The Tremolo That Shouldn’t Have Worked — Supplement Files
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This page collects the supplement files for our tremolo experiment, originally written for Pulp Circuit.
This page is not the full article. It is just the technical supplement for anyone who wants to look closer.
The supplement files
The ZIP archive includes the material we still have from the project:
- Arduino prototype code for generating the PWM-based LFO
- Tina-TI simulation files
- schematic notes and exported images
- oscilloscope captures and reference material from the experiment
The prototype was built with an Arduino Uno. The idea was that a later PCB version could use a smaller microcontroller such as an ATtiny85. The logic is the same: one input for rate control, one PWM output driving the optical control stage.
Download the tremolo experiment supplement ZIP
What this experiment was
The control path was the fun part:
Arduino PWM → LED → receiving LED → smoothed control voltage → op-amp/BJT gain control
The receiving LED produced a small photovoltaic signal when exposed to the driven LED. With a small capacitor across the sensor LED legs, the PWM ripple smoothed into a slow sine-like control signal. That signal was then amplified and used to modulate the audio stage.
This is not presented as the best way to build a tremolo. It is simply the way we made it work with parts we had on the bench.
Notes
The files are shared as experiment material, not as a polished commercial pedal design. Expect rough edges, prototype decisions, and some things that were good enough for testing but not final-product quality.
That is the point of this section: real experiments, working hacks, failed ideas, and useful notes from the bench.