I don't think this is your problem, but I'll post what worked for me....

I had a hum whenever my AVR was connected to my plasma via HDMI. Turns out, they were on seperate circuits. When I plug the sub/AVR/and Projector all to one circuit= no hum. I haven't tried the plasma on the same circuit, it's on a dedicated circuit installed after the house was built above the fireplace.

I happened to find a "THX certified" Monster cable for real cheap and tried it, no difference from my $2 Monoprice cable.


http://picasaweb.google.com/rprice54/EntertainmentCenter