Cassettes

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. DAT has the ability to record at higher, equal or lower sampling rates than a CD (48, 44.1 or 32 kHz sampling rate respectively) at 16 bits 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-Hi-MD MiniDisc, both of which use lossy data compression.

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 stereo recording is supported under all sampling rates and bit depths, but the R-DAT standard does support 4-channel recording at 32 kHz.

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.

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 '90s 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.