The deadastronaut X Fuzz is a fuzz circuit by the designer deadastronaut (Rob), published as a DIY stripboard (vero) layout on the Guitar FX Layouts blog in May 2014. It is not a factory-built pedal: players source the parts and build it themselves, which is why the discussion around it centers on parts choices, pot values and mods rather than a spec sheet. The circuit is small enough to fit a 1590A enclosure, one of the smallest standard pedal boxes, and it uses common transistors, so no rare or discontinued parts are needed1.
Parts and controls
Because this is a build-it-yourself circuit, the "controls" are the pots and parts a builder chooses. The layout calls for a PreGain control, a Volume control and a bias pot, and the comment thread on the layout records several builders' choices1:
| Part | Detail | Who suggests it |
|---|---|---|
| PreGain | 1 Meg linear reverse pot, reported to work very well | one builder1 |
| Volume | 500K log pot in the layout; one builder felt it had "not enough variance" and suggested a 250K linear instead | one builder1 |
| Bias pot | 250K suggested | the designer1 |
| Coupling cap | 1uF between first and second stage; one builder suggested 470nF to make the synthy sounds work better with both clipping types | one builder1 |
| Transistors | 2 x 2N5088 suggested; one builder settled on 2N2222s for extra high end and body | designer and builders1 |
The 1uF coupling cap between the first and second stages has voltage on both of its leads, so a non-polar capacitor is the suitable choice in that position1.
On the smallest builds, the PreGain control can be left out altogether: on a 1590A build, one builder explains that the PreGain is effectively the guitar's volume knob, so you can solder the input directly to PreGain lug 3 and control gain from the guitar1.
Clipping choices
The designer's recommendation for the clipping LEDs is specific: "stick with yellow standard diffused leds"1. Builders have taken the circuit in other directions:
- Yellow LEDs for the fuzz side and red LEDs for the rock side in the combined X-Fuzz/X-Rock build1
- 1N34A germanium diodes in place of the second LED, which one builder reported sounded great with no squeal when both knobs were maxed1
How it sounds
As with any DIY layout, the sound reports come from builders. The layout author, after listening to the designer's demo clip, said he "thought it sounded awesome for such a small circuit, so had to do the layout"1. Another builder, using 2N5089 transistors, a 33n input cap and a 1N34A in place of the second LED, described the result as "Sound awesome, raw and heavy"1. A third builder said he had been planning to build a RAT but preferred the X Fuzz instead, adding that it was "particularly good for playing Metallica"1. The layout itself was verified by an early builder, who called it a "Nice fuzz. Quick and easy build too"1.
Noise: what builders report and one fix
Noise is the one recurring criticism. One builder reported that at upper volume and gain settings the circuit was either savage fuzz or noisy to the point of being hard to use, and found that only lower gain transistors tamed it1. A suggested mod from the same discussion:
- Socket the 100p capacitor between collector and base of Q1
- Raise its value to 470p or so
- Possibly add the same change on Q2
The X Rock connection
The X Fuzz has a sibling circuit by the same designer, the X Rock. The two are closely related: one builder drew up a combined X-Fuzz/X-Rock schematic, and the designer revised the X Rock circuit after breadboarding it, with the X Rock layout updated to follow that latest version1. For players weighing the two, the combined build's convention is a useful guide: yellow LEDs for the fuzz side, red for the rock clipper1.
Videos
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Questions
Does the deadastronaut X Fuzz need rare transistors?
No. The designer notes that the circuit uses common transistors, so builders do not have to hunt down hard-to-find parts. Suggested builds include a pair of 2N5088s, and one builder settled on 2N2222s, saying they liked the extra high end and body they gave the circuit.
What enclosure does the X Fuzz fit in?
Builders have fitted the X Fuzz into a 1590A enclosure, one of the smallest standard pedal boxes. On a 1590A build the PreGain control can be skipped entirely by soldering the input directly to PreGain lug 3 and using the guitar's volume knob to control gain.
Which LEDs or diodes does the X Fuzz use for clipping?
The designer recommends yellow standard diffused LEDs for clipping. In a combined X-Fuzz/X-Rock build, the suggestion is yellow LEDs for the fuzz side and red LEDs for the rock clipper. One builder substituted 1N34A germanium diodes in place of the second LED and reported great results with no squeal at maximum settings.
How do builders reduce noise in the X Fuzz?
Some builders have reported noise at upper volume and gain settings. One suggested fix is to socket the 100p capacitor between collector and base of Q1 and raise its value to 470p, possibly doing the same on Q2. Lower gain transistors were also reported to tame the noise.
What is the difference between the X Fuzz and the X Rock?
The X Rock is a related clipper circuit by the same designer. The two are close enough that a combined X-Fuzz/X-Rock schematic was posted, using yellow LEDs for the fuzz side and red LEDs for the rock side. The designer also revised the X Rock circuit after breadboarding it, and the X Rock layout was updated to follow that latest version.
Sources (1)
- Guitar FX Layouts: X Fuzz by deadastronaut, Guitar FX Layouts (tagboardeffects.blogspot.com), 2014-05-23