EHX Big Muff Pi Replicas

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.   Note that:  Trademarks mentioned on this page belong to their owners and NOT to General Guitar Gadgets

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.


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.


Triangle Version

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.


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”. 


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.


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.


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.


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.


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.


NYC Version

Built after EHX returned fromn Russia to NYC, thus it’s name.


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 Sanford and Sonny called the Blue Beard bass distortion.  This “Tuned Version”  is  a replica using the same part values as the Blue Beard, but it is not a Blue Beard. There may be  tone differences due to the PCB layout and kit part selection.  This is an excellent distortion for bass or guitar or synth.


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.

BMP 80’s Tone Control Bypass Version Schematic


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.

Buy It

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.

 

Buy It


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.


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.

Buy It


 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.

Buy It