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{{dablink|Digital audio tape can also refer to a [[compact cassette]] with digital storage.}}
{{Infobox Storage medium
|name     = Digital Audio Tape
|logo     = 
|image    = [[Image:Dat cartridge.jpg|250px]]
|caption  = A 90-minute DAT cartridge, size compared to a AAA (LR03) [[Battery (electricity)|battery]].
|type     = [[Magnetic tape]]
|encoding = 
|capacity = 120 minutes
|read     = Rotating head
|write    = Rotating head, helical scan
|standard = 
|owner    = [[Sony]]
|use      = Audio storage
|extended from = 
|extended to   = 
}}

'''Digital Audio Tape''' (DAT or R-DAT) is a signal recording and playback medium developed by [[Sony]] in the mid 1980s. In appearance it is similar to a [[compact audio cassette]], using 4 mm [[magnetic tape]] enclosed in a protective shell, but is roughly half the size at 73 mm × 54 mm × 10.5 mm. As the name suggests, the recording is [[digital]] rather than [[analog (signal)|analog]]. DAT has the ability to record at higher, equal or lower sampling rates than a [[Compact disc|CD]] (48, 44.1 or 32 [[kHz]] [[sampling rate]] respectively) at 16 [[bit]]s [[Quantization (sound processing)|quantization]]. If a digital source is copied then the DAT will produce an exact clone, unlike other digital media such as [[Digital Compact Cassette]] or non-[[MiniDisc#Hi-MD|Hi-MD]] MiniDisc, both of which use [[Audio data compression|lossy data compression]].

Like most formats of [[videocassette]], a DAT cassette may only be recorded on one side, unlike an analog [[compact audio cassette]].

== History ==
=== Development ===
The technology of DAT is closely based on that of [[video recorder]]s, using a rotating head and [[helical scan]] to record data. This prevents DATs from being physically [[editing|edited]] in the cut-and-[[splice]] manner of analog tapes, or open-reel digital tapes like [[ProDigi]] or [[Digital Audio Stationary Head|DASH]].

The DAT standard allows for four sampling modes: 32 kHz at 12 bits, and 32 kHz, 44.1 kHz or 48 kHz at 16 bits. Certain recorders operate outside the specification, allowing recording at 96 kHz and 24 bits (HHS). Some machines aimed at the domestic market did not operate at 44.1 kHz when recording from analog sources. Since each recording standard uses the same tape, the quality of the sampling has a direct relation to the duration of the recording—32 kHz at 12 bits will allow six hours of recording onto a three-hour tape while HHS will only give 90 minutes from a three-hour tape. Included in the signal data are subcodes to indicate the start and end of tracks or to skip a section entirely; this allows for indexing and fast seeking. Two-channel [[stereophonic sound|stereo]] recording is supported under all [[sampling rate]]s and bit depths, but the R-DAT standard does support 4-channel recording at 32 kHz.

DAT "tapes" are between 15 and 180 minutes in length, a 120-minute tape being 60 meters in length. DAT "tapes" longer than 60 meters tend to be problematic in DAT recorders due to the thinner media.

=== Predecessor formats ===
DAT was not the first digital audio tape; [[pulse-code modulation]] (PCM) was used in [[Japan]] to produce analogue [[phonograph record]]s in the early 1970s, using a videotape recorder for its [[transport (recording)|transport]], but this was not developed into a [[consumer product]].

Later in 1976, the first commercially successful digital audio tape format was developed by [[Soundstream]], using 1" (2.54 cm) 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. Several major [[record label]]s like [[RCA]] and [[Telarc]] used Soundstream's system to record some of the first commercially-released digital audio recordings.

Soon after Soundstream, [[3M]] starting in 1978 introduced their own line (and format) of digital audio tape recorders for use in a [[recording studio]], with one of the first prototypes being installed in the studios of [[Sound 80]] in [[Minneapolis, Minnesota]].

Professional systems using a [[PCM adaptor]], 98'7789 /'which digitized an analog audio signal and then encoded this resulting digital stream into an analog video signal so that a conventional VCR could be used as a storage medium, were also common as mastering formats starting in the late 1970s. 

[[dbx, Inc.]]'s [[Dbx Model 700 Digital Audio Processor|Model 700]] system, notable for using high sample-rate delta-sigma modulation (similar to modern [[Super Audio CD]]s) rather than PCM, and Decca's [[PCM]] system in the 1970s<ref>{{cite web|url=http://www.mancini99.freeserve.co.uk/Decca_1.html|title=The Decca Digital Audio Recording System|author=G.Mancini|month=March|year=2004|accessdate=March 25, 2007}}</ref> (using a videotape recorder manufactured by [[IVC (videotape recorder)|IVC]] for a transport), are two more examples.

[[Mitsubishi]]'s X-80 digital recorder was another 6.4 mm (¼") [[open reel]] digital [[mastering]] format that used a very unusual sampling rate of 50.4 kHz.

For high-quality studio recording, effectively all of these formats were made obsolete in the early 1980s by two competing [[reel-to-reel]] formats with stationary heads: [[Sony]]'s [[Digital Audio Stationary Head|DASH]] format and [[Mitsubishi]]'s continuation of the X-80 recorder, which was improved upon to become the [[ProDigi]] format. (In fact, the first ProDigi-format recorder, the Mitsubishi X-86, was playback-compatible with tapes recorded on an X-80.) Both of these formats remained popular as an analog alternative until the early 1990s, when hard disk recorders rendered them obsolete.

