[sdiy] Using audio to trigger CMOS

[Justin Owen]

Hey all,

I'm hoping for some help refining a circuit I'm working on that uses an audio signal as a clock to trigger a 4024 Ripple Counter.

The audio signal is a 1/16th note sequence that is meant to represent a square wave i.e. Note On = High (or Mark), Note Off = Low (or Space).

I've got a prototype that uses an AC Coupled gain stage to take the audio input and feeds it into a comparator.

The current version works(ish) minus some problems which I think are down to some ac coupling mistakes and a lack of headroom on my power supply - all of which I think I can sort - but I was wondering if there also needs to be any type of rectification between the gain stage and the comparator?

I can be pretty specific about the type of audio signal that goes in (I'm currently using a PWM square wave with a 90/10 mark/space ratio at a fairly high pitch - which I figured would give the greatest ratio of High to Low signal when the Note was 'on') - I'm not expecting to get a square wave trigger out of a guitar input for example - but I'd like the circuit to be as safe and reliable as possible.

Any advice? Appreciated as always

J