The first master is at 0, the second master (the one that the amp was stuck on since his switch pedal was stolen) I believe is around 8 o'clock or so. It wasn't very loud at all.
The position of the sweep knob was surprising to me, as I have the Revjr. and on that it seems like anything less than about 10 or 11 o'clock is too dark to fuck with. but then I have a marshall cab with g-12's so maybe the Vader cab is considerably brighter?