CD Copies...why do they sound worse?


I had a theory that I haven't discarded yet that not all CD blanks are equal in terms of composition. Yes, they all are made of aluminum and polycarbonate, and when you burn a CD you are creating small holes, or dents in the blank. There is the red book standard that must be adhered to, but as in anything else, I'm sure there are better grades of aluminum and poly available, you get what you pay for. Since the laser reads the digital stream by optically scanning the surface of the CD and interpreting either a one or zero, you'd think it's a go/no-go operation. The original and copies do not sound the same, even to the uncritical ear. I thought for a while it may have had something to do with the relative quality of the CD blanks I was using to copy, in other words, the pressing plants simply use a better grade of master CD's. My friend has a contact and we were able to acquire bulk CD blanks from Saturn Disc that makes CD's. No difference, copies still aren't right. I guess we can eliminate the CD blanks for now. Here's where things get a little outside normal thinking in my twisted logic: we know there are error detection and correction schemes used in intrepreting the data on the CD, employed when the bit being read isn't immediately recognizable to the player. Is it possible the home-made copy that was burned using a cheap consumer grade burner, contains more errors? Are the pits burnt in the CD either irregular in shape or depth? Does the laser in these consumer grade CD burner introduce errors? If so, the EDAC is pretty busy, and doesn't always get it right, which would explain a general lack of quality due to latency delays in the data stream while the EDAC does it's work, and in the process is bound to mis-interpret zeros and ones, there is no 100% accurate EDAC. To me, this is a good place to start in terms of understanding the obvious differences in sound quality.
jeffloistarca

Showing 8 responses by carl_eber

There was a thread recently, where they thought the copies actually sounded "better". (CDR's don't use aluminum as the substrate, it's a photosensitive chemical layer). I don't think there are any simple answers to your questions! It's definitely not as simple as reading "either ones or zeros", either..........................Peruse The Complete Guide to Highend Audio, familiarize yourself with the finer points, and then e-mail a few high end digital manufacturers for their thoughts on this (but don't ask dumb questions, and don't hound them too much).
Vinyl is a totally different medium, and sounds better because there is both more dynamic and more tonal resolution stored in, and passed through the fromat. Not because of the material it's stored on, for example. Let's just keep this on CD-R's, if we could. Ejlif says he doesn't know why a CD-R would afford better performance, that "it just does". If we wanted to know why that were true (if it is) we'd have to ask several of the best designers in the field, and not just speculate about the "why". There are complex issues that would need to be dealt with, about how CD's get read in the first place. You should all read what Harly has to say about CD playback, in the back of TCGTHA.
Craig, I definitely do not believe that the edges are crisper on a CD-R. You have to understand that a CD-R is made while it's spinning, and CD's are stamped. It would be that the stamped ones have the crisper edges (all things being equal...which they aren't). AND, CD-R's use a photosensitive chemical layer, and the holes are bound to have LESS defined edges than the stamped pits, if anything. There might be other advantages, but seculating about it won't get you anywhere. Talk to some experts, and see what they have to say. And carry a CD-R to one of your friends with an electron MICROSCOPE, and compare it with a stamped CD. I think the holes in the chemical layer are bound to have some "wiggle" around their edges, just as photographic film has a grain...but that alone wouldn't necessarily cause poorer sound quality (these wiggles would be very small, compared to the hole the laser burned), and there are complex issues to consider here, that none of us are qualified to discuss...other than subjective opinion and observation........................Right now, it's just like anything else on here...Whatever you like, do it that way, and be happy. Personally, I have no opinion as to whether a copy sounds better, or worse (the CD-R's I have are copies of originals that I did not own, which is the whole point of CD-R in the first place). I'm just happy with the "tweaks" I do to both CD-R's and CD's, and enjoy both.
Jeff, I've made CD-R's on the computer too, and you have to make sure it's not writing them at several times normal speed. I did it at like 30x once, and yes, that sounds terrible, and even a deaf person could hear that difference in a blind test 100 out of 100 times. Did you burn at normal speed?
OK, I will. I'd still like to see each under an electron microscope. You could mail me one of those too, heh heh.