Updated Jul. 29, 2022

Retro Mechanical Labs 432k Rev2 Distortion

It’s hard not to gasp at the site of the Retro Mechanical Labs 432k Rev2 Distortion, a beast of a filter+distortion+fuzz pedal with enough controls to entertain even the most efficient knob fiddler for years!

The circuit consists of two signal paths:

  1. A distortion circuit followed by an active hybrid diode/transistor ladder filter (with resonant feedback) for tone control.
  2. Another with a clean pass signal.

Both signals are then merged together through a transistor drive and op-amp style fuzz, while three white toggles switches let you apply variations to the clipping, the diodes, and the low-frequency response.

This 2022 version (Rev 2) adds a Muff-inspired sustain knob and additional gain stage clipping for a smoother fuzz. A different set of transistors was used to give the unit a slightly different voice compared to V1.

A CV in lets you control the filter control remotely.

Needless to say, this is a machine that can deliver a varied range of tones from distortion to overdrive to fuzz or a combination of them with the addition of resonant or cutoff frequencies variable, dialed in through the filter.

Here’s the first video of it, we added this pedal to our article about the best unusual fuzz pedals.

Retro Mechanical Labs 432k Rev2 Distortion, Builder’s Notes

…Because vintage meters are limited and hard to find here is the “Standard meter” version. Meter is illuminated!

This model has a a couple of different mods not on the normal version. A sustain knob that works much like the sustain on the Muff pedals, additional gain stage clipping for a smoother fuzz. Those mods can drastically change the tone and texture of the pedal. In addition to the mods I’ve used a different set of transistors to give the unit a slightly different sound than the regular 432k Distortion box. This is a large pedal. Its about the same size foot print as the 5.5×7.5 wood boxes.
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…The 432k Distortion box is all about signal routing. One distortion circuit with an active hybrid diode/transistor ladder filter (with resonant feedback) for tone control. Another with a clean pass signal. Both signals are merged together and “glued” through a transistor drive and op amp style fuzz. Also equipped with CV in for filter control. ***Use a CV to control the filter.

Things I enjoy about this pedal:

• Hyper Fuzz tone
• Hybrid Diode/Transistor ladder filter.
• Enhanced resonant feedback for more expressive tones
• Clean pass lets you bring a quality signal back into the compressed distortion
• Op Amp style fuzz at end of signal chain. Dial in harsh tones and smooth them out.
• Great for guitars and keyboards
• CV filter control. Use CV in to control filter with modular gear, synth or CV pedal.
• Low cut toggle for guitar use.
• True Bypass

Controls
• Distortion: Volume of Distortion
• Filter: Filter Frequency
• Resonance: Active resonant feedback
• Clean: Clean signal
• Low Cut: low end roll off
• Transistor: Transistor gain/drive
• Op Amp: Op Amp Fuzz
• Feedback: Noise loop (works best with sequenced sounds)
• Output: Volume

**Requires a regulate 18volt DC Supply. Standard negative tip with a min of 150ma. (not included) Will run on 12volts for a dirtier sound. Lower voltage will affect the smoothness of the filter.