Ace Tone FM-3 Fuzz Master

The Ace Tone FM-3 Fuzz Master is a Japanese fuzz pedal from the early 1970s. Despite the shared name, it is not a close relation of the Ace Tone Fuzz Master FM-2, which is a Univox Super Fuzz style octave fuzz. The FM-3 is instead a V1 Big Muff variant from 1971, with a boost mode that isolates the first gain stage, as Guitar.com's Cillian Breathnach notes in a review of a modern pedal built on the circuit¹.

What it does

The FM-3 gives the player two sounds from one box: a fuzz based on the first-version Big Muff topology, and a boost built from that circuit's first gain stage. A footswitch selects between boost or fuzz, but the two cannot be used at the same time. As the Guitar FX Layouts technical write-up puts it, "Keep in mind this isn't a boost that stacks on top of the fuzz, you get either fuzz or boost. Not both"².

The circuit

Guitar FX Layouts describes the FM-3 as "Another Japanese Big Muff variant, this one has some substantial modifications"². The modifications go beyond the added boost mode:

• The boost mode has its own volume and tone pots²
• The volume pot is moved to a position pre Q4, with differences in biasing and filtering compared with the Big Muff²
• The transistors are 2SC1000s in the GR gain range, 200 to 400²

For anyone tracing the circuit from published schematics, there is one more detail worth knowing: the original has an additional 100K resistor directly at the input to ground, between INPUT and the 8k2/3n3 junction, a component missing from Kit Rae's published schematic².

In print

Guitar.com's 2024 review of the Evil Eye FX Warg Fuzz, a modern pedal built on the FM-3 circuit, gives the clearest published summary of what the original is: "It's instead a V1 Big Muff variant from 1971, with a boost mode that isolates the first gain stage"¹.

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