> From:         Dave Dilatush[SMTP:davedilatush@COMCAST.NET]
> Sent:         Saturday, October 18, 2003 10:24 AM
> To:   PICLIST@MITVMA.MIT.EDU
> Subject:      Re: [EE]: high resolution DAC

> Eric,

> One additional note about audio DACs, since you asked: I think
> you're going to find that when an audio DAC is advertised as "24
> bit", that's an expression of its signal-to-noise ratio, not its
> DC accuracy.  I'm not very familiar with these devices but I
> would expect, given their intended application, that their DC
> accuracy would be rather poor.

      That's right. A DAC meant for DC applications is referred to as a
      "precision" DAC, which means that each step is within 1/2 LSB of
      its absolute voltage. The 24 bit rating of an audio DAC means that
      it has 2 ^ 24 discrete output steps. This provides for that
      "granularity" over small ranges of output voltage. In reproducing
      audio, that is all that matters; you don't want to hear the steps in
      the output when the peak-to-peak signal is small. There is no
      guarantee that the cumulative accuracy is particularly good. In
      other words, audio DACs are designed for AC use, not DC.

      John Power

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