Rate
How fast the volume pulses.
- Turn up Faster tremolo flutter.
- Turn down Slow, throbbing pulse.
Pedals / Tremolo
Molo Trem
Tremolo · 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 deep the volume dips go.
- Turn up Near on/off chopping.
- Turn down Gentle volume shimmer.
Shape
Wave shape of the pulse (smoother vs choppier).
- Turn up More square / abrupt chopping.
- Turn down More rounded, vintage throb.
Inspired by
Joyo Ironman JF-325 Molo-Trem — compact analog photoelectric tremolo (LED + LDR amplitude mod), voicing modeled after vintage signal-shunt opto amp tremolos (Fender blackface class), not Fender bias-mod power-tube trem. Rate, Depth, Wave (Joyo copy: subtle triangle ↔ drastic square; Effects Database: sine-like ↔ square). Ninevolt display name Molo Trem and knob Shape (Wave) follow the Joyo product; circuit family reference only — no public JF-325 schematic (SMD Ironman layout).
Vintage opto trem context (Strymon — Amplifier Tremolo Technology): LFO drives a lamp; LDR resistance shunts/attenuates the signal. Classic neon/LDR circuits are fast and choppy with asymmetric duty (mostly loud, brief dips); LED/LDR pairs soften edges. Distinct from bias trem (swampy tube gain riding) and harmonic trem (dual-band phase swap). Carl's Custom Amps — tremolo types — signal-shunt opto vs bias vs harmonic overview.
Signal path
| Step | What it does |
|---|---|
| Rate → LFO Hz | Rate maps 0.5–12.5 Hz (0.5 + rate × 12); phase advances per sample, wraps at 1.0. |
| Triangle → sine → square Shape | Shape 0 = triangle; 0.5 = sine; 1 = square; all on 0..1 before blend. |
| Depth → gain target | Depth scales dip 0–100% below unity (target = 1 − depth × (1 − lfo)). No boost above dry. |
| Opto LDR lag | One-pole gain smoothing — base τ 10–16 ms, shortened at fast Rate so the LDR keeps up. |
| Multiply amplitude | input × smoothed_gain, clamped ±1. |
How we modeled it
JF-325 / vintage opto class: LFO → target gain (dip-only) → opto-smoothed multiply. Shape low = triangle/sine surf swell; Shape high = square stutter (into softened LDR). Depth at max can fully chop. LDR τ shortens at fast Rate so modulation stays audible.
Simplifications
- Digital LDR lag (single time constant, rate-compensated) vs real photocell rise/fall asymmetry - Symmetric trem depth — vintage neon opto often spends most of the cycle near full volume - Mono — no amp-style stereo tremolo pan - No input/output impedance coloring or LDR shunt tone shift