Audio hum when computer hooked upto reciever...

[Jugernot]

I've had this problem for years, but recently have been getting really annoyed as I have a system hooked up for divx. When I turn my reciever up to an audible level, I get a pretty distinct hum. If I remember correctly, this is a cable grounding problem (it disappears when I unhook my cable). Anyone know a way to fix this?

Jugs

btw: This happens with every sound card I've tried. Sound Blaster 16, DMM MX300 (Vortex 2), Crystal Audio, Sound Blaster Live....

 

[Workin']

Either plug the stereo and PC into the same outlet or use a 3-prong --> 2-prong plug adapter on either the TV or the PC.

 

[Jugernot]

Unfortunately it isn't that simple. This is a grounding problem with the cable that comes into my house that the cable company controls. Since posting this I found out this is called a Ground Loop. Basically it happens when two electronics sources are hooked together, but they are not insync electrically. One of the sources is slightly higher voltage (as little as .5v) and the grounding setups are different. Do a search for Ground loop through your favorite search engine and you should find a bunch of links to pages on it. Now I just gotta get to radio shack and build myself a converter.

Thanks guys!

 

[Workin']

<< Since posting this I found out this is called a Ground Loop. >>

Yes, I know. And the solutions I posted are "classic" solutions to ground loop problems. Plugging the 2 devices into the same outlet eliminates the voltage differential, and breaking the ground line using the adapter I mentioned eliminates a path for the loop. Either way works for all but the wierdest ground loop situations.

 

[Jugernot]

Well I tried the 2 prong to 3 prong and unfortunately it brought it's own problems (lots of waves on the TV) so now I'm back with the original hum. I found a site that has instructions on how to build a small connector that goes inline with the cable. I'm gonna goto Radio Shack tomorrw and buy some parts for it.

http://www.siber-sonic.com/broadcast/GLoopFix.html

 

[Jugernot]

Ok, just got back from Radio shack and bought two 300ohm to 75ohm transformers. The same that is shown in this Picture from the links above

Worked like a charm.

Best $5.80 I've even spent! I don't even see much degradation in my video/sound quality.

Jugs

 

[Workin']

Very interesting.

 

[Jugernot]

Yah, after more testing, the hum is COMPLETELY gone. When I used to turn my receiver upto 20 (out of 50) I would get a significant hum. Now with the transformer, I turned it upto 50 with no distiguishable noise at all. Very nice, I recommend you try it. You don't have the risk your components not being grounded as you do with the 2 prong to 3 prong method above.

Jugs