveyD4vey

well i got it all hooked up and i had no HUM!!! yippie!!! and im ust say, it was VERY easy to set up...i thought it would be a little more involved...ir probly helped that i spent about 6 hours reading and then re reading through the BFD guide here on the forum...once u get one filter set up the rest is a total breeze, especially if u are using REW.

the sound quality from my system is unbelievably better...this almost made as much of a difference as when in spent $2000 on room treatments...im running B&W 683 mains with HTM61 center and DS3 surrounds...basically the entire B&W 600 series system...my subs are HSU VTF3HO with turbo and an MBM...before i EQ'd my subs with the behringer i had a huge rise at 60hz and from 32 hz down to 10 it was about 15 db above 75db which was my "reference" point...the rise at 60hz was about the same as the one from 32hz to 10hz...after i used the BFD and got everything all dialed in i was shocked how much of a difference it made...i did do a slight house curve...i basically raised all frequencys below 35hz by an average of 2 - 4 decibals give or take...but anywho, the difference in sound quality especially while listening to music is just flat out amazing...it made everything sound better...the bass is slightly cleaner and feels much tighter than before...everything just has so much more "definition" so to speak...i can even crank the volume on my receiver higher than before without feeling like the sound is distorting...that surpised me...even voices sound much much cleaner...they sounded just a tad strained at higher volumes on music...they sound much "airier" now...the room treatments and the BFD are definately the 2 best things ive ever done for my rooms sound quality...:yay::yay:now its just a question of what my next home theater obsession will be...lol:yes:


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## bbeck

Hi everyone. First post here after lurking for quite a while. I don't feel too bad about resurrecting this thread since it's a sticky, so here goes . . .

I'm currently dealing with a low-level hum from my sub (Outlaw LFM-1 Plus) after installing the BFD (1124P) between it and my AVR (Onkyo 805). I have all my components connected to an APC H15 power conditioner/surge protector.

I have tried removing the BFD from the AVR-sub connection chain, which succeeded in getting rid of the hum. I have an attic-mounted TV antenna (not grounded, which I think is OK for those kinds of installations since it sits on a wood floor), whose cable connects to the back of the H15 to be split in two directions, one to a CM-7000 DTV converter box and the other to a TV tuner connected to my laptop for recording HD programming. (The latter connection is rarely used.) Disconnecting the input cable from the H15 did not eliminate the hum.

I then disconnected everything from the H15 with the exception of the BFD and the sub. The hum remains.

What are my options at this point? The H15 has a grounding post, and the Outlaw has a two-pronged plug. Would anything be gained by attempting to ground the sub to the H15? This seems a little risky to me. I know Axiom subwoofers have a ground-lift screw for resolving ground loop issues and wondered if that was a standard (albeit hidden) feature on all subs or just peculiar to the Axiom line. Alternatively, would a modified XBR to RCA cable (as described in this thread) work?

I love my BFD by the way, and am quite pleased at the results I've been able to get with REW and the great help instructions posted on this site. There's just this one nagging problem left to take care of.


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## brucek

> Alternatively, would a modified XBR to RCA cable (as described in this thread) work?


It's your best bet. I suspect it will get rid of the hum.

brucek


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## bbeck

Thank you for the quick reply. I don't suppose there's any place that sells these cables custom-made or off the shelf? I have neither a soldering iron nor the expertise to make the cables.


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## bpape

Try www.avcables.com They'll make up pretty much anything you want. That's GEPCO's shop.

Bryan


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## Sonnie

I have also had Blue Jeans Cable make me a few specialty cables. They are friendly and easy to work with.


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## bpape

Sure. If BlueJeans will make up custom things, they're great to work with and reasonable prices.

Bryan


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## bbeck

I might try Blue Jeans. I've purchased some cables from them in the past, and they've been great to work with. I put in an RFQ with AVcable yesterday, but haven't heard back from them yet. I really don't expect a reply at this point, as I'm sure a request like mine is extremely small potatoes compared to other custom jobs they're asked to do.


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## bpape

If you do use AVCables, calling them on the phone is usually the best way. 

Bryan


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## VERTIGGO

I was using a 2.5k -40db, BW of 60 filter on the BFD, but after I introduced the Reckhorn B1, I don't think I need it anymore.

The hum was simple to locate using the REW sine generator.


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## waldo563

> *bobgpsr* wrote:
> Most users just try to use one common power strip for all the audio equipment that uses 3 conductor power plugs, but any equipment that only has a two prong AC power plug should have a seperate wire running from the equipment's gound connection to one of the power strip's safety ground sockets or to the metal chassis of the power strip. Don't have the RCA audio interconnect cable shields providing the only earth ground for any audio equipment (esp the two prong AC powered ones) if you are working to reduce hum pickup to a minimum.


bobgpsr,
I have been following your postings and I think you may be onto something. I have been fighting a hum issue with my Onkyo TX-SR606 AVR which seems to be HDMI related and have tried disconnecting various HDMI connections, moving my sub power to the conditioner everything else is plugged into, disconnecting the Dish cable from the DVR, and have run a separate ground from the cable ground block to the Air Conditioner junction box conduit. None of these has made a perceptible difference. I just realized that this AVR has a two-prong power cord and suspect that may have something to do with it. Unfortunately, unlike the Yamaha, the Onkyo does not have a chassis ground post. Do you see any risk in running a ground wire from one of the chassis screws to a ground point on my Monster HT-800 power conditioner? Also, what do you think would be the best way to connect to the power conditioner as it has a plastic case and no ground points that I can see.
Thanks for your informative input to this thread.


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## Scooterp7

Mitch G said:


> I'm a big believer in standing on the shoulders of giants.
> In this case that means I would like to know what solution folks use for addressing The Hum.
> 
> So, what are you audio giants using to address The Hum?
> 
> Mitch


I find that mostly the humming is because they don't know the lyrics.:unbelievable:


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## johnvb

NEO Dan said:


> Apparently there are lots of "quality" AVR's out there that have some difference of potential between the Chassis Ground and the Phono Ground that it makes an audible difference.
> 
> I run my EP2500's bridged with the gains full open, and it's significantly quieter with the shield connected at both ends.


Since the folks here are such big fans of Jensen (myself included, owning several IsoMax units, and diy JT-11 trannys) they should be aware that your proposal is suggested by Bill Whitlock of Jensen in his #AN-003 white paper: 


"4 - ABOUT UNBALANCED CONNECTIONS
Please note that, in all the schematic diagrams, connections to the
unbalanced IHF plug (formerly the "RCA plug" or "phono plug") are
shown as the single point to join SH (shield) and LO (signal low or !).
This is very important to absolutely minimize the resistance of
any remaining path used by both signal and ground
currents. If connections are made as shown, the only remaining
common path is the contact resistance of the shield connection
between IHF plug and IHF socket. Use a good quality IHF plug with
high spring force contacts and make sure the contact points are clean
and free of oxides.

With a little extra effort, this small remaining shared path can be
bypassed altogether. Leave signal LO connected to the IHF plug
shield, but connect the cable shield directly to the equipment chassis.
If the equipment manufacturer has thoughtfully provided a binding
post or banana jack marked GND, this will be easy. If not, there is
almost always room to mount one and then use a mating spade lug
or banana plug on the cable’s shield."


----------



## johnvb

and one more post for a linky :^)

http://www.jensen-transformers.com/apps_wp.html

Also, I want to add another link to this excellent thread that I didn't notice was here (maybe it is?). This is Rane Notes on the subject, showing all the cabling possibilities. Very helpful:

http://www.rane.com/note110.html


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## johnvb

http://www.jensen-transformers.com/apps_wp.html

Also, I want to add another link to this excellent thread that I didn't notice was here (maybe it is?). This is Rane Notes on the subject, showing all the cabling possibilities. Very helpful:

http://www.rane.com/note110.html


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## davidl86

I recently just bought a BFD and EP4000 amp and was getting terrible hum and noise problems. I tried an unbalanced stereo isolation transformers with RCA connectors, fixed the problem but introduced a really weird distortion into my subwoofer. So out the door that went. Next was connecting the chassis of the amp BFD receiver together this significantly reduced the hum and noise but there was still hum left which annoyed me when everything was quiet in the room. I then added my panasonic plasma television to the ground loop I made with the amp BFD and receiver and this completely eliminated the hum for me. Now if I can just find a new fan to quiten it down a bit. Apart from these issues the combo kicks ,really makes my DIY 21lw1400 sub sing.


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## bobgpsr

waldo563 said:


> I just realized that this AVR has a two-prong power cord and suspect that may have something to do with it. Unfortunately, unlike the Yamaha, the Onkyo does not have a chassis ground post. Do you see any risk in running a ground wire from one of the chassis screws to a ground point on my Monster HT-800 power conditioner? Also, what do you think would be the best way to connect to the power conditioner as it has a plastic case and no ground points that I can see.


Sorry to be slow in answering your questions, I just now noticed your post.

Sure use a chassis screw to get a earth ground connection to your AVR. Might be best to do a little scraping down to shiney metal where the screw head meets the chassis.

As far as the power conditioner ground goes -- can you use the three prong wall socket safety ground where the power conditioner is plugged into the wall socket? Does the power conditioner supply 3 prong power connections? I would think that it would need to. Couldn't you just plug into the power conditioner's power output sockets, a three prong power plug with only the safety ground connected to a wire for getting a ground connection?


