Build - Pedal Project: One Knob Fuzz Face (with Video Tutorial)
The Dallas-Arbiter Fuzz Face is one of the most iconic pedals ever made, with the original germanium version being the most sought-after. Many users of original Fuzz Faces and their clones prefer to keep the “Fuzz” knob maxed, and use their guitar’s volume knob to control the fuzz amount instead. With the fuzz knob set to its max position at all times, an obvious Fuzz Face variant is a one knob fuzz with the “Fuzz” control replaced with a set resistor internally so that the pedal operates like a Fuzz Face with its Fuzz control maxed at all times.
Follow along with our video tutorial:
There are various pedals in this style (e.g. the Colorsound One Knob Fuzz and the D*A*M Meathead), but they are often silicon variants and often have a few other changes to voice the pedals somewhat differently from the original Fuzz Face. The Colorsound One Knob Fuzz and D*A*M Meathead can both sound great, and both can be built from this layout with a few small tweaks, but this layout uses the original germanium Fuzz Face values for a one-knob take on the iconic pedal.
Germanium transistor specs vary, and the Fuzz Face circuit is picky about transistor specs. Dropping two untested germanium transistors into a Fuzz Face circuit is likely to result in a mis-biased circuit. To mitigate this issue, the 8.2k resistor on the collector of Q2 is replaced with a 10K trim pot. This can be adjusted to set the bias point of Q2. Builders often aim for a voltage between -4V and -5V on the collector of Q2, though biasing by ear is also popular. Anecdotal reports suggest that original units were often biased around -5V which tends to sound nice, but there is no “correct” bias voltage for this circuit, particularly given how sensitive germanium transistors are to temperature changes. The exact bias point will change some depending on ambient temperature.
This is a PNP build and uses battery power only. With no LED indicator, this pedal will last a very long time on battery power. If you would like to build this pedal with a DC jack, please see our PNP "Positive Ground" Pedal Considerations tech article.
Figure 1: Eyelet board layout of the One Knob Fuzz Face
Figure 2: Schematic of the One Knob Fuzz Face
Parts List
| Val | Qty | SKU | Type | Note |
|---|---|---|---|---|
Capacitors | ||||
| 10n | 1 | C-MKT-D01-400 | Film cap | |
| 22u | 1 | C-BC-22-63 | Electrolytic | |
| 2u2 | 1 | C-BC-2D2-63 | Electrolytic | |
Potentiometers | ||||
| 500kA | 1 | R-VAM500KA-SS | Volume Control | |
| 10k trimmer | 1 | R-VT29U-10K | Bias trimmer | 8k2 resistor in originals |
Resistors | ||||
| 100k | 1 | R-PR02-100K | Vishay PR02 metal film resistor | |
| 470R | 1 | R-PR02-470 | Vishay PR02 metal film resistor | |
| 33k | 1 | R-PR02-33K | Vishay PR02 metal film resistor | |
| 1M | 1 | R-PR02-1M | Vishay PR02 metal film resistor | |
| 1k | 1 | R-PR02-1K | Vishay PR02 metal film resistor | |
Semiconductors | ||||
| 2N527 | 2 | P-Q2N527 | Germanium transistor | |
Other Items | ||||
| 2x6 eyelet board | 1 | P-HTB-2X6 | Board | |
| Black 1590B | 1 | P-H1590BBK | Enclosure | |
| Carling DPDT | 1 | P-H550 | Footswitch | |
| Battery disconnect switch | 1 | P-H518 | Rocker Switch | |
| Greencell 9V | 1 | S-9V-GCELL | Battery | |
| Vinyl battery snap | 1 | K-P155 | Battery snap | |
| Fairchild-style phenolic knob | 1 | P-K348 | Knob | |
| Low profile stereo jack | 2 | S-H534 | 1/4" Jacks | |
| Adhesive cable tie mount | 1 | P-HTIEMOUNT-BLK | Battery Strain Relief | |
| 10mm M-F M3 standoffs | 2 | S-HSO-M3-10 | Board mounts | |
| M3 nuts | 1 | S-HHN-M3 | Board fasteners | Package of 5, 2 used |