I was passed this URL
http://www.genesisloudspeakers.com/whitepaper/Black_CDs1.pdf
It discusses using black CDR's to make copies of your original cd's and how the black CD sounds better than the original. I have tried it. It is true. I have done a blind test with my son. He picked it in 3 seconds.
It's a good article on this subject.
When I first learnt few years ago that some Singaporean audiophiles could tell the difference of a copied CD from an orginal CD, I was very much surprised. However, after second thought, I understood it's possible. When thinking as a computer programmer, it's impossble as the data on CDs are always error free unless damaged while when thinking as a telecommunication engineer, it's possible as there is always errors in media. (From then on, I listen seriously to people who say they could hear something unbelievable.)
The author of the article shares his findings which is useful to other readers, but some of his explanations to what he observed are not quite correct and some are arguable. For example, using the linear velocity and angular velocity to explain the timing errors introduced into music is not right. The mechanical velocity variations may cause laser pickup errors but not music timing errors. Jitter is not encoded this way. The jitter people talk about in audiophile circles is not originated from this and it's about waveform degradation of digital clocks. The linear velocity of harddiscs is not the main reason why a harddisc is more reliable for data storage.
All storage media would cause some errors to the data, due to dust, imperfect manufacture, fingerprints, optical pickup mechanism, EMI, vibration etc. There being errors does not mean that data can not stored and retrieved free of errors. The technology to ensure "perfect" recording is error correction technology. The reason that harddiscs and CDROMs is practically free of errors in an error prone environment is that they use more sophisticated error correction techniques than music CDs, because computer data must be practically free of errors but music CDs can tolerate some errors.
I give a very simple example to show how errors can be corrected.
If the original signal is "2468", it can be stored as "2222444466668888" on a CD. When there is one error, say, the picked up signal is "2222434466668888". We know that the "3" can not appear at that position and it must be a "4" there. So the data can be recovered as "2222444466668888" with confidence and the original signal can be reconstructed as "2468". This is in the capability of this error correction scheme. What happens if there are two errors like "2222433466668888"? In this case, "4334" could be "4444" or "3333". So an error will be reported but not corrected. The orignal signal becomes "2*68" where * is an reported error. Now, how to handle this error will very much depend on individual manufacturers. Some would just skip it, so it becomes "2068"; some will filled it with the previous one, so it becomes "2268", which is closer to the original; some may decide to use the average of the previous one and the following one to fill it, so it becomes "2468", good guess. This is called error concealment technique. This is also why some players sound different from others. (There are some other causes too) If the errors can be corrected, which is a standardised techinique for all manufacturers, you hear the same music; If errors can not be corrected but have to be concealed, which is not a standardised techinique and up to manufacturers to innovate, you hear different music from different CD players; In this case, low cost design may just skip the error while high cost design may try to put in a sophisticated algorithm to conceal errors; if the errors even cannot be concealed, the CD is considered as damaged and the CD player may refuse to play.
On harddiscs and CDROMs, to enhance the error correction capability, the signal may be stored as "22222444446666688888" so that it can correct 2 errors.
The above is just an intuitive example. The music CDs use much more complex error correction schemes and CDROMs for computer files use even more sophisticated error correction schemes than music CDs. (This is not about the physical media but how the data are represented on the same CD media.)
In addition, stored data/music on pressed music CD, music on CD Recordable, data files on CD Recordable, CD-RW, CDROM and harddisc are embodied slightly differently, physically and logically. Logic here means the representations of the data. This explains why some old players do not play copied CDs because old CD player may only handle pressed CDs and could not "understand" the physical and logical structures of copied music on CD Recordable or CD-RW.
The quality control of pressing music CDs will result in different amounts and patterns of errors on CDs. That's why some Japanease or German pressing sounds better than American or Asian pressing for the same album.
Because the author did not understand the causes correctly, that's why he did not get the expected results by burning direct from a CDROM reader to a CD Writer.
I don't go into all details but if someone asks specific questions, I can elaborate further.
However, the process to create a good copy of a CD given in the article is sound; people can follow that. He says that you should use a good quality CD-RW but did not give a process to check the quality of CDROM reader or CD writer. Here I add a process to ensure you have a good quality CDROM driver or CD writer for music CD reading and writing.
1) Check reading quality
- put a music CD in the driver; (Do not use a data CD; data CDs are treated differently and the data on data CDs can be read as if there were no errors due to powerful error correction behind the scene)
- use a music track ripping software, like Adaptec EasyCD, to extract the music track into a WAV file on harddisc. (Must save as WAV file type!) Do this 2 or 3 times and save them with different filenames, eg. track1a.wav; track1b.wav; track1c.wav; Because some errors are random, it's good to try reading the same track several times;
- open "Command Prompt" from "Programs -> Accessories";
- use the command "comp" to compare the files; type "comp track1a.wav track1b.wav"; (This is true on Windows 2000 Pro, try if it works on your Windows. If not, post your Windows version and I may find a way for you to do the same;) it will report if there are differences between these files; If yes, you should consider not use this drive for music, but for computer files, it may be fine.
2) Check writing quality
- write the same music tracks to 2 or 3 CDs; (Must be music tracks, not computer files; try a few tracks at the same time as the writer may perform differently writing at different locations;)
- then put them into a driver with no reading errors and follow the process of reading quality check; if there are differences between tracks on these written CDs, you should consider not use this writer for music.
(On my computer, my old CDROM drive reads in music tracks differently every time while my DVDROM driver can read in music tracks exactly the same every time. The CDROM is still able to play music but certainly I listen to slightly different music every time
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