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## Fabricator

i didn't read this thread.

i had a hum in my diy subs. turns out that its the comcast cable going to my dlp. i have to figure out the issue. but just unplugging it fixes the hum.


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## waldo563

bobgpsr,

No problem...I didn't realize until I had posted that I was replying to an older posting but I appreciate your response. I did a quick test by connecting some wire to a chassis screw and then (carefully) touching it to the power conditioner F-type connectors (which I assume would be tied to ground) and did not notice any improvement.  However, I did not remove the paint from under the screw head and may not have gotten good contact. I may try it again after doing that. As for the grounding post...after giving it some additional thought I came to the same conclusion that you did to use a 3 prong plug and just connect the safety ground to the wire.


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## Wayne A. Pflughaupt

RazorX;62416 said:


> I just finished eliminating the hum so I thought I'd post an update on what I did to eliminate it.
> 
> I gained access to the ground block, and to my surprise, there was a ground wire (loosely) attached to the ground block but the other end wasn't attached to anything. I attached the other end of the wire to a clamp that was already on the main power ground wire which was connected to the ground rod. I tested my system to see if I had eliminated the hum and discovered it was still there.
> 
> My next step was to use my Dremel with a soft wire brush to remove the corrosion that had built up on the ground wire from the CATV ground block and the main ground wire. I reattached the ground wire from the CATV ground block and retested. The hum was still there. *That is when I noticed the screw on the ground block was loose.*
> 
> I decided to clean the end of the ground wire connected to the CATV ground block and snug it up. I cleaned this end of the ground wire and snugged it down. The hum is gone. Woohoo!!!
> 
> I think the cable TV picture actually looks better now too but this could just be a placebo effect. One thing that was also resolved which I know isn't just in my mind is a hum in our phones that was getting worse and worse over the last year...
> 
> Thanks for all the information and tips guys. You ROCK!


Just want to re-emphasize Razor’s experience about checking your electrical service ground. 

Recently the transformer on a utility pole that was serving my house and a few others in the neighborhood blew out. After service was restored we were having ground loop problems in our system - significant hum in the audio system that grew louder by the day, and rolling lines on the TV. 

To make a long story short, the troubleshooting process eventually culminated at the house ground stake at the service panel, behind the garage. This house was build nearly 30 years ago, and it was a bit distressing what I found. 

To start, the clamp attached to the ground stake (for the heavy-gauge ground cable from the service panel) was too large to properly secure to the stake. It could easily be rotated on the stake. In addition, the screw-down terminal for the ground cable wasn't even tight. That's right - a loose clamp with a loose cable. Yikes!

On top of that, the stake had paint overspray all over it, and the clamp had been installed on top of the paint.

But wait, it gets better! _The ground stake doesn't even appear to be copper!_ It looks like some kind of galvanized steel, and shows signs of rust at ground level. It's also really loose and wobbly where it goes into the ground, like isn't going down very deep. I'll bet it's rusted to the point that there isn't much of it left down there. I definitely need to get a proper 8-foot copper stake installed the next time we get a deluge of wet weather.

Taking care of these issues - sanding the paint off the stake, getting a proper-sized cable clamp, and securing the ground cable to the clamp good and tight - eliminated just about all the ground loop problems. The rolling lines on the TV went away, and the hum from the system is just barely audible. That's pretty much the way it was before. I never have got around to installing dedicated circuits in this house for the HT system because it's going to be an ugly job requiring cutting into sheetrock and all kinds of other fun stuff. I hope to tackle that project this winter. Hopefully between that and a new ground stake I'll be good to go with a dead-silent system.

Bottom line, if you have an older house, it would be a good idea to give your electrical ground a once-over. Focus on it first rather than last, as I did!

Regards,
Wayne


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## lcaillo

This is a very common scenario. I strongly suggest that grounds be checked regularly. One should be careful. If there is a problem with the neutral, an open ground cound be a hazard. Not likely, but if things are loose and you fiddle, there could be danger. Best to maintain a ground connection with a second clamp while working on the first if possible if working on the electrical service ground. Not much danger if just working with a cable, sat, or phone ground.

I just did a service call this morning that had a bar rolling through the pix and it was a bad ground on the cable installation.


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## waldo563

I recently purchased a DSP1124P and, with my luck, ended up with a slight hum. Disconnecting my Dish Network cable into my DVR and using a cheater plug on the BFD pretty much eliminated the hum so it appears there is a ground loop issue associated with the satellite grounding.

So I went to cable entry point and ran some #10AWG solid copper ground wire from the ground rod which was the only ground reference for the satellite/cable coax shielding to a clamp on the electrical conduit going to the breaker box for my A/C unit which should be tied back to the structure ground. As a side note, the ground rod looks like it is steel which may have been copper clad at some point but now is heavily corroded. Unfortunately, the electrical service panel is some distance from where the coax entry points are and I was unable to find the service entry grounding rod. I also replaced the ground wire which was connected between the ground rod and the grounding blocks with #10AWG and cleaned the corrosion from all of the mating surfaces. This seemed to reduce but not totally eliminate the hum so it appears that even a properly (I hope) grounded system may introduce some hum.

Based on some other postings on this thread I then made up a ground wire by connecting only a single wire to the safety ground on a 3-prong plug and plugging it into the surge protector everything else (except the subwoofer) is connected to. This was then connected to the AM antenna ground on my Onkyo TX-SR606 AVR which, amazingly, has no dedicated chassis ground point and is the only device plugged into the surge protector.

The hum from my sub was reduced to an almost imperceptible level after this point but I noticed a slight buzzing from my mains which was annoying.

When I ran the satellite coax through the surge protector (Monster HT-800) coax connections, it cleaned up the buzz coming from the mains.

So it appears that by tackling the root cause of the hum which was the ground plane mismatch between the structure ground reference and the satellite cable ground reference, I was able to virtually eliminate the hum without the need for isolation transformers or a cheater plug.:jump: Hope this helps if anyone wants to try to fix the problem without additional equipment.

However, my BFD is still connected using 1/4" mono to RCA adapters and I would like to build some more permanent XLR to RCA cables with the shield attached at the XLR end as suggested by Wayne.

My question is, do these modified cables go between the AVR and the BFD input only and "standard" XLR to RCA cables with the shield connected on both ends and pins 1 and 3 shorted used between the BFD output and the sub? Or would it be better to use the modified cables at both ends.

Sorry for the long post.


----------



## brucek

> ran some #10AWG solid copper ground wire from the ground rod


Not large enough. Should be #6 or better.



> My question is, do these modified cables go between the AVR and the BFD input only and "standard" XLR to RCA cables with the shield connected on both ends and pins 1 and 3 shorted used between the BFD output and the sub? Or would it be better to use the modified cables at both ends.


Usually from the receiver to the BFD will be enough to fix the problem.

brucek


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## waldo563

brucek,

Agreed...the #10AWG was what I had laying around so it is a temporary setup but I do need to get some #6AWG or thicker for a permanent installation and to meet the National Electric Code requirements.
Regarding the cables, I suspected as much but just wanted to make sure.
Thanks for the quick reply.


----------



## Wayne A. Pflughaupt

brucek said:


> ran some #10AWG solid copper ground wire from the ground rod
> 
> 
> 
> Not large enough. Should be #6 or better.
Click to expand...

#6 between the coax cable ground block and ground rod? Are you sure? Seems like mundo overkill...



waldo563 said:


> However, my BFD is still connected using 1/4" mono to RCA adapters and I would like to build some more permanent XLR to RCA cables with the shield attached at the XLR end as suggested by Wayne.
> 
> My question is, do these modified cables go between the AVR and the BFD input only and "standard" XLR to RCA cables with the shield connected on both ends and pins 1 and 3 shorted used between the BFD output and the sub? Or would it be better to use the modified cables at both ends.


Connect the center conductor to Pin 2, and the shield to Pin 3. Don’t jump between pins 1-3. I made both my in and out cables this way, just seemed like the thing to do since I was taking the trouble to custom-making them anyway. But as brucek says, lifting the shield on the input should suffice.

Regards,
Wayne


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## Wayne A. Pflughaupt

lcaillo said:


> This is a very common scenario. I strongly suggest that grounds be checked regularly. One should be careful. If there is a problem with the neutral, an open ground cound be a hazard. Not likely, but if things are loose and you fiddle, there could be danger. Best to maintain a ground connection with a second clamp while working on the first if possible if working on the electrical service ground. Not much danger if just working with a cable, sat, or phone ground.
> 
> I just did a service call this morning that had a bar rolling through the pix and it was a bad ground on the cable installation.


I recently did some work in an apartment complex, DirecTV and Dish dishes everywhere. None of them grounded to anything...

Regards,
Wayne


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## waldo563

Wayne A. Pflughaupt said:


> #6 between the coax cable ground block and ground rod? Are you sure? Seems like mundo overkill...
> 
> 
> Connect the center conductor to Pin 2, and the shield to Pin 3. Don’t jump between pins 1-3. I made both my in and out cables this way, just seemed like the thing to do since I was taking the trouble to custom-making them anyway. But as brucek says, lifting the shield on the input should suffice.
> 
> Regards,
> Wayne


The #6AWG stranded copper is between the cable ground rod and some electrical conduit going to the AC switch box. I believe #6AWG or larger is required by the National Electric Code when grounding a dedicated satellite/cable ground rod to the structure ground when connection to the structure ground rod is not feasible. I used #10AWG solid copper to go from the ground rod to the coax cable ground block.

