’78 Electro Harmonix Op Amp Big Muff – V4 (EH 1322)

1977-1978 ‘Op-Amp’ Big Muff Pi . Hugely sought-after & very rare, this late ’70s fuzz is most known for being favoured by legendary Smashing Pumpkins guitarist Billy Corgan.

These EHX Big Muff’s are often confused for 1977 models (Big Muff V3) due to the pot dates and murky history of parts use over at the factory. This one, sporting a EH 1322 PCB, features the pre 1978 knob layout with infamous ‘On / Off’ switch at the top of the unit instead of the more commonly seen ‘Tone Bypass’ switch at the time.

Supposedly only a few thousand of the EHX BMP V4s were ever made, making it one of the rarest types in circulation. Even fewer were made during this transitional phase from 1977 to 1978 where attributes of both are shared in a singular unit. The Volume pot dates to November 1977 and tone and gain pots date to December 1977.

Battery use has been disabled however a quick solder blob can do (we can do this for you free of charge upon purchase – we’ve just kept it in the condition that it’s come in). Factory centre positive pin socket has been replaced with standard BOSS-type centre negative tip socket.

On / Off Switch has been replaced long ago and new one now functions in reverse.

All in all the V4 is an iconic unit loved by some of the most legendary tonal-sculptors in music history; from it’s quintessential red and black graphics, the big Daka-Ware knobs and it’s ferocious, ripping chainsaw sound. A classic Muff indeed!

Made in USA.

Video: https://youtu.be/8wM-0Cbk5-0?t=345

Product Specs

• Item Number: 25648
• Make: Electro Harmonix
• Model: Op Amp Big Muff Pi
• Condition: Very Good
• Finish: Silver
• Categories: effects-and-pedals fuzz pedal
• Year: 1977-1978
• Made In: United States
• MPN: 25648