gwu@clyde.ATT.COM (George Wu) (03/26/88)
NOTE: I have added sci.electronics to the newsgroups. REMOVE IT BEFORE REPLYING unless your reply is technical in nature. If a final conclusion/consensus (about inferior CDs) is reached on one group, but not another, I'll make sure it gets posted to the other group(s). Just trying to keep down the net volume. In article <619@acf3.NYU.EDU> tmy6405@acf3.UUCP (Ted M. Young) writes: >One word of caution...a friend of mine who is very involved in the >field, tells me that some of the CDs that you get from the club may >NOT be as good as the ones that you would buy in the store! Seems >that some record companies don't want to give the CD Clubs the digital >masters, so the Clubs (with their record licenses, I guess) are making >CDs using INFERIOR masters! (You didn't think the CD & record clubs >buy the actual product from the record companies, did you? That's why >it says "licensed for manufacture...." etc. on the back! I'm inclined to disagree here. You say the original label company won't give a club the original *digital* master. This can be interpretted to mean that the club gets either a digital copy of the master, or an analog reproduction. Let's consider the analog reproduction first. This further implies that the club must redigitize the recording. This would indeed degrade the quality of the recording, so I'd be inclined to agree with you. A hunch tells me this is NOT what is done. However, if the club uses a digital master, be it umpteenth-hand, how can the recording be degraded? First, we need to know how CDs and their masters are made. Correct me if I'm wrong, but I believe they're made by "scorching" the disk in a particular way in represent high logic (1 bit, whatever), and another way to represent low logic (0 bit). If this is the case, then there's no degradation in reproducing a digital recording. This is essentially an all digital process, so one need merely reproduce all ones as ones, and all zeroes as zeroes. Likewise for any other digital process. Only, if there's something analog involved, such as the way vinyl LPs are produced by "stamping" the blank with a master to make an impression, is there degradation. As you can see, I think I remember how CDs are produced, but am not sure. If someone out there is sure, please followup.-- George J Wu UUCP: {ihnp4,ulysses,cbosgd,allegra}!clyde!gwu ARPA: gwu%clyde.att.com@rutgers.edu or gwu@faraday.ece.cmu.edu
ted@mergvax.UUCP (William Klein) (03/30/88)
In article <23843@clyde.ATT.COM>, gwu@clyde.ATT.COM (George Wu) writes: > > In article <619@acf3.NYU.EDU> tmy6405@acf3.UUCP (Ted M. Young) writes: > >One word of caution...a friend of mine who is very involved in the > >field, tells me that some of the CDs that you get from the club may > >NOT be as good as the ones that you would buy in the store! Seems > I'm inclined to disagree here. You say the original label company > won't give a club the original *digital* master. This can be interpretted > to mean that the club gets either a digital copy of the master, or an > analog reproduction. > > Let's consider the analog reproduction first. This further implies that While at the Apple CD/ROM conference last month, I conversed with a person who ran a CD pressing shop. He did audio CD's, and wanted to get the scoop on being prepared for the digital data CD/ROM's revolution. OK. Anyone who knows more than I remember, correct me please. Faulty memory may cause blathering in the below comments. A master tape (analog or digital, the final mix tape) is delivered to the mastering shop. There it is corrected (?) and eventually converted to CD-compatible digital and 'burned' onto a nickel master. This master is then used to 'stamp' glass masters. It is apparently good for not that many glass masters, I do not remember the number but is less than 100. The nickel master goes into the vault. The glass masters are then used to 'stamp' the plastic CD's. They wear out after some number of thousand pressings and are discarded. The size of a CD production run is generally controlled by the number of glass masters made * number of output copies per glass master. The reason the glass masters are 'used up' is because they have a shelf life of about 1-2 months (breakdown mechanism? I don't know). The nickel master has a shelf life (in the vault) of no more than 6 months. So. When someone else is 'licensed' to press CD's, they start from either the mix tape (often in analog) or maybe (rarely?) the final digital repro tape. This is why there is definite differences in quality (mainly noise floor) between different pressings of the same music (Pink Floyd's DSOTM is a prime example). They are using different masters. I hope this is somewhat enlightening, and not too incorrect (as it is coming from volatile organic memory). -- Life is what happens to you when you are busy making other plans. Real Life: W. Ted Klein UUCP: philabs!mergvax!ted VOICE: 516-434-2687
