BSM Black Box

The BSM Black Box is a treble booster and preamp pedal in one box, built by German maker BSM and released on 5 August 2020¹. BSM's manual describes it as "a flexible high gain treblebooster/ preamp combination optimized for medium humbucker pickups"². It is intended to hit the high treble input of a British Plexi-type amp, or other classic British oriented tube amps, hard², which places it in the same family of tools as the treble boosters players have used in front of Marshalls for decades.

Inside, the pedal is a two-stage design. The preamp stage is a mild, low-noise treble booster, followed by a high gain silicon output stage². BSM's product page describes the front end as a JFET preamp with some manipulation of the frequency response, and the output stage as a JFET circuit of highly particular design that operates with delicately adjustable overdrive and compression³. The result is a booster with overdrive capability rather than a clean volume lift alone.

What it does to your sound

The Black Box is a booster first and an overdrive second. BSM says that using the crunch control, the range extends smoothly from plain signal boosting into sweet overdrive³. Maximum gain is 46dB at 500Hz, and output can rise up to 15Vpp⁵, figures that matter most to players pushing an amp's input rather than running the pedal into a clean platform.

The pedal is optimized for medium humbucker pickups, but BSM says it also works very well with P90s and single coils⁵. Because it is a treble booster at heart, players with darker humbuckers get the most pronounced frequency shaping, while brighter pickups still work, just with the same high-frequency emphasis applied.

The controls: crunch and level

There are two controls, one for each stage of the circuit.

Because the two stages are controlled separately, BSM says you can dial in the amount of preamp drive independently of how hard you hit the amp. Announcing the pedal, the maker put it plainly¹³⁶:

BSM, 5 August 2020¹

For players who want a clean reference point, BSM gives a specific starting position: unity gain is achieved by dialing crunch to 10 and level to 12 o'clock⁵. From there, raising level pushes the amp harder, and raising crunch adds overdrive from the pedal itself.

Power: 9V to 18V

The Black Box is flexible about power. An internal 9V battery can run it, drawing approximately 3mA at 9V (5mA at 18V)⁵. Using the external DC jack, you can power the unit with 9 volts up to 18 volts for increased headroom and output⁵.

BSM describes the 18V setting as where the pedal becomes "a real monster," while admitting it still works very well with 9 volts, just a little less monstrous⁴. There is a practical caveat for pedalboard users: if you run other devices such as chorus or delay pedals in the chain behind the Black Box and in front of the amp, BSM says it is better to run the unit at 9 volts⁵.

History: Bernd C. Meiser and the Schaffer Vega concept

The Black Box was designed by Bernd C. Meiser, the designer behind BSM's booster line⁴. Its circuit concept traces back to the Schaffer Vega Diversity System, a wireless guitar system designed by Ken Schaffer and released in 1976 by the Vega Corporation⁸. BSM's earlier Black Box AY Special Booster came from Meiser taking the idea of a player using a Schaffer Vega wireless device not only live but also in the studio⁹.

For the Black Box, BSM was not interested in making a simple copy of the original circuit. The manual states the aim was "developing own ideas to realize the functions with silicon transistors"², so the pedal reproduces the concept of the Schaffer Vega's audio path with its own silicon transistor design rather than cloning it.

Where it sits among boosters

The Black Box is one of several BSM boosters aimed at players who want to drive a tube amp harder, alongside pedals like the BSM RPA Special Booster and the BSM RPA Full Quarter Booster. What separates it from a plain boost pedal is the two-stage architecture: the crunch control adds adjustable overdrive and compression from the pedal itself³, which puts its range into overdrive territory at higher settings while still working as a signal booster at lower ones.

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