PEDAL BENCH
by Stompbox Labs
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Boost1970· Sola Sound / Colorsound (UK)

Colorsound Power Boost

Two-stage silicon boost with treble/bass tone — David Gilmour's 'Animals' lead voice.

⏳
Schematic pending verification

We don't ship reference schematics until they've been hand-authored against authoritative sources (manufacturer service docs, ElectroSmash analyses, GEOFEX writeups) and reviewed in the simulator. Until then, the BOM, signal chain, controls and mod notes below are accurate, and you can still add this pedal to a project — it just won't include a circuit yet.

About

A two-stage BC184 silicon clean(-ish) boost with active Baxandall-style bass and treble controls and up to +30 dB of gain. Pushed into a Hiwatt or Marshall, it overdrives the amp into singing sustain. Gilmour's 'Dogs', 'Pigs', and much of 'Animals' (1977) used a Power Boost into his Hiwatt rig.

Signal chain preview

5 stages
Input
Input AC coupling
Q1 BC184 NPN common-emitter gain stage
Active Baxandall-style 2-band tone stack (Bass and Treble cut/boost around 1 kHz)
Q2 BC184 NPN common-emitter gain stage / recovery
Master volume
Output

Quick facts

  • Originally sold as the 'Sola Sound Power Boost' (18 V version); Colorsound rebranded it in 1973 as a 9 V unit.
  • The Pete Cornish modified Power Boost in Gilmour's rack is one of the most copied boost circuits ever.
  • Modern reissue (Colorsound Power Boost) is faithful to the late-'70s 9 V circuit.

Controls

  • Volume (10k log)
  • Bass (250k linear)
  • Treble (250k linear)
  • Master / Boost

Mod recipes Pro

3 mods
  • 18 V supply

    More headroom, more dynamic response, Gilmour-spec.

    How: Feed from 18 V DC. Replace all electrolytics with ≥25 V parts and verify both transistors stay below their Vceo max.

  • Mid control

    Add a third band for mid-cut or mid-boost.

    How: Insert a Wien-bridge mid stage between Q1 and the Baxandall network, with a 10k linear pot setting Q.

  • Clipping diodes (optional)

    Turn it into a soft-clipper.

    How: Add 2× 1N4148 back-to-back from Q2's collector to ground via a 10k series resistor, switchable on the enclosure.

References