Grooves no longer groovy in new laser audio system

O Edison, look what they've done to your phonograph now. They've replaced the needle with a laser (imagine, a beam of light), and they've traded in the record for a disc that looks like an aluminum pancake (it doesn't even have any grooves on it!).

The result, sir, is what's touted to one of the biggest revolutions in sound reproduction since the days of your old hand-crank machine.

This latest musical marvel - the digital audio disc player and its cousin, the Compact Disc - is making its debut in the United States amid a symphony of expectations in the music industry.

The duo, if successful, could eventually make today's turntables and record albums themselves - an enduring feature of millions of households - as rare as the Victrola.

The audio disc player was introduced in the US last week by Sony Corporation, after a successful launching in October in Japan and a more recent one in Europe. Another will follow under the Magnavox name within a few weeks. At least 30 other major electronics companies around the world are working on laser audio systems, two dozen of which may put models in US stores by year's end.

''It is the most exciting product since the first stereo equipment,'' says Stephen Traiman, executive director of the Recording Industry Association of America.

The digital audio system represents a fundamental shift in sound reproduction technology. For all the attempts at creating ''perfect'' sound - from gramophones through the latest generations of woofers and tweeters - one basic principle has stuck: A needle has still had to glide through grooves on a record.

Under the digital system, however, there is no mechanical arm delicately balancing on a record surface. Instead, a microscopic laser beam from the player ''reads'' digitally coded music on the disc. The digital signals are stored as billions of pits and plateaus on the disc surface. They represent strings of binary numbers, similar to computer talk, which are interpreted into a signal that reproduces the sound.

The result is free of hiss, crackles, and distortion - the closest thing, some audiophiles claim, to concert-hall acoustical clarity.

The discs themselves are 4.7 inches in diameter, have only one playing side with no grooves, and can hold up to 70 minutes of music. They sell for $17-plus, but in theory have an unlimited life. They are covered by a thin plastic layer, which shields them from dust, dirt, and deterioration. Fingerprints, for instance, are no problem.

Those buying the first laser players, however, will probably be only the most devoted audio buffs. The systems plug into conventional amplifiers and speaker systems, which means the only investment involved are the discs and the player itself. But, at $800 to $1,000 per player, that's far more than most pay for a full music system.

''It is going to be a very slow process getting it introduced into the market ,'' says Douglas Cayne, an analyst with the Gartner Group Inc., a Stamford, Conn., research firm. ''But 10 to 15 years from now it will be the dominant audio playback device.''

The hi-fi equipment and records industries are hoping the discs will lift sales. They have been smarting from recession, the rise in home taping, coin-operated video games, and record piracy. Recordmakers also hope the discs will help slow the swing from albums to cassettes now going on. For their part, laser player manufacturers believe the ''superior sound quality'' of the new systems will win over audiophiles first. Then, as prices drop - industry analysts predict they could dip to $300 within a few years - they expect the systems to gain more mass-market appeal.

''It will take time,'' concedes Harry Machida, a Sony spokesman. ''It is not another type of car or dishwasher. It is an entirely new technology.''

Just how many people will be playing laser music will hinge in part on the menu of digital audio discs (DADs) available. Three plants worldwide are now turning out the silvery discs, none of them in the US. Some 16 titles - classical, jazz, and pop - were released in US stores with the introduction of the laser player. These were imports from a Sony-CBS Inc. joint venture in Japan.

After initial trepidation, a number of major record companies are now vowing to produce discs eventually. In the US, both RCA Records and Warner Communications Inc. recently said they will release them. They join CBS and Polygram Records, who made early commitments to disc distribution. By year's end , some 200 disc titles (mainly classical and all probably imported) are expected to be in US stores.

The music industry has already been slowing adopting digital technology. Some of today's LP records, although played on conventional ''analogue'' systems in the home, were made from master tapes digitally recorded in the studio. This means there are digital tapes around for reissuing LP records as discs.

On the other hand, there are plenty of other recordings, including most rock and pop titles, for which no digital master tapes exist. These releases can still be put on discs, but they won't be of the same quality of ''pure digital'' recordings.

Makers of DADs, meanwhile, will be looking over their shoulders at other technological developments that could eventually threaten the discs. One potential rival is a digital cassette machine, now under development, which could pinch the disc trade the way cassette tapes have hurt album sales. But DAD designers are not sitting on their haunches.: They're working on portable disc players, which are expected to be only a couple of years off.