Wasp Filter

A 12 dB/oct multimode filter that channels the EDP Wasp — gravelly, dry, and grit-forward. Where a clean VCF smooths a sound, this one tears at it: push the resonance and it gets raspy and unstable rather than singing a clean sine. Reach for it when you want a filter with attitude.

How it works

It's a zero-delay-feedback state-variable filter, but its integrators are clipped through a hard, slightly asymmetric nonlinearity that models the CD4069 CMOS inverters the original Wasp "abused" as amplifiers. That hard kink and rail asymmetry are the gravel — they add raspy, even-harmonic dirt that grows with level and resonance. The resonance is deliberately capped just below self-oscillation, so it never breaks into a pure tone; it just bites harder.

Controls

  • Cutoff — the corner frequency, exponential from roughly 20 Hz to near Nyquist. Tracks 1V/oct, so it can be played like a pitch.
  • Res — emphasis at the cutoff. Low is a gentle bump; high gets aggressive and raspy, right up to the edge of instability without tipping into a clean sine.
  • Mix — blends the mix output from LP at one end through a Notch at center to HP at the other. The bandpass tap is always available separately.
  • Drive — pushes the input harder into the CMOS clipper. Clean-ish at zero, increasingly torn-up and harmonically dense as you turn it up.

Inputs & outputs

  • In — the audio (or CV) signal to filter.
  • V/Oct — 1V/oct pitch control of the cutoff, for keyboard- or sequencer-tracked filtering.
  • FM — exponential cutoff modulation; depth and polarity set by the FM attenuverter (centred is off).
  • Res — resonance modulation, summed straight into the resonance amount.
  • Mix out — the LP → Notch → HP blend set by the Mix knob.
  • Bp out — the bandpass tap, always available regardless of the Mix setting.

Tips

  • Send an envelope to FM for plucky sweeps; the dirt makes them snarl in a way a clean filter won't.
  • Park Mix at center for a notch and sweep Cutoff for raspy phaser-like sweeps.
  • Crank Drive and Res together on a bass or drum loop to absolutely chew it up.