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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

Showing 2 responses by elizabeth

elizabeth
6,726 posts
 
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.
elizabeth
6,726 posts
 
"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.
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