Digital Audio Stationary Head
Encyclopedia
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 in 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. The circuit, of course, had a sound of its own and was often not used.
There were three families of DASH recorders produced by Sony
and Studer
, with few differences among them:
With the exception of the Sony PCM-3348HR and Studer D827, all of the DASH recorders have 16-bit
resolution with a 44.1 kHz or 48 kHz sampling rate
, although it is possible to use an outboard analog-to-digital converter
of up to 20-bit resolution. The PCM-3348HR and D827 are capable of 20-bit 96 kHz operation, 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 than the S/PDIF
/ AES-EBU 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
.
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
. Given the correct bias, professional analog tape recorders could possibly benefit from the use of metal particle tape as consumer cassette decks had; but the headstacks
will wear at a significantly accelerated pace, outweighing any benefits. Due to this fact, open reel tape of this type was previously not widely available before or after these digital machines were in fashion. 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
's ProDigi
, which was available as 2-, 16-, and 32-track variations.
Digital audio
Digital audio is sound reproduction using pulse-code modulation and digital signals. Digital audio systems include analog-to-digital conversion , digital-to-analog conversion , digital storage, processing and transmission components...
tape format introduced by Sony
Sony
, commonly referred to as Sony, is a Japanese multinational conglomerate corporation headquartered in Minato, Tokyo, Japan and the world's fifth largest media conglomerate measured by revenues....
in early 1982 for high-quality multitrack
Multitrack recording
Multitrack recording is a method of sound recording that allows for the separate recording of multiple sound sources to create a cohesive whole...
studio recording and mastering, as an alternative to analog recording methods. DASH is capable of recording two channels of audio
Sound
Sound is a mechanical wave that is an oscillation of pressure transmitted through a solid, liquid, or gas, composed of frequencies within the range of hearing and of a level sufficiently strong to be heard, or the sensation stimulated in organs of hearing by such vibrations.-Propagation of...
on a quarter-inch tape, and 24 or 48 tracks on 1/2 in tape on open reels of up to 14 inches. The data is recorded on the tape linearly, with a stationary recording head
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...
, as opposed to the DAT
Digital Audio Tape
Digital Audio Tape is a signal recording and playback medium developed by Sony and introduced in 1987. 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...
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
Pulse-code modulation is a method used to digitally represent sampled analog signals. It is the standard form for digital audio in computers and various Blu-ray, Compact Disc and DVD formats, as well as other uses such as digital telephone systems...
and boasts strong cyclic redundancy check
Cyclic redundancy check
A cyclic redundancy check is an error-detecting code commonly used in digital networks and storage devices to detect accidental changes to raw data...
(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
Time code
A timecode is a sequence of numeric codes generated at regular intervals by a timing system.- Video and film timecode :...
.
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
Classical music
Classical music is the art music produced in, or rooted in, the traditions of Western liturgical and secular music, encompassing a broad period from roughly the 11th century to present times...
. 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. The circuit, of course, had a sound of its own and was often not used.
There were three families of DASH recorders produced by Sony
Sony
, commonly referred to as Sony, is a Japanese multinational conglomerate corporation headquartered in Minato, Tokyo, Japan and the world's fifth largest media conglomerate measured by revenues....
and Studer
Studer
Studer is a Swiss manufacturer of professional audio equipment, founded in Zurich in 1948 by Willi Studer. It is known primarily for the design and manufacture of analog tape recorders and mixing consoles. Studer also produce other technology solutions, such as telephony management systems and...
, with few differences among them:
- 2 track: PCM-3402, PCM-3202
- 24 track: PCM-3324, PCM-3324A, PCM-3324S
- 48 track: PCM-3348, PCM-3348HR, and the StuderStuderStuder is a Swiss manufacturer of professional audio equipment, founded in Zurich in 1948 by Willi Studer. It is known primarily for the design and manufacture of analog tape recorders and mixing consoles. Studer also produce other technology solutions, such as telephony management systems and...
D820 and D827
- TASCAMTASCAMTASCAM is the professional audio division of TEAC Corporation, headquartered in Montebello, California. Tascam is credited as the inventor of the Portastudio, the first cassette-based multi-track home studio recorders. Tascam also introduced the first low-cost mass produced multitrack recorders...
also produced a 24-track DASH recorder.
With the exception of the Sony PCM-3348HR and Studer D827, all of the DASH recorders have 16-bit
16-bit
-16-bit architecture:The HP BPC, introduced in 1975, was the world's first 16-bit microprocessor. Prominent 16-bit processors include the PDP-11, Intel 8086, Intel 80286 and the WDC 65C816. The Intel 8088 was program-compatible with the Intel 8086, and was 16-bit in that its registers were 16...
resolution with a 44.1 kHz or 48 kHz sampling rate
Sampling rate
The sampling rate, sample rate, or sampling frequency defines the number of samples per unit of time taken from a continuous signal to make a discrete signal. For time-domain signals, the unit for sampling rate is hertz , sometimes noted as Sa/s...
