Build - Pedal Project: Fuzzrite - Germanium Version

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The Fuzzrite is one of the earliest US-made fuzzes, perhaps only being preceded by the Maestro FZ-1. The Fuzzrite was made by Mosrite in California from roughly 1966 - 1968. Build styles varied, and there were two major versions of the circuit - a silicon version, and a germanium version that used one 2N2613 and one 2N408 transistor. Though there were some circuit tweaks between the two versions, the topology remains similar. The Fuzzrite uses two cascaded transistor gain stages, and the depth control mixes between the output from the first and second stage. The Fuzzrite is often the go-to if you’re aiming for the sound of The Ventures, as it is speculated that the Fuzzrite may have been inspired by a one-off fuzz box they used. The Fuzzrite is known to have been used on Iron Butterfly’s classic “In-a-Gadda-Da-Vida”.

This build is based on the germanium Fuzzrite. The build seen here is built in a YY enclosure which has been sanded with very fine sandpaper for a roughly polished look. The original was built into a bare folded-steel enclosure with black text printed on the face. Besides the germanium transistors, the component that is most difficult to find is the 350K reverse audio potentiometer used for the depth control in originals. We carry a 350K reverse audio potentiometer, R-VOMSL-350KRA, that is custom-made by Omeg, which is perfect for authentic Fuzzrite clones. The reverse audio taper may seem strange. In the original Fuzzrite, the knobs were mounted on the top of the enclosure. With knobs mounted that way, it is often more intuitive if the potentiometers are wired such that rotating them counter-clockwise results in an increase rather than a decrease in the effect setting. The potentiometers in the Fuzzrite were wired “backwards” compared to what is more commonly seen, which results in a more intuitive effect control for top-mounted potentiometers (turning the knobs to the user’s right will increase the setting). This is represented in the schematic, where you can see that lug 3 of the volume pot is grounded, while the output of the effect goes to lug 1. Because of the reverse wiring, the Depth control’s reverse audio taper functions like a typical (non-reverse) audio taper in originals.

The Volume pot was linear in the originals, so the taper would be the same whether it is wired normally or backwards.

In this build, the pots are mounted on the face of the enclosure, so they are not wired in reverse. If a 350kC potentiometer is used here with standard wiring, most of the useful range on the depth control will be in the first half or even quarter of the knob’s rotation. For that reason, we are opting to use a 470k audio taper potentiometer here. A resistor is wired in parallel with the potentiometer to reduce the effective resistance seen between lugs 1 and 3 to roughly 350k. This is a fairly common modification done on modern Fuzzrite builds. It is not exactly the same as using a 350k potentiometer, but it won’t prevent you from making a great-sounding Fuzzrite. The wiring diagram has the potentiometers wired normally (unlike the schematic which is drawn to match the originals exactly). If you choose to top-mount the potentiometers, you may want to switch the connections that are made to lugs 1 and 3, and you may want to use R-VOMSL-350KRA in place of the 470K Depth pot and the parallel 1M5 resistor.

The germanium Fuzzrite can be picky about which transistors are used, and germanium specs can vary substantially. Two types are included in the Parts List below, but you may need a larger batch of transistors you can try out in the circuit. Swapping transistors is also a great way to experiment and tweak the sound.

Figure 1: Turret board layout of the germanium Mosrite Fuzzrite

Figure 1: Turret board layout of the germanium Mosrite Fuzzrite

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Figure 2: Schematic of the germanium Mosrite Fuzzrite

Figure 2: Schematic of the germanium Mosrite Fuzzrite

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See Figure 3 in our Guitar Pedal Footswitch and Jack Wiring article for the recommended footswitch and I/O wiring.

Parts List

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