Positive Grid Bass Muff pedal is available under the Drive effect group and is inspired by the Electro Harmonix Bass Big Muff Pi
|Big Muff Pi
|Electro-Harmonix and Sovtek
|1969 – present
The Big Muff Pi (π), often known simply as the Big Muff, is a "fuzzbox" effects pedal produced in New York City by the Electro-Harmonix company, along with their Russian sister company Sovtek, primarily for use with the electric guitar. It is used by bassists as well, due to the Big Muff's squeaky frequency response.
The following is a direct quote from Mike Matthews, Electro-Harmonix founder, and president:
Back in 1969 I [Electro-Harmonix] was already selling the Muff Fuzz, which was a mild overdrive circuit in an LPB-1 box. I wanted to come out with a three knob distortion unit in a bigger box. I asked my buddy, Bell Labs designer, Bob Myer, to design a unit, one that would have a lot of sustain. When I got the prototype from Bob, I loved the long sustain. This was done by cascading the circuit into additional sections, each one clipped by twin diodes. However, when you clip, the tone can be a bit raspy. So, I spent a couple of days changing capacitors to roll off distortion in the highs, and eventually found that the best long sustaining tone that was a sweet violin-like sound was done by having three capacitors in different parts of the circuit rolling off the rasp. We plunged into production and I brought the very first units up to Henry, the boss at Manny's Music Store on 48th Street, NYC. About a week later, I stopped by Manny's to buy some cables, and Henry yelled out to me, 'Hey Mike, I sold one of those new Big Muffs to Jimi Hendrix.' 
An earlier Electro-Harmonix pedal, the Axis Fuzz, was also manufactured for the Guild guitar company as the Foxey Lady and used a similar chassis as the early Big Muffs, but had a simpler two-transistor circuit. With the introduction of the Big Muff, the Axis was discontinued and the Foxey Lady pedal became a rebranded Big Muff. It was available at least until the mid-1970s.
The Big Muff Pi was the first overwhelming success for Electro-Harmonix's line of pedals. Due to its reliability, its low price and its distinctive sound, the Big Muff sold consistently through the 1970s and was found in innumerable guitarists' pedal collections. For example, David Gilmour and Carlos Santana were some of first famous users of the pedal. David Gilmour famously used the Big Muff on the Pink Floyd albums Animals and The Wall and most recently on his 2006 On An Island tour. Other artists who used the Big Muff during the 1970s include Thin Lizzy, Kiss, Frank Zappa (though Zappa had it modified to produce a very non-typical Big Muff distortion), and Ronnie Montrose. Even after the Electro-Harmonix company was forced out of business in 1982, the pedal remained in such demand that clones of the Big Muff were made by both competing corporations and independent pedal builders, and demand for "vintage Big Muffs" rose. Unsurprisingly, when Matthews restarted Electro-Harmonix in the 1990s, the Big Muff was one of the first pedals he reintroduced to the market.
The "sustained grind" of the Big Muff was later an integral part of the sound of many alternative rock bands through the 1980s and 1990s, being used extensively by the Smashing Pumpkins, Dinosaur Jr., NOFX, Bush and Mudhoney. The name of the pedal even inspired the title of Mudhoney's 1988 debut EP Superfuzz Bigmuff, as well as Depeche Mode's 1981 instrumental "Big Muff". Lee Ranaldo and Thurston Moore of Sonic Youth used the Sovtek version of the Big Muff, and, more recently, Dan Auerbach of The Black Keys, who often uses the Sovtek version in a number of The Black Keys songs. Aside from the Big Muff, Electro-Harmonix has made the Nano Muff, the Metal Muff, which has a 3-band EQ and is a distortion; the Little Big Muff, a smaller variation of the current NYC model, the Deluxe Big Muff, the 77/78 op-amp Big Muff, designed by Howard Davis, which uses IC's to create the Fuzz whereas all others, except the Deluxe Big Muff, use transistors. There also exists a customized limited edition Big Muff, called the Mogwai Big Muff. This pedal was designed for the Scottish band Mogwai, and has a slightly more extreme sound. Electro-Harmonix produced only 100 Mogwai Big Muff pedals. In 2017 Electro-Harmonix reissued the Sovtek Big Muff, commonly known as the 'Green Russian'
Most versions of the Big Muff use four transistor stages. The first stage is a clean boost, which drives the next two clipping stages, which create the distortion. The final stage is a tone recovery stage, which recovers volume loss as the tone stack in the Big Muff is passive, and the pedal loses some volume because of this. For a short time in the late-1970s, the Big Muff used op-amps, which at the time were not as highly regarded as the discrete transistor versions. However, the op-amp Big Muffs have lately seen a revival among collectors and players alike. The op-amp Big Muff has a slight variation in sound to the transistor version.
