PEDAL BENCH
by Stompbox Labs
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Overdrive1994· Bill Finnegan (USA)

Klon Centaur

Mythical 'transparent' overdrive — clean blend, charge-pumped headroom, and a price tag to match.

⏳
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 dual op-amp design that splits the input into a clean path and a clipping path, summing them at the output. A pair of germanium diodes (1N34A) clips the drive path while the clean path preserves attack and dynamics. An internal voltage doubler (MAX1044 charge pump) runs the op-amps on ±9V for unusual headroom.

Signal chain preview

6 stages
Input
Input buffer (op-amp half)
Gain pot splits signal into clean path + clipping path
Clipping path: op-amp gain stage → 1N34A germanium diodes to ground
Clean path runs in parallel through a fixed gain
Active summing op-amp mixes clean + dirty
Treble pot, then output buffer
Output

Quick facts

  • Famously 'transparent' because the clean blend always carries the original signal underneath the drive.
  • Uses germanium 1N34A diodes — the 'magic' part, but well-matched modern subs sound nearly identical.
  • Internal MAX1044 charge pump doubles 9V to ~18V across the op-amps for extra headroom.
  • Original Centaurs sell for thousands; the KTR reissue and clones (Tumnus, Soul Food, Archer) made it accessible.

Controls

  • Gain (dual-gang 100k)
  • Treble (10k linear)
  • Output (10k linear)

Mod recipes Pro

3 mods
  • Silicon diode swap

    Tighter, more compressed clipping with more output.

    How: Replace D1/D2 (1N34A) with matched 1N4148s. Brighter, less 'open' but more pedalboard-friendly.

  • Extra headroom (24V)

    Even more clean blend authority for amp-pushing duties.

    How: Feed the pedal from an 18V DC supply; the internal charge pump will give ~36V across the rails. Verify op-amp ratings (TL072 maxes at ±18V supplies — substitute OPA2134 for safety).

  • Bass mod

    Restore low end lost on bass guitar or baritone.

    How: Increase the input AC-coupling cap from 0.1 µF to 0.47 µF and the clean-path coupling cap proportionally.

References

Community-sourced (ElectroSmash, FreeStompboxes Klon thread). Diode matching is critical.