my personal experience with my own Einstein is thus:
sure, comparatively, it's a dark amp, but the treble, especially the frequencies controlled by the presence knob are abundant. I find myself turning the channel treble down a bit more than i have become accustomed to on all previous setups - lately it's been at around 9oo or 10oo, mids turned up to about 2oo to 3oo, and the presence hovering around 9 or below. the bass really kicks, but stays taut and solid, so i set that wherever feels comfortable onstage that night. if you let the treble and presence go too much, you might find yourself being a little harsh sounding, so those are what i find myself tuning before performance most. my personal experience tells me that on Diezels, the EQ knobs serve more as a way to carve out your place in the mix instead of 'getting your tone' - Diezels have a habit of sounding good no matter where your EQ curve is set. Treble = Cut, Mids = Volume, Bass = Body. thats the way i've started to use my EQ onstage, as each venue is different and each venue has dictated a different EQ curve each time.