Old thread.. but what the heck. Thought I'd offer my two cents after FINALLY FIXING our stereo burping and buzzing.
Firstly it seems that our whole problem was due to the fact that we boondock, and use a 12V
to 120V inverter for the TV (stereo works on 12V
but not the TV) which generates noise passed into the system via the audio out on the TV.
After spending $70 Cdn on two of the Radio Shack isolation transformers (including two packages of female-female audio jackers) we finally are noise free!
Had to put one islation transformer on the audio out lines of the TV and another transformer at the subwoofer.
Thanks to the many people who have worked on a solution over the years
My wife will be a happy camper the next trip out, in a week.
PS. What a spaghetti mess behind the Sony DVD/fm/amp unit! I had already tossed out the CD changer (who uses those these days?). Lots of cables that didn't do a thing.