RIPPLES v2 /liquid filter

Github - BOM

A multimode filter

• High-pass, band-pass, and low-pass outputs.
• Switchable slope control for the band-pass and low-pass outputs. The slope of the high-pass output varies with resonance.
• The low-pass output goes through an internal VCA - the perfect "end of subtractive chain" output!

All the CV inputs you need

• Un-attenuated frequency CV, calibrated for 1V/Oct tracking of the self-oscillation tone over 4 octaves.
• Frequency CV with attenuverter.
• Resonance CV. Self oscillation starts at 4V. Control voltages above 5V are non-linearly compressed, for fine control of resonance overdrive.
• VCA level for the low-pass output.

Specifications

• Cutoff knob range: 20Hz to 20kHz.
• Fully analog, based on the V2164 low noise/distortion quad VCA chip, and LM13700 OTA for that extra bit of non-linearity.
• Frequency CV inputs impedance: 100k.
• Audio input impedance: 100k.
• Resonance input impedance: 22k.
• VCA level input impedance: 39k.
• All CV inputs handle audio-rate modulations.

Code (AVR projects): GPL3.0.

Code (STM32F projects): MIT license.

Hardware: cc-by-sa-3.0

By: Emilie Gillet (emilie.o.gillet@gmail.com)