jh901 wrote: > We first must come to agreement on S/PDIF. If anyone is having trouble > with prior point, then let's hear it. Pretty much everyone here accepts that S/PDIF has shortcomings. But you seem to be trying to establish an axiom from which we must all start any discussion that those shortcomings must necessarily degrade playback sound quality. But there is no hard evidence that the inadequacies of S/PDIF do actually cause any audible degradation. Just because something is sub-optimal in theory does not make it so in practice.
A lot of people take the view that there are just two things that can affect the fidelity of a digital transport: bit-correctness and jitter. Everyone agrees that S/PDIF delivers a perfect bit stream, so the conclusion is drawn that if a difference is heard between two digital transports, it must be down to jitter, and so the transmission jitter added by an S/PDIF connection is held up as the culprit. But you need to be very careful before drawing these conclusions. There have been few properly controlled tests regarding the audibility (or otherwise) of jitter. Two important papers are by Benjamin & Gannon and Ashihara (see below for references). Both of these studies demonstrated that jitter alone is inaudible on normal music signals at surprisingly high levels - way higher than we see in pretty much any competently-designed digital audio device. Meanwhile, a lot of people completely overlook another factor that can affect the performance of an audio system. Noise generated by the power supplies and high-speed logic circuits in a digital transport (whether it is airborne or on the ground plane) can affect downstream analogue circuitry. If two digital transports connected to the same DAC sound different, then it probably has nothing at all to do with jitter, but may be down to RFI generating noise and distortion in the analogue output of the DAC (or preamp). And this has nothing to do with the protocol that is used to deliver its output. BUT: there is a far more likely explanation for a perceived difference, and this is non-auditory clues. Scientific studies have shown time and time again that non-blind comparisons of pretty much anything tell us precisely zero about whether there are any real differences. PS. Here are those references for anyone who is interested: Benjamin & Gannon. Theoretical and audible effects of jitter on digital audio quality. 105th AES Convention, 1998 Jitter added to digital signal between transport and DAC with a hardware device. Conclusions: uncorrelated jitter inaudible below 10nS rms on pure tones; uncorrelated jitter inaudible below 20nS rms on music signal Ashihara, Kiryu et al. Detection threshold for distortions due to jitter on digital audio. Acoust. Sci. & Tech. 26, 1 (2005) Jitter simulated in the digital domain. Conclusions: uncorrelated jitter inaudible below 250nS on music signal. ------------------------------------------------------------------------ cliveb's Profile: http://forums.slimdevices.com/member.php?userid=348 View this thread: http://forums.slimdevices.com/showthread.php?t=97489 _______________________________________________ audiophiles mailing list audiophiles@lists.slimdevices.com http://lists.slimdevices.com/mailman/listinfo/audiophiles
