Somebody help! Ground loop issue is a puzzler

dmurray14 · 11-21-2005, 07:33 PM

OK guys, I'm going nuts. I have MitchJS's original USB Sirius adapter. I love it - works great, except for one thing. When the audio cable (RCA from the sirius box to headphone at line in on MiniITX) is plugged in, I get nasty alternator whine. When it's not, nothing. Both the Sirius adapter and the MiniITX are grounded to the same place. I really want to be able to listen to Sirius, but it completely ruins the whole expierence with the Alt. Whine. What can I do to get rid of it, short of a ground loop isolator (I feel this is a band-aid solution, and I hate band-aid solutions).

Thanks guys,
Dan

fantomas · 11-21-2005, 08:50 PM

try regrounding. make sure the location is bare metal and clean. if not, try another location for the ground.

Shakey · 11-23-2005, 03:41 AM

How long is your RCA cable? Is it running along the same path as a power line?

MatrixPC · 11-23-2005, 11:40 AM

Most of engine whine problem is cause by RCA cable running along with power line.

dmurray14 · 11-23-2005, 02:46 PM

Thanks guys. RCA only crosses a power line like twice. The excess is bunched up and zip-tied.

I put the Sirius tuner on a relay from a different power source, and grounded the mini-itx to the same place it's grounded. Seems to be much better.

Dan

Fusion-One · 11-24-2005, 10:27 PM

In the grounding sheild of your line in, try attaching a small potentiometer, 0 to 1kohm's seems to work quite well.. and adjust until the loop goes away, worked very well for me when I had a similiar issue. Basically, it makes the eletrical interference find an easier path to take.. you'll lose a little volume, but nothing that a little adjustment on the amp won't fix.

Daley · 11-25-2005, 11:22 AM

The bunched-up and zip-tied mass could also be causing you problems - try un-bunching.

@Fusion-One: Never thought of that - thanks for the great idea.. Certainly seems to make sense!