[sdiy] Fast envelope follower circuit needed..

Jean-Pierre Desrochers jpdesroc at oricom.ca
Thu Mar 28 14:39:28 CET 2013


You are right Tom,

I was thinking of a 'digital' solution using a PIC..
But I was slowed down in my thoughts because I 'try'
not to use that much digital stuff in my analog synth projects.
The digital way to solve analog problems is very appealing !
And for this function I think I'll need some 'inteligence'
in the way the envelope will be generated.
The average analog envelope follower circuits have flaws
and I'll have to think about what I can accept out of them
and what I won't.
JP

Le 2013-03-28 09:21, Tom Wiltshire a écrit :
> Hi JP,
>
> The typical circuit is a precision full-wave rectifier (or sometimes
> not even a full wave rectifier) followed by a filter. It works pretty
> well, but is not flawless, especially at low frequencies. The many
> Auto-wah/envelope filter circuits have examples if you need a
> schematic.
>
> You're asking for a lot if you want both "fast" and "down to 1Hz".
> After all, the rise time on a 1Hz sine waveform is 250ms, which in my
> view is "slow".
>
> Have you considered using a digital solution? Shift the signal to
> 0-5V range, then feed it to the ADC input of a PIC/AVR (You're a PIC
> programmer, I know). Digital rectification is easy. Then you could do
> the smoothing in software. This might allow you to do some clever
> tricks that you couldn't easily do with analog, like have a filter
> that responds to the incoming signal frequency. Just a thought.
>
> Regards,
> Tom
>
>
>
> On 28 Mar 2013, at 12:44, Jean-Pierre Desrochers <jpdesroc at oricom.ca> 
> wrote:
>
>> Hi List,
>> I'm sure this has been already discussed in the past
>> but I'm looking for a fast envelope follower circuit
>> schematic to rectify an incoming +/-2.5v AC waveform
>> to a rectified 0-5v wave.. The wave frequency could
>> go as low as 1 hz and sometimes will not be symetrical.
>> Any circuits welcomed !
>> JP
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