I've digged around for ideas on this, but haven't seen anything fully suitable yet. I'm designing a preamp to put in a bass guitar. It's set up to use a bipolar supply. Standard switching arrangement is to run the negative battery cable to the ring lug. Since I'm using a bipolar set up (caps and resistors between each rail, ground in center) I can't use the negative to ground. I'd have to have a switch on one or both rails that closed when something gets grounded.

I've seen one of RG's schematics using a PNP transistor, but that's made for a voltage doubler chip that only uses the positive rail. I found when trying it the rails were not anywhere near to equal voltages.

Would a relay work for this?  Also, I think the reason the PNP didn't work is because the resistors were in parallel with the voltage divider on the positive rail only, so it offset one side to a wrong value. If I used an equal amount of resistance from the negative rail to ground, would that balance the rails? Or maybe use an NPN to switch the negative rail as well?

I'm sure it's possible. I've heard that the Mike Pope preamps use stereo jack switching and a bipolar supply. My only other option is to use a switching jack, but those are rather expensive for the kind I need (normally open), so I'd like to do it on board. What would work?