125B · 3 knobs
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
Report a wrong parse| Ref | Value | Normalized | Type | Notes |
|---|---|---|---|---|
| Resistors 38 | ||||
| R1 | 10k | 10k | Metal film resistor, 1/4W | |
| R2 | 1M | 1M | Metal film resistor, 1/4W | |
| R3 | 10k | 10k | Metal film resistor, 1/4W | |
| R4 | 22k | 22k | Metal film resistor, 1/4W | |
| R5 | 100k | 100k | Metal film resistor, 1/4W | |
| R6 | 470k | 470k | Metal film resistor, 1/4W | |
| R7 | 10k | 10k | Metal film resistor, 1/4W | |
| R8 | 22R | 22 | Metal film resistor, 1/4W | |
| R9 | 150R | 150 | Metal film resistor, 1/4W | |
| R10 | 22k | 22k | Metal film resistor, 1/4W | |
| R11 | 100k | 100k | Metal film resistor, 1/4W | |
| R12 | 470k | 470k | Metal film resistor, 1/4W | |
| R13 | 120R | 120 | Metal film resistor, 1/4W | |
| R14 | 1k | 1k | Metal film resistor, 1/4W | |
| R15 | 10k | 10k | Metal film resistor, 1/4W | |
| R16 | 68k | 68k | Metal film resistor, 1/4W | |
| R17 | 220k | 220k | Metal film resistor, 1/4W | |
| R18 | 47k | 47k | Metal film resistor, 1/4W | |
| R19 | 10k | 10k | Metal film resistor, 1/4W | |
| R20 | 10k | 10k | Metal film resistor, 1/4W | |
| R21 | 68k | 68k | Metal film resistor, 1/4W | |
| R22 | 3k3 | 3.3k | Metal film resistor, 1/4W | |
| R23 | 3k3 | 3.3k | Metal film resistor, 1/4W | |
| R24 | 10k | 10k | Metal film resistor, 1/4W | |
| R25 | 100k | 100k | Metal film resistor, 1/4W | |
| R26 | 330R | 330 | Metal film resistor, 1/4W | |
| R27 | 82k | 82k | Metal film resistor, 1/4W | |
| R28 | 330R | 330 | Metal film resistor, 1/4W | |
| R29 | 100k | 100k | Metal film resistor, 1/4W | |
| R30 | 330R | 330 | Metal film resistor, 1/4W | |
| R31 | 10k | 10k | Metal film resistor, 1/4W | |
| R32 | 10k | 10k | Metal film resistor, 1/4W | |
| R33 | 470k | 470k | Metal film resistor, 1/4W | |
| R34 | 10k | 10k | Metal film resistor, 1/4W | |
| R35 | 1k | 1k | Metal film resistor, 1/4W | |
| R36 | 100k | 100k | Metal film resistor, 1/4W | |
| RPD | 2M2 | 2.2M | Metal film resistor, 1/4W | Input pulldown resistor. Can be as low as 1M. |
| LEDR | 10k | 10k | Metal film resistor, 1/4W | LED current-limiting resistor. Adjust value to change LED brightness. |
| Capacitors 25 | ||||
| C1 | 47n | 47n | Film capacitor, 7.2 x 2.5mm | |
| C2 | 47n | 47n | Film capacitor, 7.2 x 2.5mm | |
| C3 | 100pF | 100p | MLCC capacitor, NP0/C0G | |
| C4 | 47uF | 47u | Electrolytic capacitor, 5mm | |
| C5 | 10uF | 10u | Electrolytic capacitor, 5mm | |
| C6 | 47n | 47n | Film capacitor, 7.2 x 2.5mm | |
| C7 | 100pF | 100p | MLCC capacitor, NP0/C0G | |
| C8 | 100pF | 100p | MLCC capacitor, NP0/C0G | |
| C9 | 47n | 47n | Film capacitor, 7.2 x 2.5mm | |
| C10 | 1uF | 1u | Film capacitor, 7.2 x 3.5mm | |
| C11 | 1n | 1n | Film capacitor, 7.2 x 2.5mm | |
| C12 | 1uF | 1u | Film capacitor, 7.2 x 3.5mm | |
| C13 | 470pF | 470p | MLCC capacitor, NP0/C0G | |
| C14 | 10uF | 10u | Electrolytic capacitor, 5mm | |
| C15 | 1.5uF | 1.5u | Film capacitor, 7.2 x 4.5mm | |
| C16 | 68n | 68n | Film capacitor, 7.2 x 2.5mm | |
| C17 | 150n | 150n | Film capacitor, 7.2 x 2.5mm | |
| C18 | 6n8 | 6.8n | Film capacitor, 7.2 x 2.5mm | |
