I'm 64 and played a lot when Marshall amps were just about the only thing guitar players used (70's) and a V4 or V4-B no matter what you are using for a cab will just not keep up with a Marshall if the guy plays it loud and they are supposed to be played loud, some of you guys must be playing cocktail music

. I owned a V4-B back in the day and while it was a nice head and sounded pretty good it absolutely did not have enough oomph to keep up with a Marshall amp in fact most guys who played in bands with them used an SVT head with either two SVT cabs (8x10) or two V4-B cabs or both. I used to use my V4-b only for rehearsal. One more thing that head is only going to put out 100 watts no matter how you got the gain or the master volume set, it will just get more dirty sounding, the cleanest and hence the loudest way is to set the master (power amp volume) on 10 and use the gain (preamp volume) as the volume control, that is exactly the way a non-master amp works, they have no master the power amp is up all the way and the volume is controlled by the volume control (gain).