Electro-Harmonix also released a large-box version of the Big Muff known as the Deluxe Big Muff Pi. This version included an onboard compressor in addition to the standard Big Muff features. It was available in 2 versions: one with a BLEND switch and another with a SERIES/PARALLEL switch. They themselves have joined the fray with a reissue version of their original Big Muff Pi as well as a smaller "Little Big Muff Pi", that incorporates true-bypass switching, surface-mount components, and a smaller enclosure.
|The first model is a clone of the Mosrite Fuzzrite designed by Ed Sanner. Built for Guild Guitars, later versions had three knobs and are precursors of the Big Muff Pi. Foxey Lady design by Mike Mathews, the founder of Electro-Harmonix, with modifications and biasing by Bill Berko.
|The Muff Fuzz was designed to be directly connected onto the amp instead of being a stompbox, and instead of a foot switch it contained a side switch along with a level knob.
|Big Muff Pi (V1)
|1969 - 1973
|The first version of the Big Muff, commonly called the "Triangle" Muff because of the layout of the knobs forming a triangle shape, designed by Bob Myers and Mike Matthews. It contained three control knobs - Volume, which controlled the overall volume of the pedal, Sustain, which controlled both the amount of distortion and the amount of sustain, and Tone, which controlled the high-end frquency. These three knobs would appear on almost every Big Muff pedal that followed.
|Little Muff Pi
|The transistorized version of the 1969 Muff Fuzz, now as a stompbox. Later, Electro-Harmonix would modify the circuit by replacing the transistors with an op-amp.
|Big Muff Pi (V2)
|1973 - 1977
|Commonly called the “Ram's Head" model for it’s graphic on the corner of the pedal depicting the head of a ram. In order of production, this version can be further subdivided into the "47", "73", and "Violet" models. The "Violet" model was famously used by Pink Floyd's guitarist David Gilmour.
|Big Muff Pi (V3)
|1977 - 1978
|The first Big Muff which used the classic red and black graphics. Originally just a graphical redesign for the "Ram's Head", but gradually evolved into its own circuit. Later models were the first one to include a tone bypass and a power jack.
|Big Muff Pi (V4)
|1978 - 1980
|Sometimes called the "Op-Amp" for it’s op-amp chip circuitry, this version also features one less gain stage, but is housed in the same enclosure as its predecessor, the V3. This model was famously used by Billy Corgan of The Smashing Pumpkins.
|Big Muff Pi (V5)
|1978 - 1980
|Also called the "Op-Amp", this version was produced and sold in tandem with the V4, and featured the same Op-Amp circuitry as the V4 with the addition of a tone bypass.
|Deluxe Big Muff Pi (1330)
|1978 - 1982
|The Deluxe Big Muff has an EH1330A circuit board, added compressor volume and threshold controls, and features a blend-on switch, a blend-on output and a compressor output. A slightly modified version was reissued in 1980.
|Big Muff Pi (V6)
|1979 - 1982
|This pedal was last version of Big Muff before Electro-Harmonix was liquidated in 1982. It was a transistor version of the Big Muff with a tone bypass, and used the EH3034 circuit board.
|Little Big Muff Pi
|1979 - 1982
|This pedal was introduced as a compact rendition of the Big Muff, with its controls similar to the 1969 Muff Fuzz containing only a tone switch and a level knob.
|Muff Fuzz (Op-Amp)
|1979 - 1982
|Based on the 1969 Muff Fuzz, this is an Op-Amp version, and was powered by a 1458N IC chip.
|Red Army Overdrive
|1990 - 1992
|The first Muff type pedal made in the U.S.S.R. Released by Mike Matthews's new brand called Sovtek, after Electro-Harmonix went out of business for the second time.
|Big Muff Pi (V7)
|Commonly named the "Civil War" Muff because of its graphical design, made in Russia. It has a blue and white colored chassis, and used the same circuit as the "Red Army Overdrive" model.
|Big Muff Pi (V7, Green Russian)
|1994 - 2000
|Released by Sovtek and made in Russia, it has an army green chassis, and used the same circuit as the "Red Army Overdrive" and "Civil War" models.
|Big Muff Pi (V7, Black Russian)
|1998 - 2009
|Released by Sovtek and made in Russia, it has a black chassis and is a slightly modified circuit of the “Green Russian” model.
|Big Muff Pi NYC Reissue (V9)
|2000 - Present
|After the chain of Russian Muff pedals from Sovtek, the Big Muff returned to production in New York. This circuit was designed by Bob Myer, and it has some variants with slightly modified circuits. The first edition circuit board was marked EC3003 and used four 2N5088 transistors, powered by 9V.
