# Hum issues hooking up Pro Audio (Crown) amp to Home Audio Receiver (Yamaha)



## ENDEE666 (Feb 12, 2020)

Hello everyone. Hoping someone can help me solve an issue I am having. I am expanding my sound system in my den at home. Mostly with stuff I already own, while adding a few new items. I have done a lot of troubleshooting already, and wanted some guidance before I started throwing more money and parts at the problem. This forum has always been a big help, even just from searching, and resulted in a few of the items I am now integrating into my home system. I know a lot of this stuff is Old School, but I really prefer the older stuff in most cases.

So I am hooking up a Crown XLS1000 amp to power 2 separate 10" vented subs I am building. I know, Crown is mostly Pro Audio oriented, but it had RCA inputs. However, I overlooked the input sensitivity, which is adjustable on all other Crown lines with RCA inputs. But not this one, of course. Oversight that I regretted. And so hum or no hum, the output was whisper quiet. So I bought a Samson S-Convert (basically the same as Rolls Promatch & ART Cleanbox) so it would not only boost the signal, but could also convert from RCA to XLR. So in the future I could upgrade to any Pro Audio amp.

In addition, my Yamaha RX-V2095 (from ~2001, LOVE IT!) is 5.1, and also has a preamp out/in loop for an external EQ or processor, or even amps for all channels. So I wanted to utilize the out/in loop to hook up a Behringer DSP8024 EQ I have had for years, from back when I DJ'ed weddings & events. This does not have RCA in/out, only the XLR. But I already had some XLR>RCA cables, plus I now have the Samson that boosts & converts from RCA to XLR.

So that's the goals. Hook up the EQ with the Samson S-Convert on the EQ loop, and hook up the Crown XLS1000 to power the two subs I am building. Now.. Here is the situation:

When ever I hook up either the Crown or the Behringer to my Yamaha, I get a very bad hum/buzz from the speakers. I have done the following troubleshooting:

~Tried using the sub out RCA as well as the EQ out/in RCAs, to either the Crown or Behringer. All combinations get the hum/buzz from the speakers connected to the Yamaha.
~I tried with & without the Samson S-Convert in line, hum no matter what.
~I tried plugging the power for the 2 Pro items to different power strips, as well as different outlets. No changes.
~To reduce variables, I even went straight from sub out on Yamaha to the Crown RCA in, without even speakers connected to the Crown, no EQ or Samson S-Convert. and still had hum on the speakers connected to the Yamaha.
~With the RCAs hooked up on the Yamaha side, but to nothing else on the other end, NO HUM at all!
~I then took a spare receiver from a different room, and hooked that up with RCA from the Yamaha sub out to an audio input on the spare receiver, and there was no hum.

So the hum only exists when either of the Pro Audio items are connected, in any way. I know they mostly desire Balanced XLR. But the Crown has RCA inputs, so I don't see why that's an issue. If I got the hum when using the XLR>RCA adapter cables, then I could see that being an issue. I also thought the Samson S-Convert would alleviate this, but it doesn't..

To me, it seems like a ground loop. But why would the ground loop only exist with certain (Pro Audio) devices?? I know I can buy a device for ground loops, but I really do not want a ton of boxes & cables. Ideally, if there is an alternative to the Samson S-Convert (like he ART or Rolls) that does the RCA>XLR, boosts the signal, AND fixes ground loops, I would be fine with that. But to have Receiver, Samson box, EQ, Ground Loop killer, Pro Amp, all with jumbles of RCA & XLR cables, I fear that would have problems no matter what..

In the event it is indeed a ground loop, I have seen 3 main types of Isolators-

1.) One that goes onto the 3 prong plug into the wall.
2.) One that goes in-line with the RCA's, and is also powered.
3.) One that goes in-line with the RCA's but is passive, not powered.

Which one of those would fix this? I was thinking the one for the wall plug, since it is specific to 2 devices being hooked up. But unsure if the hum/buzz could have to do with Amp & EQ wanting the Balanced XLR as a connection.

I also think I tried another troubleshoot, and I will try this again tomorrow just in case. I think I also hooked up the Yamaha Sub RCA to the Samson S-Convert by itself, and it did not buzz until the amp was also hooked up to it.

Hoping you can help! Appreciation in advance!!


