Very nice! i like the sound samples, sounds really cool.
Of course, I´m already thinking about mods and hot rodding the thing... for example, the 47 and 100K resistors switched by the SPDT could be replaced with a 100K pot with a SPST to get all the variable sounds between "whirl and swirl", besides the vibrato. What do you think?
Yes, I already thought about a third pot during development, but we opted for the simplicity of a switch as this produces well defined and reproducible sounds. Nevertheless, for what you want the way to go is as follows:
1) Currently the resistance is varied from 47k to 100k to infinity (switch at center).
2) Consider removing the 100k resistor, and replacing the switch with a 500K log or audio pot (A-taper). At minimum, you have just 47k--same as before. At center, you have 47k+50k which is essentially 100k--same as before again. At max rotation you have 47k+500k, which for practical purposes is almost identical to the vibrato mode. There you have same three modes, continuously variable with a single pot.
Or, letting my mind fly freely, two of them fed by a low pass and a high pass filter respectively and recombined at the output, "leslie in a box"...
Yes, two tri-vibe boards could be used as building blocks for a more accurate leslie simulation. You will need an additional daughterboard with four opamps as follows:
1) Input buffer or TS-style stage set for low gain and soft clipping
2) 800 Hz 2nd order lowpass filter (negative gain implementation)
3) 800 Hz 2nd order hipass filter (positive gain implementation)
4) Two input adder
The two crossover filters need to have opposite polarities so when they are added phase relationships do not cancel the midrange frequencies (this is from crossover theory). Another possibility is to implement the 4th opamp as a differential opamp to do the subtraction.
The hipass filter feeds a tri-vibe set for whirl mode (rotating tweeters do have some amplitude variation as well). The lowpass filter feeds the second tri-vibe set for vibrato mode (the low frequency rotor produces almost no amplitude modulation). Both LFOs are adjusted close to each other but not identical.
Now the cherry for the cake would be controlling the LFOs to ramp up and down.
