dsj@rabbit.UUCP (David S. Johnson @ ) (03/24/84)
I'm about to buy a CD player, and although I originally joined this newsgroup in hopes of finding out if there were any differences (other than price and features) between the players available on the market, I have seen precious little advice on this issue. I'd appreciate it if those of you who have players would send me mail about your choices and experiences. In the meantime, here are six interesting articles about CD's that I haven't seen mentioned on the net: (1) HIGH FIDELITY (3/84) "Do CD's Sound Better? Not Always" by Sam Sutherland. Horror stories about how many early CD's were created from 3rd generation analog copies, even though the original was a digital tape, plus other comments on CD sound quality. (2) HIGH FIDELITY (3/84) "CD vs. LP: Little Things Matter" by E. Brad Meyer. Report on comparison of CD played by Sony CDP-101 to LP played by Denon DL-103D moving coil cartridge "in a special lightweight headshell on a Technics SL-500 integrated turntable," in which the writer concluded that inaccuracies in the response of the cartridge were responsible for it sounding less harsh than the CD. In particular, it had a dip of 2dB centered around 5kH, which, when EQ'd into the CD response, removed much of the harshness. (3) HIGH FIDELITY (3/84) "The Carver CD Fixer" by Michael Riggs. Bob Carver apparently measured the same dip in the Denon cartridge as did Brad Meyer (I'm not sure why they both used it as a standard), but he also measured another inaccuracy in the cartridge that might account for the fact that it was claimed to offer more "depth" - the L-R component of the signal from the cartridge was 5/4dB too high, apparently a common phenomenon with moving coils (suggesting that perhaps all their vaunted depth is an illusion). Carver is going to sell a gadget to impose these two inaccuracies on CD players for those who like them. (4) STEREO REVIEW (4/84) "Understanding Compact Disc Errors" by David Ranada. Someone on the net was asking about CD error counts. Well, Ranada actually measured them, concluding that a typical good CD has a "block error rate" of 30 per second, all of them completely corrected (i.e., concealment was never needed on the whole 45 minute CD). (5) AUDIO (4/84) "Error Correction in the Compact Disc System" by Toshi T. Doi (SONY). Quite technical, and I haven't read it yet. (6) AUDIO (4/84) "Philips Oversampling System for Compact Disc Decoding" by Wayne Schott. I did read this one, for the claim is made that the Philips 14-bit decoding system does not lose any information from the original 16-bit signal, which seemed preposterous, but turns out to be more-or-less correct. Since the Philips system oversamples, it has 4 samples for each original 16-bit sample, and if averaging is done before these are truncated to 14 bits, then a group of four successive 14-bit signals has 16 bits of information (approximately), since log base 2 of 4 yields the extra two bits. This means that those wishing to avoid the high frequency phase shifts of 16-bit players need not give up 16-bit accuracy by going to a Philips type player, as I had originally assumed they must.