Comb Resonator

A recursive, pitched comb filter. It feeds a short delay line back into itself to ring at a tuned frequency, turning any input — drums, noise, a held chord — into a resonant, string-like voice. Its feedback runs high by default, so it sings on its own; pull Reso back for a percussive tick or push it up for a sustained drone, and raise the damping to darken that voice into a softer, plucked decay.

How it works

Audio is written into a delay line whose length is set by pitch rather than time, then fed back into itself by an amount you dial in with Reso (high by default). That recursion is what makes it ring like a struck string (the classic Karplus-Strong trick) instead of just adding a single echo. A damping filter in the feedback path bleeds off high frequencies on each pass, so the tail darkens and shortens as it decays. Left and right run as two independent resonators, so a stereo source keeps its width.

Controls

  • Freq — the pitch the comb rings at, 20 Hz to 5 kHz. This tunes the resonance, so feed it a note or sweep it for talking, formant-like motion.
  • Damp — how fast the resonant tail loses its highs. Low keeps it bright and sustained; high gives a softer, shorter, plucked decay.
  • Mix — dry-to-wet blend. Fully up is pure resonator; back it off to layer the ring under the original signal.
  • Reso — how strongly and how long the comb rings. Low gives a short, percussive tuned tick; in the middle it settles into a singing, string-like ring; pushed high it blooms into a long, sustained pitched drone on the edge of self-oscillation.

Inputs & outputs

  • In L / In R — the stereo signal to resonate; mono sources work too.
  • Freq / Damp / Mix / Reso CV — voltage control over each knob; patch pitch CV into Freq to play it melodically, or an envelope into Reso to swell the ring from a tick into a sustain.
  • Out L / Out R — the stereo result.

Tips

  • Send a sharp transient — a click, a snare, a noise burst — and it rings out as a pitched tone; that's the Karplus-Strong pluck.
  • Track Freq from a keyboard or sequencer CV to play melodies and basslines out of percussion or noise — it's one pitch at a time, so think of it as a monophonic voice.
  • Crank Damp for short, woody plucks; drop it near zero for long, glassy sustains that ring on for ages.