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

Guy McCusker guy.mccusker at gmail.com
Sat Dec 18 13:03:01 CET 2021


Can you give us a clue on how a wavelet transform would be useful in an
envelope follower? I don't know much about the area but at first glance it
does not seem like the right tool for the job.

On Fri, Dec 17, 2021 at 11:25 PM Mike Bryant <mbryant at futurehorizons.com>
wrote:

> If anybody is thinking of doing this digitally, you might want to read up
> on the Continuous Wavelet Transform.   Then once you realise your DSP isn’t
> up to it, have a look at the Discrete Sub Band Transform, aka Wavelet
> Packet Decomposition.  This gives as accurate results as the Discrete
> Wavelet Transform with less group delay problems, and given enough
> processing power is able to decompose even the human voice in real time.
>
>
>
>
>
> *From:* Synth-diy [mailto:synth-diy-bounces at synth-diy.org] *On Behalf Of *
> Mr&MrsAccount
> *Sent:* 17 December 2021 21:41
> *To:* Jean-Pierre Desrochers; 'Tom Wiltshire'
> *Cc:* synth-diy at synth-diy.org
> *Subject:* Re: [sdiy] Best & fastest envelope follower schematic..
> anybody ?
>
>
>
> Remember that high order filters don't come without their own baggage...
>
>
>
> They suffer from greater group delay (which could be a problem) and poor
> transient response (also a problem).
>
>
>
> Especially in a use where the input could start at zero or suddenly return
> to zero, the overshoots can be a killer.
>
>
>
> I've been making filters to isolate the fundamental of Guitars for many
> (now many mnay) years.   The settling times are longer than the delay of
> the guitar signal itself, therefore the delays...
>
>
>
> ------------------------------
>
> *From: *Jean-Pierre <jpdesroc at oricom.ca>
> *To: *'Tom <tom at electricdruid.net>
> *Cc: *synth-diy <synth-diy at synth-diy.org>
> *Date: *Friday, 17 December 2021 10:39 AM EST
> *Subject: *Re: [sdiy] Best & fastest envelope follower schematic..
> anybody ?
>
> > This would be the digital equivalent to the single pole RC. It should be
> possible to get better ripple suppression by using higher order filters.
> Harald showed that he got a better response using a fourth-order filter.
>
>
> So.. how can I modify the C1 section to get for example a fourth-order
> filter ?
> To do it the way the signal flows across C1 is a bit confusing..
> The signal comes from the left side but the clamping comes from D1 at
> right side.
>
> I know how to implement high order filters in circuits but only
> if I know the signal flow direction..
>
>
>
>
>
> *De :* Synth-diy <synth-diy-bounces at synth-diy.org> *De la part de* Tom
> Wiltshire
> *Envoyé :* 17 décembre 2021 08:37
> *À :* Martin Klang <mars at pingdynasty.com>
> *Cc :* synth-diy at synth-diy.org
> *Objet :* Re: [sdiy] Best & fastest envelope follower schematic.. anybody
> ?
>
>
>
> This would be the digital equivalent to the single pole RC. It should be
> possible to get better ripple suppression by using higher order filters.
> Harald showed that he got a better response using a fourth-order filter.
>
>
>
>
>
> On 16 Dec 2021, at 16:26, Martin Klang <mars at pingdynasty.com> wrote:
>
>
>
> I think an envelope follower with no lag is called a rectifier.
>
> Jokes aside, there are a number of options available but ultimately it
> comes down to filtering.
>
> For digital envelope followers, I like to use a simple exponential average
> (aka leaky integrator, a first-order IIR filter) on the fully rectified
> signal and tune the time constant to the expected input signal. Generally
> you want it to be fast, but not so fast as to track the waveform
> oscillations, even at say 20 Hz. This makes a computationally very
> efficient follower with predictable results.
>
>
>
> best,
>
>
>
> Martin
>
>
>
> On 16/12/2021 01:36, Jean-Pierre Desrochers wrote:
>
> 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.
>
>
>
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