RE: [AH] the snappiest envelope ever

From Phil a
Sent Tue, Nov 11th 2008, 14:26

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Actually I just received this information from Doepfer=2C thought I should =
share :
The values for attack=2C 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 tha=
n fast...

Philippe



> Date: Tue=2C 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
>=20
> Hi Phil
>=20
> > So if I am right it would mean that the fastest setting of the A-140 wo=
uld make the full envelope's duration faster than the sole attack of the Cw=
ejman envelope ?
> No. The minimal allover time of the envelope consists of 50uS Attack=2C=20
> 50uS Decay=2C 50 uS Release -> 150uS.
>=20
> > Do you think this is plausible or could this be a mistake on the Doepfe=
r site which should read 0=2C5 ms instead of 50us for the full envelope dur=
ation ?
> Yes it is true. I sat together in the "Cafe Freiheit" in Munich with=20
> Dieter Doepfer=2C Andreas Merz=2C and some other well known synth freaks =
not=20
> to name here=2C when we talked about values like this one. I also own the=
=20
> schematics and the cap/resistor-values (incl the internal resistance of=20
> the switching CMOS) go for a value like that. I also modified two of my=20
> A-140's because I think the fast-value is too fast.
>=20
>=20
> And another comment to this topic in general. I often see=2C that people=
=20
> often do not really mean "envelope speed"=2C when they say "snappy" (or i=
n=20
>   other relations "punchy").
> Analogue envelopes usually are based on loading/unloading an capacitor=2C=
=20
> which is an exponential process. This has the consequence that the=20
> impression of an voltage-envelopes characterstics is mostly related to=20
> 1.) the modulation destination it serves (exponential or linear) and 2.)=
=20
> the modulation depth of this destination.
>=20
> The problem exponential and linear is quite easy to understand: If I=20
> modulate an exponential input with the exponential envelope=2C the=20
> "characteristics of the overall modulation will be double-exponential=2C=
=20
> which may cause faster/snappier sounds. The rule by thumb for=20
> VCA-modulation says: for envelope modulation an linear VCA is=20
> recommended (the envelope already offers the required exponential=20
> characteristics)=2C for any other modulation source like LFOs=2C Velocity=
=2C=20
> Audiomodulation a exponential VCA is recommended.
>=20
>=20
> More difficult is the topic modulation amount.
> "Exponential" means: most of the action happens at the start of the=20
> action. E.g. the attack goes very fast to ~80% of the overall range=2C bu=
t=20
> takes much longer for the remaining ~20%. Now think of an Lowpass-VCF=20
> with positive envelope modulation. The envelope is a typical Spike=2C wit=
h=20
> zero attack quite short decay=2C and zero sustain. It should sound=20
> something like "psiiiaaaoouuu".
> Lets now say the cutoff frequency is at 1000Hz (which is already quite=20
> bright) and the envelope amout is turned up fully=2C  so the modulated=20
> cutofffrequency reaches 20000Hz at the envelopes maximum. Now the fast=20
> 80%-part of the envelope (the "snappy" portion) happens when the cutoff=20
> goes down from 20000Hz to 2500Hz. Unfortunately you don't hear much=20
> difference between these two values. It will be between "very bright"=20
> and "still quite bright". The real audible difference in sound will=20
> happen between 2500Hz and 1000Hz=2C but unfortunately this change will be=
=20
> done by the much slower 20%-part of the envelope.
> The result is: though the envelope is infact fast (=3D could provide=20
> snappy sounds)=2C you will recognize it as slow=2C because of the envelop=
e=20
> amount and the base-offset of the modulated parameter.
>=20
>=20
>=20
> Florian

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