So I found this in an older forum post here: Looking at the D-180 schematic I'm not really sure why backing off the master would increase gain, unless they had it wired backwards. It does have a similar thing to the Hiwatt though, where the master isn't at the very end of the preamp, it's between stages, so it acts as both volume and interstage gain control. Definitely worth a look down the road, but I may have to take a vote and make everyone choose between Bass 400 and D-180, I don't really want to do two different Mesa bass preamps. I'll put it on my list,
I’d vote 400/+ as long as it was based on the “vintage” channel and included the two EQ shift options (I played with both of those engaged on mine all the time). I personally found the straight preamp drive from the 400+ far more interesting and burly than my old D-180 which for me required a graphic EQ or other creative sculpting to get where I wanted it. The EQ shifts engaged on the Vintage channel of the 400+ gave me the best tube overdrive I’ve ever heard!

