The KMA Machines Guardian of the Wurm is a high-gain distortion pedal with a parametric EQ and a built-in noise gate, made by KMA Machines. It is an HM-2 inspired circuit that fuses KMA's earlier WURM metal distortion with a versatile gate section, and KMA describes it as "the most extensive and configurable HM-2 style unit on the market"1.
Guitar.com called it "an updated version of its HM-2-inspired Wurm distortion" when it launched in July 20212, and gearnews.com described it as a souped-up version of the earlier KMA Machines WURHM that "takes off where the Wurhm left off"3. MusicRadar reported it was available to order at €299 at launch4.
The controls: four-band parametric EQ, gain and blend
The heart of the pedal is its EQ section. Where the Boss HM-2 it draws on had fewer bands, KMA added two more, for a total of four fully customizable sliders, each with its own dedicated center-frequency control7. Delicious Audio called this 4-band graphic parametric equalizer "truly unique," saying it allows "incredibly precise EQ adjustment across the entire spectrum of your signal"6.
The full control count is 14, plus an FX loop and dual footswitches5:
| Control | What it does |
|---|---|
| Gain | Sets the distortion amount |
| Low, Lo-Mid, Hi-Mid, High | Four EQ bands, each cut or boost |
| Low Freq, Lo-Mid Freq, Hi-Mid Freq, High Freq | Set the center frequency of each band |
| Gate | Noise gate threshold |
| Clip Diode | Selects clipping style |
| EQ Style | Selects HM-II, Both or KMA EQ voicing |
| Master | Output volume |
| Blend | Mixes clean signal with the distortion |
Inside the pedal are further trimmers: Distortion Level, Clean Volume, Gate Response, Trigger Source and Input Filter5.
Clipping and EQ style options
Two toggles shape the pedal's core character. A three-way clipping toggle selects between three clipping modes6:
- Silicon (Si): the clipping style of the Boss HM-21
- Asymmetric (A-S): increases headroom and gives more grit by retaining complex harmonics, with less drive compression16
- Off: diode lift, which KMA describes as "perfect for bass and baritones"1
A separate EQ Style switch offers three voicings: HMII, Both and KMA7. Selecting HM-II mode gets you the classic "chainsaw" high-mids character of the original pedal, while KMA mode is "a little more tonally balanced, less peaky and a bit wider in response"1. Guitar.com summarized the difference: the KMA mode "has a more modern character, with a wider response and more balanced EQ"2.
The noise gate and footswitch modes
The gate is a Blackmer VCA-based design with a simple threshold control, which Pedal of the Day described as providing "lightning fast and precise performance"72. An internal DIP switch changes the gate's trigger source from pre- or post-distortion, or even pre-noise gate, so you can tune where the gate listens6.
The pedal has two relay-based soft-switch footswitches6: TERROR activates the distortion side and TAME activates the noise gate7. How they work together depends on the mode1:
- Synced mode: the entire pedal switches on and off via the TERROR switch, and the noise gate can also be switched in and out of the circuit as desired16.
- Independent mode: both sides of the pedal switch on and off independently via the TERROR or TAME switches respectively16.
The pedal also carries an FX-Loop jack. Pedal of the Day notes: "You can even use this jack to put the Noise Gate section in your amplifier's FX Loop if you wish, 'cause why not?"7
Power
The Guardian of the Wurm runs on a standard 9V DC power supply, center negative, with a 2.1mm barrel connector, and draws under 150mA max1. Delicious Audio's coverage lists the same connector and polarity6.
With a current draw under 150mA max, this pedal needs a proper 9V DC supply rather than a battery, and its draw is high enough that a small daisy chain shared with several other pedals may not be ideal1.
Where it came from
The Guardian of the Wurm sits in a family of KMA HM-2 style pedals. Pedal of the Day called it "KMA's unabashed sonic love letter to the classic Boss HM-2 MIJ Heavy Metal, utilizing aspects of that pedal while developing a more flexible distortion"7. It followed the KMA Machines WURHM of 2020, which itself let players switch between the original HM-2 high control and KMA-designed EQ bands, and was later joined by the smaller KMA Machines Wurm 2 and the Wurm MK2 HM-2 Style Distortion38.
