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Sub Hum: Digital Coaxial Cable and Ground Loop Question

post #1 of 12
3/31/08 at 11:18am
Thread Starter 
My sub is emitting a nasty (and extremely loud) hum/buzz. It does this even when all components are turned off. Thinking it might be a ground loop issue, I began unplugging components and connections until I discovered the hum is drastically reduced by disconnecting the digital coaxial cable running from my DVD player to my receiver.

Are there any fixes to this specific issue of a coaxial cable producing sub hum?

Thanks
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post #2 of 12
3/31/08 at 7:31pm
Do your components have a place to attach a ground strap?
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post #3 of 12
3/31/08 at 7:39pm
Check out this thread... Go to the end of the first post....

http://www.avsforum.com/avs-vb/showthread.php?t=1004573
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post #4 of 12
4/1/08 at 1:31am
Quote:
Originally Posted by DougWinsor View Post

Do your components have a place to attach a ground strap?

Here we go again
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post #5 of 12
4/1/08 at 1:36am
Quote:
Originally Posted by alderash View Post

My sub is emitting a nasty (and extremely loud) hum/buzz. It does this even when all components are turned off. Thinking it might be a ground loop issue, I began unplugging components and connections until I discovered the hum is drastically reduced by disconnecting the digital coaxial cable running from my DVD player to my receiver.

Are there any fixes to this specific issue of a coaxial cable producing sub hum?

Thanks

It's a ground loop.

http://www.avsforum.com/avs-vb/showthread.php?t=1011229
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post #6 of 12
4/1/08 at 2:43am
Do you have cable running into the receiver from the wall? If so check to make sure the grounding block where it comes into the house has a good ground on it. There should be a wire going to the water pipes or directly into the ground.

There are ground loop isolators available just for this purpose. I know Axiom Audio sells one, but you should be able to get one from your local cable company or electronics/audio store as well.
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post #7 of 12
4/1/08 at 3:54am
Thread Starter 
Quote:
Originally Posted by NightHawk View Post

It's a ground loop.

http://www.avsforum.com/avs-vb/showthread.php?t=1011229

I've read through some of the threads, but much of it centers on TV cable or sat. Does this mean that even though I've narrowed my problem down to the coaxial cable from my DVD player, that the origin could still be the sat. cable? Could it just simply be the DVD coax cable? Is there a specific fix just for this?
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post #8 of 12
4/1/08 at 4:22am
Quote:
Originally Posted by alderash View Post

Is there a specific fix just for this?

Actually yes. A fiber optic digital audio connection only. Otherwise you will need to break the loop with some type of ground loop isolator. The digital audio coax is probably just a part of the loop and it's possible to break it in several places. The subwoofer cable is often the best place.
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post #9 of 12
4/1/08 at 4:35am
Thread Starter 
Quote:
Originally Posted by NightHawk View Post

The subwoofer cable is often the best place.

Is there a specific sub cable that would break the loop? Right now I'm using a Monster cable.

Would the fiber optic digital audio connection replace the coax from the DVD player?

Where would you recommend installing the ground loop isolator?

Sorry for all of the questions, but I appreciate any advice.

Thanks
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post #10 of 12
4/1/08 at 5:05am
Quote:
Originally Posted by alderash View Post

Is there a specific sub cable that would break the loop? Right now I'm using a Monster cable.

Would the fiber optic digital audio connection replace the coax from the DVD player?

Where would you recommend installing the ground loop isolator?

Sorry for all of the questions, but I appreciate any advice.

Thanks


No, a different sub cable is unlikely to fix the issue. If you are getting significantly less hum by removing the digital audio coax, leave it off and use a fiber optic digital audio connection instead. Fiber optic connections are naturally isolated from ground. If you still have audible hum issues with your sub then an audio isolator in the subwoofer cable connection would be my next option. They are available from several sources including Jensen transformers. Some simple fixes to try is to plug all your equipment into the same outlet but I know with remote subwoofers that's often not convenient.
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post #11 of 12
4/1/08 at 5:15am
Thread Starter 
Thank you for all of your help.
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post #12 of 12
4/1/08 at 9:36am
I had to balance most of the XLR cables a few nights ago oh, what a palver. This reduced the humming on sevreal LCR fronts the sub bass extension was still imitting a humming tone that I mannged to trace down and re-plugged the centre channel oh, what a palver.
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