Are these fancy cables banking on the same principles of other digital (SPDIF/XLR) cables ~ a well made cable reduces the margin of errors resulting in less requests for re-sends, and if there are less errors and subsequent re-sends, perhaps this higher performance results in less noise, fewer dropouts at the receiving end, and subsequently better sound quality?Under typical circumstances the reason S/PDIF and AES/EBU cables can make a difference is related to timing jitter at the point of D/A conversion, which in turn can be affected by waveform degradation resulting from impedance mismatches between the cable and the components it is connecting, and by electrical noise resulting from ground loop effects and/or RFI pickup, both of which can be affected by the characteristics of the cable. Ethernet is a somewhat different story, since the timing of the signals it conveys is unrelated to the timing of D/A conversion.
I have no specific knowledge of how frequently retransmission of ethernet data occurs under typical circumstances in a home environment. I suspect, however, that what is much more likely to have audible consequences in most cases is that any cable that is conducting high speed digital signals, such as an ethernet cable, and that is located in physical proximity to the audio system (e.g., in the same room), can radiate or couple RFI into the audio system. And in addition, noise conducted into the destination component via the cable could to some degree (depending on the specific design) conceivably couple around the ethernet interface circuitry and into other circuitry within that component that is more directly involved in processing the audio. Including circuitry that may be sensitive to noise-induced jitter.
None of this necessarily means, however, that an ethernet cable costing hundreds or thousands of dollars would be any more beneficial than an upgrade to a very modestly priced cable. You may wish to consider experimenting with inexpensive shielded ethernet cables, as member Bryoncunningham described doing in this thread, with significant sonic benefit resulting. (I consider him to be a particularly astute and perceptive listener, btw, and one who is very thorough in his approaches to evaluating tweaks and optimizing his system. Unfortunately, though, he hasn’t been posting here in recent times). See the posts in that thread dated on and around 2-16-12. Inexpensive ethernet cables are commonly unshielded, but good quality shielded cables are also readily available at low prices.
Regards,
-- Al