There are amps out there that have power options. You an run them at 50 watts or 25 watts. Or you can run them at 15, 5, and 1 watt, whatever. I gather that is to achieve tube distortion at lower volume levels. Some of the Musicman amps had that feature, but I think even at half wattage, most of them are so loud, you're not gonna notice the overdrive coming at a substantially lower volume. I think Musicman designed the half power design to give the player more leeway on the volume control, because most amps, even if you want to play completely clean, have a sweet spot on the volume knob, and if the amp is deafening at 1 or 2 on the Volume, it's hard to fine-tune. I always hear that the Master Volume is so you can turn the overall volume lower, and turn up the channel volume to get preamp tube distortion. That works as described, but I highly doubt that's what Leo had in mind ... in 1972 when the Master Volume came out on the Twin Reverb, Fender was building "Clean Machines" for Country pickers who wanted that twang. Sure, everybody was buying them, but Leo always worked toward less distortion and Max clean tones. My opinion is that Leo's aim was to achieve a lower base volume so there was some wiggle room on the Volume control at smaller venues or recording studios. And the traditional Fender Master Volume does just that. IMO, most of the bad press it gets reflect players who never actually used the Master Volume as intended.