I don't know. I'm beginning to think the amp is the problem. Something has gone bad and the power supply isn't regulating or a cap blew and DC isn't decoupled properly or something.

I also don't buy that the transformer is acting as an antenna as ferrous core toroids make lousy antennas. However I'll grant that something might be broke here too.

My 7075 isn't dead quiet. I get a little of what sounds like transformer delamination noise which is strange becasue I thought the transformers where ferrite core not laminated steel. Haven't popped it open yet to explore. The noise level is low-I can't hear it from more than a couple feet away.