evdplancke;684398 Wrote: > OK, after checking my source, a post at DIYaudio explaining how > Sigma-Delta DAC works > (http://www.diyaudio.com/forums/digital-source/15439-how-does-delta-sigma-dac-work.html), > I see where is my confusion over here. The article is assimilating S/D > DAC to pulse width/pulse density modulation and tells: > > > > After noiseshaping, such DACs might be yielding a resolution higher > than 16 bits. Sorry for the misinterpretation. > > But this article stressed also that the pulse modulation nature of S/D > DACs makes them sensitive to jitter and PSU stability. That article is 8 years old, but i guess the principles still apply although the impmentations have got better and cheaper. However it's not just the noise-shaping bit that needs to be stressed. using these techniques you can make a DAC of pretty well arbitrary resolution (subejct to the thermal noise problem). The writer himself refers to DCS DACs having 23 bits resolution. Your point about 24 bit dacs and 16 bits dacs in this context was slightly missing the point.
The designer sets out to make a dac with a particular resolution (be it 16 bit or more). s/he doesn;t want to use an old fashioned ladder resistor multibit type for reasons we don't want to go into. Being an engineer not an audiophile s/he knows that he can convert the input 24 bit data (which may or may not really have 24 bits of information) into data with fewer bits but a higher sampling rate without any information loss. a dboubling of sample rate is the equivalent of adding 6 db of snr or 1 bit. So a 6 bit needs a sample rate of 2**10 (1024) times Fs to get the same snr as the 16 bit data. There is a limit on how fast the sampling rate can be so if he wants more resoltion s/he will need more bits or noise shaping or possibly to use more than one dac. All of this can be predicted and measured. There are delta sigma dacs now which claim 128Dbr more snr. It may be that delta sigma dacs are susceptible to jitter arising from the clock or ps of the dac; but that's got nothing to do with interface jitter and therefore nothing to do with the transport or the cable going into the dac. It did occur to me when answering your orginal post, that it would not cause you to reconsider your belief in the vital importance of twaeking the the trasnport, if it turned out that the reason you had given was mistaken. -- adamdea ------------------------------------------------------------------------ adamdea's Profile: http://forums.slimdevices.com/member.php?userid=37603 View this thread: http://forums.slimdevices.com/showthread.php?t=91322 _______________________________________________ audiophiles mailing list [email protected] http://lists.slimdevices.com/mailman/listinfo/audiophiles
