Got my Ampeg V4 out of the shop and it is killer for guitar and for bass.Two guitar players checked it out (independently) and both immediately dimed the master volume, then used the channel vol to control their loudness. I have always come at the volume from the other direction. With the master channel vol set midway I adjust the channel vol / gain as high as will give me the sound I want while not clipping the pre. Then I adjust the master vol for overall volume. Are my friends weird? Do guitar players usually do that? Do most bass players use an approach like I use?