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Discussion Starter · #1 ·
So I have a HORRIBLE ground loop hum with my Cap 2400 set-up. Here is what is my set-up...


In one outlet...


Samsung Plasma

Yamaha rx-765V

Slim PS3

DirecTV


All of this is into a standard power strip and plugged into the wall. Into the same outlet, but is my XPA-3


Into another outlet but on the same breaker...


EP4000 and Mic2200


Now, recently, I had two ceiling fans put in. The switch that turns them on, is different from the breaker thats mentioned above. However, they WERE on a dimmer switch that is since now just an on/off switch. I noticed a significant hum increase when the fans were installed. This was well before my current set-up. Previously, I had an Epik Empire and only noticed the hum of the ceiling fan.


First, I know that cheater plugs are not recommended, but without one, the hum makes watching TV very not fun. 2nd, I turned off the power switch and unplugged the XPA3 and there was not any change in the hum. 3. I have 2 other dimmer switches in my house. One of which is on the same breaker as the EP4000/Mic2200. Another is in my master bath on its own breaker.


Looking for ideas/help/suggestions. (something like this maybe Hum X )?
 

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Discussion Starter · #5 ·
First, thanks for trying to help. 2nd, I isolated it to the same breaker that the ceiling fans are on AND the high hat dining room lights. Like I said in my OP, the ceiling fans used to be on a dimmer switch but is now just a simple on/off switch. With just the ceiling fans on, I can hear a hum from the fans. When the dining room lights are on, AND the EP4000, I can hear the hum change pitch when I adjust the lights from light to dark. All of this is with all of my other equipment unplugged. Now, the Directv cable is still attached to the box, but unplugged, so I dont know it that might be a culprit.


sooooooooo frustrating.
 

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Discussion Starter · #7 ·
The Directv, AVR, Apple TV, TV, and PS3 are all plugged into the same power strip. I unplugged that strip from the outlet as well as the XPA from the same outlet. Still has the hum.
 

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It is likely there are some shared neutrals and who knows what else is going on with ground connections.


As I suggested when you posted similar in the Cap thread, first ground the receiver by a phono ground terminal or the shell of the FM antenna's F connector. Next you can start by physically disconnecting all Cable/SAT connections to the system. It sounds like you have a buzz not a hum if you are hearing it change with the dimmers. The key is to resist the urge to change everything at once and step through the connections until you narrow down the culprit. You might want to start by unplugging all source components from the receiver (turning off doesn't count). Is the sound still there?
 

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Discussion Starter · #10 ·
Mark,


I will try that (Brian, I will try your idea as well). However, (and forgive my noobish questions), but just unplugging everything from a completely different circuit wont matter?
 

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Quote:
Originally Posted by Mark Seaton  /t/1468385/horrible-ground-loop-problem-with-ep4000-cap-2400#post_23206697


It is likely there are some shared neutrals and who knows what else is going on with ground connections.
+1. Using two outlets that go to the same breaker doesn't help, as that doesn't minimize the length of wire carrying ground current. Conceivably the two outlets could have separate cables all the way back to the box. Everything needs to be plugged into the same outlet, preferably one dedicated to the HT. Then you start with a minimalist setup, the AVR and sub and nothing else. If there's no problem add one component to the system at a time until the culprit is revealed. Then transformer isolate that component.
 

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Breakers only control hot-wires, not neutral-wires nor ground-wires FYI.

So it doesn't matter if the appliance is on the same breaker or a different one, the hum can still exist in both cases.


All neutral and ground wires are shared with ALL the appliances in a house, as one large circuit; independent of the breaker it uses.

and THAT enables the problem to exist.


What further enables the problem, is that RCA cables and the HDMI wires allow power to flow through the ground wire between devices.

Optical cables are immune to this effect; not sure about XLR cables, they are probably noise-resistant at least.


If all cables were shielded on both ends to a common ground, and the signal-grounds were floated but shielded from noise, then ground hums would be rare. But that ideal is never achieved.

TV box cables are known for inducing grounding issues 99 out of 100 times; this is because they are grounded at a different point to the earth, increasing the chance of a voltage difference.


Most hums are induced by induction from things such as fan motors and transformers, or a malfunctioning device that are bleeding line power.



I had a similar issue last week.

Turns out it was the HDMI cable between my TV cable box and my sound processor, it induced a hum in my RCA cables to my BFD, and all down stream amps.


The cable box itself had no ground plug (not grounded), but my sound processor IS grounded, so the power from the cable shield decided to use the grounded HDMI wire as a return path, which is the same ground that my RCA cables use.

The cable box grounded their HDMI port to the floating Cable shield instead of earth ground (made in China, that's all I have to say
).


All it takes is a few miliohms or milivolts upon the shared ground, and presto, a hum is born.


My temporary solution was to unplug the HDMI cable.


I'll have to look into grounding their coax cable as a more permanent solution.


