manicm said:
surreyfrog said:
manicm said:
People are forgetting the lasers/transport too. In the early cdps anyway not all lasers were made equal. And Linn discontinued their Sondek CD12 because Philips stopped manufacturing a specific transport the player utilised.
If the transport comes into play, I wonder if this means one would be better off copying the cd to a flash drive and playing from there, thus eliminating the transport/laser and any other moving component from the playback chain?
That's the theory amongst many, the main reason being error correction is almost removed. However other factors also come into play, like the software player, pc setup etc. I think a pc is a great source for CD res, for hires it's too much of a faff, some may rightly disagree, but I'd personally get a dedicated streamer.
I found the following on another forum, written by an engineer in the hi-fi industry, about cd reading errors, and other interesting information, little bit off-topic but very much worth sharing. Beware when reading, it was a reponse on another forum:
The data on a CD is stored with extra information, specifically added to allow correction of data errors. If the data being read from the surface of the disc does in fact contain errors (which is not at all unlikely), there are two stages of "perfect error correction" - where the extra correction data will be used to repair/replace the missing or damaged data PERFECTLY[/i]. This process happens inside the CD player, and is totally transparent to the listener or user of the data. Only if we have damage so serious (equating to a hole larger than 2.5mm in the surface of the disc) will the data coming from the drive and its electronics be less than absolutely perfect. On a computer, if a single error remains after this correction - a single incorrect bit - the disc will stop playing with an error. Most audio players include a third level of "error correction", which is intended only as a "last ditch" option after the first two stages have failed, and which will "fill in" the gap with interpolated (guessed) data. So, no, unless there's something terribly wrong, even though the data read from your CD disc may contain flaws, the data that the drive passes on to you will in fact be perfect. (And most of the better computer audio ripping programs verify this perfection by comparing a checksum of the rip against a database - thus confirming that what you have is in fact perfect.)
Of course, even though we know that the data is perfect, there is still the possibility of timing errors - jitter. However, there is also a simple way to avoid any ill effects from that as well... buffer the data, create a clock locally that you know is free from any significant amount of jitter, and then play the data using this new and near-perfect local clock. Most modern DACs do in fact use some variation on this idea. (And, yes, if the cable introduces jitter, and you've chosen a DAC that, not having any mechanism to avoid the problem, is sensitive to that jitter, then there might actually be an audible difference.) With an Asynchronous USB DAC, the clock itself is generated by the DAC, which requests data from the computer as needed, which ensures a near-perfect clock as long as the computer can keep up. (And, yes, if the computer fails to keep up, there may be data dropouts, which may affect the sound quality. Luckily, a high-speed USB connection is many times faster than necessary for sending flawless audio data. And, luckily, there are tools which can be used to spot check your system and confirm that, at least when the test is run, the system is delivering perfect data. Presumably, if your computer can deliver data for several minutes with zero errors, it's probably safe to assume that this is usually what's happening.)
Your main error is in your claim that "it's impractical for data to be resent". With modern network data transmission, the exact opposite is true, it is EXPECTED[/i] that a certain amount of data will become damaged, and EXPECTED[/i] that either that data will have to be re-sent, or that extra data that can be used to perfectly repair errors will have to be routinely sent as a precaution. (On an Ethernet network we can even calculate, based on network speed and the current amount of traffic, what percentage of the data will be garbled, and how much of it will need to be retransmitted.) And, with any CD that complies with the Red Book standard, a significant amount of extra data, to be used for error correction purposes if necessary, is part of the data stored on every disc. (You are correct that some low-bandwidth connections do in fact choose to allow or ignore errors. This generally happens because of the tradeoff between data bandwidth and quality. In other words, they've decided that the loss in quality due to uncorrected errors will be less noticeable than the loss in quality that be the result of increasing the compression enough to make room for the correction data.)
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