I have my gear set up as follows: channels A and B on the amp set with all the knobs midway (but the master down a bit). Top I, class A, pentode for both. The hd500 is conneced and I've chosen a blank patch with a BF Double  Vib Pre (no cab). I have a footswitch set to turn the amp block on and off. Toggling back and forth gets much the same sound, not identical, but close enough not to worry about it. Now the interesting part. I switch the amp to LVM and turn the master up, and now toggle the amp block on and off, and the B channel is much more distorted than the A.

Why is this? I expect the behaviour of the two channels to be the SAME between normal volume mode, and LVM.