[sdiy] Fast envelope follower circuit needed..

Dan Snazelle subjectivity at hotmail.com
Thu Mar 28 14:55:28 CET 2013

Sent from my iPhone

On Mar 28, 2013, at 9:21 AM, Tom Wiltshire <tom at electricdruid.net> wrote:

> 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

Though i work with c//arduino/AVRS not pics, this sounds very appealing! Can anyone recommend a place to learn about writing C code for an envelope follower? How do you do it? Shift signal to 0-5, then......


> 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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