The CTM-30 is 'just a grindy little amp' if you run your bass with the instruments volume on full. If you back off the instruments volume control the sound becomes quite clean. The gain in the preamp is such that it can be overloaded by a strong input signal, so the instruments volume control acts as a gain control. This works well for me using a passive Pbass with a 62' PU. I imagine that it might not work very well with instruments delivering a weaker signal.
You know, i’ve Never tried that. I always run my bass with vol full up. This amp has plenty of volume to make something like this work. I will give this a try!! It’s a really cool little amp In my opinion, and not too expensive.