EHX™ Big Muff Pi™
An Electro-Harmonix™ Big Muff Pi™ Replica known as the BMP. This project covers most of the known transistorized versions of the BMP. The Big Muff OpAmp version can be found at the bottom of this page.
The documents in this first section are shared by all versions. All versions use the same PCB and the same wiring diagram. Parts layouts and schematics for each of the versions are listed as you go down the page.
- General Build Instructions
- BMP Instructions (voltage reading reference and photos)
- BMP Modification Ideas
- BMP Wiring Diagram
- BMP Ready-For-Transfer Printed Circuit Board Layout For use only if you are a complete DIY person who wants to etch and drill your own PCB. Otherwise, we recommend you ignore this PCB mask and buy the Ready-to-Solder Printed Circuit Board or Complete Kit from the links below.
A few words about the “Versions”
Each of these versions came about by someone tracing one of the factory units and creating a schematic of it. These versions are something like general “eras” in the history of the Big Muff Pi usually with a name based on the cosmetic features of the outside of the box. The original Electro-Harmonix factory had a history of using various components as availability of the components allowed, so there are likely to be some minor variations even within each of the versions. Additional traced units from some of the same versions may expose different transistor types used, or slightly different resistor or capacitor values in various locations of the circuit. We’ve tried to document as much as we can about versions and variations in this project, we may update as more information comes available to us.
Please note: Although some of the versions of the Big Muff had PNP transistor circuits with a positive ground (earth), all of these projects and all kit variations use NPN transistors with a typical negative ground circuit.
Named after the shape of the placement of the 3 knobs on the stompbox. This is the first BMP made. It had a slider switch to turn the power off and on, a feature that we are glad NOT to include in this project. Most of these produced probably had PNP transistors and the associated power reversals in the circuit.
- BMP Triangle Version Bill of Materials
- BMP Triangle Version Schematic
- BMP Triangle Version Parts Layout
Ram’s Head Version
Named after the old EHX logo of a ram’s head that was featured on the top of the stompbox. Many of these also contained PNP transistor circuits. This version also had a slider switch to turn the power off and on but it was placed on the front of the stompbox instead of the top like the “triangle version”.
- BMP Ram’s Head Version Bill of Materials
- BMP Ram’s Head Version Schematic
- BMP Ram’s Head Version Parts Layout
Violet Ram’s Head Version
Named again after the old EHX ram’s head logo and the screen printing on the stompbox was of a violet color powder coat.
- BMP Violet Ram’s Head Version Bill of Materials
- BMP Violet Ram’s Head Version Schematic
- BMP Violet Ram’s Head Version Parts Layout
Late 70’s Version
This version doesn’t really have a recognizable version name. It is sometimes call the “3rd” version. Cosmetically it looks like the USA reissues with the same red and black screen print art work.
- BMP Late 70’s (3rd) Version Bill of Materials
- BMP Late 70’s (3rd) Version Schematic
- BMP Late 70’s (3rd) Version Parts Layout
Civil War Russian Version
Built in Russia and featuring a funky font and graphics on the stompbox that must have reminded someone of the kind of print used at the time of the American Civil War.
- BMP Civil War Russian Bill of Materials
- BMP Civil War Russian Version Schematic
- BMP Civil War Russian Version Parts Layout
Green Russian Version
Built in Russia and looking like some sort of army surplus gadget. “Army” green color enclosure and a huge button footswitch. When this version hit the scene, the BMP made a huge comeback in popular music.
- BMP Green Russian Bill of Materials
- BMP Green Russian Version Schematic
- BMP Green Russian Version Parts Layout
Black Russian Version
Built in Russia and sporting a more typical stompbox look (compared to the Green Russian). The black enclosure give it it’s name.
- BMP Black Russian Bill of Materials
- BMP Black Russian Version Schematic
- BMP Black Russian Version Parts Layout
GGG Tuned Version
This is sort of a blend between the Violet Ram’s Head version and the Late 70’s (3rd) version. More of an overdrive sound to it than the thick fuzz than some versions have.
Note: GGG was involved with building a pedal by Sandford and Sonny called the Blue Beard bass distortion. This “Tuned Version” is somewhat similar to the Blue Beard, but it is not a Blue Beard. There are some subtle differences in the tone and it is in a smaller box. This is an excellent distortion for bass or guitar or synth, but this project should not be considered a kit for a Blue Beard pedal.
Here’s a schematic of the early 80’s version with a tone control bypass switch. This version is not necessarily covered in this project, but you may be able to work it into the project with a little ingenuity. The tone control bypass might be very useful if you wanted to follow the BMP with the EQ pedal of your choice. This is always a great way to increase the flexibility and fine tune the tone of any distortion pedal.
Buy a BMP Complete Kit. Includes all the parts and materials you need to build one, all for about the price you would pay for a PCB and parts.
The following versions can be built with the kit. All parts are included for any of these versions!
Would you like a Ready to Solder Circuit Board for this project? Note: If you buy the kit, the Ready-to-Solder Circuit Board (RTS PCB) is included in the kit. You do not need to purchase this RTS PCB if you buy the kit.
Big Muff OpAmp Version
This is the Big Muff based on opamps instead of transistors. This is a completely different circuit from the other versions. It requires a completely set of components and component layout.
- General Build Instructions
- OpAmp BMP Bill of Materials
- OpAmp BMP Schematic
- OpAmp BMP Parts Layout and Wiring Diagram
- OpAmp BMP Ready-For-Transfer Printed Circuit Board Layout For use only if you are a complete DIY person who wants to etch and drill your own PCB. Otherwise, we recommend you ignore this PCB mask and buy the Ready-to-Solder Printed Circuit Board or Complete Kit from the links below.
Buy a BMP Opamp Version Complete Kit. Includes all the parts and materials you need to build one, all for about the price you would pay for a PCB and parts.
Would you like a Ready to Solder Opamp version Circuit Board for this project? Note: If you buy the kit, the Ready-to-Solder Circuit Board (RTS PCB) is included in the kit. You do not need to purchase this RTS PCB if you buy the kit.