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As new digital tape formats shape up, analog keeps its lead

technofile  by al fasoldt

Columns and commentaries in a life-long dance with technology
 

Simple gray rule


As new digital tape formats shape up, analog keeps its lead
 

By Al Fasoldt

Copyright © 1991, The Syracuse Newspapers

The lowly audio cassette, invented in the early 1960s as a dictation medium, may be staging a comeback.

The format that was designed to replace the regular cassette is not selling as well as its backers had hoped. This format, called DAT (for digital audio tape), was introduced in Japan a few years ago and arrived in North America within the past year. DAT recorders are expensive, costing $800 or more, and are available only in a few brands.

Regular cassette decks, meanwhile, have improved to the point of offering near-digital quality at an average price less than half the cost of DAT machines.

In part, the success of standard cassette decks comes from consumer confusion over two digital formats. Rather than choose one or the other, hi-fi hobbyists who have held off the purchase of a new recorder seem to be looking anew at the familiar analog cassette.

The two digital techniques will face off in a format war later this year. Buyers will soon have a choice between DAT recorders and an entirely different digital tape format developed by Philips.

The two formats are completely incompatible.

The Philips design is based on the stationary digital audio tape (S-DAT) principle, while the older DAT design, technically called R-DAT, is a rotary-head technique.

Rotary-head recording is the same method currently used in videotape recorders. In fact, R-DAT machines work just like miniature VCRs, with the tape being drawn slowly past a spinning magnetic head.

This gives a long recording time while allowing a relatively simple head design.

S-DAT recording turns the principle around. The head is held in place while the tape is shuttled back and forth. To achieve the same recording density as R-DAT machines—in other words, to get the same recording time on each tape—S-DAT recorders must use heads with many separate tracks. Each time the tape ends one pass, the head switches tracks.

S-DAT has been around for years as a technical curiosity, but it has never been tried in consumer equipment until now. The European researchers who developed S-DAT recorders for Philips say they have solved the problems of keeping the tiny tracks aligned properly, but many Japanese companies have held back from endorsing the S-DAT approach.

Complicating the issue is yet another digital recording method that Sony will market worldwide next year. It uses tiny discs, and it, too, is incompatible. Sony's new discs cannot be used on the millions of compact disc players that have been sold since CDs were introduced in the last decade.

And to make things even more complicated, an attempt to bring a new 1990s technology to standard audio cassettes seems to have failed.

The new approach, called Dolby S, improves the sound of normal audio tapes to a level that in many cases matches digital sound, yet Dolby S has appeared in only a few cassette decks. Initially, the circuit that provides Dolby S was much too expensive (costing $500 itself), but the Dolby company hasn't been able to get a cheaper version adopted by the major manufacturers.


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