Jeremy, the transducer came from an electronics store. It the element out of a piezo buzzer, only costs a dollar or two each.
Ive also had a change of mind about the pre-amp. I finished installing the setup into the guitar running passively and the bridge is giving a very hot signal . Im not sure the preamp is necessary. I wont have the neck on the guitar until the weekend so Ill make a recording with it when I do.
Heres what I did to wire it up.
1. Bought a 500k push/pull pot with DPDT contacts (double pole, double throw.)
2. Wired it in place of my existing volume pot.
3. Grounded the earth side of the piezo bridge to the volume pot case with the other pickup earths as per normal.
4. Here the clever part.....................remove the center pickup hot wire from the 5 way switch.
5. Wire the center pickup hot wire to one side of the Push/Pull pot switch.
6. Wire the piezo bridge hot wire to the other side of the Push/Pull pot switch.
7. Wire the push/pull pot common wire to the tag on the 5 way switch that used to have the center pickup wire.
Now what happens is this. With the push pull pot in, the guitar acts just like a regular Strat.
With it out, the center pickup no longer works but the piezo takes its place. Pos 1 is the bridge single coil, 2 is the bridge single coil and the piezo pickup, 3 is the piezo on its own, 4 is the piezo and the neck pickup, and 5 is the neck pickup.
This should give some nice combinations of pickup tones. Good thing is the tone and volume controls will have an effect over the piezo sound aswell as the regular pickups.
I'll report how it all works after the weekend.