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## rgoebel (Oct 29, 2009)

It is indeed a ground loop. The simplest fix is an RCA ground loop isolater. I had a similar issue, except my him only came thru my Crown amp and sub when my cable box was plugged into my receiver. I put a filter on the cable line to fix that one. 
BTW, I’d be surprised if there wasn’t enough signal coming out of your Yamaha RCA sub output to run that Crown. I run the sub out from my Onkyo straight into my Crown XLS1500 and have the gain set at 2 o’clock. Good luck!


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## rgoebel (Oct 29, 2009)

Also, you may try using the Crown amp full range with an alternate source. For example, you could use the headphone jack output on your phone/ipad etc to feed the RCA inputs on the Crown, and run the Crown into some full range speakers. That way you can hear if the amp is functioning correctly. A sub often has a very limited frequency response beyond a few hundred Hz and may mask clues that the amp is not healthy. Running it full range may reveal hissing or other sounds that indicate a problem. Did you buy it used? It is an older model (5-8yrs?). My prior sub amp (also Pro equipment) progressively failed until all the blue smoke escaped. Didn't realize it for a while except the output was "funny". Did the above testing and not much longer and poof.
BTW, the ground loop isolater I have successfully used is the RCA type that is passive. (Amazon.com: RadioShack Audio System Ground Loop Isolator (Electric hum noise reducer): RadioShack USA)


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## rgoebel (Oct 29, 2009)

I keep thinking of thins for you to check... I am not familiar with your Yamaha receiver, but often in the setup menus, there is a place to indicate what "size" your main speakers are and whether you have a sub connected. these settings affect how the built-in crossover is set. For example, when my mains are set to "large" they are fed a full range signal. If they are set to small, the have a high-pass x-over set to 100Hz. This is independent of the sub setting. Also there is usually a way to adjust the relative levels of each channel (left, right, center, etc). I apologize if you already know this, but was just trying to think of reasons your sub output would have such a low signal level.


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## RLouis (Jan 20, 2010)

I didn't read every detail of your post (it's a lot) but if you haven't tried it already>> get one of those $1 two prong to three prong AC plug adapters and put it on the amp plug then plug into the wall. What this does (without actually cutting the ground pin off of the AC cord) is lift the ground pin from the amp power cord. It will at least lessen the ground loop noise, hopefully significantly. I had this issue with a commercial amp and between this plug and making an adapter cable (RCA out from my pre/pro to the BAL IN on the amp) it almost completely eliminated the ground loop hum.


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## ENDEE666 (Feb 12, 2020)

RLouis said:


> I didn't read every detail of your post (it's a lot) but if you haven't tried it already>> get one of those $1 two prong to three prong AC plug adapters and put it on the amp plug then plug into the wall. What this does (without actually cutting the ground pin off of the AC cord) is lift the ground pin from the amp power cord. It will at least lessen the ground loop noise, hopefully significantly. I had this issue with a commercial amp and between this plug and making an adapter cable (RCA out from my pre/pro to the BAL IN on the amp) it almost completely eliminated the ground loop hum.


I had posted this same thread on other forums, and those got a lot of activity quickly. So this was brought up there, and did indeed fix the issue. However, I am now looking for a better solution than a cheater plug.

I found Hum X, but that is way over priced for what it is, so I am looking for other options like it.

I also want to find out what is actually causing it. Ultimately, only the Behringer & Crown items have a 3 prong plug. And when either of those is introduced (without cheater plug) the hum starts. A few people were saying it could be caused by the coax cable for my Verizon Fios that is intruducing the ground loop. So I have to do some troubleshooting on that.


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## RLouis (Jan 20, 2010)

The cause; There's many appliances and electronics that dump unwanted/unused voltage, as part of their normal operation, onto the ground of a house circuit. There could be many things putting noise on the ground and it'll propagate throughout the whole house quite easily because the ground is 100% common throughout the house. There's nothing wrong with using a cheater plug, it doesn't degrade power supply or performance any, it's completely passive. But another option >> cutting the ground pin off the male end of a power cord. Same benefit, no cheater plug. If the amp/s have removable power cords can even get an upgraded HD power cord like a 14/3, cut the ground pin off and there's your dedicated amp power cord. I have dedicated circuits for my amps so I just don't hook the ground wire up in the wall plug connection. Works fine, but this is a "do it at your own risk" option. I have to say this becasue it is obviously not NEC code compliant.


