The Digital Audio Stationary Head or ''DASH'' standard is a

reel-to-reel Reel-to-reel audio tape recording, also called open-reel recording, is magnetic tape audio recording in which the recording tape is spooled between reels. To prepare for use, the ''supply reel'' (or ''feed reel'') containing the tape is pla ...

digital audio Digital audio is a representation of sound recorded in, or converted into, digital form. In digital audio, the sound wave of the audio signal is typically encoded as numerical samples in a continuous sequence. For example, in CD audio, samp ...

tape format introduced by

Sony , commonly stylized as SONY, is a Japanese multinational conglomerate corporation headquartered in Minato, Tokyo, Japan. As a major technology company, it operates as one of the world's largest manufacturers of consumer and professional ...

in early 1982 for high-quality multitrack studio recording and mastering, as an alternative to

analog Analog or analogue may refer to: Computing and electronics * Analog signal, in which information is encoded in a continuous variable ** Analog device, an apparatus that operates on analog signals *** Analog electronics, circuits which use analog ...

recording methods. DASH is capable of recording two channels of

audio Audio most commonly refers to sound, as it is transmitted in signal form. It may also refer to: Sound *Audio signal, an electrical representation of sound *Audio frequency, a frequency in the audio spectrum * Digital audio, representation of sou ...

on a quarter-inch tape, and 24 or 48 tracks on tape on open reels of up to 14 inches. The data is recorded on the tape linearly, with a stationary

recording head A recording head is the physical interface between a recording apparatus and a moving recording medium. Recording heads are generally classified according to the physical principle that allows them to impress their data upon their medium. A reco ...

, 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 Pulse-code modulation (PCM) is a method used to digitally represent sampled analog signals. It is the standard form of digital audio in computers, compact discs, digital telephony and other digital audio applications. In a PCM stream, the am ...

and boasts strong

cyclic redundancy check A cyclic redundancy check (CRC) is an error-detecting code commonly used in digital networks and storage devices to detect accidental changes to digital data. Blocks of data entering these systems get a short ''check value'' attached, based on ...

(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. Digital audio recorders are fundamentally high bit-rate data recorders storing PCM encoded audio data. The main advantage of any digital recording medium is that of consistent, flat frequency response, high dynamic range audio reproduction compared to analog tape recorders, which is why some of the first uses of digital audio recording were for

classical music Classical music generally refers to the art music of the Western world, considered to be distinct from Western folk music or popular music traditions. It is sometimes distinguished as Western classical music, as the term "classical music" al ...

. To further increase usable dynamic range, early 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 complimentary de-emphasis on playback after the DAC 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. There were three families of DASH recorders produced by

and

Studer Studer is a designer and manufacturer of professional audio equipment for recording studios and broadcasters. The company was founded in Zürich, Switzerland, in 1948 by Willi Studer. It initially became known in the 1950s for its professiona ...

, with few differences among them: *2 track: PCM-3402, PCM-3202,

D820x *24 track: PCM-3324, PCM-3324A, PCM-3324S *48 track: PCM-3348, PCM-3348HR, and the

D820 and D827 * TASCAM also produced a 24-track DASH recorder, the DA-800/24. With the exception of the Sony PCM-3348HR and Studer D827, all of the DASH recorders have

16-bit 16-bit microcomputers are microcomputers that use 16-bit microprocessors. A 16-bit register can store 216 different values. The range of integer values that can be stored in 16 bits depends on the integer representation used. With the two ...

resolution with a 44.1 kHz or 48 kHz

sampling rate In signal processing, sampling is the reduction of a continuous-time signal In mathematical dynamics, discrete time and continuous time are two alternative frameworks within which variables that evolve over time are modeled. Discrete time ...

, although it is possible to use an outboard

analog-to-digital converter In electronics, an analog-to-digital converter (ADC, A/D, or A-to-D) is a system that converts an analog signal, such as a sound picked up by a microphone or light entering a digital camera, into a digital signal. An ADC may also provide ...

of up to 20-bit resolution. The PCM-3348HR and D827 are capable of 24-bit 48 kHz operation at 45 ips, and are the only machines that still find significant use today, often in only the highest-end studios for music and film production. All DASH recorders primarily use the SDIF-2 (Sony Digital Interface Format-2) as a digital interface, which is slightly different from the

S/PDIF S/PDIF (Sony/Philips Digital Interface) is a type of digital audio interface used in consumer audio equipment to output audio over relatively short distances. The signal is transmitted over either a coaxial cable (using RCA or BNC connectors ...

AES3 AES3 is a standard for the exchange of digital audio signals between professional audio devices. An AES3 signal can carry two channels of pulse-code-modulated digital audio over several transmission media including balanced lines, unbalanced ...

that nearly all other digital audio recorders use, but is technically superior because SDIF-2's word clock is not multiplexed into the bitstream. Because SDIF-2 is often only found on the expensive DASH recorders, it is also often only found on the highest-end mixing consoles, such as those made by

Solid State Logic Solid State Logic (SSL) is a British company based in Begbroke, Oxfordshire, England that designs and markets audio mixing consoles, signal processors, and other audio technologies for the post-production, video production, broadcast, sound re ...

Tape

One significant advantage offered by DASH recorders over the analog recorders of the day was that 'proper' tape biasing was unimportant, as there is no means for the tape to 'color' the sound of the recorded data. This was a nice advantage, and routine maintenance amounted to not much more than keeping the tape guides clean. Due to this fact, the formulation of tape does not change the sound quality, unlike analog machines which must be set for specific formulae. The 2-track DASH machines use 1/4" wide tape, while the 24 and 48 track versions use 1/2" wide tape. One interesting thing of note is that the 24-track machines only utilize half of the tape's width, and can be played on the 48-track machines with no modifications. Similarly, the 48-track tapes can be played on a 24-track machine, but only the first 24 tracks are capable of being reproduced. DASH recorders (as well as any other type of digital recorder using magnetic tape) require the use of metal-particle formulation

magnetic tape Magnetic tape is a medium for magnetic storage made of a thin, magnetizable coating on a long, narrow strip of plastic film. It was developed in Germany in 1928, based on the earlier magnetic wire recording from Denmark. Devices that use magnet ...

. Some examples of metal particle tape compatible with DASH machines are 3M Scotch 275, Ampex / Quantegy 467, EMTEC 931, and Sony's own tape formulation. These tape formulations are not directly compatible with any analog open-reel tape recorder. The DASH format is not compatible with the only other popular open reel stationary head digital recording format,

Mitsubishi The is a group of autonomous Japanese multinational companies in a variety of industries. Founded by Yatarō Iwasaki in 1870, the Mitsubishi Group historically descended from the Mitsubishi zaibatsu, a unified company which existed from 1870 ...

's ProDigi, which was available as 2-, 16-, and 32-track variations.

Tape

See also

Further reading