The Retro Mechanical Labs 432k Rev2 is a filter, distortion and fuzz pedal in one box, released in 2022 as a revision of the company's original 432k Distortion. Delicious Audio describes it as "a beast of a filter+distortion+fuzz pedal" that delivers tones from distortion to overdrive to fuzz, or a combination of them, with the resonant and cutoff frequencies variable through its filter section1.
The circuit is built around two signal paths. One is a distortion circuit followed by an active hybrid diode/transistor ladder filter with resonant feedback, used for tone control. The other is a clean pass signal. The two are merged and, in Pedal of the Day's words, "glued" together through a transistor drive and an op-amp style fuzz2. The Rev2 adds an extra gain stage clipping for a smoother fuzz, along with a different set of transistors that gives the unit a slightly different sound than the regular 432k Distortion box2.
What it does to your sound
The filter is the heart of the pedal. The Filter knob sets the filter frequency and the Resonance knob controls active resonant feedback, so you can place a peak anywhere in the spectrum and push it until it rings1. Delicious Audio characterizes the overall result as a "Hyper Fuzz tone"1.
The Kill knob deserves its own mention. In Delicious Audio's 2024 roundup of unusual fuzz pedals, Griffin Jennings explains what it does31:
"The fuzz's Kill knob is a low-pass filter that can turn the fuzz into a distortion with octave-up hints or a muddy, intermittent stutter"3
Delicious Audio, 20243
That means one knob can take you from a focused distortion with octave-up hints to a gated, sputtering fuzz, which is a wide range of character for a single control3.
The controls and toggles
| Control | What it does |
|---|---|
| Distortion | Volume of distortion1 |
| Transistor | Transistor gain/drive1 |
| Filter | Filter frequency1 |
| Resonance | Active resonant feedback1 |
| Low Cut | Low end roll off1 |
| Sustain | Muff-inspired sustain, added in Rev21 |
| Output | Volume1 |
| Kill | Low-pass filter on the fuzz side3 |
The Sustain knob works much like the sustain on the Muff pedals, according to Pedal of the Day2. Beyond the knobs, three white toggle switches let you apply variations to the clipping, the diodes, and the low-frequency response, and there is also a low cut toggle switch12. Pedal of the Day found that "those mods can drastically change the tone and texture of the pedal"2, so the toggles are not cosmetic: they reshape the character of the distortion and fuzz paths.
The pedal also carries a CV input for filter control, which accepts modular gear, a synth or a CV pedal2. That opens up hands-free or sequenced filter sweeps, something most distortion pedals and fuzz pedals do not offer.
Power and connections
The 432k Rev2 requires a regulated 18V DC supply with a standard negative tip and a minimum of 150mA1. It will run on 12V, but Retro Mechanical Labs describes that as producing a dirtier sound1. The 150mA minimum rules out sharing a low-current daisy chain output with other pedals.
The enclosure is large, about the same footprint as Retro Mechanical Labs' 5.5 x 7.5 wood boxes, and it includes the classic VU meter the company is known for12. Pedal of the Day called it "a big, gorgeous enclosure, complete with the classic VU meter that this great company is known for"2. Switching is true bypass12.
Where it came from
The 432k Rev2 builds on the original 432k, adding modifications to improve tone. The 2022 Rev2 version adds the Muff-inspired sustain knob1, the additional gain stage clipping for a smoother fuzz, and the different transistor set that distinguishes its voice from the regular 432k Distortion box2. Pedal of the Day reviewed it on July 29, 2022, six years after the site last featured a Retro Mechanical Labs pedal.
Videos
Pedal of the Day
Drums FX Pedals
Questions
Can the 432k Rev2 run on 9 volts?
No. The pedal requires a regulated 18V DC supply with a standard negative tip and a minimum of 150mA. It will run on 12V, but Retro Mechanical Labs describes that as giving a dirtier sound, so 18V is the intended operating voltage.
What does the CV input on the 432k Rev2 control?
The CV input controls the filter. You can sweep it from modular gear, a synth or a CV pedal, which lets you move the resonant filter frequency hands-free or in time with a sequence rather than only with the Filter knob.
What changed between the 432k and the 432k Rev2?
The 2022 Rev2 adds a Muff-inspired sustain knob, an additional gain stage clipping for a smoother fuzz, and a different set of transistors that gives it a slightly different sound than the regular 432k Distortion box.
Is the Retro Mechanical Labs 432k Rev2 true bypass?
Yes. Both Delicious Audio and Pedal of the Day list true bypass switching among the pedal's features, so your clean signal passes through untouched when the pedal is off.
What does the Sustain knob on the 432k Rev2 do?
It works much like the sustain control on Big Muff style pedals, shaping how much the signal is driven and compressed into sustain. It was added in the Rev2 update, and it feeds into the fuzz side of the circuit.
Sources (3)
- New Pedal: Retro Mechanical Labs 432k Rev2 Filter/Distortion/Fuzz, Delicious Audio, 2022-07-29
- Retro Mechanical Labs 432k Rev2 Distortion, Pedal of the Day, 2022-07-29
- The Best Crazy, Weird, And Unusual Fuzz Pedals In 2024, Delicious Audio, 2024-10-24
