Under the bonnet

The world of electronics can often feel like a closed shop to the uninitiated - all those chips and wires and blobs, how on Earth do they all fit together? Well, we Keshcologists have been making some inroads into this, through the rather yummy art of circuit bending. Circuit what, you may ask with a raised eyebrow. The art of circuit bending is basically the art of the creative short circuit. It involves taking the back off of electronic toys and testing out new connections between parts of the circuitboard, with the hope of uncovering features never intended by the manufacturer. It's a good way of learning what all the constituent parts of a circuit are there for (and which ones to avoid if you want to keep your equipment intact). People have done it with synthesizers, toys, Furbies, video game systems, but I have stuck so far with cheap keyboards.

Reed Ghazala is a king of home electronic noise mayhem and his well-detailed book Circuit-Bending: Build Your Own Alien Instruments is available through Amazon UK.

The kit you need for successful circuit bending is simply a few tester leads (the ones with crocodile clips at the ends), some wire, a soldering iron, and a few variable resistors. We'll come back to those.

On Sunday night I took out a bag with a Poundland keyboard inside. Taking the back off revealed that the circuitry was pretty minimal - one board about the length and width of a Fry's Turkish Delight, upon which were a couple of resistors, eight connections for each of the eight keys, two triggers (one for demo, one for normal play), and a little chip hidden underneath a black blob. This has the demo rhythms inside and works the same way as a musical Christmas card, i.e. they weren't demos at all but just something else that makes a tune. For one thing, the demos had three-voice polyphony whilst the actual keys can only be played one at a time.

It was really necessary to operate as a two-man team for this. Attaching one tester lead to the first resistor, we explored all the other connectable points on the circuit, and found two potential bends - one that sent the pitch and speed up by about two octaves, and one that had a kind of crumbly volume control. This is where the variable resistors come in. I had bought a grab bag of 20 from Maplin, which were all different strengths. They act as a controller for your effect, and different strengths of variable resistor will act in varying strengths. (If you want to have the option of turning the effect off completely, you have to solder in an on/off switch before the variable resistor.) After experimenting with a few of these we found a good one that could take the pitch up from merely quite fast to ludicrously quick, quite nicely.

We then tried putting a second variable resistor after the first. This was a bit of a waste of time, although the signal occasionally started wobbling as if through a chorus pedal.

Leaving that connection, we tried attaching a clip to the second resistor. There were a few possibles here. We found three connections that added harsh overtones that increased in intensity as you moved the variable resistor, until it sounded like the speaker was going to pop. Each added subtly different overtones. We then found one that dropped the pitch and speed right down into the depths, to create a great "systems failure" noise.

The soldering began at 12am and didn't finish until 2am. This was partially down to lack of practice (it's been a while) but also to the dynamics of an unfamiliar soldering iron. It took ages to heat up and needed a good clean. Also the titchy circuitboard kept moving around.

Anyway. The next step is to decide how the new connections should be housed - whether to make holes in the existing case, or to transfer the whole thing into a new case, as it would fit into a little box quite easily. I'm certainly tempted to cut off half the superfluous plastic around the edges.

Pics and video to follow...