MidiDAC acurracy measurement

[jorgen.bergfors at idg.se]

Hi all. I have now completed my dual Oakley Mididac and did some quick measuerments after trimming it.
I just measured the voltage for all Cs, to get an impression of how well the 12 bit DAC tracks.
Here are the results:
Unit A  Unit B
0,006V  0,003V
1,010V  1,001V
2,013V  2,005V
3,018V  3,011V
4,020V  4,014V
4,992V  4,993V
5,997V  5,996V
6,999V  7,004V
8,002V  8,007V
9,003V  9,009V
Of course, the exact voltages are dependent of the trimming. But it can be clearly seen that when the most significant bit changes state, it goes a little flat. Obviously the MSB contributes slightly too little voltage. Note that this is the case for both DACs. The errors are very similar between the two DACs, actually.
Maximum error seems to be 0,24 semitones. I would have expected a little better than this from a 12 bit DAC, but I do think it is perfectly good enough.

/Jorgen