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).
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).
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.
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.
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!