Wednesday, March 15, 2017

Fun with Sea Moss: 4040 Divided Oscillator

The ideas in this post largely come from Nicolas Collins' excellent book 'Handmade Electronic Music', which I would highly recommend.

The 4040 binary counter takes a clock input, and has twelve outputs. Each output (labelled Q0 - Q11 in the pinout diagram above) is a successive power-of-two division. This is summarised in the following table: 

A 40106 oscillator is used as a clock source, which is feed into pin 10 of the 4040 binary counter. The various outputs of the 4040 can be listened to by simply moving the signal connection around to different outputs. 

In terms of musical pitch and frequency, each successive output of the 4040 will sound an octave lower. For example, if the clock frequency is 3.52 KHz, then output 1 is 1.76KHz, output 2 is 880 Hz, output 3 is 440 Hz, output 4 is 220 Hz and so on.

Different outputs can be combined by using a 10k - 100k resistor per output in between the output pin and the signal connection. The waveforms will combine, creating simple additive synthesis.