Digital Audio Tape

Short description: Digital audio cassette format developed by Sony

Digital Audio Tape

A 90-minute DAT cartridge, with a AAA battery (LR03) for size comparison
Media type	Magnetic cassette tape
Encoding	Lossless real-time
Capacity	Up to 120 or 180 minutes (consumer tapes on non-LP mode)
Read mechanism	Rotating head, helical scan
Write mechanism	Rotating head, helical scan
Developed by	Sony
Usage	Audio storage
Extended to	Digital Data Storage
Released	1987 (1987)
Discontinued	2005 (2005)

Digital Audio Tape (DAT or R-DAT) is a discontinued digital recording and playback medium developed by Sony and introduced in 1987. In appearance it is similar to a Compact Cassette, using 3.81-millimetre (0.150 in), commonly referred to as four-millimitre, magnetic tape enclosed in a protective shell, but it is roughly half the size at 73 mm × 54 mm × 10.5 mm. The recording is digital rather than analog. DAT can record at sampling rates equal to, as well as higher and lower than, that of a CD (44.1, 48, and 32 kHz respectively) at 16 bits.

Similar to most formats of videocassette, a DAT cassette may only be recorded and played in one direction, unlike an analog compact audio cassette. Many DAT recorders had the capability to embed program numbers and IDs into the recording, which can be used to select an individual track, like on a CD player.

Although intended as a replacement for analog audio compact cassettes, the format was never widely adopted by consumers because of its expense, as well as concerns from the music industry about unauthorized high-quality copies. If a comparable digital source is copied without returning to the analogue domain, then the DAT will produce an exact clone, unlike other digital media such as Digital Compact Cassette or non-Hi-MD MiniDisc, both of which use a lossy data-reduction system.

The format saw moderate success in professional audio markets and for computing as the Digital Data Storage format for offline storage. Sony ceased production of new recorders, making it more difficult to play archived recordings in this format. Magnetic tape degradation has been noted by some engineers involved in re-mastering archival recordings on DAT, which presents a threat to audio held exclusively in this medium.

History

Development

DAT compared to Compact Cassette

DATs are between 15 and 180 minutes in length, a 120-minute tape being 60 metres in length. DATs longer than 60 metres tend to be problematic in DAT recorders due to the thinner media. DAT machines running at 48 kHz and 44.1 kHz sample rates transport the tape at 8.15 mm/s. DAT machines running at 32 kHz sample rate transport the tape at 4.075 mm/s.

Predecessor formats

In 1976, another digital audio tape format was developed by Soundstream, using one inch (25.4 mm) wide reel-to-reel tape loaded on an instrumentation recorder manufactured by Honeywell acting as a transport, which in turn was connected to outboard digital audio encoding and decoding hardware of Soundstream's own design. Soundstream's format was improved through several prototypes and when it was developed to 50 kHz sampling rate at 16 bits, it was deemed good enough for professional classical recording by the company's first client, Telarc Records of Cleveland, Ohio. Telarc's April 1978 recording of Gustav Holst's Suites Nos. 1 & 2 for Military Band by Frederick Fennell and the Cleveland Wind Ensemble was a landmark release, and ushered in digital recording for America's classical music labels. Soundstream's system was also used by RCA.

The first consumer-oriented PCM format used consumer video tape formats (Beta and VHS) as the storage medium. These systems used the EIAJ digital format, which sampled at 44.056 kHz at 14 bits. The Sony PCM-F1 system debuted in 1981, and Sony from the start offered the option of 16-bit wordlength. Other systems were marketed by Akai, JVC, Nakamichi and others. Panasonic, via its Technics division, briefly sold a digital recorder that combined an EIAJ digital adapter with a VHS video transport, the SV-P100. These machines were marketed by consumer electronics companies to consumers, but they were very pricey compared to cassette or even reel-to-reel decks of the time. They did catch on with the more budget-conscious professional recordists, and some boutique-label professional releases were recorded using these machines.

Other examples include dbx, Inc.'s Model 700 system, which, similar to later Super Audio CDs, used a high sample-rate delta-sigma modulation rather than PCM; Decca's 1970s PCM system, which used a videotape recorder manufactured by IVC for a transport; and Mitsubishi's X-80 digital recorder, a 6.4 mm (​¹⁄₄ in) open reel digital mastering format that used a very unusual sampling rate of 50.4 kHz.

Demise

Sony released its last DAT product with the DAT Walkman TCD-D100 in 1995 and continued to produce it until November 2005, when Sony announced that its remaining DAT machine models would be discontinued the following month. Sony had sold around 660,000 DAT products since its introduction in 1987. Sony continued to produce blank DAT tapes until 2015 when it announced it would cease production by the end of the year. Although it has been superseded by modern hard disk recording or memory card equipment, which offers much more flexibility and storage, Digital Data Storage tapes, which are broadly similar to DATs, apart from tape length and thickness on some variants, and are still manufactured today unlike DAT cassettes, are often used as substitutes in many situations.