Regarding the XLR/RCA cables, I ended up taking the lazy way out and ordered some cables from Monoprice. It appears that the hum/buzz problem was related to my Onkyo TX-SR606 AVR with HDMI inputs - a problem which seems pretty well documented for that model. I took the BFD out of the signal chain and still had the hum so, not wanting to deal with it anymore, I replaced it with a Denon AVR-1910 and it has not manifested again although I have only had it for a couple of days. So I'm counting on the Monoprice cables working as is but, if not, then I hope they can be modified without too much effort.


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## chris319

To check for ground loops other than by guessing and trial and error, you could spend $20 - $30 for a multimeter. Go to the Mouser web site and check catalog page 2092 (I don't have enough posts yet to post URLs). There is the B&K 117B analog and 2405A digital.

A ground loop will show up as a voltage between two ground connections which you can measure using the volt meter part of your multimeter. After you've solved your ground loop problems you can use it as a battery and outlet tester.


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## chrisp9446

I just wanted to reiterate what others have said about fixing my ground loop. After putting in my BFD, I had the hum/ground loop between the BFD and my (two-pronged) AVR. After trying some other things (including a cheater plug, which worked but I didn't want to gamble with), I went back and re-read some of the posts in here. I was able to modify my RCA-XLR cable to go from shield--pin 3 instead of shield--pin 1, which eliminated the hum. 

Thank you all for the great info in here, and Wayne in particular for the instructions on the cable!


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## Bruce Fisher

Like many here, but trying to eliminate the BFD hum. Cheater plug fixes it, but I know that's not a permanent solution.

I see in this post a recommended way to fix the hum... it appears this method works for many people - is this the best/easiest way?

Looking at buying the components, I found:
CablesToGo XLR to RCA cables... anybody test these to know if they are wired this way already?

Assuming they are not, it appears one way is to make your own buying something like these cables - cut them in half, and solder on RCA connectors

Has anybody found a supplier that makes these cables already? I don't mind making them, but I also don't mind paying someone to avoid having to put it together myself if I know it works 

< edit: ugh, nice Amazon logos... sorry >


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## Wayne A. Pflughaupt

I expect that any over-the-counter RCA to XLR cables is going to combine the shield and signal (-) at the RCA end. The DIY method you're contemplating is the best remedy.

Regards,
Wayne


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## Bruce Fisher

thanks Wayne. I contacted BlueJeans yesterday and they said they'd make this cable for the same price as their normal XLR to RCA - just fill out the custom cable form.


----------



## brouham

I am buying RCA to XLR cables from monoprice; what would be the easiest way to convert them to pseudobalanced cables to rid my system of hum when using the BFD in my system. I get a hum when the current RCA to TS cable is connected from my receiver to the BFD-- no hum if I disconnect the that cable but leave the BFD to Subwoofer cable connected.


----------



## Bruce Fisher

I finished building my custom cables - worked perfectly - no more hum!

I followed this post - except I used XLR connectors to RCA. Basically the same as this post but without tying it to ground (just cut the end of the shield wire).

Bought a simple XLR to XLR cable and Dayton RCA connectors. Cut XLR cable in half and soldered on the RCA end. Took me all of about 20 minutes to make  No more hum


----------



## hoofenshnoz

has anybody used the Behringer HD400?


----------



## corock

I have a terrible ground loop hum in my system. I tried an Art Cleanbox II but it dropped the sub output by several dbs so I made the conclusion that was not a very transparent method and decided to go another route. I thought converting the unbalanced signal from my receiver to balanced was supposed to get rid of it, so i put a Samson S-convert between the receiver and BFD and that made the hum worse. It amplified everything including the hum, not to mention there is always a hum even when my receiver is off because the S-convert is powered. Any thoughts would be appreciated.


----------



## Wayne A. Pflughaupt

Lots of remedies discussed and recommend on this thread. Have you tried any of them?

Regards,
Wayne


----------



## corock

yes, both the art cleanbox and the s-convert.

I can't find where the ground loop is originating from I've tried disconnecting the satellite cable etc. If converting the unbalanced signal to balanced with an S-convert doesn't remedy it should I bother modifying the XLR cable?


----------



## Bruce Fisher

I would - completely eliminated my problem


----------



## corock

I might as well try it. I'm running rca from the receiver to rca into the Samson, xlr from the samson to xlr into the bfd, trs out of the bfd to xlr into the subs. Which one of these balanced ends should I mod? does it matter?


----------



## Wayne A. Pflughaupt

The XLR mods are for unbalanced connections, not balanced. Ditch the Samson and modify an RCA to XLR or 1/4" TRS. I'd do both ins and outs, or at least the ins for sure.

Regards,
Wayne


----------



## corock

the rca to trs cables that phantom cables built me have an unbalanced 1/4 connection so I can't modify the cable into the bfd. Would it be effective to remove the sheild connection from the balanced trs 1/4 out from the bfd?


----------



## Wayne A. Pflughaupt

Can't hurt to try.

Regards,
Wayne


----------



## corock

unsoldered the sleeve of the out trs and that didn't help


----------



## ToBeFrank

I've got the ground loop hum out of my sub now that I have a BFD. If I remove both the HDMI cable out to the TV and the HDMI cable that goes to my Directv box, the hum goes away. I have to have both disconnected to get rid of it. I only have to plug one of them back in to get the hum again. I checked out my sat install and it looks like it is properly grounded. In this case, how can I identify where the ground loop is? Note that I have the BFD and the sub plugged in outlets different than the receiver since they are on opposite sides of the room. I don't know if this is an issue.


----------



## bpape

That makes sense since your TV and DirecTV box are tied together also so leaving either one connected will give you the hum.

Having them on different potential electrical circuits isn't helping anything though my first guess would be a poor ground of the satellite system. That's not at all uncommon.

Bryan


----------



## ToBeFrank

bpape said:


> That makes sense since your TV and DirecTV box are tied together also so leaving either one connected will give you the hum.


This is why I'm confused. Once I disconnect the HDMI cable from the DirecTV box to the receiver, the box isn't connected to anything anymore. This means it is not the sat ground that is the problem. I just verified this by disconnecting the sat coax and the hum is not affected. Also, both the mast and the coax appear to be grounded properly at the same place as my main electrical panel.



> Having them on different potential electrical circuits isn't helping anything


I guess my only solutions are to build a custom cable or buy a transformer.


----------



## ToBeFrank

I made a rca to xlr cable as described in this thread and that took care of the hum. I still have a very low hiss that is inaudible unless you're really close to the sub. This will work for now, but I think I'm going to get a Jensen sub-1rr.


----------



## bpape

OK. Is anything else hooked up to the TV like a VCR, cable box, etc? Just looking for another ground path.

Bryan


----------



## CraigG

Obviously, this is a long thread, with lots of possible solutions to lots of different problems with the same symptom--BFD hum. I just wanted to thank everyone for the great info here, and possibly add to the collective knowledge about this issue by noting the specific solutions which worked for me.

I've got a Denon AVR connected via HDMI to a cable box, HTPC, and an Epson projector, and via the RCA sub out jack to a BFD, which then goes to a Behringer EP2500 to drive the subs. By disconnecting everything, then adding components one at a time, I was able to determine that I had a ground loop through the projector. I temporarily ran the projector on an extension cord back to the same surge suppressor where everything else is plugged in, and *most* of the hum disappeared. Fortunately, I don't have the drywall finished in the theater room yet, so I still have the option to wire the outlets so that this fix becomes permanent.

The remaining hum was present whenever the BFD & sub amp were connected to the receiver, even if nothing else was plugged into the receiver. I was previously using an RCA-to-XLR cable (from Markertek, I think), and when I opened up the connector at the XLR end, I saw that pins 1 and 3 were bridged together. This is the configuration recommended in the BFD manual for unbalanced-to-balanced connection, but it's not the same as what BruceK proposed here.

Since I had a spare TRS-to-TRS cable, I cut an end off and soldered up an RCA connector exactly as shown in BruceK's post--no connection to the shield at the RCA end. I just tested it, and I'm pleased to report that it worked perfectly! There is absolutely no more hum, even with the amp at full gain. Thanks everyone, and especially BruceK! 

