Speed
Rate of the throbbing vibe/phase motion.
- Turn up Faster pulse.
- Turn down Slow, seasick throb.
Pedals / Uni-vibe phaser-vibrato
Purple Depth
Uni-vibe phaser-vibrato · 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
Intensity of that motion.
- Turn up Deeper, more dramatic swirl.
- Turn down Subtle movement.
Mix
Dry versus effected balance.
- Turn up More vibe in your sound.
- Turn down More dry guitar with a hint of swirl.
Inspired by
Shin-ei Uni-Vibe / Dunlop Uni-Vibe — four-stage optical phaser (incandescent lamp + four LDRs), not a chorus or pitch shifter. Hendrix Machine Gun, Gilmour Breathe, shoegaze wash (shoegaze-wall.yaml). Hardware: Speed knob + Chorus / Vibrato toggle (no Mix knob on vintage units). Ninevolt display name Purple Depth; Depth = intensity / sweep width (common on modern reissues); Mix = dry/wet (software-only — approximates vibrato when high).
Not tremolo — LFO moves phase notches, not gain (Molo Trem). Not Phase 90 — staggered caps, lamp lag (Ninety Orange). Phaser family: PHASER_MOD_COMPARISON.md.
Signal path
| Step | What it does |
|---|---|
| Preamp soft clip | Light tanh — input headroom before the lamp network. |
| Triangle LFO Speed | 0.07–4.27 Hz triangle drives primary notch motion. |
| Sine → lamp ~40 ms | Sine LFO + one-pole follower — thermal inertia rounds the sweep (not a second LFO). |
| Log corner sweep | Depth widens 90–380 Hz → 380–1880 Hz log sweep; corner_to_apf_coeff() maps to digital APF coeffs. |
| 4× staggered APF | Stage ratios 0.68 / 0.86 / 1.0 / 1.22× — spread “double beat” notches (Uni-Vibe cap spread). |
| Regen depth×0.48 | Mild feedback — Uni-Vibe color, not Block Logo resonance. |
| 50/50 chorus mix | Hardware Chorus position — equal dry + phased before the Mix knob. |
| Mix dry/wet | Blends clean input vs full phased bus; Mix → 1 leans vibrato. |
| Output | Hold chords to hear swirl; clamped ±1. |
Simplifications
- Mono in/out - No optical LDR nonlinearity — lamp = one-pole on sine - No dedicated Chorus/Vibrato switch — Mix knob - Depth is not on the original Shin-ei panel - True bypass (no engage ramp)