Digital Audio Stationary Head
The Digital Audio Stationary Head or DASH standard is a reel-to-reel, digital audio tape format introduced by Sony in early 1982 for high-quality multitrack studio recording and mastering, as an alternative to analog recording methods. DASH is capable of recording two channels of audio on a quarter-inch tape, and 24 or 48 tracks on 1⁄2-inch-wide (13 mm) tape on open reels of up to 14 inches. The data is recorded on the tape linearly, with a stationary recording head, as opposed to the DAT format, where data is recorded helically with a rotating head, in the same manner as a VCR. The audio data is encoded as linear PCM and boasts strong cyclic redundancy check (CRC) error correction, allowing the tape to be physically edited with a razor blade as analog tape would, e.g. by cutting and splicing, and played back with no loss of signal. In a two-track DASH recorder, the digital data is recorded onto the tape across nine data tracks: eight for the digital audio data and one for the CRC data; there is also provision for two linear analog cue tracks and one additional linear analog track dedicated to recording time code.
The main advantage of any digital recording medium is that of consistent reproduction, which is why some of the first uses of digital recording were for instrumentation data and classical music. For audio, uncolored reproduction is not necessarily always desired, and the uneven reproduction equalization of analog recorders or the ability to record at levels above 0 dB (to produce desirable distortion) is often exploited advantageously, such as the "fat" sound of a kick drum on analog tape. DASH recorders included a specialized circuit called "Emphasis" which was intended to help overcome the noise of analog to digital and digital to analog converters of the time by boosting high frequencies on the front end. This circuit required de-emphasis on playback after the DAC as well for accurate reproduction. While emphasis was almost a necessity in earlier units, the circuit, of course, had a sound of its own and was used less and less as converter design improved.
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