[sdiy] Best & fastest envelope follower schematic.. anybody ?

Thu Dec 16 01:36:56 CET 2021

Here is my goal..

I need a circuit that will take an AC signal and will shift level it from
a DC offset extracted from its min & max Peaks..
Ex: Suppose you have steady +/- 5v peak sine wave coming in this circuit,
The output would be the same waveform but shifted up to +5vdc. 

So 0 to +10vdc.
That final waveform would be much usable for a 0-5vdc control voltage input
than the original AC waveform.
Now the challenge is to do the same with a level changing AC signal.

In the case of a steady waveform this ‘level shifter’ could be an opamp that would add half of the peak to peak voltage as an offset DC voltage,
But here I’m looking for something that will be more versatile
to handle varying level waveform.

De : Synth-diy <synth-diy-bounces at synth-diy.org> De la part de Adam Inglis (synthDIY)
Envoyé : 15 décembre 2021 19:14
À : Synth-diy at synth-diy.org
Objet : Re: [sdiy] Best & fastest envelope follower schematic.. anybody ?

On 16 Dec 2021, at 07:44, Paul Perry via Synth-diy <synth-diy at synth-diy.org <mailto:synth-diy at synth-diy.org> > wrote:

There are no perfect followers, but sometimes there are ones that are useful for a particular application.

Exactly, which begs the question, what purpose does JP have for this no-lag follower? Because musically, most followers are ‘good enough’…

A

paul perry melbourne australia

On Thu, 16 Dec 2021 at 02:35, Benjamin Tremblay via Synth-diy <synth-diy at synth-diy.org <mailto:synth-diy at synth-diy.org> > wrote:

I lost all interest in envelope followers when I tried out some designs and observed the lag. 
These are mostly “envelope smoothers” and most are barely any better than an old incandescent vactrol attenuator circuit used in FM broadcast.
They mostly just drive non-musical effects under the category “something weird happens when I play my guitar”.  Pre-filtering the audio probably helps but there’s no guidance on best all-round EQ.
Only The Residents got much mileage out of envelope followers over the years.

> On Dec 15, 2021, at 10:05 AM, Jean-Pierre Desrochers <jpdesroc at oricom.ca <mailto:jpdesroc at oricom.ca> > wrote:
> 
> Hi Tom,
> 
>> Harry Bissell's envelope follower is well thought of for its combination of speed and accuracy.
>> https://modwiggler.com/forum/viewtopic.php?t=109067
> 
> This is a very clever project and neat design.
> But still too much ‘lag’ on the falling edges incoming signal.
> So far.. a PIC would do best with least components..
> Hmmmm...
> As usual.. Thank you for you good suggestion anyway !
> JP
> 
> 
> De : Tom Wiltshire <tom at electricdruid.net <mailto:tom at electricdruid.net> > 
> Envoyé : 15 décembre 2021 04:08
> À : Jean-Pierre Desrochers <jpdesroc at oricom.ca <mailto:jpdesroc at oricom.ca> >
> Cc : Synth-diy at synth-diy.org <mailto:Synth-diy at synth-diy.org> 
> Objet : Re: [sdiy] Best & fastest envelope follower schematic.. anybody ?
> 
> Hi JP,
> 
> Harry Bissell's envelope follower is well thought of for its combination of speed and accuracy.
> 
> https://modwiggler.com/forum/viewtopic.php?t=109067
> 
> It's a good circuit, but pretty complicated, especially for an effect pedal design. So like you, I thought "PIC!", and had a go at implementing it in firmware.
> 
> The round-robin three peaks detectors are easy enough. Doing the output filtering is more demanding on a chip with no multiply, but I managed it by being choosy about the filter coefficients and keeping things binary friendly. The end result was pretty good and used a little PIC to the maximum extent.
> 
> HTH,
> Tom
> 
> ==================
>       Electric Druid
> Synth & Stompbox DIY
> ==================
> 
> 
> 
> 
> On 15 Dec 2021, at 01:34, Jean-Pierre Desrochers <mailto:jpdesroc at oricom.ca <mailto:jpdesroc at oricom.ca> > wrote:
> 
> Hi all,
> I’m looking for a fast and accurate voltage follower circuit.
> There are plenty of them on the web to build but they all
> suffer of inaccuracy and lag on the final DC output (final stage of low pass to smooth off the incoming peaks).
> The incoming voltage will be a varying 0 to +/-5v peak.
> I thought about implementing a solution using a small PIC with ADC/DAC
> but even if these micros are very cheap this solution would be overkill.. would it be ?
> So far the available circuits have too much lag on their DC output.
> (The envelope takes too much time to get back to zero after a fast incoming peak)
> Any known & reliable circuits ?
> JP
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