The KMA Machines WURHM is a limited-edition distortion pedal from German effects firm KMA Audio Machines, announced in November 2020 as a tribute to the Boss HM-2 Heavy Metal12. It is a version of KMA's own Wurm distortion, restyled in a black-and-orange enclosure that references the HM-2's original color scheme, and produced in a run of just 200 units13.
KMA described the pedal in its own words as an homage taken further than the original4:
"our WURHM Distortion is our unabashed sonic love letter to this filthy box of doom and gloom, but taking it much further"4
What it does: a Boss HM-2 tribute
The Boss HM-2, made by Boss, is what Delicious Audio called "a cornerstone (or rather a cornerTONE!) high-gain distortion for many guitarists into metal"5. Its signature is an active EQ that can boost or cut mids through the H (high) Color Mix control, and its circuit has become known as the "Chainsaw Distortion" sound6. Producer Tom Dalgety, interviewed by BOSS, noted the HM-2's range extends beyond full gain: "I like using the HM-2 as a mild overdrive."7
The WURHM arrived at a moment when the original HM-2 was long out of production and players were waiting on a reissue. MusicRadar reported that "KMA Machines revealed a limited edition tribute, the WURHM HM-2" in that context2, and Guitar World framed it as a pedal that "could fill the void" for players who could not wait for a Boss HM-2 reissue2. Boss later brought the HM-2 back as a Waza Craft reissue with a mode toggle switch offering the classic tone or a custom mode8.
Controls and modes
The WURHM carries volume and Terror (aka distortion) knobs, alongside its EQ section1. Its central feature is a choice of voicings: players can switch between the original HM-2 high control and EQ bands designed by KMA Machines9. Delicious Audio's coverage describes the KMA mode as a "H-MIDS EQ with adjustable centre-frequency (read, parametric EQ)" in the pedal's successor, the Wurm 210.
For deeper tweaking, each EQ band has an internal trim-pot to change its center frequency, and internal DIP switches provide further tone options91.
| Control or feature | What it does |
|---|---|
| Volume knob | Sets output level1 |
| Terror (distortion) knob | Sets gain1 |
| EQ mode switching | Chooses between the original HM-2 high control and KMA-designed EQ bands9 |
| Internal trim-pots | Change the center frequency of each EQ control1 |
| Internal DIP switches | Additional tone-shaping options9 |
Limited edition and relation to the Wurm
The WURHM is a limited edition of KMA Machines' Wurm distortion, launched with what Guitar.com called "the new orange-and-black colour-scheme the Wurhm finds its terrifying, toothy artwork decked out in"3. Only 200 units were created and available in this finish93. Every purchaser could claim a free limited-edition WURHM T-shirt93.
The WURHM was a limited edition of 200 units in its black-and-orange finish, announced in November 2020. It has since been succeeded in the KMA lineup by later pedals.
What came after it
The WURHM did not stay in the lineup for long. Gearnews reported in July 2021 that KMA Machines' new GUARDIAN of the WURM "takes off where the Wurhm left off"11, with MusicRadar noting it followed "the trail of the KMA Machines WURHM Special Edition HM Distortion late last year"12. In March 2022 KMA released the Wurm 2, a smaller, top-jack version of the WURHM with an enhanced four-band EQ based on the Boss HM-2 circuit, relay-based silent switching and an external voice switch1310.
Videos
Dome
Questions
How many WURHM pedals were made?
KMA Machines produced 200 units of the WURHM in its black-and-orange finish. The pedal was positioned as a limited edition from the time it was announced in November 2020, and no further units in that finish were planned.
Does the WURHM come with a T-shirt?
Yes. Every purchaser of a WURHM could claim a free limited-edition WURHM T-shirt from KMA Machines. The offer was promoted alongside the pedal's launch as part of the limited-edition package.
What is the difference between the WURHM and the Wurm?
The WURHM is a limited-edition version of KMA Machines' Wurm distortion, finished in black and orange as a nod to the Boss HM-2's original color scheme. It also adds switchable EQ modes and internal trim-pots and DIP switches for extra tone shaping beyond the standard Wurm.
What replaced the WURHM in the KMA Machines lineup?
The GUARDIAN of the WURM, released in 2021, took off where the WURHM left off, followed by the Wurm 2 in 2022, a smaller version with relay-based silent switching, top-mounted jacks and an expanded four-band EQ.
Sources (13)
- Can't wait for the Boss HM-2 reissue? KMA Audio Machines' WURHM could fill the void, Guitar World, 2020-11-26
- Boss is bringing the HM-2 Heavy Metal back from the dead as a Waza Craft reissue, MusicRadar, 2020-11-26
- KMA Machines launches the limited-edition Wurhm, bringing a classic colour-scheme to its death metal chainsaw machine, Guitar.com, 2020-11-27
- KMA Machines WURHM Orange Terror Distortion (WURM Custom Version), Delicious Audio, 2021-01-13
- Bardic Audio Devices HM Demon, Delicious Audio, 2022-01-28
- TONEHOME, TONEHOME
- Behind the Board: Tom Dalgety with Ghost, Pixies, Royal Blood, and The Cult, BOSS (articles.boss.info), 2024-09-04
- 13 Best Distortion Pedals For 2026 (Top Picks), Tone Island (toneisland.com), 2026
- KMA Machines reveals limited edition WURHM HM-2 tribute distortion pedal, MusicRadar, 2020-11-26
- KMA Machines Wurm 2 Distortion, Delicious Audio, 2023-01-10
- 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
- KMA Machines WURM 2 Distortion, gearnews.com, 2022-03-29