, although it is possible to use an outboard analog-to-digital converter
Analog-to-digital converter
An analog-to-digital converter is a device that converts a continuous quantity to a discrete time digital representation. An ADC may also provide an isolated measurement...
of up to 20-bit resolution. The PCM-3348HR and D827 are capable of 20-bit 96 kHz operation, 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 than the S/PDIF
S/PDIF
S/PDIF is a digital audio interconnect used in consumer audio equipment over relatively short distances. The signal is transmitted over either a coaxial cable with RCA connectors or a fiber optic cable with TOSLINK connectors. S/PDIF interconnects components in home theaters and other digital high...
/ AES-EBU 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
Solid State Logic is a manufacturer of high-end mixing consoles and recording studio hardware headquartered in Begbroke, Oxfordshire, UK.- Company information :...
.
Tape
One significant advantage offered by DASH recorders over the analogue recorders of the day was that 'proper' tape biasing was unimportant, as there is no means for the tape to 'colour' 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 analogue 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
Magnetic tape is a medium for magnetic recording, made of a thin magnetizable coating on a long, narrow strip of plastic. It was developed in Germany, based on magnetic wire recording. Devices that record and play back audio and video using magnetic tape are tape recorders and video tape recorders...
. Given the correct bias, professional analog tape recorders could possibly benefit from the use of metal particle tape as consumer cassette decks had; but the headstacks
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...
will wear at a significantly accelerated pace, outweighing any benefits. Due to this fact, open reel tape of this type was previously not widely available before or after these digital machines were in fashion. Some examples of metal particle tape compatible with DASH machines are 3M
3M
3M Company , formerly known as the Minnesota Mining and Manufacturing Company, is an American multinational conglomerate corporation based in Maplewood, Minnesota, United States....
Scotch 275, Ampex / Quantegy
Ampex
Ampex is an American electronics company founded in 1944 by Alexander M. Poniatoff. The name AMPEX is an acronym, created by its founder, which stands for Alexander M. Poniatoff Excellence...
467, EMTEC
EMTEC
EMTEC is part of the Dexxon Group headquartered in Gennevilliers, France and markets consumer computer data storage products and other computer related consumables. Dexxon Group's North American subsidiary, Dexxxon Digital Storage Inc. is located in Lewis Center, Ohio. EMTEC evolved from BASF...
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
Mitsubishi
The Mitsubishi Group , Mitsubishi Group of Companies, or Mitsubishi Companies is a Japanese multinational conglomerate company that consists of a range of autonomous businesses which share the Mitsubishi brand, trademark and legacy...
's ProDigi
ProDigi
Mitsubishi's ProDigi is a professional audio, reel-to-reel, digital audio tape format with a stationary head position, similar to Sony's Digital Audio Stationary Head, which competed against ProDigi when the format was available in the mid 1980s through the early 1990s...
, which was available as 2-, 16-, and 32-track variations.
See also
- ProDigiProDigiMitsubishi's ProDigi is a professional audio, reel-to-reel, digital audio tape format with a stationary head position, similar to Sony's Digital Audio Stationary Head, which competed against ProDigi when the format was available in the mid 1980s through the early 1990s...
- NagraNagraNagra is the trademark referring to any of the series of mostly battery-operated portable professional audio recorders produced by Kudelski SA, based in Cheseaux-sur-Lausanne, Switzerland....
- StuderStuderStuder is a Swiss manufacturer of professional audio equipment, founded in Zurich in 1948 by Willi Studer. It is known primarily for the design and manufacture of analog tape recorders and mixing consoles. Studer also produce other technology solutions, such as telephony management systems and...
- OtariOtariOtari may refer to:* Otari, Nagano, Japan*Muhammad Naji al-Otari, Prime Minister of Syria...
- SoundstreamSoundstream-The Company:Soundstream Inc. was founded in 1975 in Salt Lake City, Utah by Dr. Thomas G. Stockham, Jr. It was the world’s first audiophile digital audio recording company, providing commercial services for recording and computer-based editing...
- 3M3M3M Company , formerly known as the Minnesota Mining and Manufacturing Company, is an American multinational conglomerate corporation based in Maplewood, Minnesota, United States....
- AmpexAmpexAmpex is an American electronics company founded in 1944 by Alexander M. Poniatoff. The name AMPEX is an acronym, created by its founder, which stands for Alexander M. Poniatoff Excellence...