125B · 3 knobs
OctahedronOctave Fuzz
Based on the Roger Mayer Octavia· 1 other board clones it
- Category
- Fuzz· Octave fuzz
- Controls
- Sustain · Tone · Volume
- Difficulty
- Easy
- Price
- $12.50in stock
From the vendor
An all-transistor redesign of the fuzz effect made famous by Jimi Hendrix, which adds an octave-up overtone to the harmonics.
The Octahedron Octave Fuzz is based on the Mayer Octavia, a transistor-based octave fuzz pedal originally designed in 1970 as an overhaul of the transformer version.
The circuit was designed by Roger Mayer who had built all of Jimi Hendrix’s octave units going back to 1967. The original used a transformer as the phase splitter, and underwent many iterations between 1967 and 1969, with Roger making tweaks and Jimi providing feedback, often after playing it live. The transformer Octavia was never sold commercially, so there was no final or standard version of the circuit.
Roger Mayer was never satisfied with any of the transformer versions and by 1970 he had redesigned the circuit to use all silicon transistors with no transformer. Jimi did play one of these new versions before his passing, but it has not been linked with any actual recordings.
The transistor Octavia was finally released commercially in 1980 in the distinctive “space ship” enclosure. Roger has produced versions of the transistor Octavia ever since, but he has never revisited the transformer version because he felt it was inferior.
In 2003, Roger released an updated version called the Vision Octavia, which used a more modern enclosure design and also added a passive treble-cut tone control that can reduce the harshness of the octave.
The Octahedron project is based on the Vision edition with the tone control, although the control can be omitted if you’d prefer to build the stock version. We have also included a switch to disable the octave-up effect and turn it into a more typical fuzz.
The two Octavias don’t have much in common and don’t sound alike, but both are worth building if you like octave fuzz. The transformer Octavia is available as our Octagon project.
Schematic
The schematic is in the vendor's build document, page 6. Open the build document. No KiCad fragment has been drawn for this circuit yet.
Parts list 54 rows
Report a wrong parse| Ref | Value | Normalized | Type | Notes |
|---|---|---|---|---|
| Resistors 22 | ||||
| R1 | 820k | 820k | Metal film resistor, 1/4W | |
| R2 | 180k | 180k | Metal film resistor, 1/4W | |
| R3 | 680k | 680k | Metal film resistor, 1/4W | |
| R4 | 100k | 100k | Metal film resistor, 1/4W | |
| R6 | 39k | 39k | Metal film resistor, 1/4W | |
| R7 | 220R | 220 | Metal film resistor, 1/4W | |
| R8 | 100R | 100 | Metal film resistor, 1/4W | Modification to make the gain range easier to dial in. See build notes. |
| R9 | 47k | 47k | Metal film resistor, 1/4W | |
| R10 | 39k | 39k | Metal film resistor, 1/4W | |
| R11 | 470k | 470k | Metal film resistor, 1/4W | |
| R12 | 270k | 270k | Metal film resistor, 1/4W | Part of the octave trim mod. Normally 330k. See build notes. |
| R13 | 10k | 10k | Metal film resistor, 1/4W | |
| R14 | 10k | 10k | Metal film resistor, 1/4W | |
| R15 | 2M2 | 2.2M | Metal film resistor, 1/4W | |
