Hey thanks a lot for your help. Now I only need to know which values should be changed for a bass in comparison to a guitar.
I'm not sure, but doesn't the driver need to be "stronger" to drive the bass strings? How can I make it "stronger"? Higher voltage from preamp? Or maybe a stronger magnet?
Anyways, will a regular humbucker magnet be fine for the driver, if I use it as the core of the coil?
And where in the circuit would I put a potentiometer to be able to change the sustain? Between preamp and driver? And which impedance should it have?
Between preamp and driver is also the right place to put a DPDT switch for an out of phase mode, right?