You may have heard that for a period of time in the 1970's, Electro-Harmonix changed the circuit of their legendary Big Muff Pi* from one based on discrete transistors to one based on integrated circuit operational amplifiers. This is true.

As a matter of fact, the opamp Big Muff Pi was the first fuzzbox I ever fell in love with, back in 1983. I didn’t know that it was an opamp one until I bought my own Big Muff and thought it sounded different from my friend’s. His later needed repair, and when I opened the case to check it out, I saw that the printed circuit board had a pair of integrated circuits on it, where mine had transistors.

Over the next 20 years, I never again encountered a Big Muff Pi made with opamps. Mike Matthews of E-H went out of business a couple of times, then got into the vacuum tube business, started making Big Muffs again, and then launched a new Electro-Harmonix with a mix of historical E-H effects and new ones. Still no opamp Big Muff Pi.

I myself started building and selling effects, helped greatly by the information available on the www, but when I tried building opamp Big Muffs from the schematics I found on the web, they didn’t work. Finally, I got my hands on an actual unit, and sat down with it to see if I could learn its secrets and make my own.