[sdiy] modern AD/DA chips?

Jean-Pierre Desrochers jpdesroc at oricom.ca
Thu May 7 14:52:44 CEST 2009


Some months ago I was starting a Polyphonic MIDIdac
project like you seam to do..
After several emails and suggestions from the
list members I finaly decided not to go with
the mux 4051 & s/h opamps design type
because of the ripple effect 'zipping' sound
noticable on each s/h opamp outputs at idle.
My MIDI dac will use one PIC16F877 and will
drive 6 X 1v/oct CV's,  6 X velocity CV's and
finaly 6 X gate outs.
All the CV outs will have there own MAX551 12bits dacs
for CV stability.. 12 overall.
My choice is much costly but much efficient 
and 'hearing' pleasant as a final result.
I'm now wondering if my notes CV's poly portamento
will be generated with software porta slopes calculation
or using I2C 1meg digital pots in an RC configuration...

This was my 2 cents.
JP


 On Thu 07/05/09 09:13 , René Schmitz uzs159 at uni-bonn.de sent:
> Tom Arnold schrieb:
> > By dead simple, I mean swatooth core with no
> waveshaping.   From Ian Fritz's> site, http://home.comcast.net/~ijfritz/sy_cir2.htm. 
> The VCOs are very> repeatable.  I hav stripped and ditched them as
> I was having problems with> the VCOs hard syncing and the eventually fix was
> not pretty.  I know what to> not do next time though...
> > 
> > Anyhow, in this particular case I was seeing
> very predictable errors on the CVs> themselves.  When you should see, say, 4vdc on
> everything, and you see 3.996> 4.000 and 4.004, and all that happens is the
> numbers stay the same but move> around, yeah, thats your DAC :-)
> 
> AFAIK the Paia MCV8, uses a common DAC feeding Sample and Holds for its
> individual outputs. Not all of that error is due to the DAC alone...
> 
> Cheers,
> René
> 
> 
> 
> 
> 
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