Originally Posted by drewallsbrook
*** ideally one of the tone knobs could still control tone when preamp is bypassed...
Since the preamp will be bypassed, there will be no tone controls in passive mode. If you wanted a standard passive tone control, that will require another pot.
There are a couple of specialized preamps, such as the Dingwall-modded OBP-1 on Dingwall basses, that have a treble control with an active boost and passive cut. This is done with custom pots that I have yet to find a source for, outside of paying MEC ($90, IIRC) to manufacture one, or having them custom manufactured in large quantity. Unfortunately, Dingwall does not sells theirs. And modifying a standard pot is almost impossible, as you need a dual ganged pot with the sweep of each gang spread across only half of the rotation.