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Electro-Harmonix Op-Amp Big Muff Review

Since their inception in 1967, Electro-Harmonix (EHX) has etched its name as a pioneer in the realm of effects pedals, garnering acclaim by groundbreaking musicians across various music genres.

In 1978, EHX briefly introduced what was known as their IC model (or ‘Version 4’) that switched the design of its Big Muff Pi from its traditional four-transistor circuitry over to one based around op amps (integrated circuits) and with one less gain stage. Only a few thousand of these fuzz pedals were made, and production soon passed back to transistor circuitry.

That version may have remained in obscurity were it not for the fact Billy Corgan used it on the Smashing Pumpkins’ 1993 Siamese Dream album to sonically shape their psychedelia-meets-rock vibe (hear one of the songs of it). Until now, anyone wanting to capture that tone would have had to hunt down one of these rare variants. Thankfully, EHX has released a new version that captures the essence of the late-’70s V4 IC Big Muff.

And here it is:

Save $31.70
Electro-Harmonix Op Amp Big Muff Pi Fuzz Pedal
  • Iconic sound and vibe that’s coveted by guitarists
  • Controls for Tone, Sustain and Volume, plus a Tone Bypass switch
  • True bypass switching for maximum signal integrity in bypass mode


Designed in a nano-sized form, this pedal maintains the Big Muff’s classic trio of Volume, Tone, and Sustain controls, alongside a switch that bypasses the tone control.

  • Controls: Volume, Sustain, Tone, Bypass Switch, Op-Amp Selector
  • Power: 9V battery or external supply (not included)
  • Size: 70 x 115 x 54 mm
Electro-Harmonix Op Amp Big Muff Pi Fuzz Pedal


It delivers the renowned fusion of fuzz and distortion revered by Big Muff enthusiasts. However, the sound expression obtained from this integrated circuit model imparts a distinctively rough texture, suitable for both solid riffing and dense rhythmic sessions.

While exploring the pedal’s tonality, you’ll find that adjusting the tone control can produce a whole array of different sounds. Some extreme settings might yield too aggressive or muted tones, but nestled within the control’s rotation are sweet spots that facilitate the crafting of an edgy presence or bold, unfiltered tones that penetrate through any mix. It has more a pronounced midrange and enhanced clarity than the original Big Muff Pi.

Electro-Harmonix Op Amp Big Muff Pi Fuzz Pedal

It suits various playing styles and exhibits a versatility that exceeds genre boundaries, bringing the classic Big Muff identity into today’s pedalboard setups. It adeptly reproduces the fuzzy warmth of classic rock and accommodates the drive required for modern genres. Not confined to a niche, it transcends expectations with its distinctive presence in any musical mix.

Bottom Line

  • Reimagining of a classic and exclusive Big Muff IC variant
  • Compact size suitable for constrained pedalboards
  • Genuine bypass functionality
  • Additional Tone Bypass option augments sound versatility
  • Cost-effectiveness

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About Ged Richardson

Ged Richardson is the Founder and Editor-in-Chief of ZingInstruments.com. He has been featured in Entrepreneur, PremierGuitar, Hallmark, Wanderlust, CreativeLive, and other major publications. As an avid music fan, he spends his time researching and writing about new and old music, as well as testing and reviewing music-related products. He's played guitar in various bands, from rock to gypsy jazz. Be sure to check out his YouTube channel, where he geeks out about his favorite bands.

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