The Pedal That Refused to Leave

Why one discontinued stompbox defined an entire recording scene — and why nothing else did the job

The Boss HM-2 Heavy Metal distortion pedal was discontinued in 1991. By that point it had already recorded itself into the foundations of Swedish death metal — not metaphorically, but literally into the tape of albums that were defining the sound of a generation of records. That the pedal stopped being manufactured precisely as its influence was peaking is one of the stranger industrial ironies in Nordic metal history.

Understanding why the HM-2 dominated requires a look at the specific settings documented on those recordings and the studio environment in which they were deployed. The short answer is: all four knobs turned to maximum, a setting so extreme that Boss had almost certainly not intended it. The longer answer involves the interaction between that setting, the particular gain staging in the pedal's circuit, and the way Sunlight Studio in Stockholm — specifically its Boss HM-2 units run into a Marshall or occasionally a Peavey amplifier — responded to that signal chain.

The circuit and the setting

The HM-2 runs a two-stage clipping circuit that, at maximum gain and maximum colour settings (the two tone-shaping knobs labelled Color A and Color B), produces a saturated, buzzing distortion with pronounced upper-mid content around two to four kilohertz and an artificially boosted low end. The result is what engineers working in the early 1990s sometimes called a "chainsaw" character — a description that subsequently became the standard shorthand for the entire Swedish death metal guitar tone.

At maximum settings across all four knobs, the pedal is feeding more signal into the amplifier than any conventional use case would ask for. The amp, already driven, then clips further. The two stages of clipping — pedal into amplifier input — create an intermodulation of harmonics that a single-stage distortion cannot replicate. This is documented in the technical assessments of producers and session engineers who later attempted to reconstruct the tone with other distortion sources. Other pedals, even those with higher gain ratings on paper, produce a different harmonic distribution. The HM-2's particular frequency emphasis in the mid-upper range combined with its compressed low end was a product of its specific op-amp configuration, not simply its gain level.

Tomas Skogsberg at Sunlight Studio recorded the HM-2 into the desk without additional equalization in many documented sessions. The room's relatively dry acoustic response meant the dense harmonic content of the pedal's output did not smear. Where other rooms might have needed EQ to manage the accumulated upper-mid energy, the signal chain at Sunlight sat in the mix with a directness that suited the tempo and register of the recordings being made. The studio environment and the pedal were, in retrospect, calibrated for each other — though that calibration was not planned.

After discontinuation

Boss ceased production of the HM-2 in 1991. The used market price, which had been negligible, began to rise once it became apparent that replacement units from Boss's current catalogue did not behave the same way. Subsequent Boss distortion designs used different internal architectures, and while the company eventually reissued the HM-2 in the Waza Craft series — a higher-specification reissue line — the Waza version was documented by users as capable of approximating but not fully matching the original circuit's behaviour in identical signal chains.

The secondary market response tells the fuller story. Unmodified original HM-2 units in working condition now trade at multiples of their original retail price. The pedal appears on equipment lists in liner notes and session documentation across a decade of Swedish death metal recordings, not as one option among several, but as the consistent, repeated choice. Labels compiling reissues in later years began noting the specific unit and settings in newly written liner documentation, because the signal chain had become part of the historical record of the releases.

Attempts to substitute the HM-2 in rerecording or live reproduction contexts have consistently returned to the original unit. Engineers working on documented remaster projects noted that equalizing alternative distortion sources to match the HM-2's frequency profile brought the result closer but could not replicate the dynamic compression behaviour of the original circuit. The chainsaw character is a product of a specific clipping architecture, not a frequency map, and an EQ cannot substitute for the second stage of the circuit.

The HM-2 was not a boutique unit. It was a mass-market Japanese-manufactured stompbox sold at entry-level price points throughout the 1980s. That it became the irreplaceable core of a distinct and documented recording aesthetic — through deliberate misuse of its controls rather than any orthodox application — is a small, solid piece of production history.