The Krytical Mass KM-01 Reactive Octave Fuzz is an octave fuzz pedal from Totally Wycked Audio, an American builder. Its circuit takes its inspiration from the early '70s Maestro Bass Brassmaster, and its defining trait is reactivity: the Sensitivity control adjusts the fuzz intensity and responds to picking dynamics and guitar volume settings, so the pedal cleans up and opens up with how hard you play1.
GuitarPlayer's Art Thompson summed the pedal up this way:
"A very tweakable octave fuzz that puts myriad tonal options at your fingertips: modern, but with a vintage soul, this"
From the Maestro Bass Brassmaster to the KM-01
The KM-01's lineage runs back to the Maestro Bass Brassmaster, an early '70s octave fuzz originally aimed at bass players. The KM-01 is not a straight reissue: GuitarPlayer notes it is more straightforward than the TWA prototype that engineer Robert Derby developed, and calls it "a great-sounding fuzz" in its own right1.
The pedal had a long gestation. It was originally designed in 2008 and then shelved for 15 years, for reasons that included founder Kevin Bolembach's other commitments, before finally being released1.
Controls and switches
The KM-01 gives you a main knob, a pair of mini pots, and several filter switches, which is where most of its tonal range comes from1.
| Control | What it does |
|---|---|
| Sensitivity | Adjusts the fuzz intensity; responsive to picking dynamics and guitar volume settings |
| Edge mini pot | High-frequency rolloff, useful for taming highs for a smoother fuzz tone |
| Bias mini pot | Paired with Edge as one of two mini pots for fine-tuning the fuzz |
| HPF switch | Activates a high-pass filter |
| LPF 1 switch | Activates a low-pass filter situated post clipping diodes to add low-end to the fuzz |
| LPF-2 switch | Another low-pass filter, located after a twin-T notch filter, to affect overall tonality |
| Phase switch | Recessed switch on the side of the die-cast housing changes the internal transformer's wiring from positive to negative for more or less low end, respectively |
The combination of two low-pass filters, a high-pass filter and a phase reversal switch means the Brassmaster-style octave character can be shaped from thick and bass-heavy to tighter and smoother without touching the fuzz itself1.
The LED display
One of the pedal's most distinctive features is its 21-segment LED display, made up of 21 white and yellow LEDs based on a scientific illustration of an atomic critical-mass reaction, which is where the pedal gets its name. It has two visual options: it can be set to cycle via an internal switch, with an adjacent trimpot varying the rate, or all LEDs can shine brightly when the pedal is active and dimmer when bypassed1.
The cycling mode and its rate are set with an internal switch and trimpot, so changing the display means taking off the back plate, not flipping a top-panel toggle.
Power, size and setup
The KM-01 runs from a 9VDC power jack, and the adapter is not included, so plan on a standard 9VDC supply from your pedalboard power supply. The die-cast housing measures 5.5" x 3.5" x 2" (DxWxH) and weighs 1 lb, with input, output and power jacks on the board1.
What reviewers said
GuitarPlayer's Art Thompson tested the KM-01 through a Fender Deluxe Reverb and a Marshall JTM 50, using a Guild Kim Thayil Polara and a Fender Vintera II Telecaster. His overall verdict placed it as a very tweakable octave fuzz with myriad tonal options, modern but with a vintage soul, organic and natural-sounding, and well deserving a spot on any fuzz fanatic's pedalboard1.
Videos
Mike Hermans
Godlyke Inc.
Godlyke Inc.
Questions
Is the Krytical Mass KM-01 true bypass?
Yes. The KM-01 uses a mechanical on/off footswitch with true bypass, according to GuitarPlayer's review. That means the pedal's circuit is removed from the signal path entirely when it is switched off, so it will not load down or color the tone of anything around it on your board when it is not engaged.
Does the KM-01 come with a power supply?
No. The pedal runs from a 9VDC power jack, but the adapter is not included, so you will need to supply your own 9VDC supply or use a pedalboard power supply output. The review does not list a current draw figure, so check your supply's ratings against the maker's specifications when planning a daisy chain.
What does the HPF switch do?
HPF activates a high-pass filter, which rolls off low frequencies. On a fuzz, that is useful for tightening the sound and keeping the low end from getting flabby, particularly with hotter pickups or when stacking the pedal with other gain stages.
Can the LED display be changed?
Yes. The 21-segment LED display has two different visual options. It can be set, via an internal switch, to cycle through its 21 white and yellow LEDs, with an adjacent internal trimpot varying the rate, or to have all LEDs shine brightly when the pedal is active and dimmer when bypassed.
Where is the KM-01 made?
The Krytical Mass KM-01 is built in the USA, according to GuitarPlayer's review of the pedal.
Sources (1)
- Shelved for 15 years of tinkering, Totally Wycked Audio's homage to the early '70s Maestro Bass Brassmaster, the Krytical Mass KM-01 Reactive Octave Fuzz, is finally here. And it's totally Wycked…, GuitarPlayer (www.guitarplayer.com), 2024-01-08
