On 23/07/2015, robert bristow-johnson <r...@audioimagination.com> wrote: > Peter, do you know how a sigma-delta (or delta-sigma, people don't > always agree on the semantics) converter works? > > like how a sigma-delta modulator works? oversampling? possible > dithering? noise-shaping? decimation (involving low-pass filtering and > downsampling)? > > do you have any idea what i am talking about (or writing about)?
Yes I do. Do you have any idea that 'dithering' means adding noise to the signal? Do you realize that -110 dB is a *lot* louder than the theoretical noise floor of an 1-bit dithered 24-bit signal without noise shaping, which would be at -138 dB? If - according to you - they could have a -138 dB noise floor, why do they have a -110 dB noise floor instead? Ever wondered that? That makes zero sense. Do you realize that noise shaping *increases* the amplitude of the noise? > also, even in the least-significant bits, there is signal embedded (or > buried) in the noise. it's not as if they appended 4 noisy bits to the > right of a 20-bit word. they didn't do that. Despite that, it's still *noise*, hence it is unpredictable, hence it is "unfixable". If you have an 1-bit amplitude signal, and "embed" it in 4 bits of noise, then you won't "hear" that 1-bit amplitude signal because the 4 bits of noise will mask it entirely. Hence, your lowest bits are "unusable", because the noise entirely masks it. -P -- dupswapdrop -- the music-dsp mailing list and website: subscription info, FAQ, source code archive, list archive, book reviews, dsp links http://music.columbia.edu/cmc/music-dsp http://music.columbia.edu/mailman/listinfo/music-dsp
