PEDAL BENCH
by Stompbox Labs
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Modulation1997· Boss / Roland (Japan)

Boss TR-2 Tremolo

Compact OTA tremolo — simple, reliable, the pedalboard default.

⏳
Schematic pending verification

We don't ship reference schematics until they've been hand-authored against authoritative sources (manufacturer service docs, ElectroSmash analyses, GEOFEX writeups) and reviewed in the simulator. Until then, the BOM, signal chain, controls and mod notes below are accurate, and you can still add this pedal to a project — it just won't include a circuit yet.

About

A triangle LFO (op-amp integrator + Schmitt comparator) controls an OTA (M5207 / NJM13600) acting as a variable-gain element on the audio path. Three knobs: Rate, Wave (LFO shape), and Depth. Famous Keeley 'volume drop' mod restores the lost output level when the tremolo is engaged.

Signal chain preview

6 stages
Input
JFET input buffer
Triangle LFO (op-amp integrator + comparator)
Wave control changes integrator's RC ratio → square ↔ triangle ↔ sine shape
LFO output (smoothed) drives OTA bias
OTA (M5207) attenuates audio rhythmically
JFET output buffer
Output

Quick facts

  • The TR-2 'volume drop' (~3 dB perceived) is the most-modded thing about an otherwise excellent pedal.
  • Replaces the earlier Boss PN-2 Pan/Tremolo (1990, discontinued — now a cult collectible).
  • Used by Jack White, Ed O'Brien (Radiohead), and many shoegaze acts for the deep-tremolo intros.

Controls

  • Rate
  • Wave
  • Depth

Mod recipes Pro

3 mods
  • Volume-drop fix (Fender Blender / Mod Kits)

    Restore the ~3 dB level loss when engaged.

    How: Add a discrete BJT booster stage (BC549 common-emitter, +6 dB) at the output before the bypass switch. Set bias for ~half-rail at collector.

  • Slower rate

    Sub-audio sweeps for ambient swells.

    How: Increase the LFO timing cap from 0.47 µF to 2.2 µF; minimum rate drops to ~0.05 Hz.

  • Stereo output

    Pan-style stereo by inverting the LFO.

    How: Add a second OTA driven by an inverted LFO (op-amp inverter) feeding a second output jack.

References