I was trying out some basses today at a local store and was using a GenzBenz Shuttle 6.0 through a single 12" cab. The salesman said I should turn the master all the up max and use the gain as the volume control because "It's a Class D Head". He said turning the master below max or 10 attenuates the power. I'm used to dialing in my gain just before clipping and using my Master as the volume on my MB SD1200. Any opinions? Thanks.