| R16 | 820k | 820k | Metal film resistor, 1/4W | |
| R18 | 1M | 1M | Metal film resistor, 1/4W | 2M2 for vintage version. |
| R19 | 1M | 1M | Metal film resistor, 1/4W | 2M2 for vintage version. |
| R20 | 10k | 10k | Metal film resistor, 1/4W | |
| R21 | 150k | 150k | Metal film resistor, 1/4W | |
| R22 | 100R | 100 | Metal film resistor, 1/4W | Power supply filter resistor. |
| RPD | 2M2 | 2.2M | Metal film resistor, 1/4W | Input pulldown resistor. |
| LEDR | 10k | 10k | Metal film resistor, 1/4W | LED current-limiting resistor. |
| Capacitors 14 | ||||
| C1 | 10n | 10n | Film capacitor, 7.2 x 2.5mm | |
| C2 | 470pF | 470p | MLCC capacitor, NP0/C0G | |
| C3 | 22uF | 22u | Electrolytic capacitor, 5mm | |
| C5 | 100n | 100n | Film capacitor, 7.2 x 2.5mm | |
| C6 | 22uF | 22u | Electrolytic capacitor, 5mm | |
| C7 | 22uF | 22u | Electrolytic capacitor, 5mm | Jumper for vintage version. |
| C8 | 10n | 10n | Film capacitor, 7.2 x 2.5mm | Omit (leave empty) for vintage version. |
| C9 | 100n | 100n | Film capacitor, 7.2 x 2.5mm | 10n for vintage version. |
| C10 | 22uF | 22u | Electrolytic capacitor, 5mm | |
| C11 | 22uF | 22u | Electrolytic capacitor, 5mm | |
| C13 | 100n | 100n | Film capacitor, 7.2 x 2.5mm | 10n for vintage version. |
| C14 | 100n | 100n | Film capacitor, 7.2 x 2.5mm | |
| C15 | 100uF | 100u | Electrolytic capacitor, 6.3mm | Power supply filter capacitor. |
| C16 | 100n | 100n | MLCC capacitor, X7R | Power supply filter capacitor. |
| Diodes 3 | ||||
| D1 | 1N5817 | 1N5817 | Schottky diode, DO-41 | |
| D2 | 1N914 | 1N914 | Fast-switching diode, DO-35 | |
| D3 | 1N914 | 1N914 | Fast-switching diode, DO-35 | |
| Transistors 4 | ||||
| Q1 | 2N3906 | 2N3906 | BJT transistor, PNP, TO-92 | |
| Q2 | KSP13 | KSP13 | Darlington BJT transistor, NPN | Current-production MPSA13 equivalent. |
| Q3 | KSP13 | KSP13 | Darlington BJT transistor, NPN | Current-production MPSA13 equivalent. |
| Q4 | KSP13 | KSP13 | Darlington BJT transistor, NPN | Current-production MPSA13 equivalent. |
| Potentiometers 3 | ||||
| DRIVE | 10kC | C10k | 16mm right-angle PCB mount pot | Reverse audio (reverse log or antilog) taper. |
| TONE | 50kC | C50k | 16mm right-angle PCB mount pot | Reverse audio (reverse log or antilog) taper. |
| VOLUME | 100kA | A100k | 16mm right-angle PCB mount pot | Audio (log) taper. |
| Trimmers 1 | ||||
| OCTAVE | 100k | 100k | Trimmer, 10%, 1/4”, 3362P | Part of the octave trim mod. See build notes. |
| Switches 2 | ||||
| OCT SW. | SPDT center off | SPDT CENTER OFF | Toggle switch, SPDT on-off-on | |
| FSW | 3PDT | 3PDT | Stomp switch, 3PDT | |
| Jacks & sockets 3 | ||||
| IN | 1/4" stereo | 1/4" STEREO | 1/4" phone jack, closed frame | Switchcraft 112BX or equivalent. |
| OUT | 1/4" mono | 1/4" MONO | 1/4" phone jack, closed frame | Switchcraft 111X or equivalent. |
| DC | 2.1mm | 2.1MM | DC jack, 2.1mm panel mount | Mouser 163-4302-E or equivalent. |
| Hardware 2 | ||||
| BATT | Battery snap | BATTERY SNAP | 9V battery snap | Optional. Use the soft plastic type—the hard-shell type will not fit. |
| ENC | 125B | 125B | Enclosure, die-cast aluminum | Can also use a Hammond 1590N1. |
Other boards based on the Roger Mayer Octavia
- Octa Mayer Fuzz PedalPCB · 125B · $8.00