mdemeyer wrote on Tue, 12 September 2006 05:48 |
The original post didn't say (clearly, at least to me) if he was talking about difference in CD playback when the transport was driving a DAC directly or some kind of PC setup. If the former, the DAC clock is being picked up from the S/PDIF (or AES/EBU) signal and, depending on the implementation, the signal from the transport can impact the sound not because it has bad data, but because of jitter in the recovered clock. This is a well known and measurable item.
Want to clarify the question?
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Even if the transport is your master you don't use the clock recovered from the disc itself as your master, that would be foolish since it is dependent not only on any imperfections in the CD, but also on any variation in spin speed... we'd be back in the world of wow and flutter.
Instead you use a nice solid crystal clock as your master and synchronize the mechanism to that, at least that's what we did on the mechanism I worked on and I cannot se any sensible reason to do it differently. So it is lot less variable than some people seem to think.
Though I can imagine that depending on the quality of that clock, the circuitry to drive the interface, and the quality of the receiver and PLL in the DAC you might be able to detect a difference... but I don't know how bad each would have to be to be noticable (Dan probably does), and therefore how likely it is.
It is theoretically possible for different transports to sound different, they could have differing quality of data reading off the disc, leading to more unrecoverable errors, they could have differing quality of interpolation for those errors (linear, polynomial) and they could possibly have enough variability on their clock to manifest itself in the DAC, especially one with a poor PLL.
However I have to note that firstly things would probably have to get pretty bad before you noticed these things, with the exception of the jitter most errors will most likely be few and far between and be gone in 20 microseconds. Secondly most in most audiophile reviews I've seen of these things the claims made as to what differences they can hear between transports make absolutely no sense to me considering what the nature of such errors would be and how they might manifest themselves audibly, which leads me to believe that mostly they are just self delusion by the reviewers.. with a thought process something like "It's a 20 thousand dollar mechanism with a marble base and platinum wiring, it must be better, and with my golden ears I'm sure I can pick it uy.... oh yes, there it is, the third violin is coming through better in this 300 piece orchestra, I'm sure of it"