tga@eleazar.Dartmouth.EDU (Greg Ames) (04/02/88)
In article <336@mergvax.UUCP> ted@mergvax.UUCP (William Klein) writes: >[stuff deleted] >A master tape (analog or digital, the final mix tape) is delivered to the >mastering shop. There it is corrected (?) and eventually converted to >CD-compatible digital and 'burned' onto a nickel master. To the best of my knowledge (from talking to friends in the music field, and reading various articles on the subject), the processes of correction (noise reduction, re-mastering to digital, etc.) and conversion "CD-compatible digital" is generally done by the studio, not the pressing plant. All most plants do is just that: press CD's, although some do provide preliminary processing serrvices, for a fee, of course (it's not part of the "standard deal"). The pressing plant then takes this "CD-compatible" master, which includes more than just music, including a "table of contents," start and stop marks for tracks and indices, and SMPTE (pronounced "simp-tee") time codes, which provide the timing info to your CD player (ie, length of disc, length of current track, time remaining, play time, etc.). This digital tape is then transfered directly to CD, w/out changes. This digital master is used to make the metal plates to press the glass dies. >This master is then used to 'stamp' glass masters. It is apparently good for >not that many glass masters, I do not remember the number but is less than >100. The nickel master goes into the vault. The glass masters are then used >to 'stamp' the plastic CD's. They wear out after some number of thousand >pressings and are discarded. The size of a CD production run is generally >controlled by the number of glass masters made * number of output copies >per glass master. The reason the glass masters are 'used up' is because >they have a shelf life of about 1-2 months (breakdown mechanism? I don't >know). The nickel master has a shelf life (in the vault) of no more than >6 months. The main reason that glass masters have a "shelf life" of 1-2 months is partially because the glass points "dull" from use, but, more importantly, glass is a *very* viscous liquid, which actually flows. When you heat glass, it doesn't actually melt, it just gets runnier and runnier (ie, no definate melting point). This is why very old windows (~100 years) distort your view of the outside world: the glass "flows" to the bottom of the pane, bulging it. I used to work in an electron microscopy lab. When slicing thin sections of specimens for EM slides, you use glass knives formed by breaking 1/4 inch glass into little right tringles, 1/4" thick, and 1" square on each side. Glass knives are used because they are sharper and make cleaner slices when working at such a tiny level. However, the knives only last about 24 hours. After that time, even if they aren't used, the glass has flowed enough so that the edge is now to dull to use. This is the main reason why the glass dies go bad; the glass flows and becomes inaccurate. I don't know why the nickel plates go bad, but I suppose it is because high levels of oxides building up on the surface start to plug up the holes (they ARE damn small!). >When someone else is 'licensed' to press CD's, they start from either the >mix tape (often in analog) or maybe (rarely?) the final digital repro >tape. This is why there is definite differences in quality (mainly noise >floor) between different pressings of the same music (Pink Floyd's DSOTM >is a prime example). They are using different masters. >I hope this is somewhat enlightening, and not too incorrect (as it is >coming from volatile organic memory). Yes, but ANYONE making CD's is going to have to start somewhere, and the only starting points available are the mix tapes, or copies of it. What is the difference between, say, Warner Brothers letting Columbia House make a digital master from their old mix tapes, or WB making the digital master themselves and giving that to Columbia House? I can't see how this would make any difference in quality. -Greg [-----------------------------------------------------------------------------] [ Greg Ames US Mail - HB 1362, Dartmouth College] [ E Mail - tga@eleazar.Dartmouth.EDU Hanover, NH 03755 ] [-----------------------------------------------------------------------------]