|Based on the 1969 Muff Fuzz with a nano-sized chassis and powered by 9V. This pedal could select between “single mode” - which offered the original Muff Fuzz sound, and “double mode” - which added a bit more distortion to the sound.
|Little Big Muff Pi Reissue
|2006 - Present
|The Little Big Muff sounds very similar to the NYC reissue, but a bit brighter and less bottom end to the sound. Built in a compact diecast box and powered by 9V.
|Metal Muff with Top Boost
|2006 - Present
|Redesigned for heavy metal players. This pedal has a 3-band equalizer and a separate "top boost" control.
|Bass Big Muff Pi
|2008 - Present
|Designed for bass players and inspired by the 1998 "Black Russian", this pedal has an added switch which allows for a low-end boost.
|Nano Muff Overdrive
|2008 - 2023
|Reissue of the 1969 Muff Fuzz and the 1971 Little Muff Pi, with a nano-sized chassis and powered by 9V.
|Big Muff Pi with Tone Wicker
|2008 - Present
|Classic Big Muff Pi pedal with a tone switch and a high frequency filter (Wicker) switch.
|Double Muff (Nano)
|2010 - 2020
|Nano-sized version of the 2001 Double Muff, powered by 9V.
|Deluxe Bass Big Muff
|2012 - Present
|A deluxe bass version based on the 2008 Bass Big Muff Pi. This pedal has dry blend, noise gate, high pass filter and low pass filter controls. It confains an XLR DI, and buffered dry and effect outputs.
|Nano Big Muff Pi
|2013 - Present
|Nano-sized version of the 2000 NYC Reissue, powered by 9V.
|Deluxe Big Muff Pi
|2014 - Present
|Deluxe version based on the 2000 NYC Reissue, with added attack, noise gate, midrange level, midrange frequency and midrange section controls.
|Nano Green Russian Big Muff
|2017 - Present
|Reissue of the 1994 Sovtek "Green Russian", with a nano-sized chassis and powered by 9V.
|Nano Op-amp Big Muff
|2017 - Present
|Reissue of the 1978 "Op-amp" version, with a nano-sized chassis and powered by 9V.
|Triangle Big Muff
|2018 - Present
|Reissue of the original 1969 Big Muff Pi “Triangle”, with a nano-sized chassis and powered by 9V. The pedal was released in honor of the 50th anniversary of Electro-Harmonix.
|Sovtek Deluxe Big Muff Pi
|2018 - Present
|Based on the 1991 Sovtek “Civil War”, this version has an added expression pedal input for controlled midrange frequency by foot switch, and has dry blend, noise gate, midrange level, midrange frequency, midrange section controls and the “Wicker" switch, powered by 9V.
|Ram's Head Big Muff Pi
|2019 - Present
|Reissue of the 1973 "Violet Ram’s Head", with a nano-sized chassis and powered by 9V.
|Nano Metal Muff
|2021 - Present
|Nano-sized version of the 2006 Metal Muff.
|J Mascis Ram’s Head Big Muff Pi
|2022 - Present
|J Mascis signature edition, with special artist graphics. Used the same circuit as the 2019 Ram's Head.
|Big Muff Pi Hardware Plugin
|2022 - Present
|This pedal transcends the limitations of traditional DAW plugins to bring the analog sound to digital recording. It works like a standard DAW plugin, but recorded tracks go through the actual analog circuitry of Big Muff Pi, adding analog warmth to the sound. This pedal provides a 2-in/-2-out USB for audio recording interface.
- "THE BIG MUFF π - A HISTORY OF ALL VERSIONS - Part 1". Kit Rae. Retrieved 2015-02-09.
- Tolinski, Brad (September 1994). "Welcome to the Machines". Guitar World. Archived from the original on 24 July 2011. Retrieved 2011-07-29.
- Gore, Stephen (2006-12-21). "Depeche Mode - Speak And Spell (album review 3)". http://www.sputnikmusic.com. Retrieved 2017-11-04.
- "Sonic Youth : Illustrated Equipment Guide". Sonicyouth.com. Retrieved 2014-08-02.
- "Electro-Harmonix". Electro-Harmonix. Retrieved 2018-01-24.
- "Review: Electro-Harmonix Green Russian Big Muff and Hot Wax Pedals". Guitar World. Retrieved 2018-01-24.
- Jacob. "Billy Corgan Gear, Effects, Tone, Rig Examples – In-Depth Guide". Rock Guitar Universe. Retrieved 2024-02-12.
- Official Electro-Harmonix website - Big Muff Pi page
- Website about history and development of Big Muff Pi
- Canadian documentary about the Big Muff, four parts: 1, 2, 3, 4
- Very thorough history of Big Muff models