tidy vco

TIDY VCO — flagship virtual-analog SUBTRACTIVE SYNTH VOICE: two polyBLEP oscillators with a continuous saw↔pulse SHAPE morph per osc, shared PW + audio-rate PWM CV, OSC2 octave switch + cents detune, and a −1-octave sub square, into an ALL-NEW nonlinear zero-delay-feedback DIODE LADDER filter (EMS VCS3 / TB-303 lineage — bidirectionally-coupled stages, soft warm knee into 24 dB/oct, feedback squelch limiter for a bounded near-sine self-oscillation, CUTOFF calibrated to the resonant pitch within 3 cents so keytracked self-osc plays in tune, DRIVE tanh saturation at 2× oversampling, part-compensated squelch bass dip). Two RC-curve "punch" ADSRs (CEM3310-style exponential segments, overshoot-target convex attack, analog resume-from-level retrigger): a filter EG with bipolar ±4-octave ENV amount + keytracking, and an amp EG into an OTA-flavored soft-knee VCA whose tanh bias blooms gentle even harmonics with level. 5-voice POLY on the polyPitchGate chord bus (lane i → voice i, release tails hold their pitch) AND a mono pitch/gate pair driving a REAL 2-voice unison (±7¢·WIDTH drift panned to opposite sides — true stereo beating); WIDTH also fans the poly voices across the stereo field (root anchored center). Stereo out_l/out_r pair (auto-wires R when L is patched), HOLD pad for droning the voice from the card, and a CV jack for EVERY control (27 inputs): the six original CVs — cutoff (4 oct/V, audio-rate), res, pwm (audio-rate), drive, fold (audio-rate), sym (audio-rate) — PLUS a GLOBAL block-rate per-knob CV for each remaining control: shape1/shape2/mix/sub/fsus/sus/track/width (0..1 full-swing), detune (±50¢), oct2 (discrete ±1 step/V), env (±4-oct bipolar), the six EG times (4 oct/V), and level (±18 dB/V). Every law is scaled in the shared core (lib/tidy-vco-dsp.ts) so cv = 0 is a byte-exact no-op. The rear patch panel groups its jacks into OSC·WAVEFOLD·DIODE FILTER·FILTER EG·AMP EG·OUT·POLY/OUT sections mirroring the card headers.

A flagship two-oscillator virtual-analog subtractive voice: OSC1 and OSC2 each morph continuously from sawtooth to pulse (band-limited polyBLEP), share one pulse-width control with a PWM CV jack, and OSC2 adds an octave switch plus cents detune; a sub square one octave under OSC1 fattens the bottom. The mix then passes through a STEREO WAVEFOLDER placed BEFORE the filter — the West-Coast Serge/Buchla move of folding timbre INTO a lowpass: a reflecting triangle folder (antialiased with antiderivative antialiasing over 2× oversampling) that grows a thicket of harmonics as FOLD climbs, with a SYMMETRY bias that blooms even harmonics off-center, and a genuine stereo image (L and R fold at antiphase points scaled by WIDTH, so the folder itself widens the field). FOLD 0 is a true bypass — every existing patch is unchanged. The folded mix feeds an all-new nonlinear zero-delay-feedback DIODE LADDER filter — the EMS VCS3 / TB-303 circuit family, deliberately distinct from a Moog-style transistor ladder: bidirectionally coupled stages give a softer, warmer knee into a 24 dB/oct slope, the resonance return passes through a squelch limiter so high RES compresses into a bounded, CLEAN self-oscillation whistle, and the CUTOFF knob is calibrated to the resonant pitch itself (keytracked self-osc plays in tune; the zero-res brightness knee sits well below the knob — the diode pole spread, part of the sound). DRIVE saturates into the filter for harmonic warmth (2× oversampled, loudness-compensated), and the diode ladder’s natural bass-loss at high resonance is deliberately only part-compensated — a musical squelch dip instead of a vanished low end. Two RC-curve ADSRs shape the note: real one-pole exponential segments in the CEM3310 lineage, whose attack charges toward an overshoot target and cuts over at full level — a convex, punchy front — with analog retrigger (a re-struck note resumes from its current level, never a click). The filter EG sweeps cutoff by up to ±4 octaves via ENV; the amp EG drives an OTA-flavored VCA whose tanh knee blooms gentle even harmonics as notes get louder. The voice is 5-voice polyphonic on the POLY chord bus (lane i drives voice i; a releasing voice holds its pitch), falls back to the mono PITCH/GATE pair when no lane is gated — where it plays a REAL two-voice unison, detuned ±7 cents times WIDTH and panned to opposite sides, each side with its own filter and envelopes — and WIDTH also fans the five poly voices across the stereo field with the root note anchored center. A momentary HOLD pad on the panel gates the voice by hand — the fastest way to audition or drone it while you shape the sound.

the faceplate

inputs

outputs

params

controls

source

tidy-vco.ts on GitHub.