[sdiy] Digital Potentiometers vs DACs n VCA's?

[Bill Berzinskas]

thanks harry..    as for still using the d.pot, and using it with a VCA, 
would i just set it up as a voltage divider to feed into the VCA CV?  thru 
some sort of lag generator?    is that right?   just checkin..

----- Original Message ----- 
From: "harrybissell" <harrybissell at prodigy.net>
To: "Bill Berzinskas" <wberzinskas at nc.rr.com>
Cc: <synth-diy at dropmix.xs4all.nl>
Sent: Monday, April 04, 2005 12:01 AM
Subject: Re: [sdiy] Digital Potentiometers vs DACs n VCA's?


> Hello Bill
>
> If you want zero zipper noise, I'd use either the digital pot or DAC
> driving a VCA through some filtering. This way you would get continuous
> control without any clicks.
>
> What to do depends on how fast you need to update the values. Oberheim
> did a really clever circuit in the Matrix 6 / 1000 (probably others as
> well) where
> they have can change a sample hold value either directly (fast change)
> or through
> a high value resistor (slow change). Check the web and see if that might
>
> help you...
>
> H^) harry
>
> Bill Berzinskas wrote:
>
>> Hello list.. after thinking that digital pots where the way to go, i'm
>> starting to have my doubts.. my major problems with them are audio
>> noise when audio is run straight thru them to attenuate into a mixer
>> and.Update noise.. since they're serial, i have to update them all at
>> once, i think i get noise on each update.. would I get better
>> performance if I used them to control the gain of an opamp
>> instead? OR, would it be better to go with some sort of setup of DAC
>> and VCA..  like an 8-bit DAC going into an SSM2164 or something? any
>> input on this would be spectacular, as i'm rather annoyed with the
>> background zipper sounds..  :-P
>
>