Got to thinking I once ran into a problem like that with the guitar players Blues Junior amp it would make a funny buzzing sound but the music didn't cut out and just had a weird vibration on certain notes turned out it was a capacitor on the circuit board where they hadn't used enough glue to secure it and even though it was connected fine it would be vibrate against the circuit board on certain notes. Took me a while to find it had to pull the chassis and check every component.
Thanks for the suggestion. I will probably bring it back into the shop before I start disassembling everything What's interesting is that I just played the amp for a couple hours and as it warms up the buzzing disappears almost completely. .
Awesome man! It's a heck of an amp that really should be able to do any gig. Even as venues get bigger, you should have adequate FOH support so it doesn't really matter.