The standard version remained available from the KMA Machines webstore for $349.995.
What reviewers said
Reviewers were broadly enthusiastic. Pedal of the Day called it "possibly the end-all be-all dirt pedal" and said "the Guardian of the Wurm takes high gain into the stratosphere and beyond"7. Delicious Audio judged that "the Guardian of the Wurm delivers alright!" based on video reviews from metal-inclined YouTubers, and highlighted the 4-band parametric EQ as something "not seen before on a pedal or pro audio gear"6.
Guitar Pedal X's Stefan Karlsson wrote:
"There’s no doubting the prowess of this pedal - which is surely one of the ultimate HM-2 style pedals out there - with maximum shapeability, super smart dynamic noise gait and handy FX Loop - a genuine monster of a Heavy Metal Pedal!"5
KMA itself says the pedal "can be tamed to provide impeccable clarity to your riffs," positioning it for metal, prog-rock, shoegaze, indie and beyond1, while Delicious Audio's coverage frames it as covering "chugging hard-rock, droning doom metal and grinding Swedish death metal"6. The pedal is built in a powdercoated die-cast enclosure, and every unit is designed, assembled, silkscreened, tested and numbered by hand in KMA's small workshop6.
Videos
KMA Machines
SpectreSoundStudios
Trey Xavier
News
Questions
Is the Guardian of the Wurm an HM-2 clone?
No. It is an HM-2 inspired circuit built around KMA's own WURM distortion, adding a four-band parametric EQ, three clipping styles, a clean blend and a noise gate. KMA describes it as the most extensive and configurable HM-2 style unit on the market, so it goes well beyond a straight clone.
Can the Guardian of the Wurm be used on bass?
Yes. The pedal's Off clipping position lifts the diodes, which KMA describes as perfect for bass and baritones, and Delicious Audio notes it works with guitar, baritone, bass or synths. The clean blend and parametric EQ also help it hold up on lower-tuned instruments.
Can the noise gate go in an amp's effects loop?
Yes. The pedal has an FX-Loop jack, and Pedal of the Day notes you can use it to place the noise gate section in your amplifier's FX loop if you wish, so the gate can sit after your amp's preamp distortion rather than in front.
How do you switch between Synced and Independent mode?
An internal control selects the mode. In Synced mode the whole pedal switches on and off with the TERROR footswitch, and the gate can be switched in and out of the circuit as desired. In Independent mode the TERROR and TAME footswitches turn the distortion and gate sides on and off separately.
What is the difference between the Wurm 2 and Guardian of the Wurm?
The Guardian of the Wurm is the full-size flagship, adding a built-in Blackmer VCA noise gate, an FX-Loop jack, internal trimmers and a clean blend to the HM-2 style circuit. The Wurm 2 is a smaller, slimmed-down update of the earlier WURHM with top-mounted jacks and front-panel EQ style switching.
Sources (8)
- GUARDIAN of the WURM, KMA Machines
- KMA Machines introduces the Guardian Of The Wurm, a gated HM-2 style distortion, Guitar.com, 2021-07-15
- KMA Machines GUARDIAN of the WURM: For brutal high-gain distortion, gearnews.com, 2021-07-15
- Terror tamed: KMA Machines unleashes the high gain beast with Guardian Of The Wurm distortion pedal, MusicRadar, 2021-07-15
- Guitar Pedal X, Guitar Pedal X, 2023-11-17
- KMA Machines Guardian Of The Wurm, Delicious Audio, 2022-04-07
- KMA Machines Guardian of the Wurm Distortion / Noise Gate, Pedal of the Day, 2021-09-27
- KMA Machines reveals limited edition WURHM HM-2 tribute distortion pedal, MusicRadar, 2020-11-26
