DAT, Digital Audio Tape

Click for a larger picture

The DAT (Digital Audio Tape) cassette was released by Sony in 1987. The DAT was intended as a replacement for the Compact Cassette. It never gained that position. One of the reasons why DAT failed, was that the mass production of pre-recorded tapes never really worked out.

The DAT cassette mechanics are very similar to video cassettes. The tape is recorded into one direction. The tape speed is very slow, 8,15 mm/s. The tape width is 4 mm. The recording takes place in a similar way as on a VHS tape. The record heads are placed on a head drum, that rotates very fast. The heads sweep a helical scan onto the tape, and that's what made it possible to save a large amount of data onto the tape. The format is actually called R-DAT, which stands for Rotary Head Digital Audio Tape.

DAT tape durations vary between 15 and 180 minutes. The cassette size is
73 mm × 54 mm × 10.5 mm. When the cassette is not inside the recorder, a lid is covering the tape from touching and dust. The sample rates were 48, 44.1 ja 32 kHz. The bit depth was 16 bit. The half speed mode used the 32 kHz sample rate. At half speed the tape was moving only 4.075 mm/s. In Walkman-type half-speed recorders the head drum diameter was also halved.

Being linear PCM, the sound quality of the digital DAT-tape is very good. When old DAT tapes are now copied, there are often problems with the tracking. The tracking of the replay player doesn't necessarily match with the recording on the tape. Short bits of the recording are sometimes missing.
To some extent the error correction and the interpolation are able to reconstruct the signal, but when the missing sequence gets longer, there are clicks or totally muted sections in the output. Copying such DAT tapes requires a lot of patience and sometimes a lot of time.

Sony discontinued DAT recorders in 2005.