Akashic Guitar effects PCB lookup
DISTORTIONLOWVOLUME

125B · 3 knobs

Aion FX

GravitonMetal Distortion

Based on the BOSS HM-2· 1 other board clones it

Category
Distortion· Metal Distortion
Controls
Distortion · Low · Volume
Difficulty
Intermediate
Price
$12.50in stock

From the vendor

A unique distortion effect favored by extreme metal guitarists for its characteristic “buzzsaw” sound. It also works very well as a versatile high-gain effect in other styles of music.

The Graviton Metal Distortion is a clone of the BOSS HM-2 Heavy Metal, first released in 1983 and discontinued in 1991. The HM-2 was largely overlooked while it was in production, but in the mid-1990s it got the attention of a few bands in the Swedish death metal scene who developed something of a signature guitar tone by turning all the knobs to 10, often running it into a cheap solid state amp. Here is the video that first exposed this technique:

Despite the reputation it enjoys in the extreme metal community, it is far from a one-trick pony. It’s a very flexible pedal with a balanced high-gain distortion tone that works well in many styles of music.

This circuit also made an appearance as the DOD FX-56 American Metal, released in 1984. While the pedals don’t really sound the same, the American Metal has almost the exact same circuit layout, just with different parts values and with the two tone knobs combined into one. You can build the American Metal with the Graviton PCB.

Note: The PCB-only version of this project uses a type of capacitor that has been temporarily discontinued by WIMA. Please see our news article about the issue and the substitution spreadsheet for project-specific recommendations. We are stocking a limited supply in the mean time. The build document has not yet been updated to reflect this. It does not impact the kits.

Schematic

The schematic is in the vendor's build document, page 7. Open the build document. No KiCad fragment has been drawn for this circuit yet.

