Ok Chuck, as promised, here's a few diagrams… including something that probably fits in the specified 'weird alternative' category.
The are a couple of caveats with the pickup switching diagrams:
1. As Simon stated, ideally you need to separate the 'signal' +/- from the shield/ground on the pickup, and P90's typically have a hot core and a braid or bare shield carrying the 'negative' (but it depends on your pickup). The stock PBG P90's usually have a single hot core that connects to the + of the coil and the bare shield is split at the pickup end with one branch connecting to the coil - and the other branch soldered/screwed to the baseplate. In that situation it's actually not that difficult to convert it and connect a two core shielded cable so you've got your required signal separation. The good news is that this only has to be done to the neck pickup, the bridge pup doesn't need to be touched.
2. Doing parallel, out of phase and series switching using a DP3T switch involves a compromise as it really needs to be a 3 pole 3 throw to get all the connections you need. Basically, for the 'series' mode to function the pickup selector has to be set to the 'neck' position. If it's in the middle or bridge position when in series mode the neck pickup gets shorted out and you only get the bridge regardless.
This first diagram gives you the requested parallel, parallel out-of-phase, and series options:
Diagram two is the 'weird alternative'… I'm calling it the SHoop Gambit. Instead of connecting the pickups in parallel out of phase, why not try Series Half out of Phase… like you can do with humbucker coils to get a pseudo single coil sound. Connecting two P90's in series would be sort-of like a big widely spaced fat humbucker, so I thought using a cap for the half-out-of-phase effect may give you an in-between sound. Some of the fatness of the series connection plus some of the nasally out of phase sound, but without the thinness you get in parallel mode. It's a little out there. I actually wired this up on my 1-string tester yesterday with a couple of P90s (Golden Age bridge and Tonerider neck) and it actually sounded quite nice - different but good and worth exploring. YMMV.
Last diagram is just some tone filtering options. Left is is a single cap version giving both a hi cut and low cut, and the right has separate caps for each filter. Values around 0.0022/0.0033uF will probably give you the most usable sounds, but it's something you need to experiment with for your particular guitar and tastes. From my experience a low cut (cutting out the low end) using a 0.0033 works well, but 0.0022 may be needed to thin it out more. A hi cut with 0.0022 takes off just a bit of the highs, but you may want to go to 0.0033uF or even 0.0047 if you want it a little darker.
(Note: there may have been some alcohol involved, so use at your own risk)
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Originally Posted by Simon Barden
