Thomas Henry magic tricks and circuits


this is a nice little circuit who come from “the electronic drum cookbook” by Thomas Henry. He names it the “Beat follower”. This circuit produces a CV stepped-staircase waveform from an external clock. I have slightly improve it by modifying the clock input, adding a reset input, and an indicator led for the cv signal output.
Here is some documentation who will give you an idea of ​​what it is possible to do with this circuit which I consider as a small bonus :slight_smile:
Have fun :wink:

The original schematic:

My mod:

I’m sure that it existing same type of circuits who are better and more complete as this one but it is a really cool little project for add in a drum box for exemple

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I’d suggest putting the LED to the left of the 3.3k resistor, to avoid having it affect the CV out.

The R1/R2 voltage divider gives ~5 V output with 15 V power. You’d probably want to modify it if you use 12 V.

Your clock input seems to be inverting the clock, was that the intention? Also, since he says the clock input is supposed to be 1 ms long, maybe a gate to trigger circuit there along the lines of your reset circuitry (with ~1 ms RC) would be a good idea.

On the other hand the reset pin really is reset/hold, it says, so allowing long gates there would make sense to me.

Have you built this?


Thank you for your explications, so I does modify the place of my led indicator! Yes I have build it and it work, but I have test only with the original clock input, so I’m going to modify it, I did not notice that the input was inversed… And I want to add a trigger conditionner for the input.

What value do you suggest me for R1/R2 ?
thank you a lot !

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Today a simply and usefully pulse-burst generator who I want to use in my dedicated drum rack for have more controls.