[sdiy] discrete DAC accuracy

[Ken Stone]

I use 1% resistors in 8bit R-2R networks driven by common old CMOS and find
they are accurate enough for VCOs, at least to my ear, and I am quite
sensitive to out-of-tune instuments. VCAs could tollerate 5% resistor
networks without (humanly detectable) audible errors.

Ken

>
>Hello list!
>
>I'm trying to calculate the absolute error of a discrete R-2R 16-bit DAC. If
>the resistor tolerance is 2%, is then the overall accuracy 2% for any binary
>code? At least it seems so in the 3-bit case. I don't have the tools for the
>16-bit case.
>
>This should also imply that the maximum relative error between two
>consecutive binary codes is 4% since each code has a maximum absolute error
>of 2% and two consecutive codes can have opposing errors (as 0x8000 and
>0x7fff). Am I right? 
>
>This is of course not accurate enough for a VCO control voltage, but should
>be ok for a VCA, don't you think?
>
>
>Fredrik C
>
>
>
_______________________________________________________________________
Ken Stone   sasami at hotkey.net.au  
Modular Synth PCBs for sale <http://www.blaze.net.au/~sasami/synth/>
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