Article explaining how CD players work


My basic understanding is that there are three elements to how CD players work:

1. The transport "reads" the digital information, extracting it from the CD

2. The DAC translates the digital information into analog form

3. The analog circuitry turns the analog signal into a line-level output

Can someone recommend an article that explains this in more detail? What I am most interested in is understanding the various design issues that account for why one CD player can be so much more expensive than another.
jimjoyce25
Ken C Pohlman "Compact disc Handbook of theory and use"
It has EVERYTHING.
The biggest news (I read it years ago) is the error correction.
It is an amazing way of doing something. The data is now straightforward.. it is cut up, encoded, reaaranged into packets with an error code mark. If the packet "as read" does not match the packets error code the device knows the bits are wrong, and applies error correction...
The packets are not in serial order, they are mixed up.. the machine puts them back in order.
So your idea: the transport reads the bits.. more to it.
THEN the bits get sorted, the machine decides if the bits make sense, if yes they go to the dac. If no, it MAKES SOMETHING UP!! (For real) that it 'thinks (or is programmed) to guess at what is messed up.
All this has to be correctly timed. The machine has a timing mechanism, that connects the raw code to a time
(The infamous "JITTER" that always crops up starts here)
Then the bits and the timing get sent to the DAC.
The DAC does what you want, changes the bits into a voltage/ or analog form.
The error correction can be done in many ways, and the decoding of the bits can be done in a lot of ways too.
And it's doing this calculation millions of times a second
A miracle.
"The data is NOW straightforward" is a mistype. The line should read "the data is NOT straightforward when it is read off the CD"
A further explaination:
The data is coded into those packets before it is put on the CD. (There is another step about the pit length I forgot how it is done, but most of it is here) The information on the CD is not in a straight sequential form. It is cut up, made into packets, error codes added and the packets are scrambled in predefined ways THEN it is put on the CD as little pits. The laser reads the data off the CD and assembles the packets, reads the error codes, rearranges the packets back into correct order, fixes by educated guessing the ones read as errors, then adds the timing and sends this reconstructed stream to the DAC.
There is a great intro to a review that opened my eyes to how CD players work. It doesn't quite answer your question but goes a long way to explain some of it. The article is a review of the PS Audio Perfect Wave in the Dec. '09 issue of 6moons.com by Marja & Henk.
Well worth the read.
Elizabeth..."Educated guessing" is not an error correcting code. The recovered data, that may contain errors, includes redundant data such that the correct original bits are determined. I won't try to explain it. Google "CRC code".

Digital data transmission and storage today almost always involves error correcting coding. It is NOT a band aid for hardware deficiencies that cause errors. By using an error correcting code the transmission bandwidth can be increased to the point where some acceptable frequency of errors, depending on the degree of redundancy, occurs. Although some bandwidth is lost to the redundant data, the overall result is beneficial.
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My electrical engineering professor told us this about CD data retrieval. Music CD's came first. There were errors in reading the data, but they were small enough that our ears did not detect the difference. :-) For the data CD's to become useful, error correction algorithms were developed. Your data cannot have any errors in it, especially when you are dealing with data like your bank statement. The data you get off the CD must match perfectly or data is of no use. Most of the differences between CD players are going to be how jitter is handled and how the analog output is done. My professor was one of the researchers who developed the blue laser technology. The pits that mark the data on the surface of the CD are smaller with the blue laser, resulting in greater storage.