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SUSTAINTONEVOLUME

125B · 3 knobs

Aion FX

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

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RefValueNormalizedTypeNotes
Resistors 22
R1820k820kMetal film resistor, 1/4W
R2180k180kMetal film resistor, 1/4W
R3680k680kMetal film resistor, 1/4W
R4100k100kMetal film resistor, 1/4W
R639k39kMetal film resistor, 1/4W
R7220R220Metal film resistor, 1/4W
R8100R100Metal film resistor, 1/4WModification to make the gain range easier to dial in. See build notes.
R947k47kMetal film resistor, 1/4W
R1039k39kMetal film resistor, 1/4W
R11470k470kMetal film resistor, 1/4W
R12270k270kMetal film resistor, 1/4WPart of the octave trim mod. Normally 330k. See build notes.
R1310k10kMetal film resistor, 1/4W
R1410k10kMetal film resistor, 1/4W
R152M22.2MMetal film resistor, 1/4W
R16820k820kMetal film resistor, 1/4W
R181M1MMetal film resistor, 1/4W2M2 for vintage version.
R191M1MMetal film resistor, 1/4W2M2 for vintage version.
R2010k10kMetal film resistor, 1/4W
R21150k150kMetal film resistor, 1/4W
R22100R100Metal film resistor, 1/4WPower supply filter resistor.
RPD2M22.2MMetal film resistor, 1/4WInput pulldown resistor.
LEDR10k10kMetal film resistor, 1/4WLED current-limiting resistor.
Capacitors 14
C110n10nFilm capacitor, 7.2 x 2.5mm
C2470pF470pMLCC capacitor, NP0/C0G
C322uF22uElectrolytic capacitor, 5mm
C5100n100nFilm capacitor, 7.2 x 2.5mm
C622uF22uElectrolytic capacitor, 5mm
C722uF22uElectrolytic capacitor, 5mmJumper for vintage version.
C810n10nFilm capacitor, 7.2 x 2.5mmOmit (leave empty) for vintage version.
C9100n100nFilm capacitor, 7.2 x 2.5mm10n for vintage version.
C1022uF22uElectrolytic capacitor, 5mm
C1122uF22uElectrolytic capacitor, 5mm
C13100n100nFilm capacitor, 7.2 x 2.5mm10n for vintage version.
C14100n100nFilm capacitor, 7.2 x 2.5mm
C15100uF100uElectrolytic capacitor, 6.3mmPower supply filter capacitor.
C16100n100nMLCC capacitor, X7RPower supply filter capacitor.
Diodes 3
D11N58171N5817Schottky diode, DO-41
D21N9141N914Fast-switching diode, DO-35
D31N9141N914Fast-switching diode, DO-35
Transistors 4
Q12N39062N3906BJT transistor, PNP, TO-92
Q2KSP13KSP13Darlington BJT transistor, NPNCurrent-production MPSA13 equivalent.
Q3KSP13KSP13Darlington BJT transistor, NPNCurrent-production MPSA13 equivalent.
Q4KSP13KSP13Darlington BJT transistor, NPNCurrent-production MPSA13 equivalent.
Potentiometers 3
DRIVE10kCC10k16mm right-angle PCB mount potReverse audio (reverse log or antilog) taper.
TONE50kCC50k16mm right-angle PCB mount potReverse audio (reverse log or antilog) taper.
VOLUME100kAA100k16mm right-angle PCB mount potAudio (log) taper.
Trimmers 1
OCTAVE100k100kTrimmer, 10%, 1/4”, 3362PPart of the octave trim mod. See build notes.
Switches 2
OCT SW.SPDT center offSPDT CENTER OFFToggle switch, SPDT on-off-on
FSW3PDT3PDTStomp switch, 3PDT
Jacks & sockets 3
IN1/4" stereo1/4" STEREO1/4" phone jack, closed frameSwitchcraft 112BX or equivalent.
OUT1/4" mono1/4" MONO1/4" phone jack, closed frameSwitchcraft 111X or equivalent.
DC2.1mm2.1MMDC jack, 2.1mm panel mountMouser 163-4302-E or equivalent.
Hardware 2
BATTBattery snapBATTERY SNAP9V battery snapOptional. Use the soft plastic type—the hard-shell type will not fit.
ENC125B125BEnclosure, die-cast aluminumCan also use a Hammond 1590N1.

Other boards based on the Roger Mayer Octavia