Mark is correct BTW, you have to disconnect all conductor paths, turning a device off is almost never sufficient.
 

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Discussion Starter · #13 ·
Thanks for all the replys, it's a lot to take in. As a firefighter/paramedic, my knowledge of electronics and circuitry is, at best, on par with a 5th grader. I am going to follow al, the advice here, starting with Mark's suggestion of a phono ground terminal. Even after a few minutes on Google, I'm still not sure if I know what that is. Is he talking about http://www.turntableneedles.com/Technics-SJPB7M-Ground-Wire_p_3819.html
 

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Do you have one of those cheater plug adapters that takes the gound plug out ? Try putting that on the plug of the amp and then plug in the amp with the cheater adapter in the mix... Take the ground out. for a test
 

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Discussion Starter · #15 ·

Quote:
Originally Posted by mantha3  /t/1468385/horrible-ground-loop-problem-with-ep4000-cap-2400#post_23207628


Do you have one of those cheater plug adapters that takes the gound plug out ? Try putting that on the plug of the amp and then plug in the amp with the cheater adapter in the mix... Take the ground out. for a test

Yes, I am using that now and I know that its not good, but it is only a temp solution. It has no effect on any of my components whether its in the mix or not. As far as the amp goes, with it, its very manageable meaning that I can deal with it. Without it, its ridiculous.
 

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Quote:
Originally Posted by BassThatHz  /t/1468385/horrible-ground-loop-problem-with-ep4000-cap-2400#post_23207390


Breakers only control hot-wires, not neutral-wires nor ground-wires FYI.

So it doesn't matter if the appliance is on the same breaker or a different one, the hum can still exist in both cases.
True, but that's not the whole story by any means. This is. It explains why ground loops aren't the result of bad grounding or most of the other reasons usually attributed:
http://www.rane.com/note110.html

Ground loop noise is the product the clash of perfectly valid grounding techniques and unbalanced audio connections. When audio uses properly implemented balanced connections ground loop noise never occurs, but consumer grade electronics aren't balanced. Add another path to ground via a TV cable connection and it's a wonder that HT sound works at all.
 

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Discussion Starter · #17 ·

Quote:
Originally Posted by Bill Fitzmaurice  /t/1468385/horrible-ground-loop-problem-with-ep4000-cap-2400#post_23208027


True, but that's not the whole story by any means. This is. It explains why ground loops aren't the result of bad grounding or most of the other reasons usually attributed:
http://www.rane.com/note110.html

Ground loop noise is the product the clash of perfectly valid grounding techniques and unbalanced audio connections. When audio uses properly implemented balanced connections ground loop noise never occurs, but consumer grade electronics aren't balanced. Add another path to ground via a TV cable connection and it's a wonder that HT sound works at all.

Bill,


When you say TV cable connection do you mean DirecTV as well?
 

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Quote:
Originally Posted by ratm  /t/1468385/horrible-ground-loop-problem-with-ep4000-cap-2400#post_23208225


Bill,


When you say TV cable connection do you mean DirecTV as well?
Yes. I know it's not the same as cable per se, but since it involves electronics there are paths to ground the same as with an AVR or DVD player, so it can be a ground loop source. It's easy enough to find out. Hook up the AVR, sub and TV. If there's no hum then so far so good. Plug in the feed from the direct tv box to the TV or AVR, if hum occurs you've found the problem. The only TV source that would not be a possible source of a ground loop is a passive antenna.
 

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Trying random changes will more likely drive you nuts rather than solving the problem. Disconnect things, see if there is noise with nothing but the receiver and subwoofer connected. If so we can help. If not, start connecting things one at a time and note which causes the noise. From there we can help. At this point we could give you a dozen possible fixes of which probably only 2 will work.


I had linked the full description in the JTR thread about grounding the receiver. You can either connect a coax cable from your FM antenna input to a surge protector with cable/or sat output (the shield is grounded in the surge protector) or you can connect any wire to the phono ground screw on the back of your receiver and the other end to either a ground lug on an rack style surge protector or to any other item grounded to the 3rd pin ground (could be the case of another component, but has to be under a screw as the black coating insulates).


The primary issue is that the receiver has a floating ground, so any other ground connection will create a path for possible noise generation.
 

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I agree with Mark Seaton.


Disconnect all the sources from the amp/receiver and have just the amp/receiver hooked up to the speakers. Set the volume to about 30 % and test Does it hum? If not... Take off the AC cheater plug and test again. No hum.. You should not run an amp/receiver without a source connected for a long time if at all but I've done it for some troubleshooting for short times like this without issue.


Then add a simple source like a cd player or perhaps a MP3 player hooked up.. Does it hum


working from the amp/receiver back can shed light on the component that triggers the hum. Lots of times the pieces are fine alone but some combo triggers this hum


On a side note... Cable boxes and or Dish boxes that you get fror service providers can be junkey at times.
 
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