BSM RPA California II Special Booster

The BSM RPA California II Special Booster is a treble booster stompbox from German maker BSM. It emulates two pieces of Ritchie Blackmore's Deep Purple Mk3 live setup from 1974 in one pedal: the preamp stage of the AIWA TP-1011 tape echo unit, which Blackmore used as a booster, and the treble boost, technically a highpass function, that was built into his heavily modified Marshall Major 200 amp¹².

BSM describes the design goal in its own words: rather than only emulating the AIWA preamp stage, the pedal also integrates the important highpass function with the original cutoff frequency¹. The result is a booster aimed squarely at players chasing Blackmore's Mk3-era tone, from the raw and fat sound of the April 1974 "California Jam" recordings to the biting, piercing treble with tight bass of the "Live in London" period later in the Mk3 era¹.

Where the circuit comes from

The RPA California II traces directly to Ritchie Blackmore's rig. In his Deep Purple Mk3 live setup, he ran the AIWA TP-1011 echo unit's integrated microphone preamp as a booster into his modified Marshall Major 200, whose treble boost, a highpass function, shaped the final tone². BSM's founder, Bernd C. Meiser, had already explored this territory with the BSM Custom TP-1011, which was expanded with the second Marshall factory mod as well as an additional sound switch⁵.

The RPA California, the pedal this model grew out of, emulated both sound-shaping functions in one stompbox, which BSM called another BSM first⁶. The California II was announced as a companion rather than a replacement, and BSM's news page reported it as finally released on 24 August 2016³.

Controls

The pedal keeps things to two knobs.

The Volume knob is the core of what a treble booster does: it sets how hard the amplifier's input stage is driven. The Presence control is not a simple tone cut. In BSM's description it governs saturation and dirt, so it shapes the character of the drive rather than just the brightness¹.

Power and output

The unit runs on a 9V battery with a current consumption of approximately 400 µA¹. At that draw, a battery lasts a very long time. Because of the external DC jack, you can also power the RPA California II with 9 volts from a supply¹.

On the output side, the maximum output voltage when the strings are struck really hard is 7V max¹. That is a hot signal, enough to push an amp's first tube well into saturation, which is the intended use.

How it differs from the RPA California

BSM positions the California II as a sibling, not a successor. The company describes it as "the soul-mate of our California unit, complementing it with a different goal in mind," namely mapping Blackmore's tone even with small amps⁷. Where the original RPA California has an EQ control for tonal fine tuning with different pickups, amps and speakers, with a sweet spot between 12:00 and 03:00 depending on the pickups², the California II instead adds a volume control²⁶⁸. BSM also notes that the new RPA California II "now calls for the correct pickups"⁷, so the two pedals suit different setups rather than different quality levels.

Both pedals share the same placement rule: inserted between guitar and amplifier, not into the FX loop⁴. A treble booster works by hitting the amp's input tube hard, which an FX loop cannot do.

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