[sdiy] Cheapest, simplest but still reliable VCO & VCA for polyphonic project

[George Hearn]

There are many reasons I'm fond of analogue ADSRs.  For a digital equivalent
(specially in a polysynth) one would need to model device to device
variations in line with those experienced in analogue, such as non-ideal
capacitor effects (dielectric absorption for example), varying time
constants, varying attack peak voltages, curve distortions due to feedback
design etc. in order to match all the subtleties which I would argue is what
sets one instrument apart from another.  This is not a simple task, and for
a digitally generated adsr I would want the DAC to update at above audio
rates with at least 16 bits, more even, amounting to expensive components
and system complexity I would like to avoid.  
	Branded an "analogophile" I may be but this is just my opinion!  Of
course there are innumerable merits to digital design too, and it might suit
other instruments to go this way. I would go for digital env's if I already
had a fast processor and fast high res DAC in a system, but I wouldn't cut
corners and squeeze it into an underpowered or under-specced digital system.
In my opinion that would not give the ADSR the importance weighting it
deserves in how it affects the instruments sound.  Just my thoughts. G

-----Original Message-----
From: Paul Maddox [mailto:paul.maddox.mail-list at synth.net] 
Sent: 09 January 2009 19:19
To: George Hearn
Cc: synth-diy at dropmix.xs4all.nl
Subject: Re: [sdiy] Cheapest, simplest but still reliable VCO & VCA for
polyphonic project

George,

>  Believe me I
> would love to cut corners in components and cost but sound is  
> paramount to
> me, LFO's can be digital, but not env's.

oooo, them's fighting words them is....

Why do not think digital is suitable for ADSRs?
Defender's EGs are digital (MAX541 for VCF cutoff EG, with Vref  
controlled by another DAC for EG depth).

Paul