04-01-12: Fmnp
I don't dispute that the s/pdif could introduce some jitter. But it will much, much less then that introduced by the optical device, mechanical parts and vibrations, Power supply, correction errors, angular velocity corrections, etc, etc. and time misalignment.
I don't think that either of us is in a position to conclusively assert which jitter source is generally worse. But here is a relevant quote from the Charles Hansen white paper I referenced, referring to his highly respected firm Ayre Acoustics:
Since introducing the radically innovative Ayre D-1 DVD Player in 1999, we’ve been a leader in digital audio technology for the succeeding ten years. Yet in all that time Ayre has never offered an outboard D/A converter box, instead concentrating on one-box disc players. The reason for this is quite simple — the standard S/PDIF (Sony/Philips Digital Interface Format) digital connection used with two-box solutions is flawed, unavoidably and needlessly introducing jitter into the audio playback system.
Ayre did not introduce a standalone DAC until the development of asynchronous USB technology, enabling an essentially jitter-free interface to be established between the DAC and a computer.
And previously, when they presumably considered and rejected the idea of introducing a two-box transport + DAC combination linked via S/PDIF, they most certainly would not have felt constrained by the need to design the transport such that it could be sold at the sub-$100 price point of your media players!
And it would be something to prove that the toslink S/PDIF introduce jitter (at lest, audible). Why? there's no RF interference (unlike coaxial).
Ask what the studios use in there's SPDIF connections.
The only losses could be the quality of the fiber or the lengh. But with so small lenght's (1 to 2 m)...
As I understand it professional equipment generally doesn't use S/PDIF at all. It uses AES/EBU, which while subject to some of the downsides of coaxial S/PDIF, will generally be subject to those effects to a considerably smaller degree, as a result of its balanced configuration, presumably faster risetimes and falltimes, and larger signal amplitudes.
With respect to Toslink, I agree that glass is highly preferable to plastic. But although Toslink is not subject to a number of the jitter-related effects that can occur with coaxial S/PDIF, Toslink is arguably even more prone to jitter, as a result of its limited bandwidth, slow risetimes and falltimes, and questionable transducer quality, all of which can cause jitter when the optical signal is transformed to or created from the corresponding electrical signal. And, furthermore, BOTH Toslink and coaxial S/PDIF face the problem of extracting a clock having minimal jitter from the conglomeration of data, clock, and other information that is combined into the single S/PDIF signal.
I'm just about certain that if you were to research posts by audiophiles who have systems in which either Toslink or coaxial S/PDIF could be chosen, with everything else remaining the same, you would find that more often than not their listening assessments resulted in coax being chosen.
Finally, quoting from the last of the four references I provided:
Another interesting thing about audibility of jitter is it's ability to mask other sibilance in a system. Sometimes, when the jitter is reduced in a system, other component sibilance is now obvious and even more objectionable than the original jitter was. Removing the jitter is the right thing to do however, and then replace the objectionable component. The end result will be much more enjoyable.
Jitter can even be euphonic in nature if it has the right frequency content. Some audiophiles like the effect of even-order harmonics in tubes, and like tubes, jitter distortion can in some systems "smooth" vocals. Again, the right thing to do is reduce the jitter and replace the objectionable components. It is fairly easy to become convinced that reducing jitter is not necessarily a positive step, however this is definitely going down the garden path and will ultimately limit your achievement of audio nirvana.
It would therefore seem possible that the reason your media players, costing less than $100, provided subjectively better results than the expensive Meridian transport you compared them to was that the media players caused an INCREASE in jitter, whose spectral characteristics happened to be pleasing.
Regards,
-- Al
