The PastFX M-1-A Stacked Sheep's Head is a fuzz pedal built around two classic effects in one box: a Ram's Head Big Muff-style fuzz circuit driving into a Power Booster circuit. PastFX describes the result as a slightly mids-boosted fuzz that delivers scorching sustain and distinct shades of gritty character, with the ability to clean up with volume knob adjustment1. The maker says the pedal's foundational stacked character can be heard most famously in David Gilmour's guitar solo on Pink Floyd's "Comfortably Numb"1.
Where it comes from
The M-1-A is a pedalboard-friendly recreation and expansion of the Buffalo FX M-1 Ram's Head Fuzz, a fuzz pedal that itself takes on the Big Muff Pi Ram's Head circuit12. Pedal of the Day's 2017 review of the Buffalo original called the Ram's Head sound "one of the most well-known, coveted and revered sounds in the history of gu"itar effects, and judged the M-1 "one of the best examples we've come across, and really gets into the nitty-gritty of how a Ram's Head fuzz sh"ould sound2.
"The M-1 is one of the best examples we've come across, and really gets into the nitty-gritty of how a Ram's Head fuzz sh"
The stacked idea, a fuzz feeding a boost, is what gives the pedal its mids-boosted, sustaining character rather than the flatter response of a Muff on its own1.
Controls and design
PastFX says the traditional Level and Sustain controls establish the pedal's core tonal range and output1. On the Buffalo FX M-1 that the M-1-A expands, Pedal of the Day described the controls this way: Level sets the output volume, Sustain "brings you the sonic qualities of the Muff, but with a slightly less harsh rou"nder tone and more midrange, and the single Tone knob of the original Muff is separated into two active EQ controls, Bass and Treble2.
The stacked design puts two classic effects layered together, with six active gain stages in the circuit and a low noise floor, according to PastFX1. The reviewer also noted on the Buffalo original that "there's no volume drop when the M-1 is engaged"2.
Power and practical details
The M-1-A runs on a 9vDC center negative tip power supply or a 9V battery connected via battery snap, and draws under 10mA1. True bypass operation keeps the pedal out of the signal path when off1. The enclosure measures 112 x 60 x 31mm (4.4" x 2.36" x 1.22"), enclosure only, which PastFX positions as pedalboard-friendly1.
PastFX states that product specifications are subject to change without notice1.
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Questions
Is the PastFX M-1-A Stacked Sheep's Head Fuzz true bypass?
Yes. PastFX lists the M-1-A as having true bypass operation, so when the pedal is off your guitar's signal passes straight through to the amp without going through the fuzz circuit. That matters on a pedalboard where several effects sit in line, since a buffered or non-true-bypass pedal can affect the signal even when switched out.
Can the M-1-A run on a 9V battery?
Yes. PastFX says the M-1-A requires a 9vDC centre negative tip power supply or a 9V battery connected via battery snap. Current draw is listed at under 10mA, which is light by pedal standards, so it is easy on a battery and unlikely to strain a shared power supply.
What transistors does the M-1-A use?
PastFX describes the M-1-A as an NOS BC239C comprised circuit, meaning it is built around new-old-stock BC239C transistors. Those are the silicon transistors associated with the Ram's Head era of the Big Muff Pi, which is the circuit the M-1-A's fuzz section draws from.
What is the input impedance of the M-1-A?
PastFX lists the input impedance at 1mΩ (one megohm) and the output impedance at under 10k. A high input impedance like that presents an easy load to a guitar's pickups, and the low output impedance helps the pedal drive the rest of the chain.
Can the M-1-A clean up with the volume knob?
Yes. PastFX describes the M-1-A as a slightly mids-boosted fuzz with scorching sustain and distinct shades of gritty character, and says it has the ability to clean up with volume knob adjustment. Rolling back the guitar's volume takes the fuzz from full sustain toward cleaner tones.
Sources (2)
- M-1-A Stacked Sheep's Head Fuzz, pastfx.com, 2026
- Buffalo FX M-1 Ram's Head Fuzz, Pedal of the Day, 2017-11-25
