arnyk wrote: > Modern audio ADCs (of sigma-delta design) generally noise shape the > quantization error, in effect turning it into dither without adding any > additional noise: > > http://www.ti.com/lit/an/slyt423/slyt423.pdf page 16: > > "Multi-order modulators shape the quantization noise to even higher > frequencies than do the lower-order modulators." > > > > There is no such question that is relevant to the vast majority of audio > ADCs because they use Sigma-Delta technology to turn the quantization > error signal into dither by shaping it in the time domain. > > > > The cited text does not seem to be updated to describe the vast majority > of ADCs that are used in audio which are Sigma-Delta designs. This adds > more complexity, and if included right up front might make an > introductory text in DSP technology overly complex for newbies. > > If one measures real world gear on a test bench, this is what one > typically finds. Arny I donlt think the delta sigma thing is relevant if we are discussing 16 bit quantisation. The adcs will produce a single or multibit stream at several megaherz. Getting it to pcm is a different story. Leaving aside gettign it to 24 bits of pcm, once it is in 24 bit form (at which it will probably be mastered) it WILL be downsampled in software to 16 bits. Delta sigma does not come into it. The downsampling may or may not be done using noise shaping but is quantisation in the sense described in the text. The point remains that there is nothing particularly special about adding quantisation noise of the same power as the existing noise in the channel.
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