[sdiy] Sigma-Delta DAC schematic?

[Grant Richter]

Hi Phil,

Thanks for the links.

This is what I was thinking about. An arbitrary function generator just
generates an arbitrary voltage "wiggle". Perhaps there are cheap, low parts
count circuits that would generate interesting sets of "wiggles" also.

A pseudo random shift register outputs a serial bit string. Depending on the
length of the shift register, it will repeat in some number of clock cycles.

So if you had a neat and smooth way to turn the serial bit string into
analog levels, you could make an LFO with different kinds of repeating
"wiggles" instead of the more traditional waveforms.

If you have access to all the bits in the shift register, you could just
hang a parallel DAC on it, but a DAC that took a 1 bit input would be ideal,
because the PSSR outputs a serial 1 bit string.

Most random source designs deliberately avoid repetition, but in this case
we are looking for it.

I was also thinking about "parsing" a bit string in different ways. For
example, a 24 bit serial A/D converter output could be parsed as 12 * 2 bit
values or 8 * 3 bit values etc., so a static input voltage could point to
different patterns or shapes of "wiggles".

Just musing on new CV generators...

> From: "phillip m gallo" <philgallo at attglobal.net>
> Reply-To: <philgallo at attglobal.net>
> Date: Wed, 9 Jul 2003 11:36:48 -0700
> To: "Grant Richter" <grichter at asapnet.net>
> Cc: "synth diy" <synth-diy at dropmix.xs4all.nl>
> Subject: RE: [sdiy] Sigma-Delta DAC schematic?
> 
> Grant,
> 
> 
> Do you mean anything special "beyond" the fact that it is a 1 bit DAC
> architecture?
> 
> Some ref's:
> 
> http://www.stereophile.com/showarchives.cgi?374:0
> 
> http://www.sscs.org/jssc/00bp.pdf
> 
> http://www.nalanda.nitc.ac.in/industry/AppNotes/BurrBrown/appnotes/DesignSem
> 5.pdf
> 
> regards,
> p
> 
> 
> 
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