I have a 7500 too. I am getting ready to send it back for repair under warranty. It has a static sound in one channel (right surround) that does not vary with volume, and is heard when muted too. I did all kinds of input cable swapping and speaking wire swapping to isolate the problem. It is the amp. I have a plasma too, but I don't hear transformer noise in any of the channels. I do use ferrites on the power cord to the amp and TV.