| C19 | 100n | 100n | Film capacitor, 7.2 x 2.5mm | |
| C20 | 4n7 | 4.7n | Film capacitor, 7.2 x 2.5mm | |
| C21 | 47n | 47n | Film capacitor, 7.2 x 2.5mm | |
| C22 | 1uF | 1u | Film capacitor, 7.2 x 3.5mm | |
| C23 | 100uF | 100u | Electrolytic capacitor, 6.3mm | Power supply filter capacitor. |
| C24 | 47uF | 47u | Electrolytic capacitor, 5mm | Voltage reference filter capacitor. |
| C25 | 100n | 100n | MLCC capacitor, X7R | Power supply filter capacitor. |
| Diodes 8 | ||||
| D1 | 1N5817 | 1N5817 | Schottky diode, DO-41 | Polarity protection diode with low voltage drop (~0.2V). |
| D2 | 1N914 | 1N914 | Fast-switching diode, DO-35 | |
| D3 | 1N914 | 1N914 | Fast-switching diode, DO-35 | |
| D4 | 1N914 | 1N914 | Fast-switching diode, DO-35 | |
| D5 | BAT46 | BAT46 | Schottky diode, DO-35 | The HM-2 uses Ge diodes here, but Schottky is a better modern |
| D6 | BAT46 | BAT46 | Schottky diode, DO-35 | replacement. They only set the gate threshold and do not affect tone. |
| D8 | 1N914 | 1N914 | Fast-switching diode, DO-35 | |
| D9 | 1N914 | 1N914 | Fast-switching diode, DO-35 | |
| Transistors 4 | ||||
| Q1 | 2N5457 | 2N5457 | JFET, N-channel, TO-92 | The HM-2 uses 2SK30A-Y (a Japanese equivalent). |
| Q2 | 2N5088 | 2N5088 | BJT transistor, NPN, TO-92 | The HM-2 uses 2SC2240-GR (a Japanese equivalent). |
| Q3 | 2N5087 | 2N5087 | BJT transistor, PNP, TO-92 | The HM-2 uses 2SA970-GR (a Japanese equivalent). |
| Q4 | 2N5088 | 2N5088 | BJT transistor, NPN, TO-92 | The HM-2 uses 2SC732TM-GR (a Japanese equivalent). |
| ICs 3 | ||||
| IC1 | JRC4558D | JRC4558D | Operational amplifier, DIP8 | |
| IC2 | JRC4558D | JRC4558D | Operational amplifier, DIP8 | |
| IC3 | JRC4558D | JRC4558D | Operational amplifier, DIP8 | |
| Potentiometers 4 | ||||
| VOL | 10kA | A10k | Potentiometer, 16mm right-angle | Audio (log) taper. |
| DIST | 250kA | A250k | Potentiometer, 16mm right-angle | Audio (log) taper. The HM-2 uses D-taper which is similar to A. |
| HIGH | 10kA | A10k | Potentiometer, 16mm right-angle | Audio (log) taper. The HM-2 uses G-taper which is similar to A. |
| LOW | 10kA | A10k | Potentiometer, 16mm right-angle | Audio (log) taper. The HM-2 uses G-taper which is similar to A. |
| Switches 1 | ||||
| FSW | 3PDT | 3PDT | 3PDT stomp switch | |
| LEDs 1 | ||||
| LED | 5mm | 5MM | LED, 5mm | Adjust LEDR resistor to set brightness depending on the LED used. |
| Jacks & sockets 6 | ||||
| IC1-S | DIP-8 socket | DIP-8 SOCKET | IC socket, DIP-8 | |
| IC2-S | DIP-8 socket | DIP-8 SOCKET | IC socket, DIP-8 | |
| IC3-S | DIP-8 socket | DIP-8 SOCKET | IC socket, DIP-8 | |
| IN | 1/4" mono | 1/4" MONO | 1/4" phone jack, closed frame | Switchcraft 111X or equivalent. Open-frame types can be used instead, |
| OUT | 1/4" mono | 1/4" MONO | 1/4" phone jack, closed frame | but the top side drill template is different. See drill template for details. |
| DC | 2.1mm | 2.1MM | DC jack, 2.1mm panel mount | Mouser 163-4302-E or equivalent. |
| Hardware 1 | ||||
| ENC | 125B | 125B | Enclosure, die-cast aluminum | Can also use a Hammond 1590N1. |
Other boards based on the BOSS HM-2
- BOSS HM-2 Experimentalists Anonymous