What's Dat? Yet Another Audio Innovation

November 11, 1990|By Ron Gasbarro

Still in a quandary over whether to convert your vinyl record collection to compact disc? Hold off a wee bit longer and you can own a machine that plays DATs.

DATs -- digital audio tapes -- play up to four hours of music without anyone's ever having to flip them over. When it comes to sound quality, nothing like it has ever existed.

Compared with compact discs, DATs are even more compact, measuring about 1 by 2 inches. One of the big faults of CD players, especially in cars or in Walkman form, is that they skip when jostled. The sounds from a DAT do not waver no matter how deep the pothole you drive or jog into.

Unlike standard audio cassettes, DATs do not hiss. Anyone who has listened to a regular cassette through a Walkman has heard the background whooosh between cuts on an album. DATs offer crystal-clear recording with astoundingly low signal-to-noise ratio and 1/100th the distortion of audio cassettes.

Needless to say, DATs are in high demand by audiophiles.

"To most people, digital audio tape is an extremely good tape, the way a CD is an extremely high-quality record," says Brian Hudkins, owner of Gramophone Ltd., a stereophonic equipment dealer in Baltimore and Columbia.

"Upon hearing a DAT, customers say that the sound is as good as a CD. But DATs can perform in some ways that CDs and audio cassettes cannot."

Take your average cassette deck. The longest you can listen to music -- provided the deck has an auto reverse feature -- is 90 minutes. And say you only want to hear songs No. 3, No. 8 and No. 1, in that order. You're out of luck -- unless you have a programmable DAT machine that makes getting around the tape easier.

By pressing a few buttons, the DAT machine knows which albums cuts you want to hear, whizzing right by the ones you dislike.

Compact disc players let you program track orders, too. But as of now, you cannot record onto them. You can, however, record from CD to DAT, capturing the CD's clarity.

"The people that come in looking for a DAT player already have a CD player," says Mr. Hudkins. "But they want the ability to make their own tapes. The DAT is an evolution of that."

How does the digital audio tape recording process differ from that of standard tape?

"The perfect quality of sound reproduction on DAT is a factor of its digital nature," says Jim Disney, manager of Stansbury Audio in Dundalk. "Using standard tape, you are actually recording the sound right on to the tape, in analog fashion. But recording music digitally means that a series of commands is transferred to the digital tape. The machine reads these commands and expresses them as the music you have recorded."

The conversion of music to digital is a two-step process, adds Richard Krueger, a spokesman for the Sony Corp. of America, a company that manufactures DATs.

First, the music is divided into discrete segments or samples. In the DAT format, each second of music is broken into 48,000 samples. Each sample is assigned a 16-bit binary code, similar to computer data. This process is called quantizing. The combination of sampling and quantizing enables virtually any signal to be coded with incredible accuracy, whether it is Leonard Bernstein or Faith No More. The DAT format records over 3 million bits of information for every second of music.

"The whole process is similar to a puzzle," says Mr. Krueger. "Each sample is like a piece of a puzzle. The puzzle can be disassembled and reassembled as often as desired. But each time the puzzle is assembled, it looks exactly like it did the first time."

You cannot say the same for vinyl records or audio cassettes, which wear out over time.

Standard audio, or analog, tape has been used since World War IIand was designed primarily for dictation. It is now nearly fully developed, as good as it is ever going to be, limiting future improvements to minor changes.

Analog tapes' inherent limitations -- signal-to-noise ratio, for example -- are caused by several factors: the interaction of the tape and the deck; the basic limitations of the recording and the playback head electronics; and the tape itself.

"DAT eliminates many of these problems by recording a representation of the music rather than the music itself," says Mr. Krueger. "As a result, the music is re-created after the tape/head interaction, in the electronics of the machine."

But digital or not, any tape can tear, rot or clog the rollers and guides inside a tape deck. Compact discs are touted as eternal -- they will supposedly last forever with proper treatment.

DATs still have it over regular tape because they feature protective covers for the tape, a high-quality shell and user recording tabs. The DAT tape is also made from a new tape formulation called "metal" tape that is significantly higher in quality than a standard cassette tape, from both a recording and structural standpoint. Metal tape has nearly seven times the shelf life of normal oxide tape.

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