Fast analog sw. as VC resistor

[Daniel Oberfeld]

Hi Brad,
 
> I'm not trying to be argumentetive here, but just pointing out some
> design issues I'm unclear on. Is the idea to build a VC ADSR gen - or
> to build the perfect VC pot? ADSR is pretty easy - VC pot might be a
> bit harder.
> Another question, just for the heck of it: does this HAVE to be VC? I
> mean, if the idea is a small preset synth and you need multiple
> controls, you can get a Maxim chip with 8 8bit Iout DACs in a package.
> You CAN use a micro to set it, but all you really need is a shift
> register. To control many, use the same shift reg with an extra
> control bit to enable another device. One of these chips costs 5
> bucks: that's less than a buck a control. Five bucks to control two
> ADSR gens. Not too shabby, and it's easy to lay out one 20 pin chip. 
> 
That sounds promising but I have to confess that I didn't see the 
schematics for a *discrete* VC ADSR yet, just CEM3310 stuff (e.g. in 
Thomas Henry's book). Soooo- could you provide some schems or name 
some sources for that (I have no acess to Electronotes :-(  ).

This multi-dac stuff also sounds interesting but how to do it with 
just a shift 
register - you'd like to have realtime acess, how does the shift 
register 'learn' about the actual pot-values on your synth? Without 
ADC and all that stuff?  As before: all informations on this topic 
would be welcome!!

Regards,
Daniel