evdplancke;689106 Wrote: > Nyquist theorema tells there is no benefits but is based on the > following assumptions: > 1) sampled signal is made of perfect dirac pulses... practically they > will look like square pulses resulting in a quite bad low pass sin x/x > filtering that zeroes at 1/T where T is the width of the pulse > (staircase sampled signal being the worst with 1/T equals to sample > freq) > 2) sampled pulse has a constant time period... but in reality time > period is varying due to jitter > 3) signal reconstruction is using perfect brickwall filters... but in > practice it is very difficult to have steep filter slope without > artifacts > > In conclusion, there might be a (big?) gap between theory and > practice. > > According to the 3 assumptions above, here are the (audible?) benefits > of 96khz: > 1) higher sample freq is reducing the low pass effect of square pulses, > rejecting the resulting zeroes to higher freq > 2) doubling the number of pulses adds redundancy to the signal that > increases immunity to jitter > 3) less steep brickwall filters are needed for signal reconstruction, > reducing artifacts and improving linearity > > So hi res might technically improve the accuracy of reconstructed > signal even if baseband signal does not contain any freq above 20 khz. > > The question remains however: are those benefits audible or not? I'd > say it makes it at least more robust against less than optimal receiver > implementation.
I am not really sure what you mean by 1)except as a corollary of 3). and I'm not sure about 2) either -surely a higher sampling rate would require more accurate timing in the ADC? not that I think this is an issue. The real point is that doubling fs halves the quantisation noise in the audible spectrum.This the equivalent of adding 1 bit albeit very inefficiently since you have doubled the data rate whilst increasing the amount of information by the same amount you could have achieved by adding one bit which would have increased the data rate by 1/16.It does give you some room to play with for noise shaping though. I think 3) is the real time domain issue. But it's worth pointing out that the fundamental issue is that increasing fs enables you to have less steep filter in the anti alias stage of ADC. But it all begs the question - given the ability to create very steep digital filters with negligible passband ripple or phase issues, what are the artefacts? I note however that daniel weiss indicated in an interview that he thought 16/88 would be more beneficial as a consumer format than 24/48. I don't think he spelt this out but I assume it was because he thought there was chance that there was something in the time domain issues. Even then though it's worth stressing that there should not be any time domain issue if the pre-filtering pre ADC signal has no energy above 20kHz - there will not be any time smear then![I Hold my breath and wait to be shown up as an idiot] Equally If there is no signal above 20KHz in the 24/96 file then either there was none in the pre recording sound [no time smear with sensible filtering] or there was but it has been filtered out anyway ie the time smear will have occured. . IN that case I can't see how there could be any worthwhile improvement in a 96kHz file over a 44.1 kHz. -- adamdea ------------------------------------------------------------------------ adamdea's Profile: http://forums.slimdevices.com/member.php?userid=37603 View this thread: http://forums.slimdevices.com/showthread.php?t=93483 _______________________________________________ audiophiles mailing list audiophiles@lists.slimdevices.com http://lists.slimdevices.com/mailman/listinfo/audiophiles
