4 ms·

Sorry, but no! 1.0 1.1 1.9 2.0 2.1 2.9 3.0 is still a better approximation of a linearly increasing list of numbers than 1.0 1.0 2.0 2.0 2.0 3.0 3.0

by cnvogel 12y ago

Sorry, but no! 1.0 1.1 1.9 2.0 2.1 2.9 3.0 is still a better approximation of a linearly increasing list of numbers than 1.0 1.0 2.0 2.0 2.0 3.0 3.0 and I doubt that any 24bit DAC or ADC in existence will interpolate as bad as I did in this example. Whatever distortion due to quantisation the latter creates, the former will create less of it.

emn13 12y ago
Notably, with such a small sample size and multiple testing, it's to be expected to see small deviations in preference such as the one in the article. The article mentions p=0.28, which isn't entirely easy to interpret given that he doesn't quite explain what that p value is actually measuring (did he correct for multiple testing, for instance?), but it's certainly not a claim of any meaningful significance.
mark-r 12y ago
Your example is overly simplistic. Dithering is what allows a low bit sample to emulate a high bit one, and I don't see any evidence that you applied any; even if you did you wouldn't get a feel for how it operates with such a short sample.
- cnvogel 12y ago
  The initial statement was: "lowest bits of a D/A converter are the most non-linear. By avoiding them you might get a more accurate waveform overall." You can of course apply dithering to any signal to mask quantization noise. It's just that a perfect N-bit DAC will require less dithering to mask its quantization distortion/noise than a non-perfect/not-quite-linear N-bit DAC which again will introduce less quantization distortion/noise than the (N-k) bit DAC. In fact, you could say that a N-bit DAC is just "perfect reproduction" plus a non-linearity that amounts to the step-width of 1-LSB, e.g. it's resolution. And a 24-bit DAC that unfortunately is off by 8 LSB (2^3) along its 0...2^N-1 to 0V..Uref curve is still as good or better as a 21-bit DAC (24bit-3bit) in reproducing a waveform, and still better than a 16 bit DAC. A graphical representation of this is commonly found in datasheets and called "integrated non-linearity."

by cnvogel 12y ago

emn13 12y ago

Notably, with such a small sample size and multiple testing, it's to be expected to see small deviations in preference such as the one in the article. The article mentions p=0.28, which isn't entirely easy to interpret given that he doesn't quite explain what that p value is actually measuring (did he correct for multiple testing, for instance?), but it's certainly not a claim of any meaningful significance.

mark-r 12y ago

Your example is overly simplistic. Dithering is what allows a low bit sample to emulate a high bit one, and I don't see any evidence that you applied any; even if you did you wouldn't get a feel for how it operates with such a short sample.

cnvogel 12y ago
The initial statement was: "lowest bits of a D/A converter are the most non-linear. By avoiding them you might get a more accurate waveform overall." You can of course apply dithering to any signal to mask quantization noise. It's just that a perfect N-bit DAC will require less dithering to mask its quantization distortion/noise than a non-perfect/not-quite-linear N-bit DAC which again will introduce less quantization distortion/noise than the (N-k) bit DAC. In fact, you could say that a N-bit DAC is just "perfect reproduction" plus a non-linearity that amounts to the step-width of 1-LSB, e.g. it's resolution. And a 24-bit DAC that unfortunately is off by 8 LSB (2^3) along its 0...2^N-1 to 0V..Uref curve is still as good or better as a 21-bit DAC (24bit-3bit) in reproducing a waveform, and still better than a 16 bit DAC. A graphical representation of this is commonly found in datasheets and called "integrated non-linearity."