Depends entirely on the input. The kind of bass, strings, pickups, effects, right hand technique, etc. Start turning knobs and using your ears.
Start by eliminating the “smiley face” graphic EQ. Set it to flat. Dial in your best sound using all the other controls first. Then use the graphic EQ to selectively remove small amounts of frequency that are problematic. If you want “more” something, turn up the volume and cut back on what you don’t want. Or not.
A couple of suggestions to try... First, lose that smiley-face eq. If nothing else, a more flat if even a teeny bit of a frown will help with the right kind of grind. Second, start with the post gain set pretty low. Then use the pre gain to adjust volume up. This gives you better chances of finding a sweet spot in whatever distortion the preamp has to offer. If you are going to put a pedal in front of the amp, use the post knob set high (if not all the way up) and use the pre gain as your volume. This will give you the cleanest tone the preamp has, as well as sending the eq settings more prominently to the power section. As far as the specific tones you're after, I don't have any specific suggestions. Do some twiddling.
