Boss HM-2 Heavy Metal pedal schematic
The Boss HM-2 Heavy Metal pedal generates a unique distortion effect specially designed for Heavy Metal music. It has an interesting design with both asymmetric soft-clipping diodes, hard clipping diodes and a Ge diode pair in series with the signal for crossover distortion and simple noise gate. A wide variety of tone color creation is made possible with the 2 color mix controls.
Fig. 1: Boss HM-2 Heavy Metal guitar pedal schematic diagram
Fig. 2: Boss HM-2 PCB - component side
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Boss OD-1 Overdrive
Boss OD-2 Turbo OverDrive
Boss SD-1 Super Overdrive
Boss MT-2 Metal Zone
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Boss CE-2 Chorus
Boss CE-2B Bass Chorus
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Pearl CH-02 Chorus
Boss BF-2 Flanger
Pearl FG-01 Flanger
Boss DM-2 Analog Delay
Boss DD-2 Digital Delay
Boss NF-1 Noise Gate
Boss TR-2 Tremolo
Boss GE-7 Equalizer
Boss GE-7B Bass Equalizer
Boss OC-2 Octave
Specifications:
- 4 Control Knobs: Level, Color mix (Low, High) and Dist.
- Connectors: Input, Output, AC Adaptor
- Input Impedance: 1MΩ (FET input)
- Recommended Load Impedance: more than 10 kOhm
- Recommended AC Adaptor: ACA Series
- Current Draw: 10mA (DC 9V)
- Weight: 400g
- Dimensions(mm): 70(W) x 55(H) x 125(D)
- Dimensions(inches): 2-3/4(W) x 2-3/16(H) x 4-15/16(D)
ICs, transistors and diodes used in the HM-2:
- IC1-IC3: M5218L or NJM4558S (dual operational amplifiers)
- Q1,Q4,Q5,Q10: 2SK30A-Y (Silicon N-channel JFET transistors)
- Q2,Q3: 2SC732TM-GR (NPN silicon transistors)
- Q8,Q9: 2SC945-P (NPN silicon transistors)
- Q6: 2SC2240-GR (NPN silicon transistor)
- Q7: 2SA970-GR (PNP silicon transistor)
- D1,D3,D5,D8-D12: 1S2473 (switching diodes)
- D2: S5500G (400V/1A rectifier diode)
- D6,D7: 1S188FM (Germanium diodes)
- D13: RD5.1EB-3 (5.1V Zener diode)
- D14: SLP135B (red LED)