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Old 23rd November 2015, 13:25   #5  |  Link
pandy
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Join Date: Mar 2006
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Quote:
Originally Posted by raffriff42 View Post
No, a DAC adds a small amount of noise, called Dither aka Noise Shaping. More dither is needed for a lower-precision digital format. Increasing "precision" by adding zeros fools the DAC into not adding enough dither, which may result in digital harshness on the output (albeit at a very low level). Decreasing precision by truncating, without dither, has the same problem.
http://www.digido.com/articles-and-d...16-dither.html
https://en.wikipedia.org/wiki/Dither#Digital_audio
Well not particularly true... - fair for some Delta Sigma DAC and not correct for most monolithic converters.

Dither and/or Noise Shaping are usually added at post processing stage, dither is sometimes added to improve overall Delta Sigma DAC stability (usually important for 1 bit DS, usually not so important for multibit DS DAC).

16 bit to 24 bit is equal to multiplication by known number and it is fully lossless and reversible - more important is that usually 16 bit data is anyway converted for more bits to perform processing - classical example are lowpass filters where 16 data are multiplied by for example 12 bit coefficient and as such result is 28 bit new sample value. Nowadays 56 and more bits for audio is not unusual especially in IIR filters (which are more common in consumer audio than FIR filters).

Quote:
Originally Posted by raffriff42 View Post
I believe the answer is 'yes.' A well-designed DAC will add noise with an amplitude of (I think) 1 LSB. So in the first case, the amplitude will be 1/(2^24) and in the second, 1/(2^16).

EDIT After re-reading the question, I'm not so sure. I don't know how a given 24-bit DAC will handle 16-bit data. Would have to look at the spec sheet.
Well designed DAC will NOT add dither - adding dither is only to deal with DAC limitations - to improve stability for DS DAC i.e. is a workaround.
And this is clear operation from mathematical perspective for this - multiplying by integer value ie shifting bits (8 bits give us 256).

DAC conversion is something else than quantization error processing (dithering and/or noise shaping).

And dither level for TPDF is 2LSB - rectangular dither can be 1LSB but it is insufficient from signal perspective - usually instead TPDF a HP TPDF is used.

Last edited by pandy; 23rd November 2015 at 13:33.
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