DCC CURRENTS
Cassette with a Digital Twist
Philips invented the Compact Cassette and co-invented the Compact Disc, so what could be more natural than the company's combining them? Reports swept the industry through much of 1990 that they'd done just that, with a cassette that would be compatible with all current analog players and recorders but would also carry digital audio for use with players and home recorders yet to come.
Not quite, as it turned out. Philips has now announced that the system, to be called the Digital Compact Cassette (or DCC for short) won't allow both digital and analog recording on the same cassette but will permit either to be done on the same recorder. And the analog tape format it will use will be today's standard Compact Cassette.
For digital recording and playback, DCC will use a linear track format, similar in principle to S-DAT. (The S-DAT format is still on the books as an official standard, but only the alternative R-DAT helical-scan system is actually in use today.) Since Philips had been showing the system to record companies (who'd be happy to see a system that can't digitally clone CDs) but not to home recorder manufacturers, rumor had suggested that DCC would use a unique encoding format that would not allow such cloning. And the terse initial press release that Philips issued in October 1990 did state that "The system is based on a new, revolutionary coding technique." However, two Philips sources have confirmed to Audio that this new technique will allow digital cloning of a CD's program material-though not of its subcodes.
Guy DeMuynck, Philips' Senior Director of Marketing in the U.S., says that DCC's cloning of CDs will be subject to limitations "similar to" those imposed by the SCMS system now used in DAT. That's no surprise, as SCMS is based on a Philips anti-copy system called Solo. It has been suggested that the DCC anti-copy system will be more restrictive than SCMS, either preventing any digital recording's being copied more than once or adding a flag to any DCC tape that's been copied so it cannot be recopied thereafter.
Philips won't release much further information until the Winter CES, a few weeks after this issue comes out. But Audio Week, a trade newsletter, reports that DCC's coding technique is Precision Adaptive Sub-band Coding (PASC), a system developed in Europe for digital radio broadcasting. To save bits, PASC rations its resources, encoding audible portions of the signal more precisely than it does those portions less likely to be audible. This technique is said to yield a dynamic range of 110 dB. Digital inputs of any standard sampling rate will be accepted, but all signals will be recorded on the tape at 44.1 kHz.
According to the report, DCC will have auto reverse, using a 16-track head to provide eight digital tracks in each direction of play. Tape speed will be the same as for analog cassettes, but the digital cassette will have a tape cover like that on a DAT or an 8-mm videocassette. One Philips spokesperson confirmed without further comment that the Audio Week story is "rather correct, but not completely so." Why a new digital tape system, just as DAT is reaching the U.S. market? Besides offering a degree of compatibility with Compact Cassette, DCC will also allow high-speed tape duplication, Philips says, which would lead to far lower digital software costs than DAT. But this presumes that DAT duplication costs won't drop dramatically by 1992, when Philips hopes that DCC will reach the market. Both Sony and BASF have been working on high-speed duplicators that would accomplish this.
Hardware costs for DAT and DCC should be about equal, in any case. Philips says that DCC recorders will be available in the first half of 1992, for about $500 to $600, as compared to the $900 and up charged for DAT machines today. But DAT prices are a moving target and may well drop to Philips' projected levels by that time.
Even last June, I was able to pick up a DAT recorder (Aiwa's portable) for about $650 in Japan-and Japanese stores don't do U.S.-style discounting.
Before the industry settled on the R-DAT standard, there was some talk that S-DAT machines might be unsuitable for use in portable and car players, due to tracking problems.
While DeMuynck would not address the question directly, he did say that "Use in the car is certainly very important to us. It is our intention to make DCC as widely applicable a system as the present Compact Cassette," and that the system would allow for use in both home and car.
Tandy has signed on to make and market DCC tapes and players, and the system has been endorsed by several record companies. Those companies include not only PolyGram (which Philips has a stake in) but EMI, Bertelsmann (which owns RCA Records), and Warner Bros.
Philips is not the first company to announce a digital recorder with Compact Cassette compatibility. In 1985, Sharp showed a prototype, the CX-3, that made digital recordings on standard CrO2 cassettes. The system used a stationary, thin-film head and recorded on 18 tracks, of which 16 were for data and the remaining two were for control and other purposes.
