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Big Muff Op Amp 1977

You can find here circuits & schematics, modifications, information and error reports of some famous pedals. They are useful for reference purpose and everyone can learn much from 'em. They can also be used to build your own clone (BYOC).

Big Muff Op Amp 1977

Postby maz » January 17th, 2020, 7:44 pm

Here's another favorite of mine.

Back in 1977, the Big Muff then had other electronic components than conventional transistors, these were operational amplifiers, so called Op-Amp or simply IC (integrated circuits). These components gave a particular sound to the famous Fuzz / distortion pedals produced by Electro-Harmonix, only some 2000 of these circuits have been made. Because of this, it can rarely be found on the second hand market, and at exorbitant prices. Also, IC Muff seems to be very popular since Billy Corgan used his famous Big Muff Op-Amp V4 to record "Siamese Dream" with his band Smashing Pumpkins, that was in 1993.

Compared to other units made of transistors, the op-amp Big Muff has slightly more low end, is not as scooped and is known to cut better through the mix in a band situation. This version offers 3 gain stages instead of the usual 4 but still sounds just like the original with a dark and warm tone, just a hint of mids and a fat lower end. Some earlier version doesn't have any tone bypass switch, therefore the circuit is exactly the same as the V5 1978, including the typical tone stack giving to the Big Muff that special dirty, compressed and mid scooped tone.

Below are the schematic and vero layout of the early 1973 version, which doesn't have the tone switch. Note that the proposed version include a slightly modified power supply filter section, this doesn't affect the sound but only gives a quieter circuit when used with a noisy power supply. Also, a parallel protection diode has been chosen over the serie schottky, which would add another 0.2V in addition to the 47 ohms resistor voltage drop, that could possibly cause the circuit to die faster on battery. At the input section, a 180nF replace the typical 150nF allowing a little more bass to pass in the signal, and finally a 150nF instead of the typical 120nF at the tonestack, giving a better sweep between low and high. After hours of breadboarding, based on several schematics found here and there, this is the final version. I built one for myself and will be a keeper for sure, feel free to use it as reference or to built your own Big Muff Op Amp 1977 clone.

The Schematic :



:pdf: Download the complete pdf project file for direct PnP transfer, layout and schematic.

:txt: Download Bill of Materials in txt format.

The Big Muff Op Amp 1977 built on veroboard :


For those interested by the V5 1978 version, which have the tone bypass switch, have a look at tagboardeffects

Have fun ! :)
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