:T


----------



## NEO Dan

CraigG said:


> Obviously, this is a long thread, with lots of possible solutions to lots of different problems with the same symptom--BFD hum. I just wanted to thank everyone for the great info here, and possibly add to the collective knowledge about this issue by noting the specific solutions which worked for me.
> 
> I've got a Denon AVR connected via HDMI to a cable box, HTPC, and an Epson projector, and via the RCA sub out jack to a BFD, which then goes to a Behringer EP2500 to drive the subs. By disconnecting everything, then adding components one at a time, I was able to determine that I had a ground loop through the projector. I temporarily ran the projector on an extension cord back to the same surge suppressor where everything else is plugged in, and *most* of the hum disappeared. Fortunately, I don't have the drywall finished in the theater room yet, so I still have the option to wire the outlets so that this fix becomes permanent.
> 
> The remaining hum was present whenever the BFD & sub amp were connected to the receiver, even if nothing else was plugged into the receiver. I was previously using an RCA-to-XLR cable (from Markertek, I think), and when I opened up the connector at the XLR end, I saw that pins 1 and 3 were bridged together. This is the configuration recommended in the BFD manual for unbalanced-to-balanced connection, but it's not the same as what BruceK proposed here.
> 
> Since I had a spare TRS-to-TRS cable, I cut an end off and soldered up an RCA connector exactly as shown in BruceK's post--no connection to the shield at the RCA end. I just tested it, and I'm pleased to report that it worked perfectly! There is absolutely no more hum, even with the amp at full gain. Thanks everyone, and especially BruceK!
> 
> :T


I go this route, it allows me to ground at the AVR and complete the shield end to end:


----------



## Wayne A. Pflughaupt

Not sure how that would do anything to help a ground loop? The barrel (sleeve) of the RCA jacks have continuity with the chassis of the AVR. IOW, it’s functionally the same as the black wire and shield being tied together.

Regards,
Wayne


----------



## santaclaus

Run your whole sound syetem + TV and everything else that is connected to your system on one or if needed two dedicated circuits on a 20 a breaker and don't hook up anything else to it, that is relatively easy if you have room for one or two more breakers in your breaker panel,the cables don't have to run inside the walls, that doesn't look to pretty,but may be try it , that worked in my case.


----------



## mdfire

Ive had a BFD in my system for about 6-7 months now with no problems....until recently. I have a popcorn hour A-200 which was in the system for about 2 months with no problems. I changed the casing on the PCH to a 3rd party metal casing as the original plastic one was terrible and had a fan inside it which was noisy. Anyway, changed the casing and put back into my system. It connects via HDMI to a pioneer AVR.

A few weeks ago I had to do a strip down of the system and upon reconnecting everything up I know can hear the PCH through my sub:unbelievable: In fact when it boots up I can hear the hard drive in it taking off. I dont understand how this can happen when it wasnt there before. Ive tried changing cables round etc but no luck. Ive had to disconnect BFD and connect Sub direct to AVR. Any ideas?


----------



## santaclaus

I did have a similar problem,with 2 subwoofers connected one as master and one as slave , all of a sudden one of them had a hum.I tried allot of things.I ended up putting each sub on it's own new circuit with it's own beaker and the rest of the system on it's own circuit with it's own breaker and what i learned is that it's important that every component is connected to a good ground, meaning that if you measure you r outlets with a multi tester the voltage between the positive and the negative must be the same as the voltage between the positive and the ground ,no more than + or - about 2Volts . and this should be on the whole system, so on every outlet or extension cord and every outlet from any power strip, so what I would do is just check all outlets with a multi tester and see if the voltage between all of them is the same, again check between positive and negative and positive and ground. That might be the problem , but no guaranties, good luck, I know ground loops can be a pain in the butt.


----------



## sticknstones

I use the HUM-x on one of my subs and it works great. It is rated at 6A. I did not want an isolater that had cheap looking connects for the sub power connection.


----------



## mdfire

sticknstones said:


> I use the HUM-x on one of my subs and it works great. It is rated at 6A. I did not want an isolater that had cheap looking connects for the sub power connection.


Is this similar? and how does it connect to the sub?

http://www.amazon.co.uk/Behringer-M...4?ie=UTF8&s=electronics&qid=1276794962&sr=8-4


----------



## perritterd

Hi-I have purchased BFD 1100P along w/the rest of the necessary eq. to use with the REW program. My system is hooked up via a Panamax M5100-PM line/surge protector. Before I hooked up anything, I plugged one of those ground check plugs (that you can buy in any hardware or electronic stores) into the outlet and it showed the line properly grounded w/no other problems. If I go and hook up the 1100P, would only a ground plug adapter be sufficient to make sure that the outlet/wire is properly grounded for the 1100P so that I don't get this "Hum" problem or do I need to use some other equipment to properly insure that the grounding of the outlet/line coming from the wall is correct? 

Thanks for any help.
Bob


----------



## Wayne A. Pflughaupt

Not sure I followed all that, but...



> If I go and hook up the 1100P, would only a ground plug adapter be sufficient to make sure that the outlet/wire is properly grounded for the 1100P...


...if you're talking about using one of these, the BFD will no longer be grounded at all.










Regards,
Wayne


----------



## perritterd

Wayne A. Pflughaupt said:


> Not sure I followed all that, but...
> 
> ...if you're talking about using one of these, the BFD will no longer be grounded at all.
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> Regards,
> Wayne


Sorry for the confusion Wayne. No, all I am talking about is one of those plug-in ground fault plugs that let you know if you have a grounding fault in the line somewheres...I am simply trying to determine the best way to make sure I have no grounding issues before hooking up my 1100P and doing all the cable connections. 

Bob.


----------



## Wayne A. Pflughaupt

If you’re talking about one of these...










...it will only tell you if you have a functioning ground. That has nothing to do with a ground loop. A ground loop occurs when there is differing potential between to grounds – see Post #241 by santaclaus, above.

Regards,
Wayne


----------



## sticknstones

mdfire said:


> Is this similar? and how does it connect to the sub?
> 
> http://www.amazon.co.uk/Behringer-M...4?ie=UTF8&s=electronics&qid=1276794962&sr=8-4












This is what I use for my sub and got it for around 50$ at amazon. I will be ordering another for the BFD once I get it all working.


----------



## gdstupak

*fix for hum from cable coax*

Fix for a hum from cable coax.
I haven't been able to read this whole thread so please forgive me if this has already been discussed.

For a month I was tearing everything apart looking for the cause of my very loud hum. Ended up being my cable coax.
My cable coax is grounded but there is still a difference in potential between the coax ground and my outlet ground. My solution was to connect the two grounds (and it worked), I took a piece of wire, about 14 guage, wrapped it around the ground area of the coax cable connector and stuck the other end of the wire into the ground hole of the nearest electrical socked. Whalla, balanced ground and perfect silence (except of a little hum from my light dimmer which I'll have to investigate through this thread).


----------



## lcaillo

Please do NOT use this solution. You should find where the grounding problem is located and correct that. The cable line, or any signal line entering the home MUST be grounded to the electrical service at or near the entry point to the home, not at the system level. You are patching a problem that could result in bringing dangerous currents into your home where they should be earthed at the entry. A better, though only supplementary way to get the ground you have is to use a surge suppressor on your system that has ports for your cable line.

Refer to the link below and solve the problem at the source.

http://www.hometheatershack.com/forums/general-service-technical-information/7442-grounding.html


----------



## mdfire

mdfire said:


> Is this similar? and how does it connect to the sub?
> 
> http://www.amazon.co.uk/Behringer-M...4?ie=UTF8&s=electronics&qid=1276794962&sr=8-4


This fixed it for me...nice and cheap

http://www.amazon.co.uk/gp/product/B000NVWB9O/ref=oss_product


----------



## sticknstones

mdfire said:


> This fixed it for me...nice and cheap
> 
> http://www.amazon.co.uk/gp/product/B000NVWB9O/ref=oss_product


I prefer the Hum-x as it is at the power outlet source. I have a hard time rationalizing the purchase of a BlueJeans or other premium analog cable and then putting something that looks so inferior inline with my components. Nice to have choices though!:sn:


----------



## goonstopher

If my pro amps picked up too much noise when using them on my speakers does this mean I will get the hum?

It sounds like everyone gets the hum.

This make it sound more and more like the SMS-1 is the way to go wince they fixed the distortion and roll off issues with the new firmware


----------



## pierreye

I had try Brucek's method cutting the shield but didn't help much in my system. The buzz is there even with the BFD turn off. When I unplug the power cable from the BFD, the speaker is complete silence. Note that my Onkyo 805 and Emotiva XPA-5 is using 2 pin plug. I manage to eliminate the electrical hum by connecting a ground cable from BFD (at the bottom, there is a ground screw) connected to Onkyo 805 ground screw. Now I just had a low level hiss from the speaker that I can't hear 2 feet onwards.

Is there a way to reduce the hiss? The hiss is not there if I plug the receiver out directly to the power amp. I'm using the BFD to EQ my speaker.


----------



## Wayne A. Pflughaupt

> Is there a way to reduce the hiss? The hiss is not there if I plug the receiver out directly to the power amp. I'm using the BFD to EQ my speaker.


The only way to eliminate the hiss is to get a better equalizer. The BFD is not suitable for use on the main channels. There’s a Yamaha YDP-2006 digital parametric EQ on eBay right now that you might want to consider. Check the “BFD Alternatives” sticky thread; you’ll find links in my post to user comments on the YDP.

Regards,
Wayne


----------



## pierreye

But when I unplug the RCA to XLR cable from the receiver, the hiss stop. So, I don't think the hiss is generated by the BFD.


----------



## lcaillo

There is a base level of noise in any unit. If you are hearing hiss, you have the gain too high at some point in the system. Each device should be level set to maximize its signal to noise ratio, meaning that the input signal to it must be very large relative to the noise. That means turn up the output on sources and turn down the gain on devices later in the system when possible.


