Rebbi, good to see you here again! It has been a while.
Regarding your quest for an explanation of what could account for the sonic differences you found to occur between the optically connected CD player and the optically connected transport, I think that the posts early in the thread by Kijanki and Mapman pretty nearly said it all. And I agree with their comments 100%.
I would add one more possibility, though, to the two they cited (those having been timing jitter and read errors, with jitter being the more likely culprit if the player and disc are in good condition). It seems conceivable to me that in some cases sonics might be affected by differences in the amplitude and spectral characteristics of digital noise at RF frequencies that might find its way via power wiring (or perhaps even via the air) from those components to downstream points in the system.
A number of other well intentioned responses, especially early in the thread, asserted that differences in the design and quality of various parts of the players, such as power supplies, laser mechanisms, digital circuitry, etc., could account for the differences you perceived. I don’t doubt that those assertions are correct in many cases. But understandably such assertions fall short of explaining ***how*** differences in those things end up affecting sonics. And the only means I can envision by which such differences in design can affect sonics, given that ground loops, impedance mismatches, signal reflection effects, and other such things that can come into play when electrical (rather than optical) interconnections are used, is by having effects on jitter, or on read errors, or on coupling of electrical noise to downstream points in the system via pathways that are unintended and non-obvious.
All the best,
-- Al
