Mutable Instruments Ripples, 2020 version — the analog four-pole filter that earned its reputation as the no-fuss, elegant choice. Discontinued since Mutable closed in 2022.

Build and provenance — please read: This is a DIY build, not a factory unit. The panel and knobs are genuine Mutable Instruments parts purchased directly from Émilie Gillet. The PCB was fabricated from her open-source design files, with SMD components machine-placed by JLCPCB. Through-hole assembly, testing and calibration done by hand.

What it does:

A big-sounding analog filter in 8HP, fully analog throughout — built on a quad VCA for the filter core with an LM13700 OTA in the feedback path bringing resonance under voltage control and acting as a soft-limiter for clean self-oscillation.

Three simultaneous outputs: high-pass, band-pass and low-pass. A switch sets the slope of the BP and LP outputs to 2-pole or 4-pole; the HP output's slope varies with resonance.

Two input paths, mixed together:

• Input 1 runs through a soft-clipping circuit with a drive control — distort the signal, or use the gain to bring line-level sources up to modular level
• Input 2 stays completely clean, preserving the tonal character of the original Ripples mkI

Resonance and character: self-oscillates on all modes, producing a clean sine wave on the low-pass output. Unlike most classic 4-pole designs, there's no loudness drop as resonance climbs — the compensation circuit adds a slight coloration reminiscent of Japanese classics from the 80s, with a round, liquid resonance.

The VCA: the low-pass output passes through an internal VCA with its own CV input. 0V silences it, 5V gives unity gain, and values above +5V compress progressively. With nothing patched, a 7V signal is applied internally. This makes Ripples a strong "final stage" for a compact subtractive voice — filter and VCA in one 8HP module.

CV inputs:

• Un-attenuated frequency CV, calibrated for 1V/oct tracking of the self-oscillation tone over 4 octaves
• Second frequency CV with bipolar attenuverter, -1V/oct to +1V/oct
• Resonance CV — self-oscillation starts at 4V, and control voltages above 5V are non-linearly compressed for fine control over resonance overdrive
• VCA level CV for the low-pass output

Specs:

• 8 HP, 25 mm deep
• Power: +12V 35mA / -12V 35mA
• Cutoff knob range: 20 Hz to 20 kHz
• Genuine Mutable Instruments panel