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

If you are going from a digital source to digital source and use any recorder that has jitter reduction you can often improve the sound. Professional equipment usually has very good clocking and you can often improve the sound. PCs can too improve the sound, but as Rec points out, if you are using an analog source you need to have a good sound card or your copy will sound considerably worse than the original.

In digital, unlike analog, re-recording can actually make it better (not just sound better, but really technically better). Jitter occurs at both the record end and the playback end. If you can eliminate or reduce the jitter at the recording phase, then the result is a better disc that has less jitter on the playback. Now, how does this work? First assume the original disc has jitter of X. Your playback system has jitter reduction to some degree and will reduce the jitter to only 50%. Now you load the system onto a hard disc and then into RAM where it is heavily buffered, the process involves reclocking the data stream as it is written to disc. Let's say you can reduce the jitter by 90%. So now you only have 0.1X as your jitter being recorded. Now you playback and because the jitter is low you only reduce the remaining jitter by 20%. The result is playback that was original 50% of the original jitter vs the copy that is now only 8% of that original jitter. These are, of course, hypothetical numbers, but the principle is sound (no pun intended). This is one of the few areas that copies can actually be (not just sound) better than originals.

Jacks: That's helpful and clears up some of the confusion. I had confused jitter and error rate. I had been told by someone in the industry of CD mastering and manufacturing that there are clocking errors on the record end that can be reduced by extracting the data and reclocking it. I equated this error to jitter as jitter is a clocking error, but as you have pointed out it is an error rate and not really jitter at all. At any rate, it does seem the case that the error rate can be reduced by making a copy that re-clocks the data, and does so in a superior method to the original. At least this is what I have been told by those in the CD industry.

Unsound: That's the same experience I've had. I can make copies of some pretty poorly mass produced CDs that sound much better once I've made the copy. But take a JVC XRCD--I can't make it any better it only gets worse. I used a Genesis digital lens to read the error rate (at least I think that's what it measures). I would play the original, then make a copy and replay it. For those poor quality original CDs the copy had a lower error rate as measured by the digital lens. Now, the ones that were really good to begin with never improved--usually got worse. I have heard that people have used the Genesis digital lens in front of a CD recorder and gotten similar results. I have not done this as my only CD recorder is the one attached to my computer. Perhaps someone else has tried this experiment. So any ideas to what's going on here?

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.