Monday, October 15, 2007


I have been working on a circuit i call 'onehander'. The idea is to have a linear, one dimensional parameter space (for example, a potentiometer) that someone can play with one hand. And although this simple parameter space changes only one parameter (in the case of this breadboarded example, the speed of a control oscillator), the amount of variety in the audio output of the circuit is relatively large.

You can listen to a direct-input recording here. Please note that the audio has not been edited and has been recorded in a single, continuous take changing only the potentiometer. You can also watch a video of the thing in action here.

You can see a schematic here. Choose values from 22kΩ and above for R2 - R16.


MikMo said...

Thats an amazing variety of sounds . Do you have any schematics of the oscillator(s) you use ?

Sebastian Tomczak said...

Hey mikmo,
I added the schematic. I know it looks a bit all over the place (the logic of the schematic is what i mean) but i was just making it up as i went along.


MikMo said...


I'm becoming a fan of your site :-) And also the Milkcrate project, especially the "Call the doctor" session recrdings. Some really nice tracks.


Sebastian Tomczak said...

your work on computer interfacing with circuit bent toys is excellent. I have had similar ideas, and I don't think this is something that is a normal practice when it comes to bent stuff.

I recently have been teaching a class that combines aspects of circuit bending, digital logic ICs, physical computing, physical interfacing and breadboarding basics. In this class, we have been using Arduino boards, 4066, 4051 etc.

So yeah, it is quite similar to your setup in a way. Nice work on the screen-based pseudo vactrol control for pitch manipulation.


MikMo said...


The Vactrol solution works quite well. I guess it could have been made a little more predictable with a digital pot like the ones yuo have been working with, but when i first made the thing, the digital pots were extremly expencive and only had 16 different values.

Sebastian Tomczak said...

Digital pots still have their own problems, being limited to 5V power supply and 5V maximum handling. Also, I have only seen digital pots in values up to around 100KΩ, however for bending stuff higher resistances are often very useful (which is where a vactrol using an LDR comes in handing). It is also possible to construct simple digital pots by one's own hand, so to speak by chaining a set of multiplexer together and tying them to multiple resistance ladders.

This example:

could be easily expanded to include 16, 24, 32 steps. And this way, you get to choose operating voltage (3V - 15V) as well as resistance.

Still, use of a vactrol in the method you describe is a nice and simple solution to the problem. And takes much less effort!

Anonymous said...

Hey, are those ICs 74HC series?

Sebastian Tomczak said...

nope. 4000 series.