the 4040 cmos IC is a 12bit ripple counter, which divides the incoming clock frequency by 2, 4, 8, 16, 64 etc up until 4096, over 12 outputs, labeled Q1 – Q12. if we take an oscillator from previously and use a 1uf capacitor to generate a slow, LFO like, clock pulse and feed it to the 4040, the outputs will pump out some interesting rhythmical sequences when you connect 1 or more of the Q outputs to the amp. this in itself sounds great, but they can also be used as clock sources themselves for other things. i got the idea of using the counter from nicholas collins book, but below are some of my findings and uses for the basic circuit.

the 4040 pattern generator

We’ll need:

• bread board
• 9v battery & connector
• jumper wire
• 40106 IC
• 4040 IC
• 1uf capacitor
• 1meg pot
• various pots, diodes, led’s, a vactrol, flex resistance strips and resistors or just about anything you can think of to change the outputs.
• the 100k resistor to ground on the 4040 clock input just helps to pull it low when there is no signal, and provides a more stable pulse.

you can knock up the circuit above on strip board to use for other things, it comes in handy for testing ideas. if you have anything that requires a clock pulse, such as a sequencer, then connecting various outputs of this to it instead of the normal clock pulse, will make skip through the steps in order, but in a far more interesting pattern, creating pauses, quick notes and long notes. in turn, it can also be connected to a synth for control voltage. i’ve had variations of this connected to a moog and a patched out soundlab mini synth, in the same way you would use an external lfo or voltage controller keyboard.

in the ripple synth i used a vactrol to control the resistance of a second oscillator, thus affecting the pitch of its output in the same way as a pot would do but automated. the vactrol is fed a control voltage from any source, such as a pot or pulse from another lfo or something, but i used the outputs of  the 4040 to switch on the led in the vactrol.

a vactrol is a type of optocoupler. it has an led and a light dependent resistor in a sealed unit. you can make these yourself or buy them, but they can be expensive. i found the easiest way to make them is to take a bic pen, chop a bit off the case/tube and insert an led and ldr in each end, then a splodge of silicon to seal the ends and hold everything place. be careful not to let the legs of the led and ldr touch and short circuit, then wrap the whole lot in a bit of electrical tape or heat shrink tubing.

the current of the outputs is a little too high to drive the vactrol directly, and will eventually burn out the led, so make sure to use a suitable resistor in between them, 1k should do.