[sdiy] CV from soundcard

[Olav Martin Kvern]

re: DACs for MIDI to CV

Like most engineering problems, there are probably as many ways to do this 
as there are engineers to implement it!

Another approach is to use 6 bits of an 8-bit DAC for note values over a 
5.25 volt range (.08333 volts per DAC step). This is roughly what the 
Pro-One does, using an AD558 (which is around $10, these days--but my 
testing shows that even this is probably overkill). For MIDI *notes*, this 
approach makes perfect sense, because they're always whole note values. For 
continuous controller information, you can use a higher resolution DAC over 
a smaller voltage range, then add to/subtract from the output of the DAC.

Yet another approach is to use a higher-resolution DAC over a smaller 
range--say 12 bits over 1 volt. Your MIDI to CV conversion software can then 
use solid voltage references (or some other approach) to transpose the note 
into the proper octave. (This points out that you could do away with the DAC 
chip entirely and simply have your microcontroller switch to the relevant 
voltage.) Again, I'm just talking about "standard" notes, not continuous 
controller information or microtonal tunings.

My point is that, too often, we get hung up on DAC accuracy when there are 
other solutions to the problem. I see people spending $50+ for DAC chips 
when their projects, for their purposes, would work just as well with a 
6-bit R2-R resistor DAC. Think outside the box--or at least outside the 
DAC!:-)

Thanks,

Ole