[sdiy] Re: Inexpensive 16 bit DAC?

[James Patchell]

Building a 16 bit DAC from discrete components (i.e. R-2R ladder) will 
probably be disappointing....although, it will also probably be difficult 
to find out how close you actually got because the measurements are 
difficult to do.  I am not sure what kind of matching you actually need on 
the resistors in the ladder to get 16 bits...but I would bet you are 
talking about better than 0.01%...and resistors of that tolerance are very 
expensive.  Also, great care must be exercised in selecting the DAC 
switches as their resistance enters into the equation as well.

As far as building a Delta Sigma converter...yes, that can be done in an 
FPGA...in fact...I did one that was a combination of a CPLD and firmware 
running in an ARM...however...only up to 2nd order Delta Sigma converters 
can be done easily.  Higher order converters are unstable and require a lot 
of work to make them so (even on commercial converters, it is possible to 
make them lock up if you do something weird, but this is almost impossible 
to do thank goodness).

Delta sigma converters are available for very reasonable prices these 
days...about $7...and they have already done the work of stabilizing them.

At 12:40 AM 4/24/2005 -0700, Mete BALCI wrote:

>Will I get enough (or good) performance from a DAC
>built with discrete components (high accuracy
>resistors and a good vref) ? How do you compare all
>-discrete component DAC, IC DAC and oversampling DAC
>(sigma-delta etc.)- ?
>
>I have an FPGA board, I think it is very easy to
>implement a sigma delta dac on it. Do you consider
>using sigma-delta DACs on sound generation ? I know it
>is not recommended for audiophile circuits (I dont
>know if its reason is actually technical or
>psychologic), but I dont know if they are used on
>synth circuits or not.
>
>When are 16-bit DACs widely accepted in synth products
>? 90s ?
>
>Mete

         -Jim
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