HC-2 handclapper

Some time ago i started a handclapper project. The design is not based on Roland TR808, but Boss HC-2 (or Amdek HCK-100 if you like). With some problems I completed the prototype and made an eurorack module – it works really well.

Boss circuit is different form Rolands. It uses CMOS based digital noise source (only 2 states at output – 0V or ~4,5V), which gives possibilities for some modification. As opposed to 808, this device has more sound sculpting options, more then just “level” control – 4 knobs in total to tweak and lick. I’ve tried many mods, but only 3 last as “fun and usable”. For such a simple sound, PCB is quite complex. The final schematics HQ pdf used in this project can be found here. The topolgy of the circuit is very simple – one 1x digital noise generator (CMOS ICs based), one EG (generates burst of pulses) and one VCA (BA6110 based).

Hard prototyping of the clap
Hard prototyping of the clap

First, I prototyped the circuit on self-etched PCB (I don’t like to make complex analog projects on breadboards) in a beautiful cartoon box, leftover from SDSV drum synth project. I made an small error in BA6110 connection, so I had to put an additinal small PCB with transistor converter (original circuit uses BA622, I have forgotten about it).

Box of secrets opened
Box of secrets opened

After tests, I moved to final , professionally manufactured PCB (I made only one small error in prototype) and put in into 8HP eurorack module. The front panel doesn’t look as good as it should – I used acetone for aluminum cleaning, which caused the water decal to peel off. Now I use simple soap, works so much better.

HC2 top shot
HC2 top shot

The trigger indication LED PCB (the small green one) is mounted in somehow silly way – sticked with a two-sided adhesive tape to a back of the pot. But you can still remove it without problem, in opposite to hot gluing.

HC2 eurorack module "Vegeta" was born
HC2 eurorack module “Vegeta” was born

The front panel is simple and every knob makes a difference to a sound. All pots are Alpha Taiwan 16mm with dust cover – very cost effective in synth DIY and much better then no-name asian devices. The CLOCK control is my favourite one – can make the clap sound really BIG!



  • HALL (“fake reverb” level),
  • DRY (noise source output filter cutoff),
  • BURST (pulses count in envelope),
  • CLOCK (noise source clock speed),
  • LEVEL (output level).


Inputs / outputs:

  • TRIGGER (trigger pulse input),
  • OUTPUT (handclap output),
  • NOISE (noise output),
  • LED (indicates trigger).



  • PCB size: 80×100 mm,
  • module front panel size – 8HP (~41×129 mm).


Power consumption – maximum (only positive rail is used) :

  • 0 mA @ -12V, 20mA @ +12V,
  • 0 mA @ -15V, 15mA @ +15V.


And now, all you are waiting for, a demo! (Handclap demos are boring by definition, this one is made even more boring by me ).

A more complex approach to handclap synthesis was used in my SnapClap project, chect it out!


3 thoughts on “HC-2 handclapper

  1. The ‘here’-link to your schematics seems inactive. Would be nice to see you fixing that. : )

    Cheers from Germany! Nice blog : )

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