I think I finally isolated my amp's noise problem to the reverb. As you may recall, I was having trouble with my Hughes & Kettner Edition Tube breaking up on the clean channel. I thought it was tube trouble, but the breakup wasn't a nice and smooth tube one. It's pretty harsh and nasty.

I don't why I didn't do this earlier, but today I turned the reverb down all the way and lo and behold it held a nice clean tone up to a decent volume. I turned the reverb up and got the nastiness.

I sprayed the contacts to the spring reverb with cleaner, but that didn't do the trick.

Anything else I should try?