[sdiy] CV from soundcard

Antti Huovilainen ajhuovil at cc.hut.fi
Fri May 8 17:05:35 CEST 2009


On Fri, 8 May 2009, Paul Schreiber wrote:

> If I've said it once, I've said it 10 times.....resolution does NOT EQUAL 
> accuracy.
>
> Google 'INL'.

Also 'gain error', 'offset', 'temperature coefficient'.

Looking up the datasheet of a random audio codec (Wolfson WM8590) gives 
typical 1.16% (0.1dB) gain error between the channels. The absolute gain 
error is not even specified! Assuming the same figure (probably 
unrealistically good assumption), that gives tuning error of 70 cents for 
highest note in a 5 octave converter.

Now let's pick a dirt cheap 12 bit DAC (MCP4821). Gain error is 0.1% 
typical, which gives tuning error of 6 cents. And this for the cheapest 12 
bit DAC I could find in a pinch.

Antti

"No boom today. Boom tomorrow. There's always a boom tomorrow"
   -- Lt. Cmdr. Ivanova



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