[sdiy] CV from soundcard

[Derek Holzer]

The Volta hype says that it should work with any DC-coupled soundcard, 
but yes of course they want to sell you their soundcard, which 
incidentally the year before they warned people not to use for control 
voltage ;-)

Anyways, another half hour of experimentation and I discovered that 
while the main outputs of my HDSP aren't actually DC coupled (they drift 
back to 0V over about a second), the *headphone* outlets are actually 
capable of delivering continuous DC voltage. Go figure. So now I've got 
a 2 Octave CV source.....

best,
D.

Paul Schreiber wrote:
> You are probably *not* going to be able yo hack just any soundcard for 
> Volta (I mean, part of the reason for Volta in the first place is to 
> sell more I/O cards).
> 
> I'm sure as Volta gets more and more tinkered with, there will be at 
> least 10 websites about 'Volta compatible cards' and ' Is your your card 
> hackable for Volta?".
> 
> Meanwhile: here are the issues
> 
> a) Many sigma-delta DACs used for audio output are *specifically 
> designed* for no DC offset (what Volta is forcing). Chip designers spend 
> 100s of hours making sure their designs have minimal DC offset.
> 
> b) the card designers add external DC offset correction, can be as 
> simple as a big (say 220uf) cap in series with the output or a fancy 
> DC-Servo loop.
> 
> c) dynamic range issues. If my synth wants 1V/Oct output how can a sound 
> card, that is specifically designed for audio at 2V pk-pk full-scale 
> going to do me any good?
> 
> Volta is a clever app, but it is an app *designed* to sell you a *new* 
> I/O card :)
> 
> Paul S.
> 
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-- 
::: derek holzer ::: http://blog.myspace.com/macumbista ::: 
http://www.vimeo.com/macumbista :::
---Oblique Strategy # 193:
[blank card]