WHY ARE THE TRANSISTORS LABELED IN THE REVERSE ORDER? - Note that Q1-Q4 and D1-D4 are labeled in reverse order from input to output on these schematics, the reverse of what they they are on a typical schematic. This is due to the fact that they are printed in this order on the actial V1, V2, and V3 Big Muff PCB's. To keep it from being confusing for those reading their PCB's, since this site originated primarily as a reference for vintage Big Muff owners, and to keep the EH tradition, we have used this order on all Big Muff schematics, including post 1980's Big Muffs. If you are just making a clone and your brain can't handle this, don't cry, just reverse the number order. I have also tried to keep the cap and resistor part numbers consistent from schematic to schematic.

DON'T ALL BIG MUFFS SOUND THE SAME? - Some do, and many do not. The BMP circuit is very forgiving of minor value changes, so some of these variants do not sound significantly different from one another, but others sound very different. Using a clean amp with lots of head room and single coil guitar pickups (my preference) will allow you to clearly hear the differences in the variants and clones. Using humbuckers through a dirty amp will tend to make many of these sound similar, since a dirty amp will color the tone of the distortion.

VERSIONS are typically defined by enclosure changes or major color and graphics changes. Within each version are numerous circuit VARIANTS, each with unique sets of component values and types. These variants were each made in large production runs. Determining the release year order was based on pot dates, circuit board colors and markings, component types, differences in enclosure graphics, rubber foot styles, knob styles, advertising dates, and other features. Examining each of those gives a clear chronology. For a mostly complete rundown on the release dates of the Big Muff variants, visite the Fuzz and Muff Timeline page.

WHY DID ELECTRO-HARMONIX CHANGE THE PRODUCTION SCHEMATIC SO OFTEN? - There are many reasons, but the simple answer seems to be, to fit the parts on hand at the time. Caps and resistors were bought in bulk, and exact values from batch to batch varied. For example, if 500pF caps were not available, 560pF caps were substituted, and other related cap and resistor values tweaked in an attempt to keep a similar sound. If there was a surplus of 33k resistors, you may see them used in R2, R5, R8, R13, and R11 positions. The next run could change to 27k. Basically, wherever there were changes they could get away with and not drastically affect the sound, they did it, but often these changes did affect the sound. There were hundreds to thousands of each variant circuit made, at least until the next bulk purchases required the schematic to be tweaked again for the next production run. At other times the schematic was intentionally changed specifically to revise or update the sound.

If you are a do-it-yourself home tinkerer, the best way to try out the different versions and mods is to socket everything so you can trade out different caps and resistors. Each of these schematics have been double checked, and most are verified, but I don't guarantee each one is absolutely perfect. If you spot a mistake, or know of another unique variant or would like to contribute to The Big Muff Page, email me: nasnandos @ kitrae.net.

REPAIRS - Since there were so many variant schematics used that are similar to others, I have not shown every one in this article. I do have practically every schematic however, so if you are making a repair and need to verify a component value, email a photo of the circuit, say please, and I can email you the schematic for that variant: nasnandos @ kitrae.net.

This article is for educational purposes, as a reference for repairs, to show a history of the circuit changes throughout the years, and offer up some of the more interesting and inventive changes the DIY community and cloners have done with the circuit that you home tinkerers may try. Production or boutique clones of the BMP circuit that have been off the market for a long while, or that use commonly known mods, are open game for anyone to post schematics as far as I am concerned. For current clones still in production, I have tried not to post the entire schematics, just the Big Muff part of the circuit, or anything else copied or modded from an EHX circuit or a using a common modification to the circuit that previously existed. I will not post the schematics of anything in the current EHX line, like the current Big Muff, Tone Wicker Big Muff, or Bass Big Muff, so don't even ask. I am not interested in doing anything that may damage EHX business, or to help anyone clone their current products. THE PEDALS THAT ARE CURRENTLY IN PRODUCTION ARE ALL RELTIVELY INEXPENSIVE, SO I HIGHLY ENCOURAGE YOU TO BUY ONE.

In an attempt to show the evolution of the transistor based Big Muff Pi circuit, and a reference for repairs, this article examines some key schematics for the different vintage Electro-Harmonix variants, in chronological order, or as near as I can determine. Also included are several clones of the Big Muff circuit with unique component values or interesting modifications. The Big Muff Pi was, and still is one of the most cloned circuits in the history of effects pedals. I have tried to give traces of only variants that sound different from each other, or that were the more common circuits for a particular version.