The BSM RM Metal Treble Booster is a treble boost pedal from BSM, a German builder of booster and treble booster pedals. It is based on the British Range Master unit produced between 1965 and 1969, and BSM describes it as a modified '69 RM model like Mr. Iommi's unit, a reference to the Range Master-style booster Tony Iommi is associated with. The circuit includes the same germanium transistors as the original 1965 version.1
BSM says the RM and the RM Metal produce, with the volume control of the guitar turned up to the max, "a fat, biting and penetrating lead sound, minus any shrill characteristics".1 Like other treble boosters, it is meant to sit between guitar and amp and push the amp's input stage, not to be used as a standalone clean boost.
Placement and power
The manual is explicit about where the pedal goes: "The Treble Booster is inserted between guitar and amplifier, not into the FX loop".1 That is standard practice for treble boosters, which are designed to overdrive the amp's front end rather than to feed a loop return.
The manual states: "Note: The positive pole of the battery is ground". Positive ground is typical of germanium circuits, and it means the RM Metal should not be daisy-chained from a standard center-negative pedal supply. Power it from its 9V battery or from an isolated output rated for positive ground.1
The unit is powered by a 9V battery with a current consumption of aprox. 250 µA, a very small draw by pedal standards.1
Specifications
| Specification | Value |
|---|---|
| Circuit basis | British Range Master, produced 1965 to 19691 |
| Transistors | Germanium, same as the original 1965 version1 |
| Power | 9V battery, positive ground1 |
| Current consumption | aprox. 250 µA1 |
| Average output level | 10dBm1 |
| Max output voltage | 7V max, when the strings are struck really hard1 |
| Placement | Between guitar and amplifier, not into the FX loop1 |
| Made in | Germany1 |
Pickups and output
BSM designed the RM Treble Booster specifically for pickups with a relatively low or medium inductance. The manual names1:
- Single coil pickups
- Humbucking pickups
- Examples: pickups in Fender, Gretsch, Burns or Gibson guitars1
Two output figures from the manual give a sense of what the amp receives: the average output level is 10dBm, and the maximum output voltage when the strings are struck really hard is 7V max.1
Where it sits in BSM's range
The RM Metal is one of several Range Master-based designs from BSM, alongside the BSM RM Treble Booster, the BSM RM Early Days Treble-Booster and the BSM RM Velvet Treble-Booster. Players after a clean level lift from the same family can look at the BSM RMG Clean Boost, and the BSM HS-S Treble Booster covers a different vintage booster design.
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Questions
Does the BSM RM Metal Treble Booster go in the effects loop?
No. BSM's manual states that the treble booster is inserted between the guitar and the amplifier, not into the FX loop. Like most treble boosters, it is designed to drive the front end of a tube amp, where the boosted signal interacts with the amp's input stage, rather than sitting after the amp's preamp and effects loop.
Does the BSM RM Metal Treble Booster use germanium transistors?
Yes. According to BSM, the RM Metal includes the same germanium transistors as the original 1965 version of the Range Master circuit that the pedal is based on. Germanium transistors are part of what gives the pedal its vintage-style treble boost character.
What does positive ground mean on the BSM RM Metal Treble Booster?
The manual notes that the positive pole of the battery is ground. Positive ground is common in germanium transistor circuits and means the pedal cannot share a standard center-negative daisy-chain supply with typical pedals without risk of a short. Power it on its own, or use an isolated supply output that supports positive ground.
Which pickups is the BSM RM Metal Treble Booster designed for?
BSM designed the RM Treble Booster for single coil and humbucking pickups with relatively low to medium inductance, such as the pickups found in Fender, Gretsch, Burns or Gibson guitars. Pickups in that range leave the treble boost with the right amount of top end to work with.
Where is the BSM RM Metal Treble Booster made?
The RM Metal Treble Booster is made in Germany, according to BSM's product documentation.
Sources (1)
- Neutral_neu, treblebooster.net, 2025
