I own one. Apparently, mine is one of the "blessed" ones that makes a lot of noise when gain is turned up. I've sent it back to the factory & changed tubes and everything...still makes a bit of noise. Mesa said there was some cleaning they did to a tube socket or something, but the problem was not fixed. I've never had an amp that hums so much....BUT...it also sounds better than anything else I've ever owned, tone-wise. If only I could get a handle on that hum....
Theres a vid on YouTube of a guy who posted his noise problem in vid format, I've commented on it as well.....same thing. People always say "Send it back to Mesa, they have good customer service!". I can't afford to send it in every two weeks because they didn't fix it the last time. Kinda sucks...