The Expresso FX Custom Dual Ge/Si Fuzz & Ge Boost is a hand-built, two-in-one pedal: a germanium and silicon fuzz circuit on the right side and a germanium boost on the left, each with its own foot switch. Expresso FX describes it as "a custom dual-circuit pedal with a Ge/Si Fuzz on the right side and a Ge Boost on the left"1. It sits in the maker's range of germanium-based builds alongside the Expresso FX Germanium Boost Mini, the Expresso FX Germanium Boost "Mojo Edition" and the Expresso FX Custom Ge Fuzz / Ge Boost / Octave Up.
The fuzz side
The fuzz is a two-transistor circuit built around hand-selected new-old-stock parts. Its first transistor, Q1, is switchable between a Newmarket CV7005 (germanium) and a low-gain Mullard OC202 (silicon), which gives the player two different clipping characters from the same pedal. A Mullard AC188 sits in Q21. The circuit also uses a NOS ERO KT1800 film capacitor1.
The four transistors in the pedal, as listed by the maker:
| Position | Transistor | Type |
|---|---|---|
| Fuzz Q1 (switchable) | Newmarket CV7005 | Germanium1 |
| Fuzz Q1 (switchable) | Mullard OC202 | Silicon, low gain1 |
| Fuzz Q2 | Mullard AC188 | Germanium1 |
| Boost | Mullard OC45 | Germanium1 |
Expresso FX lists the full complement as "1x Newmarket CV7005, 1x Mullard OC202 (Silicon), 1x Texas Instruments or GE 2N1307, and 1x Mullard OC45 hand selected NOS germanium and silicon transistors"1.
Germanium transistors vary from unit to unit, and Expresso FX addresses that directly on the sibling Custom Dual Germanium/Silicon Fuzz with Filter Control, which is "fitted with an external bias knob, on top of the classic Volume and Fuzz knobs, to help compensate for the" variation between transistors4. That design carries across the family, and it matters in practice: the bias control lets a player dial the fuzz back to its sweet spot rather than relying on the luck of the transistor draw.
The boost side
The left side is a germanium boost fitted with a Mullard OC45 transistor1. Its main control is a 7-way rotary switch "for selecting a range of tones from treble-focused, to mid-focused, or to more bass-focused tones"3, so the boost can be voiced to suit a bright single-coil guitar or to push the front of an amp from a different part of the frequency range.
The two sides at a glance:
| Fuzz (right) | Boost (left) | |
|---|---|---|
| Circuit | Two-transistor Ge/Si fuzz1 | Germanium boost1 |
| Key parts | CV7005 or OC202 in Q1, AC188 in Q2, NOS ERO KT1800 film capacitor1 | Mullard OC451 |
| Tone shaping | Volume and Fuzz controls, Q1 germanium/silicon switch14 | 7-way rotary tone switch14 |
Build, bypass and power
The pedal is housed in a genuine Hammond enclosure, powder-coated in a choice of finishes1:
- Matt Translucent White on Gold
- Metallic Emerald Green
- Metallic Midnight Blue
- Metallic Red Copper
- Metallic Sky-Blue
- Translucent Bronze on Chrome
Switching is by Alpha foot switches, one per circuit, and the pedal is true bypass1.
Each pedal is built by hand around NOS transistors, and Expresso FX asks buyers to allow 1 week for shipping3. The maker's sibling Custom Dual Germanium/Silicon Fuzz with Filter Control is a single-circuit version of the same idea, measuring 121 x 66 x 40 mm2, so check which version a listing refers to before comparing sizes.
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Questions
Is the Expresso FX Dual Ge/Si Fuzz & Ge Boost true bypass?
Yes. Expresso FX lists the pedal as true bypass, so when it is switched off the signal passes through without the fuzz or boost circuits in the path. The pedal uses Alpha foot switches for its switching, and both sides of the dual circuit can be operated independently.
Which transistors are in the Expresso FX Dual Ge/Si Fuzz & Ge Boost?
The pedal carries four hand-selected NOS germanium and silicon transistors: a Newmarket CV7005, a Mullard OC202 (silicon), a Texas Instruments or GE 2N1307, and a Mullard OC45. On the fuzz side, Q1 is switchable between the CV7005 germanium and the low-gain OC202 silicon, with a Mullard AC188 in Q2. The boost side uses the Mullard OC45.
What warranty does the Expresso FX Dual Ge/Si Fuzz & Ge Boost come with?
Expresso FX gives the pedal a 3 years warranty, as stated on the maker's product page. The pedal is built to order, and the maker asks buyers to allow 1 week for shipping.
How big is the Expresso FX Dual Ge/Si Fuzz & Ge Boost?
The pedal measures 90.5 x 115.7 x 54.9mm (W x D x H), housed in a genuine Hammond enclosure powder-coated in a choice of colours. That is a two-footswitch enclosure, since the fuzz and boost are separate circuits with their own switches.
Sources (4)
- Custom Dual Ge/Si Fuzz & Ge Boost, Expresso FX, 2024-09-15
- Custom Dual Germanium/Silicon Fuzz with Filter Control, Expresso FX, 2024-05-23
- Custom Dual Ge/Si Fuzz & Ge Boost, Expresso FX, 2024-09-15
- Custom Dual Germanium/Silicon Fuzz with Filter Control, Expresso FX, 2024-05-23