Parts list 91 rows

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RefValueNormalizedTypeNotes
Resistors 38
R110k10kMetal film resistor, 1/4W
R21M1MMetal film resistor, 1/4W
R310k10kMetal film resistor, 1/4W
R422k22kMetal film resistor, 1/4W
R5100k100kMetal film resistor, 1/4W
R6470k470kMetal film resistor, 1/4W
R710k10kMetal film resistor, 1/4W
R822R22Metal film resistor, 1/4W
R9150R150Metal film resistor, 1/4W
R1022k22kMetal film resistor, 1/4W
R11100k100kMetal film resistor, 1/4W
R12470k470kMetal film resistor, 1/4W
R13120R120Metal film resistor, 1/4W
R141k1kMetal film resistor, 1/4W
R1510k10kMetal film resistor, 1/4W
R1668k68kMetal film resistor, 1/4W
R17220k220kMetal film resistor, 1/4W
R1847k47kMetal film resistor, 1/4W
R1910k10kMetal film resistor, 1/4W
R2010k10kMetal film resistor, 1/4W
R2168k68kMetal film resistor, 1/4W
R223k33.3kMetal film resistor, 1/4W
R233k33.3kMetal film resistor, 1/4W
R2410k10kMetal film resistor, 1/4W
R25100k100kMetal film resistor, 1/4W
R26330R330Metal film resistor, 1/4W
R2782k82kMetal film resistor, 1/4W
R28330R330Metal film resistor, 1/4W
R29100k100kMetal film resistor, 1/4W
R30330R330Metal film resistor, 1/4W
R3110k10kMetal film resistor, 1/4W
R3210k10kMetal film resistor, 1/4W
R33470k470kMetal film resistor, 1/4W
R3410k10kMetal film resistor, 1/4W
R351k1kMetal film resistor, 1/4W
R36100k100kMetal film resistor, 1/4W
RPD2M22.2MMetal film resistor, 1/4WInput pulldown resistor. Can be as low as 1M.
LEDR10k10kMetal film resistor, 1/4WLED current-limiting resistor. Adjust value to change LED brightness.
Capacitors 25
C147n47nFilm capacitor, 7.2 x 2.5mm
C247n47nFilm capacitor, 7.2 x 2.5mm
C3100pF100pMLCC capacitor, NP0/C0G
C447uF47uElectrolytic capacitor, 5mm
C510uF10uElectrolytic capacitor, 5mm
C647n47nFilm capacitor, 7.2 x 2.5mm
C7100pF100pMLCC capacitor, NP0/C0G
C8100pF100pMLCC capacitor, NP0/C0G
C947n47nFilm capacitor, 7.2 x 2.5mm
C101uF1uFilm capacitor, 7.2 x 3.5mm
C111n1nFilm capacitor, 7.2 x 2.5mm
C121uF1uFilm capacitor, 7.2 x 3.5mm
C13470pF470pMLCC capacitor, NP0/C0G
C1410uF10uElectrolytic capacitor, 5mm
C151.5uF1.5uFilm capacitor, 7.2 x 4.5mm
C1668n68nFilm capacitor, 7.2 x 2.5mm
C17150n150nFilm capacitor, 7.2 x 2.5mm
C186n86.8nFilm capacitor, 7.2 x 2.5mm
C19100n100nFilm capacitor, 7.2 x 2.5mm
C204n74.7nFilm capacitor, 7.2 x 2.5mm
C2147n47nFilm capacitor, 7.2 x 2.5mm
C221uF1uFilm capacitor, 7.2 x 3.5mm
C23100uF100uElectrolytic capacitor, 6.3mmPower supply filter capacitor.
C2447uF47uElectrolytic capacitor, 5mmVoltage reference filter capacitor.
C25100n100nMLCC capacitor, X7RPower supply filter capacitor.
Diodes 8
D11N58171N5817Schottky diode, DO-41Polarity protection diode with low voltage drop (~0.2V).
D21N9141N914Fast-switching diode, DO-35
D31N9141N914Fast-switching diode, DO-35
D41N9141N914Fast-switching diode, DO-35
D5BAT46BAT46Schottky diode, DO-35The HM-2 uses Ge diodes here, but Schottky is a better modern
D6BAT46BAT46Schottky diode, DO-35replacement. They only set the gate threshold and do not affect tone.
D81N9141N914Fast-switching diode, DO-35
D91N9141N914Fast-switching diode, DO-35
Transistors 4
Q12N54572N5457JFET, N-channel, TO-92The HM-2 uses 2SK30A-Y (a Japanese equivalent).
Q22N50882N5088BJT transistor, NPN, TO-92The HM-2 uses 2SC2240-GR (a Japanese equivalent).
Q32N50872N5087BJT transistor, PNP, TO-92The HM-2 uses 2SA970-GR (a Japanese equivalent).
Q42N50882N5088BJT transistor, NPN, TO-92The HM-2 uses 2SC732TM-GR (a Japanese equivalent).
ICs 3
IC1JRC4558DJRC4558DOperational amplifier, DIP8
IC2JRC4558DJRC4558DOperational amplifier, DIP8
IC3JRC4558DJRC4558DOperational amplifier, DIP8
Potentiometers 4
VOL10kAA10kPotentiometer, 16mm right-angleAudio (log) taper.
DIST250kAA250kPotentiometer, 16mm right-angleAudio (log) taper. The HM-2 uses D-taper which is similar to A.
HIGH10kAA10kPotentiometer, 16mm right-angleAudio (log) taper. The HM-2 uses G-taper which is similar to A.
LOW10kAA10kPotentiometer, 16mm right-angleAudio (log) taper. The HM-2 uses G-taper which is similar to A.
Switches 1
FSW3PDT3PDT3PDT stomp switch
LEDs 1
LED5mm5MMLED, 5mmAdjust LEDR resistor to set brightness depending on the LED used.
Jacks & sockets 6
IC1-SDIP-8 socketDIP-8 SOCKETIC socket, DIP-8
IC2-SDIP-8 socketDIP-8 SOCKETIC socket, DIP-8
IC3-SDIP-8 socketDIP-8 SOCKETIC socket, DIP-8
IN1/4" mono1/4" MONO1/4" phone jack, closed frameSwitchcraft 111X or equivalent. Open-frame types can be used instead,
OUT1/4" mono1/4" MONO1/4" phone jack, closed framebut the top side drill template is different. See drill template for details.
DC2.1mm2.1MMDC jack, 2.1mm panel mountMouser 163-4302-E or equivalent.
Hardware 1
ENC125B125BEnclosure, die-cast aluminumCan also use a Hammond 1590N1.

Other boards based on the BOSS HM-2