Rate
Flange sweep speed.
- Turn up Faster motion.
- Turn down Slower motion.
Pedals / Flanger + echo
Echo Flange
Flanger + echo · 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
Flange sweep depth.
- Turn up Stronger whoosh.
- Turn down Gentler motion.
Echo
Extra echo / delay blended with the flange.
- Turn up More audible repeats trailing the notes.
- Turn down Mostly flange with little echo trail.
Inspired by
Electro-Harmonix EH-1311 EchoFlanger (1970s) — same MN3007 BBD core as the PolyChorus and PolyFlange. Kurt Cobain In Utero; factory presets reference “In Utero Tour” and “Priest Called Him.” Original knobs: Rate, Width, Tune, Feedback, plus a 4-way mode switch (chorus / vibrato / filter / flange). We expose Rate, Depth (Width), Echo (Tune + feedback + echo mix) and run flange + echo in parallel.
Signal path
| Step | What it does |
|---|---|
| High-pass ~85 Hz | Sub trim before BBD (PolyChorus input path). |
| Input LP ~7 kHz | Tames pick transients entering the delay line. |
| Echo read | Echo sets 120–480 ms delay (Tune range); fractional interpolated tap. |
| Recovery LP ×2 | BBD bandwidth limit; cutoff tracks clock Nyquist. |
| Feedback × Echo | Wet echo tap fed back into write; soft-limited near oscillation. |
| Anti-alias LP + BBD write | Pre-write filtering and mild MN3007 nonlinearity. |
| Triangle LFO | Rate → 0.06–2.46 Hz comparator-style sweep. |
| Flange modulated read | Depth (Width) sets center ~1.2–4.7 ms and sweep up to ~12 ms. |
| Blend dry + flange + echo | Weighted sum plus (wet − dry) comb term for jet-plane notches. |
How we modeled it
PolyChorus-family path: condition → echo read + fb → BBD write → modulated flange read → recovery LPs → dry + flange + echo blend. Triangle LFO sweeps short delay for jet-plane comb; Echo sets longer tap time and feedback for spacey repeats.
Simplifications
- Parallel flange + echo instead of 4-way mode switch - Digital delay at audio rate (no VCO clock ripple or BBD resampling) - No compander or chorus/vibrato/filter-matrix modes - Mono only