Alesis Digital Audio Tape

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An ADAT XT 8-channel digital audio recorder

The Alesis Digital Audio Tape or ADAT (eng. Alesis digital audio tape ) was created in 1992 by Alesis Corp. introduced. ADAT is a trademark of Alesis Corp. On the one hand, it means the recording system that enables audio signals to be recorded digitally on S- VHS cassettes and, on the other hand, the audio interface for the transmission of audio signals using fiber optic cables (“ADAT Lightpipe”).


Recording system

In general, the ADAT tape (or the S-VHS tape) has eight tracks, which can be dubbed as often as required, and that with practically no loss of audio quality, at least until the tape through the mechanically problematic helical track -The recording process is so worn out that the implemented error correction is no longer sufficient to reconstruct the original.

In the 1990s, ADAT was very widespread in semi-professional applications and home recording studios, as this format made it possible for the first time to carry out digital multi-track recordings on a low budget - with more than eight tracks when several devices are linked. With three ADAT devices and two ADAT sync cables in between, you get up to 24 tracks and - in terms of the number of tracks - is already in the range of some professional studios. The system should make it possible to connect up to 16 ADAT recorders to a system with a total of 128 tracks, absolutely phase-synchronized .

In any case, the fundamental weak point is the principle-based use of a tape-based and thus linear system. The associated disadvantages are primarily mechanical wear and rewind times. In addition, helical-track tapes cannot of course be edited - cut - directly. For these reasons, the tape-based ADAT recorder systems have been almost completely replaced by non-linear computer-based hard disk recording systems that can simultaneously record and store a large number of tracks - at a significantly lower acquisition cost.

ADAT recorders, which are currently (2015) traded quite cheaply as used devices, can still serve musicians well today if one does not want to rely solely on the use of software . ADAT recorders can be used as a parallel instance to be protected against computer crashes. B. use it as a mixdown medium. The devices are digitally connected to the recording system and can be synchronized with the audio sequencer / virtual studio using SMPTE time code, as well as seamlessly integrated into the most modern studio setups, or also serve as D / A converters.

Even with 20-bit systems, the analog quality of the recording unit is still clearly superior to simple computer sound cards and USB recording systems, as high-quality analog input and output stages and professional connections are built in. Therefore, ADAT is definitely a high-quality and affordable alternative, with which the handling is very reminiscent of classic tape recorders and should be possible for anyone interested within a very short time. When buying second-hand, however, you should make sure that the tape heads do not have too many operating hours. The wear and tear is actually relatively high here (similar to VHS recorders).

Audio interface

Computer audio interface with ADAT IN (ol)

The ADAT interface for the transmission of digital audio signals via fiber optic cables, which was introduced at the same time, continues to enjoy great popularity and has become the standard for multi-channel, digital audio transmission in small and medium-sized recording studios. The original ADAT format has eight digital sound tracks and used S-VHS tapes. The sampling rate was 48 kHz, the sample depth 16 bits with linear quantization. The ADAT interface itself transmits audio data with a sample depth of 24 bits. The ADAT system uses optical transmission via TOSlink to transmit the eight data channels .

Audio data with sampling rates higher than 48 kHz can be transmitted with the S / MUX protocol (sample multiplexing): The S / MUX protocol fragments data streams with higher sampling rates and multiplexes them on several ADAT channels. An audio signal with a sampling rate of 96 kHz is split over two ADAT channels using S / MUX. This reduces the number of possible channels to 4 for sample rates of up to 96 kHz, or to 2 for 192 kHz. In the studio setups currently used (2014) with 192 kHz, this results in one stereo channel per fiber optic cable. To compensate for this, the fiber optic cables can be cascaded ("switched in parallel") in order to achieve the original number of channels again.

You can find ADAT interfaces across manufacturers on audio converters, digital mixers, effects devices and sound cards. In multifunctional recording cards for computers, the ADAT interface is often combined with the optical S / PDIF interface.

See also

Web links

Individual evidence

  1. Adat. 8 Track Professional Digital Audio Recorder. Operation manual. P. 10, 38. ( Memento from November 20, 2014 in the Internet Archive ) (PDF; 3.2 MB)
  2. The ADAT® Optical Interface. ( Memento from May 4, 2015 in the Internet Archive )
  3. ADAT (Alesis digital audio tape): ADAT interface. ( Memento from January 8, 2017 in the Internet Archive )