Operational Muff – Eagle and Gerber Files

Product Format Clarification

This product includes digital design files only — no physical PCB is shipped.

With these files, you can order PCBs directly from a manufacturer (e.g., JLCPCB, PCBWay) for as little as $2 for 5 boards.
Typical production time is 3 days, and international shipping starts at $12, taking about 4 days via DHL to most locations.

You’re free to edit the design and add your own branding.

Upon Purchase, You’ll Receive:

• Eagle CAD files (.SCH & .BRD) — fully editable and compatible with KiCad

• Industry-standard Gerber files for PCB fabrication

• Quick-start guide explaining how to use the files

• Download link for the free version of Eagle CAD

After purchase, you will receive a payment link by email. Once the payment is completed, the design files will be sent to you within 8 hours. We’re currently working on automating this process, but for now, orders are handled manually.

Note: You must use these files with a PCB manufacturer to produce your boards.
No pre-assembled or pre-made circuit boards are included.

These design files are intended for personal use and small production runs of your own pedals, not for resale as kits or standalone PCBs.

Project Overview

With authentic late-70s Op-Amp Big Muffs selling for absurd prices on the vintage market, Mike Matthews decided to take the power to the people and reissue this classic pedal at a price that players could actually afford!

We wanted to go a step forward by allowing anyone to build their version of the Op-Amp Big Muffs.

Now you can get all the classic sounds that made this pedal so popular without having to break the bank.

Introduction

Ready to make your tone muffin-style? Inspired by Op-Amp Big Muff Pi, we made the Operation Muffin, a true bypass pedal that faithfully recreates the classic circuitry of the original while adding enhancements for a modern sound.

This is the sound of rock and roll. In 1993 the Op-Amp Big Muff was popularized by Billy Corgan on his masterpiece Smashing Pumpkins album Siamese Dream. Since then, it has become one, if not the most, iconic fuzz sound ever created!

This pedal leans on op-amps instead of the usual transistors and three gain stages rather than four to create its signature sound.

It has controls for Tone, Sustain, and Volume, plus a Tone Bypass switch and a true bypass switching for maximum signal integrity in bypass mode, all while fitting in a practical 125b enclosure.

I could write a lot o content describing the Op-Amp Big Muff Pi sounding, but it’s better to quote the historian Kit Rae, one of the biggest Muff collectors of all time:

“A huge, crushing Big Muff sound with more crunch… 

great for grungy,

 wall-of-sound distortion, 

heavy rhythm playing, 

and heavy leads.”

Controls

Potentiometers

• Sustain
• Tone
• Volume

Switches

• Tone Bypass

For any technical questions regarding this build don’t forget to check out our Facebook Group and our forum at Free Stomp Boxes.

Operational Muff – Building Docs

Operational Muff – Drilling template