Electro-Harmonix Op-Amp Big Muff (V4)
Op-amp variant of the Big Muff — the Smashing Pumpkins 'Siamese Dream' wall of fuzz.
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
Instead of the four NPN transistor gain stages of the classic Big Muff Pi, the V4 (1978-81) uses two TL022 op-amp gain stages with hard-clipping diodes to ground after each. Combined with a different tone stack, the result is brighter, more aggressive, and more compressed than the transistor V1-V3 muffs — the 'Pumpkins muff' that Billy Corgan used on Siamese Dream.
Signal chain preview
6 stagesQuick facts
- Discontinued in 1981; the reissue 'Op-Amp Big Muff' (2018) faithfully recreated the V4 circuit.
- Billy Corgan stacked two of these into a Marshall for the Siamese Dream lead tones.
- Lacks the mid-scoop of the classic Muff — the op-amp variant has a flatter midrange.
Controls
- Volume
- Tone
- Sustain (gain)
Mod recipes Pro
3 mods- Mid scoop switch
Add the missing classic muff mid scoop.
How: Add an SPDT switch that places a 6.8 nF cap from the tone pot's wiper to ground — restores the classic V2-style mid notch.
- TL072 swap
Lower noise and slightly more headroom.
How: Replace TL022 with TL072 (drop-in pinout). Trim power-supply decoupling caps up to 100 µF since TL072 draws more current.
- LED clipping
Louder, more dynamic clip.
How: Replace one pair of diodes with red LEDs back-to-back — increases output ~+4 dB and opens the upper mids.