The Big Muff Pi Circuit. The usual values for this cap are decs to some hundreds of pF, l, The clipping Stage is made of a passive voltage divider (sustain potentiometer) and. I have written more about Jen and the Jen Jumbo Fuzz here. Written January 2012 ©Kit Rae. Passive Tone Control Stage. 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. PART 2 • Note: In the calculation, the diodes feedback network is not taken into consideration because it contains big capacitors C6 and C7 which disconnect the path for DC conditions. Very similar sound to the violet schematic that would follow. Within each version are numerous circuit VARIANTS, each with unique sets of component values and types. It also shows that the tone control is not able to archive a flat response. 4 NPN Transistors: BC239 or equivalents 2N5088, 2N5089, BC549C, SE4010, 2N5210, 2N5113: Q, 4 Silicon Diodes: 1N914 or equivalent 1N4148: D. 3 Potentiometers 100K Lin: Sustain, Tone, Volume. The schematic can be broken down into 4 simpler blocks: Input Booster, Clipping Stage, Passive Tone Control and Output Booster. 1N125 is a germanium diode, but these are Silicon. 5.1 Big Muff Pi Output Impedance.6. TRIANGLE BIG MUFF PI - This is one of the common circuit variants, from around 1971, easily identified by the large green capacitors used. For some interesting mods to this circuit, see the Pharoah BMP clone schematic here. The red curve illustrates the output after the first clipping, with a maximum gain of 23.4 dB and band limited with two poles at 55Hz and 1.78KHz. The same circuit was also used in the Guild Foxey Lady and Marveltone Distortion Sustainer, OEM versions made by Electro-Harmonix. Note that most of the original Silicon diodes from this period are unknown, simply marked with a black band, but some were marked 125. Last update June 2015. WHY ARE THE TRANSISTORS LABELED IN THE REVERSE ORDER? The only change made was the high pass cap in the tone section at C9. The same circuit was also used in the Guild Foxey Lady version. Copyright Kit Rae. The low pass filter cap at C10 in the input stage was omitted, likely because of a shortage of 500pF caps during that production run. The input/output caps, coupling caps, and and clipping caps were all large 3µF electrolytics, not found on any other version of the Big Muff Pi. This, in turn, decreases the emitter current, correcting the original increase. These are considered among the best sounding and most desirable of the 1970's Big Muffs, with a perfect balance of lows, highs, medium gain distortion, and a mid range that was not overly scooped. The Input Booster sets the pedal input impedance, shapes the frequency response and adds some gain. Big Muff Page Note: Use the GGG schematic for mods on this page. SEKOVA BIG MUFF by Shin Ei - Another Japanese builder that made a clone of the Big Muff was the effects company Shin Ei. ±0.6V. I have written more about Jordan and the Creator here. This email address is being protected from spambots. The blue curve shows the output after the second clipping, with a maximum gain of 25.2 dB (48.6 - 23.4 = 25.2) and band limited with two poles at 94Hz and 1.17KHz. So, the value of the input resistor R2=39K accounts for almost all of the signal loading at the input. The General Guitar Gadgets Violet Ram's Head, MJM Foxey Fuzz, and many other violet clones were based on the 470pF version of this schematic. 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. Enlarging this cap will make it clip more bass harmonics, make it smaller for more high-end clipping and archiving more saturated tone, more sustain, and compression. include a back to back diodes to create the symmetric clipping. Co.) sometime around 1973. 2.2 Input Booster Voltage Gain Calculation. 1N125 is a germanium diode, but these are Silicon. The Output impedance of the common emitter transistor stage is equal to RC = R6 = 10K. It is very similar to the perf board version shown above, but with one major change that makes this one of the most uncommon circuit variants of the V1 Big Muff. Feedback BJT Amplifier Analysis by Dr. Ahmed Saadoon.Feedback BTJ Amplifier Analysis by the University of Vigo.BMP Mods and Tweaks.BMP Questions in DIYaudio.BMP tone Control by AMZ.Teemuk Kyttala Solid State Guitar Amplifiers, the Holy Scripture. Feedback resistors at R9/15/17 were dropped to 390k for less gain, but the collector resistors at R13 and R11 were also reduced slightly to increase the gain in the clipping stages. 2.1 Big Muff Pi Shunt Feedback Common Emitter Stage, In common emitter amps, the approximate voltage gain is collector resistance divided by the emitter resistance (R. effect of the feedback resistor has to be taken into consideration: While it results in a reduced overall voltage gain and input impedance, a number of improvements are obtained: More immune against variations in temperature and transistors Beta. Component values seem to be based on a few different V1 circuits, with the 470pF caps from the 1973 V2's thrown in for good measure. This operation occurs just before the distortion stage; clipping a low-passed signal usually sounds better, smoother and less harsh. At first glance this appears to be a 1973 violet era schemo, but closer inspection reveals the base and emitter resistors are all 100Ω, rather than 150Ω like the violet era. There is also an extra .1µF cap in the tone section at C14, and a polarized electro added to the 9v for power filtering, not found on the original violet BMP circuits. This, in turn, decreases the emitter current, correcting the original increase. JORDAN CREATOR - One of the first clones of the V1 Big Muff, from around 1971. Output Stage. in the input and output sections and the resistors grouped: : Voltage-Shunt Gain without feedback formula: Replacing the Input Booster circuit values R. 2.3 Big Muff Pi Input Impedance Calculation. the most comprehensive site about BMP by Kitrae. This page is not authorized, affiliated, or associated with Electro Harmonix in any way. These variants were each made in large production runs. Each of the two consecutive Q2/Q3 clipping stages keeps the same topology as the Input Booster. The primary difference between this variant and the violet circuit variant below is that all of the collector resistors and the limiting resistors are 10k here. These are considered among the best sounding and most desirable of the 1970's Big Muffs, with a perfect balance of lows, highs, medium gain distortion, and a mid range that was not overly scooped. Component values seem to be based on a few different V1 circuits, with the 470pF caps from the 1973 V2's thrown in for good measure. The blue and red color curves have the tone at full treble/bass respectively. V2 "73" RAMS HEAD BIG MUFF PI - First Circle Face version, V2 "VIOLET" RAMS HEAD BIG MUFF PI / LYLE DISTORTION SUSTAINER / MARVELTONE DISTORTION SUSTAINER / GUILD FOXEY LADY. In common emitter amps, the approximate voltage gain is collector resistance divided by the emitter resistance (RC/RE), but the effect of the feedback resistor has to be taken into consideration:The resistor R9 from collector to base also called Shunt Feedback resistor or RF is a method to apply negative feedback to the amplifier. It is the output of the first Clipping Stage, the previous signal is amplified 25 dBs and the amplitude is clipped to. A revised version of the violet Big Muff shown above, circa 1974. The volume pot, normally placed after the output stage, has been moved between the tone stage and output stage. Guitar stuff, gear stuff, soundclips, videos, Gilmour/Pink Floyd stuff, photos and other goodies. Most of the Big Muffs I have seen with this same circuit variant had .1uF caps where my V1 of this variant uses .12uF. It might cause asymmetric clipping if the input signal is bigger than 0.2Vpp. If the level is high, the signal will be more clipped and the distortion effect will hold even if the guitar input signal is not strong.

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