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Overdrive1981· Boss / Roland (Japan)

Boss SD-1 Super Overdrive

Asymmetric-clipping cousin of the Tube Screamer — slightly more open and aggressive.

⏳
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

Same JRC4558D non-inverting op-amp gain stage as the TS-series, but the clipping diodes are asymmetric (two in one direction, one the other) which produces second-harmonic-rich, slightly more open clipping than the symmetric TS topology.

Signal chain preview

5 stages
Input
JFET input buffer
JRC4558D non-inverting op-amp gain stage (Gain pot in feedback)
Asymmetric clipping diodes to ground (1× 1N4148 one direction, 2× 1N4148 series the other)
Active tone control (Tone pot)
JFET output buffer
Output

Quick facts

  • First Boss pedal to use the asymmetric clipping arrangement later borrowed by countless boutique ODs.
  • Same tone-control filter as the TS-808/TS-9 — that classic mid-hump is still here.
  • Zakk Wylde stacks an SD-1 into a high-gain Marshall as his lead boost.

Controls

  • Level (100k audio)
  • Tone (20k linear)
  • Gain (500k audio)

Mod recipes Pro

3 mods
  • Symmetric clipping

    Turn it into a TS-style symmetric clipper for a smoother voice.

    How: Remove one of the series diodes so both legs of the clipping pair use a single 1N4148.

  • Keeley mod

    More low end, less mid-hump, cleaner clipping.

    How: Increase input cap C3 from 0.047 µF to 1 µF, output cap C5 to 1 µF, and swap clipping diodes for asymmetric Si + LED.

  • True bypass

    Eliminate JFET-bypass tone-suck.

    How: Rewire the input/output jacks through a 3PDT footswitch and lift the FET bypass switching.

References