Actually, I hate to disagree with all you guys, but I think this is probably doable, especially if he's had it working in an external box.
First off, don't worry about pickup impedances for the purpose of this discussion. The circuit is designed to work with Alembic pickups, but that shouldn't put you off. On a Series bass, the SC-1 pickups are wound with very little wire, so they have very low natural output, but I believe most of the other models are not radically different than normal passive levels (the pickups are not buffered before the panpot). Impedance matching is important for full frequency range, but the Alembic output isn't low impedance until after it has passed through *this* circuit, which *is* the buffering amp.
I'm not sure exactly what this circuit is (the factory folks can easily identify it), but I think it's likely that the blue trimpot on the side is a level control. Now it might be a true gain control (modifies the amplification of the op-amp, but isn't in the signal path) or it may be a pre- or post-trimmer in the audio path.
I'd also be willing to bet that the two pin molex is the signal in, plus and minus (this would have been fed from the pickup balance pot). The three pin molex is probably the output side, signal plus, ground, and +9V power, since these three lines would normally terminate in the same place, the output plug. Power ground would normally be the same as signal ground for a low-impedance unbalanced output.
If you had access to the external box that this was in, it should be easy to verify.
On a stock bass, I think the panpot would be a plain pot as would the master volume pot, so all the electronics are built on the tone pot like this.
The folks at the factory should be able to provide the color code as should anybody that has a bass that has a circuit like this.
David Fung
