Master volume works? yes it does. Does it sound good? Yes if you know what you're doing... But does it sound the best? absolutely not. I have been advised by some guitar players that I don't need an attenuator for a MV amp... Also some believe that you definitely would benefit from it and they can't use their amp without having one. Well... I agree with the second group. My Marshall Silver Jubilee 2555x and my 2203x came alive as soonas I connected them to the Power station, notes are more pronounced, have a lot of saturation, more sustain and my Marshalls roar. Can't think of using my amps without my PS2A anymore. Shoutout to Fryette for building such an amazing product. Now you should decide too, which side are you? if you are in the same side as me... Fryette Power Station is one of the best attenuators money can buy...if not the best. Good luck