[sdiy] Using audio to trigger CMOS

[anthony]

The Polyfusion Envelope Follower is similar, having the variable threshold, 
but no lag. It's an easy circuit though. I've built one: it's great for 
using guitar signals to trigger, well, just about anything.

----- Original Message ----- 
From: "Jason Proctor" <jason at redfish.net>
To: <synth-diy at dropmix.xs4all.nl>
Sent: Monday, April 28, 2008 1:12 PM
Subject: Re: [sdiy] Using audio to trigger CMOS


> sounds like a job for an envelope follower with gate. IIRC, the fine 
> Oakley implementation of this involves a rectifier feeding a comparator 
> with a variable threshold. there's variable lag on the output of the 
> rectifier too so that the comparator doesn't flap all the time if the 
> input signal varies a lot in amplitude.
>
> when i had one, it worked like a charm.
>
> hth
>
>>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
>>
>>
>>_______________________________________________
>>Synth-diy mailing list
>>Synth-diy at dropmix.xs4all.nl
>>http://dropmix.xs4all.nl/mailman/listinfo/synth-diy
>
> _______________________________________________
> Synth-diy mailing list
> Synth-diy at dropmix.xs4all.nl
> http://dropmix.xs4all.nl/mailman/listinfo/synth-diy
>
>