[sdiy] Using audio to trigger CMOS

[anthony]

Ray Wilson has a circuit on his Music From Outer Space website that I think 
would do what you want.

I'll describe a simple circuit that I would try: use an opamp like a TL071 
or TL081 (or TL082, etc...) with a fair amount of gain (put in a pot to 
adjust maybe) and then connect the output to a Schmitt trigger like a 40106, 
4584 or even a 4093 connected like an inverter (both inputs tied together), 
and then run in through a second stage so it's positive again.

I can't remember if this is one of those situations where you want to run 
the opamp from a bipolar supply and power the CMOS gate by tying VDD (+) to 
ground and VSS (-) to the -15V (or whatever you're using) rail. I do know 
it'll work that way anyway. Don't know if you NEED to do it that way...

The Carol Burnett Show,
Anthony

----- Original Message ----- 
From: "Justin Owen" <juzowen at googlemail.com>
To: <synth-diy at dropmix.xs4all.nl>
Sent: Monday, April 28, 2008 9:07 AM
Subject: [sdiy] Using audio to trigger CMOS


> 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
>
>
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