Sony DASH Digital Audio Recording Format
Sony introduced the Digital Audio Stationary Head (DASH) standard in early 1982 as an alternative to analog recording methods for high-quality multitrack studio recording and mastering. DASH is a reel-to-reel, digital audio tape format capable of recording two channels of audio on a quarter-inch tape and 24 or 48 tracks on 1/2-inch-wide tape on open reels of up to 14 inches. (The Sony PCM-3348HR being one example)
Unlike the helical recording method used in the DAT format, DASH records data linearly with a stationary recording head. The audio data is encoded as linear PCM and has strong cyclic redundancy check error correction, allowing the tape to be physically edited with a razor blade and played back with no loss of signal.
Early DASH recorders included a circuit called “Emphasis” to overcome the noise of analog to digital and digital to analog converters, which boosted high frequencies on the front end and required complimentary de-emphasis on playback. The three families of DASH recorders produced by Sony and Studer have few differences among them, with the exception of the Sony PCM-3348HR and Studer D827, which are capable of 24-bit 48 kHz operation and are still used in the highest-end studios for music and film production. All DASH recorders primarily use the SDIF-2 as a digital interface, which is technically superior to S/PDIF or AES3 because its word clock is not multiplexed into the bitstream.
Due to the cost of DASH recorders, SDIF-2 is often only found on the highest-end mixing consoles, such as those made by Solid State Logic. Digital audio recorders are high bit-rate data recorders storing PCM encoded audio data and provide consistent, flat frequency response and high dynamic range audio reproduction compared to analog tape recorders.
Compared to analog recorders of its time, DASH recorders offered a significant advantage in that proper tape biasing was not necessary, as the tape did not affect the sound of the recorded data. This made routine maintenance simple, as all that was required was keeping the tape guides clean. Unlike analog machines, the formulation of the tape did not impact the sound quality.
The 2-track DASH machines used 1/4″ wide tape, while the 24 and 48 track versions used 1/2″ wide tape. Interestingly, the 24-track machines only utilized half of the tape’s width and could be played on 48-track machines without modifications. Similarly, 48-track tapes could be played on a 24-track machine, but only the first 24 tracks could be reproduced.
DASH recorders, as well as any other type of digital recorder using magnetic tape, required the use of metal-particle formulation magnetic tape. Compatible tape examples with DASH machines included 3M Scotch 275, Ampex/Quantegy 467, EMTEC 931, and Sony’s tape formulation. These tape formulations were not directly compatible with any analog open-reel tape recorder.
It is worth noting that the DASH format was not compatible with the only other popular open reel stationary head digital recording format, Mitsubishi’s ProDigi, which was available in 2-, 16-, and 32-track variations.