# Hum Help!!!



## allredp (Feb 7, 2007)

I apologize for posting in the components something that I had posted a few weeks ago in the BFD forum; however, I've isolated the "hum" problem to my amp and avr and not the BFD. 

I've unhooked everything from the system but the speakers and the power plugs, and every time I start adding the RCAs from my Yamaha 1800 pre-outs to my Sherbourn 5-210A the hum comes back. I've tried any number of combinations with the line outs, but once I get 3 or more hooked up the hum is back.

BTW, I have been outside to check the cable ground and it is tied right into the ground for main electrical service and the phoneline. I don't actually have a cablebox--I've been running it through my HTPC (which is down at the moment and unhooked from the system). 

I've also connected my own ground wire between the AVR (phono) to a screw on the Amp's chassis. I've also tried cheater plugs for the 2 power cords for the Sherbourn. I've tried plugging all three power cords (Sherbourn's 2 and the Yammy's 1) into a surge protector so I can be sure they are on the "same leg"--and nothing gets rid of it!

When I just hook everything up to the AVR, no hum; when I just have the Sherbourn hooked up and not RCA to the Yamaha, no hum. These two just don't want to play together! I've even tried moving them both to different shelves in my closet (high and low) and still hum...

I've been at this for some hours now and am worried I'm either going to have to live with it (it isn't that audible) or I'm going to have to go back to just an AVR powering my system! 

So, my questions are: 

1. What would you try next?! 

2. If I can't fix this, how bad is it--other than that I know it is there? Does it actually corrupt the signal, or is it just raising the "noise floor"?

I really appreciate the help. I've never had this problem before and was so excited to add some real POWER to my system--this has truly sucked the joy out of this upgrade I tell you!


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## salvasol (Oct 31, 2006)

I think your best option is to contact customer support for the Sherbourn ... maybe they can help you :dontknow: ... I found the manual for your amp online, and the troubleshooter doesn't say anything about ground loop or hum ... I was looking to see if this amp has a ground lift (some have them) but yours doesn't.

I had a hum on my system that it was casued by the buttkicker amp ... I got a groung isolator and solved the problem ... but I don't know if it will help in your case because you don't know what is casuing this hum ....


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## salvasol (Oct 31, 2006)

I re-read the manual and I found this (look # 4: Does not enter Power Standby) http://www.spatz-tech.de/sherbourn/7-2100A_5-5210A_manual.pdf 

It seems that you need a ground isolator for every channel you're using ...:scratchhead::scratchhead:


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## brucek (Apr 11, 2006)

> every time I start adding the RCAs from my Yamaha 1800 pre-outs to my Sherbourn 5-210A the hum comes back. I've tried any number of combinations with the line outs, but once I get 3 or more hooked up the hum is back.


I see you have balanced XLR inputs on the Sherbourn. Why not use those instead of the RCA inputs. That way you won't need to use the pin 1 ground on the XLR. Hook the RCA positive to (pin 2+) of the XLR and RCA ground to the (pin 3-) of the XLR. They do sell these in a standard RCA to XLR cable, but you'll need to lift the pin 1 on the XLR side.

brucek


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## allredp (Feb 7, 2007)

I really appreciate the help--I've been racking my brain and seriously considering sending the amp back and just limping along with an AVR only. 

I just hate to give up the power and the sound of power! 

Brucek: So, I need to get some XLR - RCA cables and "lift" pin #1 on the XLR? 

Does that mean I'll snip it with wire cutters? Or what will I do exactly with pin #1 (I'm assuming #1 is the top/bottom of the three pins).

Salvasol: I noticed that too in the manual and wondered about it, but I called the Sherbourn tech (Joe--a very nice guy) who walked through a bunch of different things, including running a ground between my phono gnd on the Yammy to a chassis screw on the Sherbourn. If I can't get the XLR - RCA suggestion to work, I'll call Sherbourn back and see if they suggest those ground isolators for each channel! Yikes...

Thanks so much!


