I have a groove tubes 12ax7-m in V1 and V2 and other 12ax7's i had laying around in v3-v5. I was wondering if anyone knows what each preamp tube position does what exactly? I had Mesa Boogie 12ax7's in V1 and V2...moved those over to V4 and V5 and put the GT 12ax7-m's in V1 and V2. I really liked what that did for the amp. Also, I've had the amp plugged into an Avatar 2x12 open back loaded with a Weber Alnico Blue dog and a G12H30 and disconnected the stock speakers. These speakers made the amp sound sweeter to my ears too. I'll probably end up moving those two speakers out of the Avatar and into the BC30.