IMO and IME, there is still something going on with the top end that results in a lot of character and not the 'clean snap' of some of the other heads out there. The treble control doesn't work like the typical 'shelving' treble control (Eublet did some scopes in another thread), and if you try to make it 'sparkle', it gets a bit 'ganky and spikey'. Again, not so much a negative as a design goal by the manufacturer... it is meant to (IMO and IME) be fat and warm, and is focused down low much more than up top. It is kind of the 'anti-GK' head (again, not implying 'better or worse' here... just very different).
You can definitely get it so that there is no 'distortion' in the sense of an overdrive pedal, but there is always a lot of 'midrange harmonic complexity' that give it, like the DB750, its characteristic tone.
Again, back to the TC112/115/212, it is a pretty nice matchup if you want to benefit from the amazing 'size/weight/low end/max volume performance of the Thunderchild cabs, but want to get back a little more to a more classic 2 way bass cab voicing (i.e., add a bit of break-up and warmth into that very clean, transparent box).