If you happen to own a video-cassette recorder you may be more than halfway to the glories of digital audio. A new sound processor from Toshiba -- its model PCM Mark II -- will convert sound (live or from another recorded source) into digital code for stereo recording on Beta- or VHS-type video cassett machines. The same video tape used for pictures may be used for the audio. When digitally recorded, the tape can be played back on the VCR and fed through the Toshiba processor, which then changes it back to conventional analogue sound.

While the ultimate quality of the recorded digital sound, or of its playback after reconfersion to analogue sound, is determined by the source or by the playback amplifier and speakers (or headphones), what happens to it when the PCM device takes over and transfers it onto the tape is "something else." Our tests of this system indicate taped material that boasts higher specifications than are likely to be obtained from most high-grade, professional chaliber open-reel tape decks of the analogue type. Frequency response runs with 2 dB from "zero Hz" to 20,000 Hz. Distortion measured is less than 0.03 percent. The tape's dynamic range covers a span of 85 dB. Wow-and-flutter are simply not measurable.

With specs like these you can make stereo tapes at home that are at least as good as, if not better than, the master tapes made in studios on huge tape consoles. Played back through a high-quality stereo system such tapes may well be the best-sounding material you ever have heard -- at home or anywhere else.

There's more. With the Toshiba device and two VCRs you can copy a digital tape from one video machine to the other in digital form, without changing it to analogue sound enroute. You also can mix an already recorded digital signal with a new analogue signal. With only the one VCR you still can mix analogue sound sources from the PCM processor's microphone and line inputs.

If wow-and-flutter are things of the past with the PCM device, so too is tape saturation. The response curves remain the same at all recording levels up to "zero dB" -- and there is just nothing above "zero dB." The device also has a built-in error detection and correction system that fills in for any dropout of informational "bits" during the pulse-code-modulation process.

To use the PCM Mark II, you must interconnect it with a video cassette recorder and then feed in the signals to be recorded from any external source. Some of the controls and features will probably be unfamiliar at first, but they are within the grasp of any serious audio enthusiast. Probably more of a stumbling block is the unit's price, which has been announced at "about $5,000." The processor itself is about the size of a receiver, and it weighs 50 pounds.

Is the Toshiba PCM Mark II a dream machine come true for a limited number of very affluent enthusiasts, or is it the harbinger of lower-priced things to come for a large market? Only time will tell of course, but the fact is, the "future technology" does exist in tangible form, and it works very much as claimed -- which is to say, better than anything before.