----------



## shinksma

I noticed the Dread Pirate Roberts...I mean hum as soon as I hooked up my BFD. For the purposes of getting the EQ all set up via REW, I used a cheater plug, but knew that wasn't the ideal long-term solution.

I threw together an RCA-XLR cable as suggested by brucek's post #155:

http://www.hometheatershack.com/for...-folks-use-dreaded-bfd-hum-16.html#post108942

Lowered the hum dramatically, say by 90% to 95% (but didn't eliminate it completely like the cheater plug did).

So I'm happy the system is safer overall, but annoyed there is still a bit of hum. Disconnecting the cable box didn't help, and running either XLR or regular shielded RCA from the BFD to the SW didn't make any difference.

Since the DSP1124 is "designed for pro-audio connections" via balanced XLR or TRS, I wonder whether Behringer took some shortcuts that would have made unbalanced TS connections less noisy. I have a bunch of Behringer gear in my guitar and vocals effects rack, and there is no annoying noise like this (and those connections have unbalanced signals due to some non-Behringer equipment not supporting balanced signals).

Oh well, good enough for now, 

shinksma


----------



## shinksma

hmm, here's an interesting observation. Last night when I powered off my AVR (Onkyo 606), the hum returned in the BFD/SW combo. I guess the AVR lifts the grounds and signal returns when it shuts off. So I had to turn off the SW and BFD (I would normally leave them on in standby).

I then used the cheater plug on the BFD to see if that made any difference. It did, massively in the wrong way. I got a HUGE hum after powering back up the BFD and SW with the AVR off.

So...I won't try that again.

Now I'm wondering whether there is a latent design bug in the Onkyo and other receivers that is pairing with a non-ideal grounding design in the BFD for unbalanced inputs: either by itself is not noticeable, but together the hum manifests itself.

Meh, too early on a Sunday to be thinking about such stuff,

shinksma


----------



## psg

Is this an argument to buy the miniDSP instead of the 1124p since it doesn't use XRL? The miniDSP is a bit more expensive, but with the 1124p I also need to but XRL-to-RCA cables from monoprice and possibly deal with this hum issue (of which I was unaware until today).


----------



## Wayne A. Pflughaupt

The hum issue has nothing to do with XLR connections. If the Mini DSP is better in this regard, it’ll be because it doesn’t use grounded electrical power.

Regards,
Wayne


----------



## psg

Nothing to do with XLR? I read that on post #2 of the thread!


----------



## shinksma

psg said:


> Nothing to do with XLR? I read that on post #2 of the thread!


Well, the problem on the 1124 is solved by using balanced XLR signals the whole way. The XLR connections aren't causing the issue, per se, it is Behringer's design (with grounded chassis) being incompatible with most/many/some (???) AVRs that output unbalanced via typical RCA.

It is an annoying issue, and I would be much happier if there was a solution that didn't involve either modified cabling to lift the signal ground or using a cheater plug to isolate the 1124's chassis.

Maybe I should toss this as a thought-experiment to one of my electrical engineers at work...

shinksma


----------



## lovingdvd

I had the hum issue. It was really annoying. With posts in this thread and help by Wayne I was able to make wire a cable. I am very grateful for the help I received on this and it worked out great. If you do decide to go with the 1124 I think you'll find the info in this thread helpful.


----------



## psg

Ok, I agree that it's not the 1124p's fault, exactly, since you're supposed to use it with balanced cables. But since I plan to do: receiver RCA sub out -> EQ -> EP2500 -> THT, then that could look like:

receiver RCA sub out -> XLR input on 1124p -> EP2000 using XLR -> THT
or
receiver RCA sub out -> miniDSP -> EP2000 (using RCA-to-XLR on input side) -> THT

I wonder if either is a safer way to go wrt hum. Note that I don<t have the EP2000 yet either.


----------



## shinksma

Just thought I'd mention that while trying to eliminate hum and you suspect the BFD even after using cheater plug or XLR ground lift trick, check your cables. A while back I did some cable "upgrades", replacing temporary cables (stereo coax cables from a cable-box) with what should have been equal-or-better quality cables from Monoprice. It seems they weren't even equal-quality.  They introduced additional ground-loop-like 60Hz hum and lots of higher-order harmonic - picked up due to poor shielding around the connector ends, I suspect.

Swapped back to my temporary cables and the hum is diminished greatly (still there at low levels - now I need to figure out how to eliminate that completely or at least reduce it further). So I will experiment with other cables and configurations.

The hum I'm tackling is nowhere near as severe as the hum introduced natively by the BFD, so don't think I'm dealing with the end of the world. I would just like complete and utter silence when the audio signal is mute. 

shinksma


----------



## RickD1225

I returned my BFD in favor of a MiniDSP because I couldn't deal with the hum issue. I tried everything I could think of at the time with no results. I just had another thought has anyone ever tried grounding the BFD to their AVR phono ground (assuming they have one)? Could this work?


----------



## lovingdvd

RickD1225 said:


> I returned my BFD in favor of a MiniDSP because I couldn't deal with the hum issue. I tried everything I could think of at the time with no results. I just had another thought has anyone ever tried grounding the BFD to their AVR phono ground (assuming they have one)? Could this work?


Several pages back (and years ago) Wayne provided some very good information on how I could make an adapter. It worked great and totally solved my hum problem (which was significant).


----------



## TreyS

lovingdvd said:


> Several pages back (and years ago) Wayne provided some very good information on how I could make an adapter. It worked great and totally solved my hum problem (which was significant).



Is this what you did?












If so wouldn't this work: http://www.parts-express.com/pe/showdetl.cfm?Partnumber=240-430












> 3-pin XLR-F to RCA plug. Perfect for connecting a source with a balanced XLR output to a device with an unbalanced RCA input. *Pins 1 and 3 are shorted with no connection to the shell.* Note: This connector is not impedance matching.



.


----------



## lovingdvd

I did this several years ago (5?). I just pulled out my notes. I have that first figure you included, and scribbled on the page "center = pin 2" and "sleve = pin 3". I also updated the figure to show the black line connecting to pin 3 instead of pin 1, and I can't tell but it looks like I crossed off the connection of pin 1 (so maybe it is not connected - I can't recall). And underneath the drawing it says "This produces an unbalanced audio cable".

I'm not sure how to compare this to the plug you put in the post with the product. This would best be addressed by Wayne and perhaps others.


----------



## TreyS

I bought this RCA to XLR cable from monoprice.com and it has pins 1 and 3 already shorted just like this:


----------



## lovingdvd

I'm not sure thought that's the solution. As I noted, in my sketch for what I wound up doing I did not use that wiring (I think!). At any rate, did this work to take care of the hum?


----------



## TreyS

I bought all of that before I connected the BFD1124. Got it connected last night and no Hum issues. Could be that my grounds are all correct so don't know if my cable is helping...def not hurting anything.


----------



## TreyS

Now have hum issues..not only on the sub. 

I've disconnected pretty much everything in my system and it's still there. I'm wondering if it's my power conditioner, Belkin PF60. I just installed that a few weeks ago and that's basically when the hum started in my rear surrounds. It has a ground point on it but I don't know where I would ground it to other than running a very long cable from it to the basement grounding point for my plumbing/ direcTv.

Could I run grounds from each of my devices in my system to the ground terminal on the PV60 so they're all terminated to the same point?

I'll go ahead and modify my rca to xlr cable like you did lovingdvd to see if that at least makes the sub no longer have the hum. It's slight but there.


I re-read your previous post and had a question. Which one did you end up doing below?


----------



## ghost rider

I have been using a cheater plug and started to read some of this thread, will something like this work?

http://www.parts-express.com/pe/showdetl.cfm?Partnumber=240-438 plugging this into the back of the BFD and using unbalanced cable from the processor?


----------



## patchesj

I know this isn't an option for most, but I purchased a prepro with balanced outputs... Previously I had narrowed the ground loop down to my projector. The loop was going from the BFD, to the prepro via XLR-RCA, to the blueray player via coax digital, to the projector via HDMI. Insane... So first I replaced the coax digital with fiber, that worked but then I found I liked the sound of the analog outs on the Oppo better than my old HK doing the DA. So I put a cheater plug on the projector instead of the BFD. Ended up getting a new prepro and that changed it all. I guess my point is that you may be able to find a solution that doesn't involve the BFD if you try to track down the other "end" of the ground loop.


----------



## TreyS

Thanks for the suggestions but if I lift the ground on the XLR - RCA cable then I won't need a cheater plug. I just need to verify what picture above if the correct way to modify PIN 1.


----------



## vann_d

I'm having this problem now in my new home and just noticed it now that I'm getting around to setting the sub levels, etc. Is minimal if I keep the gain on the sub amp to 1/2 or less (which is where I've had it) but now I want to turn up the gain because I want to turn down the sub level at the receiver. I'm clipping the BFD input when I set the sub out level where I want it.

Anyway, I'm using 1/4" TRS to RCA cords from RadioShack. I decided to try what one poster on this thread had done and connect the ground screw on the bottom of the BFD to my HT receiver. I chose the ground on the AM antenna connections. This made a big difference in regard to the hum issue. It is not totally gone up has gained me some wiggle room in my sub gain setting. Bonus was that it cost nothing and is easy to do.


