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Low hum (ground loop?) when I plug my computer into my receiver

post #1 of 11
2/25/09 at 10:58am
Thread Starter 
I've been dealing with this minor problem for a while now, but I thought I'd finally try and get it fixed. Anyway, I sometimes listen to music from my computer on my receiver in another room, and I connect the two with a coax cable. Whenever I connect the two, my stereo in the other room starts humming.

The humming increases in volume as I increase the volume on my stereo (and the other way around), and it also varies in volume as I switch inputs (but it's still present no matter which input I'm listening to). It does seem louder on the input I have the computer coax plugged into, though.

I've tried unplugging my both my cable and my subwoofer to see if that would help. Unplugging the cable made the humming softer, but it was still there, and I can't remember what unplugging the sub did (the hum didn't totally go away, I remember that at least). Also, I've never seen any interference on my TV.

I bought a ground loop isolator from Radio Shack. It seems designed to be used with two coax cables at once (stereo sound, one channel on each, I assume), but I figured I'd just not use one set of plugs. When I put it in line between my computer and my receiver, I can't hear anything at all, so that doesn't help. I also tried putting it between my sub and my reciever ... and I'm pretty sure my sub stopped making sounds, although I can't clearly remember.

So I'm not really sure where to go from here. I live in an apartment, so I'm not sure how much work I could do as far as unifying grounds and that sort of thing. Anyway, some help would be appreciated. Thanks!
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post #2 of 11
2/25/09 at 4:32pm
You have some kind of ground problem, try having everything connected except your video (cable, DBS, OTA) source.
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post #3 of 11
2/26/09 at 8:06am
Odds are no manner of wiring changes are going to fix the problem, practically. The run-length of your house AC is probably the culprit, though the ground chain may be broken.
You could try running an AC extension from one location to the other, so that both are effectively run from the same circuit, but even that may not solve it totally. And it sure aint practical

Suggest biting the bullet with 'Bluetooth'. Not foolproof but if you get it working right, it also is multi-use. Meaning you can use it for other applications

go to 'Amazon' and search for 'Ge Bluetooth Home Stereo'
{I would post a link but am blocked because I'm a 'newby' here. Only used this handle on net for 24 yrs, after all}

do your research carefully before buying. Meaning look for other products, too and on other sites
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post #4 of 11
2/26/09 at 9:10am
Quote:
Originally Posted by pettyfog View Post

Odds are no manner of wiring changes are going to fix the problem, practically.

?

Once you determine the source(s) of the issue, which is typically due to improper grounding of the incoming cable or DBS coax, it's a simple matter to resolve the issue.

In decades of A/V experience, I've never seen 'run-length of your house AC' causing a ground problem.
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post #5 of 11
2/26/09 at 9:45am
Losstarot,

Is the following link to the isolator you have?

http://www.radioshack.com/product/in...14&tab=summary

If so it is designed to be used with R&W stereo audio cable connections.
Red to Red for the Right channel and White to White for the left channel.
Did you try using both the red pair and the white pair?
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post #6 of 11
2/26/09 at 10:37am
Ken:
Mea Culpa. In deference to your A/V experience and 32000 posts v my 2.. ...you're right, I misstated.
Run length itself is not likely to be the problem in that environment. MORE likely to be somewhere in the circuit chain through outlets.
But he lives in an apartment building and even if he isolates the problem, he may not be able to get it fixed.

Walford also points out relevant info. Depending on how the isolator is wired, hooking up only one side could mask proper results. Hint, there, is loss of subwoofer output, correct?

Also note that many of the RS user reviews showed success for this very application - PC to stereo
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post #7 of 11
2/26/09 at 5:41pm
Thread Starter 
Well after reading your posts I messed around with my stereo some more. I'd already tried unplugging the cable from my TV to see if that was the problem, but I thought I'd try it again just to be sure I wasn't insane. That was when I realized I still had my cable modem connected to the wall, and I run the cable that goes to my cable modem through the same surge protector that I have my TV cable plugged into. So this time I unplugged both cables from the wall, and the humming stopped.

I feel a little dumb, but I guess I solved the problem. Thanks for your replies, I really do appreciate it. So I guess what I need now are one or two of those little cable ground loop isolators?
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post #8 of 11
2/26/09 at 6:05pm
What I think you need now it to insure that your cable input is properly grounded. Your cable company should do that for you.
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post #9 of 11
2/26/09 at 6:09pm
Quote:
Originally Posted by walford View Post

What I think you need now it to insure that your cable input is properly grounded. Your cable company should do that for you.

Bing!
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post #10 of 11
2/26/09 at 7:15pm
If your receiver supports optical, try that. It might be a work around for a time but still need to resolve the ground loop.
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post #11 of 11
2/27/09 at 5:01am
Thread Starter 
I'd probably try an optical cable, but my sound card doesn't support it. All I've got is a 3.5mm digital output.

Looks like I'll be calling my cable company here in the near future
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