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

[harrybissell]

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