DAT

DAT (DAT), a variety of magnetic tape cassettes used for sound recording and reproduction.

Digital recording on magnetic tape was developed for professional use in the 1970s and for the consumer market by the late 1980s. Digital recorders convert audio signals into digital data on a magnetic tape by means of a microprocessor (an analogue-to-digital converter) and convert the data back into analogue audio signals (by means of a digital-to-analogue converter) for playback with the amplifier of a conventional stereo sound system. In digital recording, sound waves are sampled several thousand times per second and transformed into a series of pulses that correspond to patterns of binary numbers that are recorded on tape (or optical disc).

Digital recorders/players for professional use appeared in the 1970s in the form of pulse code modulation adapters for video recorders. By 1983 the compact disc (CD) developed by Philips (the Netherlands) and the Sony Corporation (Japan), which used a laser beam to read optically pre-recorded digital information on the disc, had brought digital sound into the home market. Digital recordings provide higher-fidelity sound reproduction—greater dynamic range and frequency response and less distortion—than conventional analogue methods.

The last obstacle to marketing digital audio tape for home use—the potential to make copies that are indistinguishable from original, copyrighted recordings—was overcome in the late 1980s. Manufacturers adopted the Serial Copy Management System, which limits the ability to make digital copies of copies while allowing direct, first-generation digital copying of CDs and other digital sources (analogue copying remains unlimited).

The only successful form of DAT recorder commercially available at present is effectively a miniature version of a video recorder, with special metal particle-coated tape, 3.81 mm (ƒ in) wide, which is carried in a very small cassette. The tape runs past two rotating heads on a small drum of 30 mm (1ƒ in) diameter, which is inclined at a small angle to the tape travel, so that it works like a helical scan video recorder. However, unlike video recorders, the tape is in contact with the scanning heads and drum only through an angle of 90°. The analogue audio signal coming into the recorder is sampled and quantized in the usual way, with sampling rates of 32 kHz, 44.1 kHz, 48 kHz, and now 88.2 kHz being used, depending on purpose.

Although intended for ordinary domestic use, the system has not been successful with the general public, but it is now widely used for professional purposes, including sound recording for motion pictures. DAT machines have also been adapted for the recording of digital computer data, and to record sound which would not be picked up using other means.