Boomstar 8106 Filter

Designer Tim Caswell: "The 8106 is a 6db/oct hi-pass filter followed by a recreation of the Roland® IR3109 module, which is a 4 pole, 24 db/oct voltage controlled lowpass filter with voltage controlled resonance. Three dual OTAs with similar topology to the BA662 used in the Jupiter 8 (and the IR3109 module) were employed, one amp for the hi-pass filter, four (with added buffers) for the low-pass, and one for the resonance. This filter takes a wide range of input signals, and tracks control voltage extremely well. Tap points are available for 6db, 12db, and 18db/oct. Although the topology is similar to the 4075, the tonality, especially when overdriven, is distinct." Distinctly satisfying and musical we think.

Interface and feature Maestro Greg St. Regis, opted for the 6dB over the 12dB/18dB "tap" for the second filter output, due to its colorful, and starkly contrasting character.

And yes this INPUT drive hits harder—much faster than our other filters—so there is plenty of dirt to go around, but a familiar and comforting Roland-y (We can say that right?) quality/tonality/flow is definitely home base, especially with a nice SLIM O top-dead-center square wave is riotously coursing and pulsing through the 8106's veiny through-hole circuitry.

7 Pots
FREQ, RES, FREQ CV, RES CV, HPF, INPUT, OUTPUT
2 Switches
FULL/HALF TRACK, 6dB/24dB
Patch Points
1V/O, FREQ CV, 6dB OUT, RES CV, INPUT, OUTPUT

All Controls and Switches
FREQ – Frequency, or cut-off attenuator.
FULL/HALF TRACK – Full and half keyboard/voltage tracking switch.
RES – Resonance attenuator.
FREQ CV– Frequency control voltage attenuverter.
RES CV – Resonance control voltage attenuverter.
HPF – Hi-pass filter attenuator.
INPUT – Audio input.
OUTPUT – Audio output.
6dB/24dB – Filter slope switch.

PCB Mounting Scheme - Through-hole.
Size - 12hp.
Depth - 38mm including connectors.
Power Usage - 40mA, 35mA (+12 / -12)