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## ENDEE666 (Feb 12, 2020)

rgoebel said:


> It is indeed a ground loop. The simplest fix is an RCA ground loop isolater. I had a similar issue, except my him only came thru my Crown amp and sub when my cable box was plugged into my receiver. I put a filter on the cable line to fix that one.
> BTW, I’d be surprised if there wasn’t enough signal coming out of your Yamaha RCA sub output to run that Crown. I run the sub out from my Onkyo straight into my Crown XLS1500 and have the gain set at 2 o’clock. Good luck!


Yeah, I was hoping the Yamaha had enough volts to drive the Crown, but it very much did not. It seems that most other Crown products (and other brands) that have RCAs would also have an adjustable input sensitivity that would have worked. So I was on the fence of either selling the Crown and getting one with the input sensitivity adjustment, or getting a booster box like the Samson S-Convert or ART Cleanbox, etc. Found a great deal on the Samson, so I went that way, since it also allows me to use the EQ with XLR inputs the correct way, instead of just an adapter cable.

As mentioned in last post, I put this same subject up on other forums, and it got a bit more action over there. So I have since done some experimenting and the cheater plug for 3-2 prong got rid of the hum almost entirely. A few others have also pointed to the coax leading to my Verizon Fios cable box as a likely culprit, so I will do some more experimenting with that at some point too. I would rather fix the problem than mask the symptoms.

If I end up having no choice but to use adapter plugs like the cheater plugs, I would prefer a better option than a $2 one. So the Hum X seemed good, but $80 is stupid for that, and I would need at least 2, unless it can go between the power strip & the wall, and not just on each device's power cable.


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## ENDEE666 (Feb 12, 2020)

RLouis said:


> The cause; There's many appliances and electronics that dump unwanted/unused voltage, as part of their normal operation, onto the ground of a house circuit. There could be many things putting noise on the ground and it'll propagate throughout the whole house quite easily because the ground is 100% common throughout the house. There's nothing wrong with using a cheater plug, it doesn't degrade power supply or performance any, it's completely passive. But another option >> cutting the ground pin off the male end of a power cord. Same benefit, no cheater plug. If the amp/s have removable power cords can even get an upgraded HD power cord like a 14/3, cut the ground pin off and there's your dedicated amp power cord. I have dedicated circuits for my amps so I just don't hook the ground wire up in the wall plug connection. Works fine, but this is a "do it at your own risk" option. I have to say this becasue it is obviously not NEC code compliant.


Yeah, a cheater plug or even the Hum X is not the end of the world. But as I said, I would love to solve the cause itself. I am in the Home Improvement business, so I like things safe & code compliant. But it's not like a cheater plug is holding my electrical system together with bubble gum. And the room all of this is in was an extension on the house. So it was permitted, inspected, and only about 20 years old. So I trust the electrical in there a lot more than I would an older part of the house.

My biggest suspicion is the cable service. So I will do some testing & experimenting on that, and maybe just ground the splitters or add a filter on the coax. If it is not the cable system, I will likely just use a cheater plug or Hum X type device. I will also have one of my electricians see if the overall electric system is not grounded properly.


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## RLouis (Jan 20, 2010)

Could be refrigerator compressor, computer power supplies, microwave or FiOS ONT power supply. Any or all. Many devices like TV's and desktop PCs these days actually stay on in low power modes even when you (think) you've turned them off. Take the cheater plug and other stuff out then power up the system so it's humming nice an loud. Then turn your circuit breakers off one at a time. That'll at least tell you which circuit or circuits the noisy devices are on.


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## bennett89 (Dec 26, 2019)

> In the event it is indeed a ground loop, I have seen 3 main types of Isolators-
> 
> 1.) One that goes onto the 3 prong plug into the wall.
> 2.) One that goes in-line with the RCA's, and is also powered.
> 3.) One that goes in-line with the RCA's but is passive, not powered.


In some cases, with different initial data, I've had even more. Those problems can happen with any models of audio receiver. Even with my good old Pioneer receiver it happened as well. Then I've found this website ( here: https://chooserator.com/bеst-av-receiver-under-500 ) and after some comparisons, I've purchased Yamaha RX-V683, cause it the most modern model under 500 dollars.


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