[sdiy] Modulated ADSR Generator

[Andre Majorel]

On 2011-07-09 10:22 +0930, Matthew Smith wrote:

> Current concept is an ATMega128 reading 8 parameter pots, doing some
> sums/lookups, sending values via SPI to a Microchip MCP4821 12-bit
> DAC, which then outputs a 0-5V control voltage.
> 
> I was wondering if there would be any value in sacrificing one of
> the pots in favour of sampling another control voltage, which would
> be used as a multiplier for the value already being fed to the DAC.

Popular as it is, ADSR is not a very good model because it has
linked variables.

D is redundant when S is set to maximum.

How often do you set S to non-zero when A is set to maximum and
D to minimum ?

How often do you set S to anything other than minimum or maximum
when A is longer than a few tenths of a second ?

On the other hand, ADSR cannot do two-stage attacks or decays,
which would be genuinely useful.

There is probably a way to describe all common envelopes with
less than four parameters. Maybe two or three parameters and a
few mode switches.

-- 
André Majorel http://www.teaser.fr/~amajorel/