CD Recordings..... What Do U Know?

Rives, I've got an intriguing question here:

What if you simply transfer your CD into simple analogue cassette than you won't realy have any jitter issues will you?

Your right that analog tape won't have jitter issues, but I'm not sure I understand how that relates to this thread. I really would like to understand if these error rates can not be corrected through reclocking and re-recording why do I (and apparently a few others) have the experience of copies actually measuring better from an error (and/or jitter) rate. I am not a recording engineer, but will pose this question to the recording engineers I know. In the meantime, if anyone knows the answer to this (and it could be that my method of measuring is completely invalid for some reason--and you really can't correct the problems on the original disc) I would like to know the answer.

Okay, I spoke to a recording engineer that I know. He's forgotten more about this subject than I'll probably ever know, but I will relay what he told me. In the recording process errors occur in producing the glass master from which the final CD is made. The reason we know this is where the errors occur is if you take 3 CDs of the same title and production you will get the same error rates (or extremely close). If you take a mass produced CD and a high quality re-master you are very likely to get a very low error rate on the re-master as opposed to the mass marketed one. He says this is normal. It is caused by clocking errors in producing the glass master. Some production houses are better than others. All DACs make an attempt to correct errors, whether they are caused by jitter or by error in the recording process. Some DACs do a better job than others. Some buffer the information and read the bits on both sides of the error and average them to correct the error. Some simply take the adjacent bit and fill in the error. The process of re-recording the CD can improve the error rate. It will fill the error bits with whatever protocol it uses. The result will be a disc that has a lower error rate. This still leaves a question of is the original better than the copy. The copy now has a lower error rate, but it is just processed the errors and "pre-corrected" them prior to burning the copy. If the protocol for correcting the error in the computer prior to burning the CD is a better protocol than the DAC being used, the result should be a better sounding copy than the original. For example if the computer corrects by bi-interpolation and the DAC uses only adjacent bit correction, then the copy will be better in THAT DAC. In another DAC that uses a superior error correction scheme this might not be the case. Well, I think that answers it. I hope I was clear in translating a recording's engineer's wisdom on the subject.

I agree with this point of view. So the copy may sound better if it is played on a machine or DAC which has a worse error correction capability than the machine on which the copy was made. For example playback on a portable CD, copy made on HHB burner.

But the copy can never sound better than the original when both are played on the machine which makes the copies ... you can't doubly correct the errors : the copy will not benefit from the error correction when it is played on the burner since its errors are already corrected.

So I think you'd do better to buy the best possible CD playback machine, rather than a cheaper playback and a copy machine.

And the high error rate on the original is caused by poor mastering, not by jitter inherent in the disk. Jitter is a function of the transport, not the disk itself.

The correction in a CD is NOT in the DAC. The correction is in the encoding of the CD data - IF it plays back it is lossless! This is Reed-Solomon encoding and the way it works is that the data is NOT serially encoded, it is interleaved with a type of checksum that makes it possible to recreate a certain amount of missing data. Beyond that amount, you get an audible glitch.

So, the "correction" takes place in the uproccessor chip that *reads* the data from the CD itself.

No DACs that I am aware of do ANY error correction at all. It is possible that the Digital filters (they do upsampling) *may* have some sort of provison for making sure the bits that get in, get out, but they don't do error correction afaik.

A digital to digital copy, done with EAC or a similar program, should be identical to the original.Pro gear or not, if the data is identical, it is identical.

The question of how it sounds will depend upon some details that include jitter on *playback* - and that will in turn depend upon the details inside the particular unit chosen for the playback chore.

It is possible that on the mastering end that some details that are related to the clocks used in the transfer *can* have an effect on the final product. This was a big problem early on in the CD duplication industry, but presumably has been identified and eliminated.

Having said all that - in practice all bets are off. Ymmv.

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