Re: [AH] the snappiest envelope ever

From Amos
Sent Tue, Nov 11th 2008, 15:23

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I think Florian makes some good points and offers good descriptions here.
Further thought on this topic should suggest the question: "how fast do I
need an envelope to be, for what purpose?"
If you are generating or emulating sounds, there is a certain order of
magnitude on which changes occur over time, depending on what changes we ar=
e
talking about.  Below or above a certain order of magnitude you will not
gain anything useful for the kind of sound you are trying to synthesize.
-amos
On Tue, Nov 11, 2008 at 8:26 AM, Phil <redacted@example.com> wrote:

>
> Actually I just received this information from Doepfer, thought I should
> share :
> The values for attack, decay and release are about 1/2 of the full envelo=
pe
> time (e.g. about 20-25 us for the shortest time).This is getting faster
> than fast...
>
> Philippe
>
>
>
> > Date: Tue, 11 Nov 2008 12:45:36 +0100
> > From: fanwander@mnet-online.de
> > To: redacted@example.com
> > CC: redacted@example.com
> > Subject: Re: [AH] the snappiest envelope ever
> >
> > Hi Phil
> >
> > > So if I am right it would mean that the fastest setting of the A-140
> would make the full envelope's duration faster than the sole attack of th=
e
> Cwejman envelope ?
> > No. The minimal allover time of the envelope consists of 50uS Attack,
> > 50uS Decay, 50 uS Release -> 150uS.
> >
> > > Do you think this is plausible or could this be a mistake on the
> Doepfer site which should read 0,5 ms instead of 50us for the full envelo=
pe
> duration ?
> > Yes it is true. I sat together in the "Cafe Freiheit" in Munich with
> > Dieter Doepfer, Andreas Merz, and some other well known synth freaks no=
t
> > to name here, when we talked about values like this one. I also own the
> > schematics and the cap/resistor-values (incl the internal resistance of
> > the switching CMOS) go for a value like that. I also modified two of my
> > A-140's because I think the fast-value is too fast.
> >
> >
> > And another comment to this topic in general. I often see, that people
> > often do not really mean "envelope speed", when they say "snappy" (or i=
n
> >   other relations "punchy").
> > Analogue envelopes usually are based on loading/unloading an capacitor,
> > which is an exponential process. This has the consequence that the
> > impression of an voltage-envelopes characterstics is mostly related to
> > 1.) the modulation destination it serves (exponential or linear) and 2.=
)
> > the modulation depth of this destination.
> >
> > The problem exponential and linear is quite easy to understand: If I
> > modulate an exponential input with the exponential envelope, the
> > "characteristics of the overall modulation will be double-exponential,
> > which may cause faster/snappier sounds. The rule by thumb for
> > VCA-modulation says: for envelope modulation an linear VCA is
> > recommended (the envelope already offers the required exponential
> > characteristics), for any other modulation source like LFOs, Velocity,
> > Audiomodulation a exponential VCA is recommended.
> >
> >
> > More difficult is the topic modulation amount.
> > "Exponential" means: most of the action happens at the start of the
> > action. E.g. the attack goes very fast to ~80% of the overall range, bu=
t
> > takes much longer for the remaining ~20%. Now think of an Lowpass-VCF
> > with positive envelope modulation. The envelope is a typical Spike, wit=
h
> > zero attack quite short decay, and zero sustain. It should sound
> > something like "psiiiaaaoouuu".
> > Lets now say the cutoff frequency is at 1000Hz (which is already quite
> > bright) and the envelope amout is turned up fully,  so the modulated
> > cutofffrequency reaches 20000Hz at the envelopes maximum. Now the fast
> > 80%-part of the envelope (the "snappy" portion) happens when the cutoff
> > goes down from 20000Hz to 2500Hz. Unfortunately you don't hear much
> > difference between these two values. It will be between "very bright"
> > and "still quite bright". The real audible difference in sound will
> > happen between 2500Hz and 1000Hz, but unfortunately this change will be
> > done by the much slower 20%-part of the envelope.
> > The result is: though the envelope is infact fast (=3D could provide
> > snappy sounds), you will recognize it as slow, because of the envelope
> > amount and the base-offset of the modulated parameter.
> >
> >
> >
> > Florian
>
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