----------



## lovingdvd

TreyS said:


> Now have hum issues..not only on the sub.
> 
> I've disconnected pretty much everything in my system and it's still there. I'm wondering if it's my power conditioner, Belkin PF60. I just installed that a few weeks ago and that's basically when the hum started in my rear surrounds. It has a ground point on it but I don't know where I would ground it to other than running a very long cable from it to the basement grounding point for my plumbing/ direcTv.
> 
> Could I run grounds from each of my devices in my system to the ground terminal on the PV60 so they're all terminated to the same point?
> 
> I'll go ahead and modify my rca to xlr cable like you did lovingdvd to see if that at least makes the sub no longer have the hum. It's slight but there.
> 
> 
> I re-read your previous post and had a question. Which one did you end up doing below?


In looking at the diagram I saved as a reference to what I had done, I have squiggly lines through the wire coming off of pin 1. I think that means I do not have it connected, but can't be sure. I also have written on the page "center pin 2, sleeve pin 3".

I really had no idea of what I was doing at the time and even less of an idea now.  But I can say it solved my problem 100%. Please check with Wayne as he was my definitive resource and spoon fed me the solution so he probably knows off the top of his head what needs to be done.


----------



## Wooderson

Hello fellow hummers--

I just got my first of 2 DIY subs up my stairs and all hooked up. HUMMM..... :unbelievable:

Onkyo-606 -> RCA -> RCA-to-1/4"-TRS -> BFD -> XLR -> EP4000 -> Sub

When I disconnect my cable coax from my DVR, or the HDMI cable from DVR to Onkyo, pretty much all hum goes away. Enough at least. I checked the earth ground of the dish coax. It appears to be well done and right next to my outside electrical mains, so there's nothing I can do to improve that.

Will this fix it? :dontknow:

http://www.mcmelectronics.com/product/33-8700&CAWELAID=220406689

* 5MHz ~ 2.4GHz bandwidth
* Compatible with antenna, cable television and satellite systems
* Reduces or eliminates the effects of ground loops
* Female "F" input and output connectors
* Insulated metal housing

I tried searching these 28 pages and other areas of the forum, but I couldn't find anyone that's tried this thing.

Thanks!
--Myles


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## Wooderson

Or similarly:

http://www.amazon.com/VSIS-EU-Cable-Ground-Loop-Isolator/dp/B0017I3K9M/ref=pd_sim_e_3

57 5-star reviews. Sounds like it'll probably work. I still find it weird that I can't find any mention of these filters in all 28 pages of chatter about hum.


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## Wooderson

Whoops. The one from Amazon only has 860MHz bandwidth, so I ordered the one from MCM w/ 2.4GHz BW.


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## Wooderson

Worked! My hum is completely gone :T. Not a trace. And my satellite signal is fully intact. If removing your coax from your dish receiver gets rid of your hum, then this device should work for you. $30-shipped.

Isolation Transformer / Ground Loop Isolator
Distributed By MCM Part #: 4170


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## jboiler76

I tried the MCM Ground Loop Isolator with Dish Network but without success. I was unable to get the signal to pass thru the Isolator to my Dish VIP722 receiver. 

I ended up contacting Jensen Transformer and bought their Model SUB-RR. No more hum!


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## Jessicagogo

cool~~ nice sharing


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## BandidoAzul

A few have mentioned the behringer hd400 but there arent really any detailed specs available even the manual gives only the dimensions. Nothing mentioning its effectiveness at passing <20hz material signals, or better yet any negative effects on lower hz material like loss of volume..

Any input on this device?


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## BandidoAzul

vann_d said:


> I'm having this problem now in my new home and just noticed it now that I'm getting around to setting the sub levels, etc. Is minimal if I keep the gain on the sub amp to 1/2 or less (which is where I've had it) but now I want to turn up the gain because I want to turn down the sub level at the receiver. I'm clipping the BFD input when I set the sub out level where I want it.
> 
> Anyway, I'm using 1/4" TRS to RCA cords from RadioShack. I decided to try what one poster on this thread had done and connect the ground screw on the bottom of the BFD to my HT receiver. I chose the ground on the AM antenna connections. This made a big difference in regard to the hum issue. It is not totally gone up has gained me some wiggle room in my sub gain setting. Bonus was that it cost nothing and is easy to do.


I also used this method and the hum is just about gone. i will still look around for ways to eliminate it altogether but the wire from the bfd to my avr made a big difference in the hum. I can now turn my amp gain full on and lower the avr sub lvl so my bfd doesn't clip on lfe peaks.

Thanks HTS!!


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## THX-UltraII

Hi guys,

I just bought a FBQ1000 (the 'new' DSP1124) and I have 2 different humming/distortion problems (at least I think it are 2 different problems)

*problem 1:*
As soon as I turn on the volume knob of my AVR I get a humming noise on my speakers. It is NOT there when I FULLY turn down the volume knob of my AVR but comes in as soon as I give 'one click' volume up on my AVR. The thing I should mention is that this problem is ONLY with my R, L and C channel. For these (R, L and C) channels I use a separate amplifier that is unbalanced (RCA) connected with the R, L and C rca pre-outs of my AVR. The hum is NOT present at my SR and SL channels (which are directly connected to the speaker outputs of my AVR). The hum from the R, L and C channels DOES NOT go away when I turn off the FBQ1000. The hum is the same, wether the fbq1000 is on of off. The hum only is not present when I unplug the cable going from my AVR sub pre-out to the FBQ1000 1/4 jack input. 

*problem 2:*
The subwoofer is humming like hell with the FBQ1000 turned on. It is very noticable when scrolling and clicking with my mouse :scratch:

*My setup:*
Marantz SR5005: SR and SL are amplified directly by my SR5005 and my R, L and C channels are amplified by my NuForce MCH-2-C5
NuForce MCH-2-C5: connected with my Marantz SR5005 with unbalanced monster rca cables. Only R, L and C are amplified my my NuForce
Behringer FBQ1000: connected between AVR and subwoofer as follows: rca subwoofer pre-out avr => 1/4'' jack input 1 of fbq1000 with rca/jack plug => fbq1000 output 1 to rca input of subwoofer, also a rca/jack plug for fbq1000 output.


Could you guys tell me if they are both different problems and if I can eliminate one or maybe both of the problems with a cheater plug?


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## Wayne A. Pflughaupt

If the noise started when you plugged in and connected the FBQ, then yes it’s all the same problem. As far as a solution, it’s impossible for us to troubleshoot long distance, so you'll need to wade through this thread and try some of the different remedies mentioned for yourself. But the first thing I’d try is a custom cable that lifts the ground connection at the BFD’s input and output, as noted in brucek’s post at the top of Page 5 of this thread. The same thing could be accomplished with an RCA to XLR cable that has the connection to Pin 1 (of the XLR) disconnected.

Regards, 
Wayne


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## THX-UltraII

Wayne,

thxz for your reply. Could the problem be the plug I am using?
http://www.bax-shop.nl/jack-rca/procab-vc104-rca-female-jack-male-adapter/product-details.html

Because on page 5 in this thread I see a different 1/4'' jack plug with TWO black rings instead of ONE on the adapter that I am using.

You are saying I could also use a adapter like this? http://www.bax-shop.nl/xlr-rca/neut...-rca-female/product-details.html#!prettyPhoto
But how do I disconnect the pin 1? I can t open the adapter can I?

Could I also try a custom made power cable with the ground not connected?


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## THX-UltraII

EDIT ON ABOVE POST:
I m using the cheater plug now and no hum anymore. In what situations will the cheater plug be dangerous?


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## lcaillo

If a device is designed to use a grounded a.c. outlet, it usually is not using a dual isolation power supply. If something opens up or shorts that makes the chassis hot, there is no place for the current to go so it looks for another path like through the body of a person touching the chassis or through the grounds on other equipments. If you had a hum, you had current flowing on the chassis ground to that ground on the a.c. line. That path is broken when you lift the ground, so now that current is looking for another path and cannot find one. If the current remains minimal, no problem. If it is high because of a defective device or something wired wrong somewhere in the system, it could be dangerous. If there are any protection devices internally that depend on that ground, such as MOVs, again, lifting the ground prevents this path.

Lifting grounds is just a patch on the problem. The problem should be corrected with a proper adapter or lifting a signal ground rather than lifting the a.c. ground.


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## moreira85

Will something like this work? A xlr ground lift adapter?
http://www.amazon.com/Hosa-GLT-255-...id=1353533701&sr=8-1&keywords=xlr+ground+lift

I had a hum and it disappears when I unplug the wire going from receiver to bfd. Currently I am using the cheater plug and it fixed the hum problem,however sometimes when I turn on the fan or light in that room I can here a little soft thump in the sub. If this xlr ground lift adapter works is it just doing the same thing the cheater plug is doing or is it a better fix? Would I need 2 of them to go from the bfd to the sub also or just one going from receiver to bfd?


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## Wayne A. Pflughaupt

The noise you’re hearing comes from the light or fan being on the same electrical circuit as the sub (or possibly because they’re on the same phase), and it’s coming through the power line, not the signal chain. So I’ll be surprised if the XLR ground lift would work. Aside from that, the device you linked designed to work with a balanced signal chain. When you have an RCA to XLR connection, you have an unbalanced signal, so it would only be useful (if at all) if you have a balanced connection between the BFD and your subwoofer.

