RIPPLES v1 /liquid filter

Github - BOM

Features

A multimode filter

• 2-pole band-pass.
• 2-pole low-pass.
• 4-pole low-pass.
• 4-pole low-pass processed by 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 LP4>VCA output.

Specifications

• Cutoff knob range: 18Hz to 18kHz.
• 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: 75k.
• Resonance and VCA CV input impedance: 30k.
• 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)