=== R-DAT and S-DAT ===
For a while, the DAT format was produced in two physically incompatible formats: one with helical scanning heads, called R-DAT, and one with a stationary head block, called S-DAT. S-DAT failed to gain market share <ref>[http://aroundcny.com/Technofile/texts/newtapeformats91.html As new digital audio tape formats shape up, the analog cassette keeps its lead], The Syracuse Newspapers, 1991. Retrieved January 26, 2009.</ref> as it required more expensive technlogy in the machine, compared to the relatively simple (and much cheaper) spinning head approach of R-DAT. 

Philips later recycled the basic mechanical design of S-DAT into [[Digital Compact Cassette|DCC]]. {{Fact|date=November 2008}}

== Anti-DAT lobbying ==
In the late 1980s, the [[Recording Industry Association of America]] unsuccessfully lobbied against the introduction of DAT devices into the United States. 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 [[LP]]s, [[CD]]s, and prerecorded cassettes. One of these efforts, the [[Digital Audio Recorder Copycode Act of 1987]] (introduced by [[Al Gore|Sen. Al Gore]] and [[Henry Waxman|Rep. Waxman]]), instigated 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, would have distorted sound. A [[National Institute of Standards and Technology|National Bureau of Standards]] study showed that not only were the effects plainly audible, but that it wasn't even effective at preventing copying. Thus the audible pollution of prerecorded music was averted.

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.<ref><!--this reference applies to the entire paragraph up to this point-->{{cite journal|last=Goldberg|first=Michael|date=September 21, 1989|title=Labels Back Down on DAT|journal=Rolling Stone|issue=561|pages=26}}</ref> This requirement was enacted as part of the [[Audio Home Recording Act]] of 1992, which also imposed "royalty" taxes on DAT recorders and blank media.
{{Mergesection|Audio Home Recording Act|History and Legislative Background|date=October 2007}}

== Uses of DAT ==
=== Professional recording industry ===
DAT was widely used in the professional audio recording industry in the 1990s, and is still used to some extent today, as the archives created in the 1990s are still widely used, although most labels have a program in place to transfer these tapes to a computer-based database. DAT was used professionally due to its lossless encoding, which allowed a master tape to be created that was more secure and did not induce yet more tape noise (hiss) onto the recording. In the correct setup, a DAT recording could be created without even having to be decoded to analogue until the final output stage, since digital multi-track recorders and digital mixing consoles could be used to create a fully digital chain. In this configuration, it is possible for the audio to remain digital from the first AD converter after the mic preamp until it is in a [[CD]] player. 

DAT's were also frequently used by radio broadcasters. Until recently, they were still used by the [[BBC]] as an emergency broadcast that would initiate if the player detected a lack of noise continued for more than a pre-determined time. This would mean that if for any reason the broadcast from the studio stopped, the DAT would continue broadcast until normal service could be resumed.{{Fact|date=October 2008}}
{{Expand-section|date=June 2008}}

=== Amateur and home use ===
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; however, the technology was never as commercially popular as [[CD]]. DAT recorders remained relatively expensive, and commercial recordings were generally not made available on the format. However, DAT was, for a time, popular for making and trading recordings of live music, since available DAT recorders predated affordable CD recorders.

In the United States, the RIAA and music publishers continued to lobby against DAT, arguing that consumers' ability to make perfect digital copies of music would destroy the market for commercial audio recordings. The opposition to DAT culminated in the passage of the resulting Audio Home Recording Act of 1992, which, among other things, effectively imposed a tax on DAT devices and blank media.

=== Computer data storage medium ===
The format was designed for audio use, but through the ISO [[Digital Data Storage]] standard it has been 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 sequential-access media and is commonly used for [[backup]]s. 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<ref>{{cite web|url=http://ask.slashdot.org/article.pl?sid=99/09/29/0451243|title=Can you Rip DAT audio? (Ask Slashdot forum thread)|publisher=Slashdot|accessdate=January 26, 2009|date=October 1, 1999}}</ref>) 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"<ref>{{cite web|url=http://homepage.ntlworld.com/adrian.rixon/personal/ade/dat-dds/drives.html|title=DAT/DDS hardware|date=March 26, 2003|accessdate=October 25, 2007}}</ref>.

== Future ==

In November 2005, [[Sony]] announced that the final DAT machines would be discontinued the following month.<ref>[http://www.animenewsservice.com/archives/nov30.htm Anime News Service], Anime News Service. Retrieved January 26, 2009.</ref> However, the DAT format still finds regular use in [[film]] and [[television]] recording, principally due to the support in some recorders for [[SMPTE time code]] synchronization, although it is slowly being superseded by modern [[hard disk]] recording equipment which offers much more flexibility and storage. In 2004, Sony introduced the [[Hi-MD]] Walkman with the ability to record in linear PCM. Hi-MD has found some favour as a disc-based DAT alternative for field recordings and general portable playback.

==See also==

*[[ADAT]]
*[[Magnetic tape]]
*[[PCM adaptor]]
*[[Digital Audio Stationary Head]]
*[[ProDigi]]

== Notes ==
<references/>

==References==


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{{Audio format}}

[[Category:Physical sciences]]
[[Category:Electrical engineering]]
[[Category:Electronics]]

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