The middle 3-position mini toggle allows me to dictate which pickup (bridge/both/neck) is impacted by the Stellartone Tone-styler rotary mid-notch control (the big black knob up front). This is a passive rotary vari-tone style control that is voiced specifically for bass and one of the more useful, impressive versions of a vari-tone currently available. This Tone-styler is the first thing the pickup signal sees, but there is a true bypass setting, which essentially removes it from the circuit when desired.
After this, each Distiller filter has a 3-position mini toggle switch that allows you to select between 3 different resonance boost settings: +0dB, +5dB, +9dB. At the first, +0dB setting, the filter essentially acts like the ultimate tone control, in that it's a perfectly smooth, gradual treble roll-off that maintains the tone of your pickups crystal clear. The other two settings create a resonant boost at whichever frequency the filter is set to, which is where the magic happens. Above that frequency is a clean cut-off, at that frequency there's your selected level of boost and below it is the otherwise unaffected remainder of your pickup signal. That's the easiest way I can describe it, but those boost levels (+5dB and +9dB) can completely change the voice of your pickup, making for seemingly infinite possibilities. Then when you blend the signals between two separate sets (of pickup+distiller) the signals are buffered and summed in a way that neither affects the other - unlike when a bass has 2 separate passive tone controls, they tend to affect each other unless you add a resistor in the circuit.
Anyway, Jerry (the man himself) can probably explain it better than I can:
Having owned several Alembic basses, I've always found their electronics to be truly special. Unlike most other basses using passive tone controls or conventional 2- or 3-band EQs, Alembic basses come equipped with a unique 12dB-per-octave low-pass filter that features a widely adjustable cutoff
www.jtex.ca
After the filters come the volume controls. Since the filter buffers the signal, you want something like a 25k potentiometer for your volume(s), which will allow you to have a perfectly smooth, gradual volume cut, all the way from 10 to 0. I went with the standard EMG 25k volume pot, per Jerry's recommendation.