an idea + zipper noise

[Rob Hukin]

>        Seriously, the 8051 route seems good, cheap component cost, 
>        cheap (or free) developement tools also using the chips i/p
>        sorry should be i/o, ports you do away with a lot of the
>        glue logic you normally need.

I agree. I'be been anxiously waiting for the Paia MIDI2CV8 to come out
(probably about a year now, eh John?) to use that as a starting point...

>        Someone mentioned zipper noise when using ADC/DAC. I thought 
>        that zipper noise was only caused like this. You have a signal
>        (audio) going through a VCA the gain of which is controlled by
>        a DAC. If the DAC output voltage is changed when the signal is
>        not at the zero crossing point, you get a sudden jump in signal
>        level giving rise to the unwanted distortion. Maybe the system
>        needs some zero crossing feedback or the DAC/MUX outputs need toi
>        be suitable filtered.

Zipper noise is basically the quantised steps being audible. This can
happen with console VCA's if the DAC feeding it doesn't have high enough
resolution - you can hear the discrete steps. This could also be a problem
for pitch bends, glides and such like.

rob.

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Robert Hukin                            phone: +44 1273 678639
Laboratory of Experimental Psychology   fax  : +44 1273 678611
University of Sussex                    email: robh at epunix.susx.ac.uk
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