I've noticed it first on my CoreDuo XP system and thought it might be the old card in trouble on new hardware, so I've set up the Asus/PIII/Win98 system again - same result.
No matter if Scope 3.1 or 4.5, old or fresh install - TD distorts bass frequencies, the lower the frequency, the more.
I'm pretty sure I used that plugin on electric bass and didn't notice any artifacts at all.
Wtf can it be on my card, that only THIS plugin is affected ???
Of course the instrument level has been double checked and the parallel 'clean' channel plays perfectly.
Attentuator in TD is engaged, too. With 3 ticks attack increase to the right the effect is very prominent, but I wouldn't buy a distortion pedal with that sound either...

cheers, Tom