Digital Audio Tape
The Digital Audio Tape (DAT ) is a digital audio magnetic tape ( tape) for corresponding audio recorder. The recording format and the sound quality essentially correspond to those of the audio CD and declined significantly in some devices beyond. The first devices appeared in the late 1980s. The technology was intended to succeed the very widespread audio cassette, but could not prevail in the mass market. It has today only in professional niche applications, such as in recording studios, and as a backup medium for computer data meaning.
Technology
Storing the information carried on a magnetic tape. Quality and comfort are, however, increased significantly compared to analog cassette recorders because of digital recording. With a sampling rate of up to 96 kHz and a maximum resolution of 24 bits, the sound potential is higher than that of the audio CD, but this was not available in all devices. Was the most used, the equivalent to audio CD format with 44.1 kHz sampling rate and 16 bits.
The R - DAT recorder (R for rotary head, rotary head ) is used as the basic structure similar from VHS video process an azimuth recording method. Both heads have 20 ° angle. The band of the R-DAT is a data- dense metal powder tape. On it even subcodes are in addition to the audio signal is recorded, manufacturer-specific codes (eg recording date) or information about individual tracks (eg song title, artist) can contain. A track on a DAT tape can be found similarly as in the audio CD of the start markers also Fast- reliable. Furthermore possible to set jump and end markers to specific parts of a recording or just skip to " bring forward " the tape end.
The band is in its cassette (73 x 54 mm) well protected. As with the video recorder it is pulled from the mechanics of the cartridge case and - in the form of an "upside down " standing Omegas - transported around the heads. The wrap is in this case usually 90 °. Characterized the sound into finite segments which are significantly longer than the belt width, recorded and read. The actual tape transport speed of 8.15 mm per second ( in contrast to 4.75 cm / s in the Compact Cassette). By 2000 rpm with a rotary head drum (typically 30 mm diameter ), however, a relative tape speed of 313 cm / s is achieved.
Per minute, the recording requires about half a meter strip material. In standard tape speed of 15 to 180 minutes are possible depending on tape length seasons. The use of ribbons with more than 60 meters in length as well as the use of DDS tapes ( Digital Data Storage ) for audio purposes, the manufacturers recommend, even if it means having DDS5 bands up to 11.5 hours of continuous recording in Long Play mode are possible. Recordings with double sampling frequency ( 96 kHz ), however, halve the season. The tape is recorded only in one direction.
Playback and recording devices ( " DAT " ) were originally designed for three sampling rates of 32, 44.1 and 48 kHz, 44.1 kHz, but were able to ( artificially limited ) record only analog. After the end of 1989, the U.S. and European music companies and the Japanese electronics manufacturer it agreed to restrict the copy protection of DAT, the end of 1990 were the second-generation devices offered in Germany, a digital recording also allowed at a sampling rate of 44.1 kHz, a digital 1:1 copy of a CD to produce. However, such devices had to be equipped in Europe and the U.S. with the copy Serial Copy Management System ( SCMS ) and only allowed a one-time dubbing from CD to DAT. A copy of the DAT to another DAT was still excluded. Other sampling frequencies are 32 kHz depending on the equipment, which also long play recordings are possible (doubling of the season with a reduction in bit depth from 16 to 12 bit with non-equidistant quantization) and 96 kHz for high-quality home and studio equipment. However, long-play and "high resolution" images are not compatible with any device. The introduction and following several changes of copy protection were due to fears of the music industry that the market would collapse for CDs by the possibility of lossless digital copies.
The uncertainty of whether other, less copy -restricted DAT recorder would come on the market in the near future, leaving many potential buyers considering the initially high prices by purchasing wait. This, however, no large numbers were reached, by which the price would fall to. This is regarded as one of the reasons why DAT never got beyond a niche.
The end of 1990 there was with the DATman also a portable DAT recorder. He weighed 450 g and had a battery life of up to 2 hours. In 1991 he was for around 1,500 DM (about 767 euros ) offered in Germany.
In the study area there are also devices that work with a resolution of 24 bits. These usually have average ability, timecode and professional XLR connectors instead of the usual at home hi-fi RCA connections (also known as RCA), which makes them only partially integrate into plant off of a studio. There, too, AES / EBU digital connections are used. Many studio devices allow the setting and deleting the SCMS bits and a display of read errors. This will normally be in the range of 0-50 defects per second; according to a manual of Panasonic, values below 300 normally. At higher values, either the head is dirty, worn, or adjusts the tape guide. In the related DDS devices a head drum life of 100,000-200,000 hours is specified, therefore, the drum should last a whole lifetime devices.
History
The international conference DAT advised 1983 on a digital recording system with the claim of a long-term replacement of the Compact Cassette. In two competing laboratories the concepts of S -DAT (stationary multi-track tape head ) and R -DAT (rotating head, as the video recorder ) have been developed. 1985 recommended the DAT Conference R -DAT, despite its complicated mechanism than the immediately realizable system. Although S -DAT represented an interesting alternative, however, the production of multi-track tape heads was not yet technologically manageable. After all, so did the customer a system war of formats spared. Only in 1993, developed by Philips S- DAT system DCC (Digital Compact Cassette) reached market maturity.
For a time, was offered a small selection of pre-recorded DAT cartridges at retail. However, by the time-consuming duplication as well as by the integrated copy prerecorded DAT tapes did not reach market significance. The format was opposed by the International Federation of the Phonographic Industry for fear of piracy. They threatened the potential DAT importers in the United States with millions of lawsuits. Therefore, the DAT Conference wrote to the use of a double copy protection ( blocking copy bit while trying digital dubbing and complete record lock on the CD sampling rate of 44.1 kHz) before, although the recognized previously as a reason for a possible setback for the format introduction had been. Ready for series production as early as 1986, the DAT machines were under pressure from the music industry for the time being in the drawer. In Germany you could only purchase the first devices in the commercial end of 1987 - limited to the possibility of a digital recording from a CD. The agreement on the SCMS copy protection system in 1989, which allowed the unique digital copy, marked a turning point and made DAT finally functional, yet the devices cost in the summer of 1989 to around 3,500 DM and DM 50 DAT cassette from 1990, brought more and more Manufacturer DAT recorder on the market. Shortly thereafter, in 1992, the 1000 - DM- limit for DAT machines in Germany was reached. Enforced itself had the format in the professional field, where it was used by eg broadcasters and the recording industry for program exchange and archiving.
Competition received DAT in 1991 by the Japanese MD ( MiniDisc ) and soon after by the DCC format, the Digital Compact Cassette. This led to uncertainty among potential buyers. The introduction of the CD recorder for home users in 1995, the standard features of personal computers with CD burners, as well as the relative still high purchase price of DAT recorders heralded the end of DAT in the consumer sector. In a studio or in the professional field to DAT, however, was able to establish good, it still offers the advantages of a long time ( up to three hours), an uncompressed, lossless, high-quality recording and not least the possibility to build compact, mobile- DAT recorder. Thanks to its reliability DAT was used by HP as a base for the DDS format for data backup.
DDS was then quickly established itself as a PC backup system with a storage capacity of more than 24 GB per tape, and it came Streamerbandlaufwerke on the market that also read audio DAT tapes, play, and could describe. Today, new drives, apart from the activities of a producer, no longer developed or produced.