While the CX-3 used the same 44.1-kHz sampling rate as CD, it used 14-bit linear encoding rather than CD's 16-bit system.
Encrypted History
Our legacy of literature is fairly safe. Pick up a centuries-old book and, despite differences from modern language and typography, you'll still be able to read it. Today's books will likewise be readable centuries from now (at least those whose paper doesn't crumble in the meantime).
But what about our legacy of recorded sound? That legacy requires hardware to "read." And as the number of recording formats grows, the odds on a given audio library having the hardware to play each of them diminishes. In just a century and a smidgen since Edison's tin-foil phonograph, we've had at least two kinds of cylinder phonographs and 13 flavors of analog disc (counting only major variations in speed, groove structure, direction of play, and size).
Magnetic analog recording has given us at least three media (wire, tape, and magnetic disc), five sizes of tape, six speeds, about a dozen track arrangements, and at least eight kinds of cartridge or cassette.
Digital, being younger, has brought us only one type of cassette, five or six kinds of master tape (not counting variants with different widths and track arrangements), PCM-encoded recordings on three different videocassette formats (in both NTSC and non-NTSC versions), plus the Compact Disc-and there are doubtless more to come. (I know of at least five new digital formats that have been shown in prototype.) Someday, music lovers will look on audio archivists the way we now look on medieval monks, guardians of knowledge that would otherwise disappear forever. But the monks had it easier-all they had to deal with was hand-copied (often miscopied) manuscripts in Latin, Greek, or, occasionally, Hebrew, Aramaic, or Arabic--a piece of cake, compared to what tomorrow's audio archivists will face.
Bye-Bye Home-Brew?
Home-brew repairs and modifications keep getting harder to do. That's not just because the systems involved (in everything from audio to autos) are growing more complex, but the parts and assembly techniques are also growing harder to deal with. A shade-tree mechanic can no longer count on being able to pull a car's engine out with a mail-order chain hoist and an overhanging oak limb; the way most cars are built today, with engines mounted from below, you have to pull the car up off its engine. In electronics, its bad enough (from the home-brew standpoint) that big tubes and discrete components have given way to ICs of the caterpillar-like DIP type--now DIP ICs are giving way to surface-mount devices designed for automated mounting. Their pins are so finely spaced that few technicians, if any, will be able to mount and dismount them by hand. Sooner or later, they'll come up with ways to do without even these components maybe using rays or particles that modify the circuit boards' internal structure to create the necessary circuits.
In electronics, at least, new construction techniques have resulted in lower cost and greater reliability. But they do mean less fun-and less chance for electronics fans to challenge and stretch their ingenuity.
"Did You Hear What Mama Said?"
Babies explore the world through all their senses. Every year, about 5,000 infants--one out of every 750 births--are born with hearing losses that handicap them in learning speech and language and that limit their ability to realize the comfort of their parents' words. Yet such losses are not identified until the children are, on average, 21/2 years old. Now, there's a simple test that parents and grandparents can use to check the hearing of children from infancy to 3 years old.
The testing methods are available in a leaflet from the American Academy of Otolaryngology-Head and Neck Surgery. The leaflet first covers factors that put children in high-risk categories for hearing loss.
These factors include: Family history of hearing loss; the mother's illness or drug use during pregnancy; prolonged labor, premature birth, or other problems attending the newborn; and meningitis, chronic ear infections, and/or chronic upper respiratory allergies. Appropriate home tests for children less than a year old and for children from 1 to 3 years old are also in the leaflet.
For a copy, send a self-addressed, stamped envelope to the Academy at One Prince St., Alexandria, Va. 22314.
A Balanced View
Balanced-line connections, once restricted to professional audio components, have now become so common that we noted their use in our Annual Equipment Directory last October. A 13-page background paper on balanced lines, written by Mark Levinson and Tom Colangelo of Cello Ltd., is now available from that company for $2.50 ($5 for readers who live overseas) to cover postage costs. Requests and checks may be sent to the attention of Ms. Pat McCullough at Cello Ltd., 315 Peck St., Bldg. 23, New Haven, Conn. 06513.
(adapted from Audio magazine, Jan. 1991)
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