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## brucek (Apr 11, 2006)

> So, I need to get some XLR - RCA cables and "lift" pin #1 on the XLR?
> 
> Does that mean I'll snip it with wire cutters? Or what will I do exactly with pin #1 (I'm assuming #1 is the top/bottom of the three pins).


Yeah, you can just snip it off where it solders to the pin #1 of the XLR. No, it's not the top/bottom pin. It's pin#1 and it's location is identified by the #1 next to the pin - look close. Its location is dependant on whether the connecter is male/female, so identify the pin correctly.

brucek


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## allredp (Feb 7, 2007)

Fantastic! 

I'm going to track these cables down, snip and connect!

I am crossing my fingers!!!

Big-time thanks!


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## rubbersoul (Nov 12, 2007)

Hello I am relatively new to this forum and I read your thread on the unrelenting hum and I hope that you could help.

I have a hum that I hear in every speaker. I had an electrician friend of mine come over twice and for the most part have eliminsted the hum except from two locations. The cable box, which does not surprise me and my projector. I have the Infocus 7205. I am now running the 7205 on an (outside dedicated room) 15 amp circuit and there is no hum. I would like to reconnect the 7205 to the outlet in my Home Theater Room but then I have the hum. 

This is my situation. Prior to having the electrician come over I dissconnected everything and re connected every piece of equipment. I still had the hum. However I ran a heavy duty extension cord to an 15 amp outlet outside my dedicated room and the hum was gone.
I have four dedicated 20 amps in my room.
Thirteen 20 amp circuits on my 100 amp service. My friend said that was not an issue. However most of the 20 amp circuits are on the one side of the box. 
I was thinking of two things.
One was to move at least two of the 20 amp circuits to the other side of the box or make two 20 amp circuits 15 amps. I had read somewhere that there should be a balance in the circuit breaker box. If not you could have problems.
I believe that I could interchange the breakers without changeing the wire since it is 12 gauge wire for the 20 amp and I would be reducing the amperage not increasing it.

I do not know what else to do. I have a ground rod. I have a ground bar attached to my line conditioners and in turn hooked to a cold water pipe. 
The electrician checked all of the circuits for proper grounding.

I would appreciate any ideas you would have and also your opinion on mine.

Thank you and....Happy New Year!!

Frank



--------------------------------------------------------------------------------
Infocus 7205,Da Lite Screen 
Outlaw 990/7700
B&W 804's mains,HTM3S center,3-DS7's surrounds/rear center,Fathom 113 subwoofer
Pioneer Elite laser, Pioneer Elite multi disc cd player
Sony 777 multi disc DVD player,Toshiba 5 disc DVD player
MX 3000 remote,Monster 3500,3600 line conditioners
Comcast, MIT & Monster cable

A Splendid Time is Guaranteed for All!


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## doubeleive (Oct 31, 2007)

sounds like you need some sort of external ground isolator, like a "black box" so to say with built in ground isolation inputs on one side and outputs on the other, i know someone makes something like this, sorry to sound so hazy but just an idea


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## brucek (Apr 11, 2006)

> However most of the 20 amp circuits are on the one side of the box.


The two 120 volt legs are alternated vertically in the service panel (box), not one side or the other, as you are presuming. You could have all the breakers on one side and it would be perfectly balanced. From the top of a row of breakers it alternates A, B, A, B, A , B, etc.

Identify that each of the four circuits you are using in the theatre are on the same leg. That's usually the problem that creates a hum (other than cable or satellite grounds). It's fairly easy to identify if different receptacles are on the same leg (if you aren't squeamish about sticking the leads of a DVM in a receptacle)...