Regards, 
Wayne


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## moreira85

Is there a better option than this cheater plug?


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## Wayne A. Pflughaupt

If you’re asking about eliminating hum, any of the options found on this thread are better than the cheater plug, at least from the standpoint of safety. If you’re asking about the pop when lights are turned on, the cheater plug does nothing for that. The best way to solve that problem is to install a dedicated electrical circuit for your system, or lacking that plug all your gear into an existing circuit where there are no lights or fans.

Regards, 
Wayne


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## spaceape

I tried removing all except the power cable but the hum/buzz still eminated from within my FBQ 1000 not the speakers. I've tried placing the power cable directly into the socket and also tried two other sockets (230V).

I find it a little strange that the hum fix should be placed in the audio path as the hum seem to be an electrical problem. Can anyone explain this to me?


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## elinter

My simple solution - connected a small wire from the ground terminal on the back of my receiver (Denon 4311) to the outside metal part of the RCA plug connecting the receiver subwoofer output to the BFD TRS input.


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## Wayne A. Pflughaupt

With most receivers, the RCA sleeve (signal -) is common with the chassis. So you could probably attach that wire to a screw, which is probably easier than trying to connect something to the RCA plug itself. If there's a phono input with ground post, that would work too.

Regards,
Wayne


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## MurphyLuth

I have tried many things to get rid of the hum. I have the Lexicon MC12HD sub-woofer output connected to the BFD DSP1124P input. The output of the BFD is connected to a JBL 6290 power amp for the sub-woofer. The original configuration had all balanced cabling and I got a hum. I turned off everything except the BFD and the power amp with no improvement. I have done the following:
changed the connectors to the BFD to unbalanced -- no change
put a ground lifter connecter between the BFD and the amp -- no change
tried a cheater plug on the BFD -- no change

What should be the next attempt?
Any help will be greatly appreciated.


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## Wayne A. Pflughaupt

Welcome to the Forum, Murphy!

You might try floating the ground in the balanced connections (i.e., clipping the shield from the connector at one end), but it sounds to me like your problem is probably “upstream” of the BFD and amp, like maybe a cable TV or satellite dish feed that’s not properly grounded. It won’t do to turn off everything in front of the BFD/amp. It needs to be _disconnected_ from the BFD/amp. I’d first try disconnecting any cable/sat service antenna cables from the system. If that doesn’t isolate the problem, then disconnect each component from the system and then add them back one at a time to see where the noise starts.

Regards, 
Wayne


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## MurphyLuth

Thanks for the suggestions. I disconnected the Lexicon processor, the TiVo unit, the Z-box, the DVD players. We turned off all computers and wireless networks just in case they were adding in anything. The hum was still there. We do not have cable or satellite only off-air antenna and I disconnected that also. The only things I did not disconnect were the other 4 power amplifiers. The equipment is in a equipment closet and to disconnect the other amplifiers is a major tear down. Is there a different unit that can do the same thing as the BFD with adding in the hum?

Getting desperate and annoyed,
Murphy


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## EarlK

> Getting desperate and annoyed,
> Murphy


The simplest ( though not cheapest ) solution is to provide the offending component ( the Behringer unit in this case ) with  *Galvanic Isolation*  ( in the form of ground lifted, audio transformers ) .

(i) Here's a set . You should ( hopefully ) only need them on the output of the 1124 .
- Jensen Transformers are TOTL ( spec wise ) & quite transparent in the circuit ( more so than even the Behringer unit that they would follow :whistling: ) . 


(ii) Here's a much cheaper solution at @ 1/5 the price ( though utilyzing the same approach of providing galvanic isolation with ground lifted transformers ) .
- These are just "alright" ( spec wise ) and within a clean circuit ( not yours at the moment ) are apparent ( to the trained ear ) when they are inserted into the signal chain .
- I'd recommend starting with these & then moving on to something better ( if you figure the system warrants the extra monies spent ) .



NOTE : The Urei/JBL 6290 amp ( & the rest of that series ) are pin 3 hot .  *6290 OM pdf* 
- Your Lexicon unit ( like all newer balanced electronics for the last couple of decades ) are pin 2 hot . 
- Mixing electrical protocols ( such as you are ) can often lead to hard to trace noise problems / especially with single phase electrical services ( that may already be at a tipping point / current balance wise ) .
- (FWIW ) if those were my amps, I'd modify their front ends & rewire the XLR connectors ( by simply swapping the wires at pins 2 & 3 ).

:sn:


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## Wayne A. Pflughaupt

MurphyLuth said:


> Is there a different unit that can do the same thing as the BFD with adding in the hum?


So you were not having any hum before inserting the BFD into the signal chain?

Most home theater users get the hum with the BFD because they’re inserting a component with a grounded electrical plug into a system that has only two-prong power cords. Since you already have grounded-plug components in your system (the amps), that suggests to me that you might have a defective BFD, or else used bad cables to make the connection.

A couple of other suggestions: Is there a ground cable for your antenna? If so, it should be connected to the house electrical ground stake.

Also - it sounds like you have your amps in one location and your other electronics in another? If so, there’s a good chance the two circuits in use are on different electrical phases. This is a common source of a hum and noise.

Regards, 
Wayne


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## MurphyLuth

Ok, I spent the money and purchased a Jensen ISO-MAX. I installed it on the output side of the 1124. It did not remove the hum.

Any more suggestions? Please!!


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## EarlK

MurphyLuth said:


> Ok, I spent the money and purchased a Jensen ISO-MAX. I installed it on the output side of the 1124. It did not remove the hum.
> 
> Any more suggestions? Please!!


Things to try ;

(i) Locate the 1124 to the location of your amplifiers ( & power the 1124 with the same AC service as the sub-woofer amp ) . Put the ISO-MAX on the input of the 1124 .

(ii) If you bought the 2-chnl ISO-MAX, isolate the input & the output of the 1124 .
- Under those conditions of galvanic isolation , the 1124 should be quiet ( apart from it's inherent circuit hiss ) . If it still produces a loud hum & buzz , then the 1124 either can't work with the AC it's getting ( it happens, but is quite rare ) / or the unit itself is defective ( much higher odds ) .

:sn:


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## MurphyLuth

Thanks for everyone's help. I had to get another XLR cable so that is why this replay was delayed.

This is what I did last:

I put the equalizer on the same power circuit as the sub-woofer amplifier.
The ISO-MAX is 2-channel, so I put the input to the equalizer on the first channel
I put the output of the equalizer on the second channel.
The hum/hiss is still there but maybe slightly reduced. So does this mean I have a defective equalizer?

Murphy


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## Wayne A. Pflughaupt

If you remove the equalizer from the signal chain and the noise goes away, then it is definitely the equalizer.

Regards, 
Wayne


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## Aleph30

Hello everyone. I just joined this group recently when I decided to do some upgrades to my home stereo. After years of powering by NHT 1259 subs with a Carver 225wpc TFM24 I decided is was time to pull the trigger on something with more headroom and also apply some room eq using a FBq1000. I don't mean to hijack this tread but short of reading through all 300+ replies in the hope of finding an answer I was hoping someone here might have already come across this. Anxious to get things up and running I set up the new Behringer EP4000 and FBD last night using a Samson S-Converter to get me from RCA to XLR. The signal path is Preamp Sub Out => Samson => FBD => amp. At power on everything worked as it should except for static (digital noise) on the subs. No problem with hum. To isolate the problem I removed the FBD and ....no noise. Has anyone come across this issue before and figured out a possible cause?

Dan


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## Wayne A. Pflughaupt

For starters, the FBQ isn’t especially known for its stellar noise characteristics, and you’re merely boosting the noise with the S-convert. There is no reason to use it merely for RCA to XLR conversion; the downstream equipment, both the EQ and amp, will accept unbalanced connections, so you merely need RCA to 1/4" cables readily available at your local guitar shop. Feeding the output straight from your receiver to the FBQ, you might be able to get away with using its rear panel switches in the quieter -10 dB position. If you end up needing a signal boost for the amp, insert the S-convert after the FBQ, and boost just enough to drive the amp to max, and no more. More details in the article on gain structure you can find in my signature.

Regards, 
Wayne


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## Aleph30

Wayne

Thanks for the reply. I will give your suggestion a try and see how it works. It sounds like I should have maybe done a little more homework before giving this eq a try. I was intrigued by the possibility of using this with REW to improve on sub performance but I guess in practice there are always trade offs. I have a lot of high end equipment which without the BFD is dead quiet. As I see it it's a worthwhile experiment even if I can't find a workable solution. If after 30 days of tinkering I can't quiet this unit it'll be heading back to Parts Express. Thanks again.


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## Wayne A. Pflughaupt

It’ll cost a bit more than the BFD, but the Yamaha YDP2006 digital parametric EQ is dead silent. The drawback is that they are a vintage product and you can only get them used. See here for a quasi-review.

Regards, 
Wayne


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## Aleph30

Wayne,
I read through your series on gain structure this morning and while I don't pretend to understand all of the technical details I have a pretty good idea of how to go about using the BFD in my system now. I haven't tried this yet but I was planning on testing the noise performance of the BFD using the same connections mentioned in my first post, except using the -10db input setting on the BFD and dropping the gain on the Samson converter. Dropping the gain will undoubtedly limit the power of the EP4000 but frankly, at least for the subs I'm currently running should still be more than enough.


