I played a Mark V again today (head/4x12) even though I haven't bonded with it in the past. I think there's a lot of different tones in there but I just couldn't get rid of a really pinched, nasally mid range on most light crunch to heavy settings. I actually found myself liking the MK1 setting on CH 2 the best for higher gain stuff. Kill the bass and get the treble and presence up and it's pretty rockin'. Overall I hated the pinched midrange peak it seemed to have across the board.
It's funny too, at first it sounded off in some way. I checked settings on the back and noticed the caution light was on for the bias select. Someone had set it to EL34