> or make two 20 amp circuits 15 amps


What would be the reasoning for that?

brucek


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## rubbersoul (Nov 12, 2007)

This is how my panel is setup. Based on this should I move 24 and 28 to 21 and 23 







1 15AMP 2>100 amp main shared with #2 & #4
3 15AMP 4
5 15AMP 6 20 AMP Home Theater Recpt. toSUB 
7 15AMP 8 20AMP
9 20AMP 10 15AMP
11 20AMP 12 20 AMP
13 15AMP 14 20 AMP
15 20AMP 16 20 AMP
17 15AMP 18 20 AMP
19 15 AMP 20 20 AMP
21 BLANK 22 15 amp Home Theater Lights 
23 BLANK 24 20 amp Home Theater Recptacles
25 BLANK 26 20 amp Home Theater Recptacles
27 BLANK 28 20 amp Home Theater Recptacles
29 BLANK 30 BLANK


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## brucek (Apr 11, 2006)

Well, most panel alternate legs vertically and are the same horizontally.

So, vertically 1, 3, 5, 7, 9, etc are B, A, B, A, B, A, etc

and horizontally 1, 2 are both the same.

The vertical alternating between legs allows the use of tie-bar breakers ensuring they're on a different leg.

So, it would appear (but then I don't really know your panel) that your three circuits to the HT receptacles of 24, 26, 28 would have one circuit of the different leg. 24 and 28 would be common and 26 would be the other leg. You need to have it confirmed though. This is a question an electrician can answer standing at your panel is a second. They can also move the breaker and wire very easily to ensure all receptacles are on the same leg......

brucek


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## rubbersoul (Nov 12, 2007)

Brucek, thank you for your help.
Something that I have to admit is that I did not want to do the electrical manipulating of wires on this job, so I called a friend. 
This friend of mine did not think it would make a difference but was willing to make some changes in the box.
All circuit breakers for the Home Theater are now on the same leg.
Yes there was a difference.
This is how it ended up in design. 
After the electrical work was completed we test ran the system. Now remember the cable system is not in operation nor is it hooked up. However the component cables and optical cable is still connected to the processor, something until this morning that I realized I did not do.(DISCONNECT) 
Everything was turned on except the projector. NO HUM. 
Once we turned the projector that was plugged into the line conditioner we had a hum. 
We deceided to unplug the projector and plug it into one of the wall recptacles...NO HUM. I am using all of the recptacles, however I wanted to have the protection of the line conditioner for the projector. I am assuming that it is somewhat protected because of everthing being grounded but not the way I prefer.

Now I am concerned about the cable and getting the hum back. There are a couple of products on line that I was considering to buy for ground loops relating to cable systems.

Thank you again I feel most of the problem is solved. Let me know your thoughts on what I have done.

Frank


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## brucek (Apr 11, 2006)

> We deceided to unplug the projector and plug it into one of the wall recptacles...NO HUM. I am using all of the recptacles, however I wanted to have the protection of the line conditioner for the projector.


Yeah, once everything is on the same AC leg, you have a fairly good chance at not getting any hum. I don't have anything specifically against line conditioners, but their benefit isn't that great. They can filter some EMI/RFI noise and provide some local surge protection. They do a decent job, but most electronics equipment in your system will have a very high EMI/RFI noise rejection built in already. The power supply transformer, bypass capacitors, the filter capacitors, voltage regulators and the chips themselves all provide a high frequency noise rejection.

Line conditioners can provide a convenient place to plug all your equipment, but a good power bar with some MOV protection can accomplish this for a lot less money. I think a decent power bar and the installation of a whole house surge protector is your best bet for protecting your equipment.
The whole house surge protector mounts at your AC service panel. These are typically in the $100 range, but are quite effective. In addition you get the added benefit of protecting your other equipment too.

There are a couple of types. The circuit breaker type that plug in like any other circuit breaker would into your panel. These of course have to be made by the company that makes your loadcenter (Seimens, SquareD etc). There are also generic standalone types (obtainable from Home Depot, etc) that mount on the service panel backboard and are wired into the service panel. These have the advantage of not having to search out the exact breaker type.



> Now I am concerned about the cable and getting the hum back. There are a couple of products on line that I was considering to buy for ground loops relating to cable systems.


Yeah, with respect to the cable hum eliminators, you have to be careful that it's of a type to pass the entire bandwidth you require.

brucek


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