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EHX Op-Amp Big Muff - The Pumpkin Pi Review

Updated: Apr 4, 2022

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The #ElectroHarmonix reissue of their 1977-1978 Op-Amp based #BigMuff is a great box whose huge, raucous tones belie its pedalboard friendly size.

The #OpAmp reissue pays homage to Billy Corgan, who - with The Smashing Pumpkins - made this pedal so desirable, and includes some additional features to bring it into the new century.

So, what's an op-amp anyway?

When this version originally came out, op-amps were used instead of transistors, mainly for financial reasons. These are basically small integrated circuits that put out a massively larger signal than that which is fed in, thus resulting in distortion. The pedal also had only three gain stages instead of the standard four that the transistor Muffs had used. These changes meant that this version had a noticeably different sound, which made it pretty unpopular on first release and is why the version was only around for a year or so.

Why the reissue?

Scroll forward to 1993 and #TheSmashingPumpkins' release of #SiameseDream and suddenly the Op-Amp pedal was all the rage and in demand for its unique sound.

The combination of huge demand and very little supply, the pedals having only been built for around a year, led to them fetching a very high price, and this is the reason #MikeMatthews has given for remodelling and re-releasing the pedal - so the average Joe like you and I can afford one. And for only £75 new or around £50 used on different online auction sites, it's a pedal well worth trying out.

The original was similar to other Big Muffs in that it was pretty unwieldy - large and heavy. The new rendition though has rectified that. It's snugly housed in a standard MXR-sized enclosure, has an LED and takes a standard 9v centre negative adapter as well as being true bypass.

Now things don't get much more pedalboard friendly than that.


If you're familiar with a Big Muff you won't be surprised by the layout. There are three main dials - Volume, Sustain and Tone. Volume is the overall level of the output, Sustain is the amount of drive/distortion, and Tone is, well, the tone...

The interesting addition to the Op-Amp version is the Tone Bypass switch, which bypasses the tone stack.

In Use

I fired up this beauty with a Two Rock Studio Pro 35 with a matching 2x12 cab mic'd with an industry standard Shure SM57. The guitar was a Fender Telecaster with #Bareknuckle pickups.

I was initially slightly surprised by the aggressive sound of this pedal. It certainly does sound different to traditional Big Muffs and I wasn't sure what to make of it. I guess this was similar to the feeling that people had back in '77-'78. However, within a few minutes not only did I feel pretty comfortable with the sound, I found it very inspiring. The rough edges and huge sound made me play more aggressively than I might normally and I ended up with a track that I just wouldn't have played without using this great pedal. And isn't that what we all want from new gear - something that inspires us to play, that takes us effortlessly into new sonic territories?

With the Sustain at minimum, the Op-Amp provides us with a very useable bluesy tone with a crunch around the edges, it never gets truly clean of course but dialling back on the guitar volume knob gets us almost there. As we increase the amount of Sustain the pedal starts roaring into life. It's very organic and open sounding and feels more like an overdrive at times than the fuzzy goodness one might expect from a Muff, a definite crunch going on.

The tone control sweeps through a wide enough range to be able to find sweet spots with any guitar and the tone bypass switch adds in a bit more snarl. To me it sounds more open with the tone stack in the circuit, but having the extra sonic option is great for a different texture.


If you want to add some animalistic grunt to your board, you can't go wrong with this pedal. Keep in mind that it won't sound the same as some other Muffs, so if you're after Gilmour-like tones, this one isn't for you - check out the Triangle reissue. However, if you check out the video link at the start of the article, you'll get a good idea of the sounds available.

I can tell you this, the Op-Amp reissue is a fire-breathing beast of a pedal perfect for aggressive, wall of noise textures and tones, and it is inspiring to play. I've got mine, and it's staying.

Also, take a look at this video to get a comparison of the Russian, Triangle and Op-Amp pedals:

Check it out on the EHX site:

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