Digital Compact Cassette

The DAT recorder mechanism was considerably more complex and expensive than an analogue cassette deck mechanism due to the rotary helical scan head, therefore Philips and Panasonic Corporation developed a rival digital tape recorder system with a stationary head based on the analogue compact cassette known as S-DAT. The Digital Compact Cassette (DCC) was cheaper and simpler mechanically than DAT, but did not make perfect digital copies as it used a lossy compression technique called PASC. (Lossy compression was necessary to reduce the data rate to a level that the DCC head could record successfully at the linear tape speed of 4.75 cm/s that the compact cassette system uses.) DCC was never a competitor to DAT in recording studios because DAT was already established, and studios favor lossless formats. As DCC was launched at the same time as Sony's Minidisc format (which has random access and editing features), it was not successful with consumers either. However, DCC proved that high-quality digital recording could be achieved with a cheap, simple mechanism using stationary heads.

Anti-DAT lobbying

Aiwa HD-S1 portable DAT recorder from 1990 with DAT tape for size comparison. It is 146 mm high and 95 mm wide; the thickness is 38 mm.

In the late 1980s, the Recording Industry Association of America (RIAA) unsuccessfully lobbied against the introduction of DAT devices into the U.S. Initially, the organization threatened legal action against any manufacturer attempting to sell DAT machines in the country. It later sought to impose restrictions on DAT recorders to prevent them from being used to copy LPs, CDs, and prerecorded cassettes. One of these efforts, the Digital Audio Recorder Copycode Act of 1987 (introduced by Sen. Al Gore and Rep. Waxman), initiated by CBS Records president Walter Yetnikoff, involved a technology called CopyCode and required DAT machines to include a chip to detect attempts to copy material recorded with a notch filter, meaning that copyrighted prerecorded music, whether analog or digital, whether on LP, cassette, or DAT, would have distorted sound resulting from the notch filter applied by the publisher at the time of mastering for mass reproduction. A National Bureau of Standards study showed that not only were the effects plainly audible, but that it was not even effective at preventing copying. This opposition by CBS softened after Sony, a DAT manufacturer, bought CBS Records in January 1988. By June 1989, an agreement was reached, and the only concession the RIAA would receive was a more practical recommendation from manufacturers to Congress that legislation be enacted to require that recorders have a Serial Copy Management System to prevent digital copying for more than a single generation. This requirement was enacted as part of the Audio Home Recording Act of 1992, which also imposed taxes on DAT recorders and blank media. However, the computer industry successfully lobbied to have personal computers exempted from that act, setting the stage for massive consumer copying of copyrighted material on materials like recordable CDs and by extension, filesharing systems such as Napster.

Uses

Pre-recorded albums

DAT recorder (Kenwood DX-7030)

DAT was also used in professional environ­ments like recording studios and broadcasting institutions. The depicted device is a professional Sony PCM-7030 DAT recorder, which had a recommended retail price of 8000 US dollars.

In December 1987, The Guitar And Other Machines by the British post-punk band The Durutti Column, became the first commercial release on DAT. Later in May 1988, Wire released their album The Ideal Copy on the format. Several other albums from multiple record labels were also released as pre-recorded DATs in the first few years of the format's existence, in small quantities as well. Factory Records released a small number of albums on the format, including New Order's best-selling compilation Substance 1987, but many planned releases were cancelled.

Amateur and home use

Sony DAT Walkman TCD-D7

DAT was envisaged by proponents as the successor format to analogue audio cassettes in the way that the compact disc was the successor to vinyl-based recordings. It sold well in Japan, where high-end consumer audio stores stocked DAT recorders and tapes into the 2010s, and second-hand stores generally continued to offer a wide selection of mint condition machines. However, there and in other nations, the technology was never as commercially popular as CD or cassette. DAT recorders proved to be comparatively expensive, and few commercial recordings were available. Globally, DAT remained popular, for a time, for making and trading recordings of live music (see bootleg recording), since available DAT recorders predated affordable CD recorders. In the 1990s, fans of jam bands, such as the Grateful Dead and Phish, recorded and stored high-quality audience recordings of live concerts on the format.

Computer data storage medium

Main article: Digital Data Storage

The format was designed for audio use, but through the ISO Digital Data Storage standard was adopted for general data storage, storing from 1.3 to 80 GB on a 60- to 180-meter tape depending on the standard and compression. It is a sequential-access medium and was commonly used for backups. Due to the higher requirements for capacity and integrity in data backups, a computer-grade DAT was introduced, called DDS (Digital Data Storage). Although functionally similar to audio DATs, only a few DDS and DAT drives (in particular, those manufactured by Archive for SGI workstations) are capable of reading the audio data from a DAT cassette. SGI DDS4 drives no longer have audio support; SGI removed the feature due to "lack of demand".

Digital video

Eight years before the introduction of the miniDV digital video format, Samsung had announced plans in early 1987 to release camcorders recording video onto DAT tape. The format would have been named "4 Vision", the first camcorder SVC41, with plans for an entire product line. Instead, no video products using DAT were ever produced serially.

See also

• ADAT
• Digital Audio Stationary Head
• Digital Data Storage
• Digital Tape Recording System
• Digital Compact Cassette
• Magnetic storage
• Magnetic tape
• MiniDisc
• NT (cassette)
• PCM adaptor
• ProDigi