BSM Spectrum

The BSM Spectrum is a fuzz-booster pedal made by BSM, and the company describes it as a tribute to Tommy Bolin, the guitarist who joined Deep Purple after Ritchie Blackmore and who also played as a studio guitarist on Billy Cobham's 1973 jazz fusion album "Spectrum", the record that gives the pedal its name¹. It is a copy of the Sam Ash Fuzz that Bolin used, and it sits between a boost pedal and a fuzz in the way it behaves: one control moves the sound from a clean treble boost all the way to a full fuzz attack².

The heart of the pedal is what BSM calls the attack control, which "can smoothly blend from treble boost to fuzz"². With the guitar's volume control turned up to the max, BSM says the Spectrum produces a fat, biting and penetrating lead sound, minus any shrill characteristics, and that by lowering the guitar's volume control, many shades of crunch can be easily dialed in¹. That volume-knob responsiveness is the classic behavior of boost-style circuits: the pedal adds gain and character, and the guitar's own controls set how much of it hits the amp.

A fuzz-booster that blends from treble boost to fuzz

The Spectrum is not a pure fuzz in the modern sense. BSM builds it as a fuzz-booster, a circuit type descended from the treble boosters of the late 1960s and early 1970s, and the attack control is what lets one pedal cover that whole range. Rolled back it works like a treble booster, pushing the amp harder in the upper frequencies; turned up it becomes a fuzz, clipping the signal into a saturated lead tone².

BSM says the tone control on the Spectrum was expanded up to almost 6 octaves compared with the original circuit, which gives the player more room to shape where the boosted and fuzzed frequencies sit⁴. As with other boost-derived pedals, the intended way to work it is with the guitar volume: full up for lead, rolled down for crunch¹.

Power and connections

The Spectrum runs on a 9V battery, and it also accepts an external "Boss style" DC jack, meaning a 2.1mm plug with tip negative polarity². That is the same connector and polarity as the vast majority of 9V pedalboard power supplies, so it drops onto a powered board without an adapter cable.

Current consumption is listed at approximately 800 uA, a fraction of a milliamp². For comparison, most digital pedals draw tens or hundreds of milliamps; at 800 microamps the Spectrum is gentle on both a battery and a power supply. On the output side, BSM lists an average output level of 0dBm and a maximum output voltage of 2V when the strings are struck really hard¹².

The Sam Ash Fuzz behind it

The name ties the two threads together. BSM points to Bolin's guitar playing as a studio guitarist on Billy Cobham's "Spectrum" jazz fusion album from 1973 as the playing the pedal honors, while the circuit itself follows the fuzz he later used with Deep Purple¹. Premier Guitar made the same connection in its September 2007 review of four BSM pedals:

That review tested the Spectrum alongside the BSM HS-C, HS-S and FireBall, tracing their lineage to the Hornby-Skewes treble boosters associated with Ritchie Blackmore and to Bolin's Sam Ash Fuzz³.

Pickups and matching the pedal to a guitar

BSM designed the Spectrum for single coil or humbucking pickups with relatively low to medium coil inductance, and names Fender and Gibson style pickups as examples². Coil inductance affects how hot and how dark a pickup's output is; low and medium inductance pickups, typical of vintage-style single coils and PAF-style humbuckers, are the match BSM built the circuit around. The fat, biting lead sound the company describes is stated for that pickup type with the guitar volume maxed¹.

Players with questions about matching the pedal to their setup can contact the designer directly, at info@treblebooster.net or through the contact form on the BSM site¹.

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