Rate
How fast the chorus swirls.
- Turn up Faster warble — more vibrato-like motion.
- Turn down Slow, gentle shimmer.
Pedals / Analog chorus
Nano Chorus
Analog chorus · play-tested
seth — fish
seth@ninevolt:~$
Knobs
In the TUI each knob runs from low (left / 0%) to high (right / 100%). Start near noon, then nudge while you play.
Depth
How wide the pitch/wobble motion is.
- Turn up Deeper, more watery chorus.
- Turn down Subtle thickening — almost like doubling.
Inspired by
Electro-Harmonix Small Clone — MN3007 bucket-brigade chorus. Kurt Cobain's watery clean tone on Come As You Are, Teen Spirit pre-chorus, and several In Utero tracks (Ground Guitar — Nevermind gear). Hardware: Rate knob + Depth two-position switch. Ninevolt exposes Depth as a continuous knob (common DIY mod; CE-2-adjacent control layout). Display name Nano Chorus follows the project's compact pedal naming; circuit family reference only.
BBD chorus mechanism shared with Boss CE-2 (ElectroSmash — CE-2 analysis (PDF mirror)): triangle LFO modulates MN3007 clock (CD4047 on Small Clone) → variable delay time and pitch wobble, mixed ~50/50 with dry. Not tremolo — the LFO never scales signal level (Molo Trem is AM gain; this pedal is BBD delay modulation only). Small Clone LFO: LM358 relaxation oscillator, triangle wave (Stompbox Electronics — Small Clone LFO).
Signal path
| Step | What it does |
|---|---|
| Input LP ~6 kHz | One-pole lowpass — BBD bandwidth rolloff before the line. |
| Write to delay buffer | Conditioned dry stored in a circular buffer. |
| Triangle LFO Rate | Rate → 0.15–2.35 Hz; relaxation-oscillator triangle −1..1. |
| Clock swing × Depth | delay = 17 ms / (1 + depth × 10% × LFO) — fixed center, BBD clock wobble (not 6–40 ms sweep). |
| Fractional read ~17 ms center | Smoothed read head; interpolated tap behind write. |
| Wet recovery LP ×2 | BBD bandwidth limit; cutoff tracks effective delay. |
| ~50/50 dry/wet | Fixed equal mix — Depth scales clock swing only. |
| Output | Watery analog chorus, clamped ±1. |
How we modeled it
Small Clone path: input LP → write delay line → triangle LFO clock swing around ~17 ms center → smoothed fractional read → wet recovery LP ×2 → 50/50 dry/wet. Depth scales ±10% BBD clock wobble (CD4047/LFO path). Rate sets LFO speed. Chorus = subtle pitch detune; not tremolo, not a full-range delay sweep.
Simplifications
- Digital delay at audio rate (no MN3101 dual-phase clock or BBD resampling) - Continuous Depth vs two-position switch - One-pole input LP vs full anti-alias before write - Mono — no Small Clone stereo mod
Time/mod family: see TIME_MOD_COMPARISON.md for how Nano Chorus differs from Ana Echo, Memo Man, Poly Chorus, Echo Flange, and Classic Flange in code.