Dan


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## Wayne A. Pflughaupt

Aleph30 said:


> Dropping the gain will undoubtedly limit the power of the EP4000 but frankly, at least for the subs I'm currently running should still be more than enough.


Dropping the S-Convert gain has no affect on the amp’s power output. You can simply increase the amps gain controls to compensate – that’s what they’re there for, to accommodate a wide variety of input signal levels.

Really, you probably don’t even need the S-Convert. The EP4000 can be driven to maximum power with a mere 1.23-volt input signal. Most modern receivers’ sub outputs generate way more than that. If you’re not sure if yours can, it’s easy enough to determine your output voltage – Part 7 of the gain structure article outlines an easy-to-accomplish process that anyone with a digital volt meter can do.

Regards, 
Wayne


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## Aleph30

For what it's worth I thought I would give a quick update on my progress in trying to solve the noise issue with the BFD. Wayne, as you suggested I removed the S-Convert and used a RCA-to-TR adapter on the input of the BFD. This didn't solve the noise issue but it was one less piece of electronics in the signal path. I still have plenty of output from my preamp/xover to drive the BFD. As a cheap experiment I built an AC box with the reverse polarity parallel N5401 diodes and a 22R parallel resistor to ground to see if I could break the ground loop. FWIW, this is the same scheme used by Nelson Pass in the A-75 amplifier I built 15 years ago. I had high hopes this would solve the problem but after trying several combinations of plugging in the AC using this box the noise was still there. What I found is after powering up everything if I touch the chassis on the BFD the noise level drops, but then comes back again intermittantly. It's not so much a hum as it is just noise. I ordered a ART DTI box today from Sweetwater Music and hope this solves the problem. In the grand scheme of things the fan noise from the EP4000 is much louder than that from the BDF, but that problem will be solved by replacing the fan with one that is quieter. I really like the ability to measure room response using REW and then send the filters to the BFD using the MIDI connection. It would be great to put the BFD before the preamp and correct the entire system but I'm concerned fidelity would suffer. Some day when I have nothing to do I might give it a try. 

Dan


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## RonS1958

I have been living with the hum for years. Recently bought a new surge protector and was plugging all the power cords back in and decided, like Popeye, "That's all I can stands and I can't stands no more". (The cheater plug removes the hum) I want to try making the RCA to XLR plug to try and eliminate the hum. I have a male XLR connector and a Monster Bass 300 RCA Subwoofer cable that I had used before adding the BFD DSP1124P. I have stripped one end of the RCA and after looking at what's inside I am confused as to what connects (and what doesn't connect) to the XLR pins. I will attach a picture. This is a description of Monster Bass 300:

Balanced Subwoofer Cable Improves Bass Response
• More Accurate, Realistic Home Theater Bass w/ Greater Clarity
• 24k Gold Contact Straight-Cut Turbine Design Connectors
• Special Low Frequency Wire Network Delivers Deeper, Tighter Bass
• 12 Ft Length

Any help would be appreciated. 
Thanks in advance
Ron


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## Wayne A. Pflughaupt

Basically there are only two functioning connections from the RCA: The signal (+), which appears at the connector tip, and the signal (-), which appears at the connector sleeve. 

You’ll need an ohm meter to determine where all the wires are showing up on the connector. I expect that the two insulated wires have continuity with the RCA tip, and the two bare wires with the RCA sleeve. However, it’s possible that only one of the insulated wires is actually connected to the tip, ditto with the bare wires and the sleeve.

As far as the XLR connections, the signal (+) will go to Pin 2 and signal (-) to Pin 3, with a jumper to Pin 1. If the hum and noise persists, try disconnecting the jumper.

Regards, 
Wayne


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## RonS1958

Hello Wayne.
Had to run out to the hardware store to get a new multimeter as the one I had has died. Had to watch a short you tube video to get up to snuff on using it as I have never really used it much. 
The brown wire goes to the tip by itself. The black, bare silver, and the ground shield are all connected to the sleeve. 
So, does this mean that all 3 of the sleeve connecting wires need to go to Pin 3?
Just so you know, my understanding of this kind of stuff is limited!
Thanks,
Ron


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## Wayne A. Pflughaupt

> So, does this mean that all 3 of the sleeve connecting wires need to go to Pin 3?


Yes. You might want to trim out a good portion of the strands of the copper shield wire to make it all fit the XLR. BTW, you can find soldering tips in my article on making your own cables. Link in my signature.

Regards, 
Wayne


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## RonS1958

Wayne,
I have tried with and without the jumper. The hum is still present. I plugged the cheater in as test, and the hum goes away 100%. I had read through all the posts where the cause of the hum is solely from the BFD and the cheater plug stops it cold. (True for my case) I thought part of this fix was to "leave the ground/shield open". (Page 7 post 68 from Bobqspr). I don't really know what that means but what I have done is connect everything from the RCA to the XLR. Am I supposed to leave somethings unconnected? I have the cheater plug in right now listening to some Pandora and it is so much better without that dag gum hum!
I realize this is a really old topic for everyone but I'm hoping for a solution. Sorry for bringing back such a difficult topic!
Thanks 
Ron


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## Wayne A. Pflughaupt

Bob was referring to leaving no connection for Pin 1, like you have already done.

What are you using for the BFD’s output? I’d suggest a XLR/RCA cable like you have for the input. Don’t know if it’ll make a difference, but it can’t hurt.

Failing that, I’d suggest getting back to the basics: Disconnect all source components from the system, and then re-connect them one at a time. Typically the offending piece is a cable box or satellite receiver.

Regards, 
Wayne


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## RonS1958

I have no doubt that it is the BFD. My AVR is a Denon with unbalanced sub output to the BFD. I just tried an XLR to RCA like you suggested from BFD to subwoofer. Same hum. I happened to have one because I had gone to Guitar Center last week and bought a Direct Box PDI passive ground lifter. (I had to use the XLR in order to connect it to the BFD). I put it between the Denon and BFD and the hum disappeared. But it cut the output from the Denon to the BFD (hence the subwoofer) so much that I thought the connectors weren't working. It was only after I increased my output from the receiver to the BFD (subwoofer) from -1.5 to +8.5 that I heard the sub again. I was afraid it was mucking up my BFD filters I have set so I took it out and I plan on taking it back. I was thinking of trying the Hum X but guitar center didn't have one on hand and the girl suggested the direct box. Should I just go the hum x route and see if that works? Like I said it is not my cable or anything else causing the hum. It is solely the BFD. If I take the BFD out and go straight to the subwoofer there is no hum whatsoever on anything anywhere anytime. But I really like what the BFD does for the sound of my system and want to keep it going. I do appreciate your time.
Thanks again,
Ron


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## RonS1958

Wayne,
Well back to the basics didn't take long. I just unhooked my cable feed to the DVR and the hum went away. (I had just the BFD and subwoofer on.)
Went outside and looked into the box and the ground cable was not connected at the grounding block. Cable guy just did some work a couple of weeks ago. But after I hooked it back up the hum is still there just a whole lot less but still noticeable. I will read into the solutions for the cable feed. 
Thanks,
Ron


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## RonS1958

I ordered the Jensen ISO-MAX VRD-1FF cable Isolator from cable Solutions on EBay on Sunday, got it today, hooked it up and pleased to say that the hum is gone. No discernible difference in sound at all. 
I never understood that the root of the hum was because of the way that cable must be grounded. (I did test the cable ground and it was proper). I had always thought the problem was because of the AVR to BFD connections. I sure did learn a lot. Thank you so much for your help and getting me pointed in the right direction Wayne.
Ron


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## andyr

Mitch G said:


> I'm a big believer in standing on the shoulders of giants.
> In this case that means I would like to know what solution folks use for addressing The Hum.
> 
> Right now I'm using a cheater plug, but I would like to solve the problem the right way. I saw the links to Jensen and Ebtech stuff, but Jensen has a bunch of different products, and the Ebtech links are qualified with words like "possible."
> 
> So, what are you audio giants using to address The Hum?


Not living in the USofA, I have no idea what "_the dreaded BFD hum_" is!

Can you - or someone - explain for me?

Thanks,
Andy


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## Wayne A. Pflughaupt

60-cycle hum from a ground loop.

Regards,
Wayne


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## andyr

Wayne A. Pflughaupt said:


> 60-cycle hum from a ground loop.
> 
> Regards,
> Wayne


Thanks for the prompt response, Wayne.

And I now understand that 'BFD' stands for 'Behringer Feedback Destroyer' - so presumably this particular component has an earthing problem?

Andy


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## Wayne A. Pflughaupt

It’s typically a problem with some people’s system, or their having a less-than-ideal electrical situation, not the unit itself.

Regards,
Wayne


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## bjc

In my experience it's the combination of consumer equipment with the Pro equipment that causes many of the noise issues especially with rca from the consumer equipment (Yamaha receiver) to xlr (BFD, pro amp, etc)...aka unbalanced to balanced connection!


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## Andre

I had a problem with ground loop and it came from the cable going into the set top box which was hooked to the receiver which had an outboard Crown amp that didn't like it. I added a Jensen Transformers VRD-1FF between the incoming cable and the set top box and the hum disappeared.


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