SnapClap – the only handclap you will ever need!

This is a successfull attempt to bring famous ClapTrap drum synthesizer (analog version) into eurorack synth world. It was not very easy.

This particular device intrugued me for a long time. It is definitely well-known, but except pictures there is not a lot of info all over web. You can find schematics without any semiconductors types specified and some sample packs – the real problem is no one specifies if sounds were recorded form analog or digital version. Generally, there were 3 revisions: 2 analog and 1 digital (this one is easiest to find I think). With big help of my friends I’ve got samples, as well as some very informative videos. With them I was able to name all IC ans tune the circuit (big thanks to Arne). Thats how analog ClapSnap* was born.

* I think I was a little scatterbrained while I designed the thing, so at some point I have changed the name from SnapClap or SnapTrap to ClapSnap. The final name of the project is ClapSnap (or just CS handclap). But the front panel still says SnapClap.

There are some other analog handclap circuits fe. Roland TR808 HC or Boss HC-2. Both uses filtered noise for “clap” and “fake echo” part. This circuit uses filtered noise for “fake echo” and triangle wave output VCO for “clap” part. But you don’t hear triangle waveform. It is frequency-modulated (from envelope and sine generator) so fast, it resembles series of positive and negative, almost random pulses – thats why every clap sounds a little different. VCO envelope consists of not equally spaced pulses, and their number is three or four (in other circuits there are three evenly spaced pulses). This envelope is also modulated from sine generator. A lot of modulation is happening here.

Circuit uses some sometimes hard to obtain ICs – CA3080 (operational transconductance amplifier) and NE566 (voltage controlled generator). Full BOM can be found at the end of page. I performed minor mods:

  • redesigned Humanizer – to fit eurorack +/- 12 V power standard (original circuit outputs 42 V p-p sine! ),
  • changed some resistors values in noise generator circuit to get rid of strange values,
  • increased the range of clap (ensemble) pitch setting,
  • “pulse length” modification – lets you to alter the pulse length, resulting in “fatter” sound; pulse (VCO) pitch is more noticable, so it is not a good idea to strech pulses to much,
  • filter break – you can add a jack to route existing noise source signal somewhere  else, or inject external signal right into noise VCA.

Considering that is a handclap, there is a lot to tweak – the circuit needs a lot of love, but with proper knob settings you can get really nice claps. Interface consists of 2 main sections – NOISE (also called “crash”) and CLAP (sometimes referred as “ensemble”). Each has its own PITCH and DECAY setting, NOISE has also additional switch for “pulse length mod” (I used simple DPDT, but for more options rotary or switch with center position can be used). There are many triggering options. Device can be triggered from: external pulse (“synth” trigger input), external audio signal (“audio” trigger input with SENSIVITY control), front panel pushbutton (not included in my design), foot switch (I also didn’t need this) and autotrigger (internal generator with SPEED control). The Humanizer circuit doesn’t have any control, but you can use break points to add modulation level pot.

The PCB is 80 x 100 mm, very tight-packed. Looks simple, but there is really a lot of soldering to make.

ClapSnap PCB soldered
Soldered SnapClap PCB

I tried to keep the front panel tight and clean, so as I mentioned I didn’t included manual trigger switch, foot switch input (and autotrigger LED). 12 HP should be enough for handclap module, I don’t want to end with second Clangora 🙂

SlapSnap eurorack module, top view
Completed eurorack module

This is the clip from tests, the prototype is build in a shoe box. A fast way to make an enclosure for your project. The pot in top left corner is a noise level control, replaced by trimmer in later versions.

Final device build as eurorack module. Notice the “pulse length” mod switch (marked as VAR) in the top right corner.

If you like this one, PM me, maybe we can figure something out.



Edit: 16.12.2017

Found a small error in wiring: INPUT SENSIVITY pot, tap marked as GND should be not conected. This is corrected in manual revision 1.02.



5 thoughts on “SnapClap – the only handclap you will ever need!

  1. Hi There

    I’m interested in building this project.
    Have you got any PCBs ?

    Kind Regards

  2. Love your blog Jack. Very inspiring and educating.

    This Clap Trap project would be a perfect match to fill empty slots on many original SDS V drum brains. Have you discussed this with anyone?

    Have you tried to rework any of your CA3080 design to use LM13700? This article by Don Sauer are interesting reading in this regard.


  3. Hi there, your projects are so inspirational! And the finish is so beautiful and appealing.
    Do you sell PCBs for this particular project as well as others? As I would be very interested in buying a set. Many thanks for you hard work and inclination to share you’re talent with the world.
    Kind regards and respect Ryan

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