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

Tom Wiltshire tom at electricdruid.net
Wed Dec 15 10:08:06 CET 2021

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 <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.


       Electric Druid
Synth & Stompbox DIY

> On 15 Dec 2021, at 01:34, Jean-Pierre Desrochers <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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