A Real-World Example; Sync Issues; Hard Disk Backup - Alesis ADAT-LX20 Reference Manual

A R
EAL
Suppose you did a great tape on your ADAT at home, and now want to edit it in a
hard disk recording setup at a commercial studio. You then want to transfer the
hard disk material over to a different digital tape format, which happens to be
the digital tape recorder used by a musical collaborator, who will then mix this
down using a digital mixer while adding more tracks. Furthermore, suppose the
studio saves all their hard disk sessions to magneto-optical drives, but you need a
safety copy on ADAT format tape.
Before the ADAT Optical Interface, this scenario would have been a nightmare.
Now it's relatively simple to do these sorts of tasks.
First, the hard disk editing system needs an ADAT-compatible interface. These are
available for both Windows and Mac computers from a variety of manufacturers.
This allows transferring 8 tracks at a time between the LX20 and hard disk editing
program. You can later use the same interface to bounce the edited tracks over to
ADAT for the remixing project, or as redundant storage should the main backup
system fail.
After editing the material on the hard disk system, a device such as the Spectral
Translator Plus can convert the audio to a variety of other formats. When it's time
to mix down those tracks, no problem. Yamaha, RSP Technologies, Korg,
RAMSA/Panasonic, and Mackie all make digital mixers with either optional or
built-in ADAT Optical Interfaces.
S I
YNC SSUES
Transferring more than 8 tracks at a time requires some special considerations.
Suppose you have two LX20s and need to transfer 16 tracks over to a PC hard disk
recording program, but your interface can handle only 8 channels at a time. You
would need to sync the ADATs to the hard disk recorder so that the second group of
8 tracks ended up in the proper timing relative to the first group of 8 tracks.
However, this transfer will not be sample-accurate unless the ADAT 9-pin sync
connection is used as well as the ADAT Optical Interface (the Alesis, E-mu Darwin,
Digidesign, Sonorus, and Korg 1212 interfaces can provide this signal).
Nonetheless, using SMPTE or MTC sync will still be at least as tight as slaving two
24 track analog machines together, and people didn't seem to mind that. The only
time you might hear a problem is if you transferred one half of a stereo pair on one
pass, and the other half on another pass.
Another option is to transfer all tracks in real time. Otari's UFC-24 universal
format translator can accommodate up to 3 ADAT optical connections. If the source
ADAT-compatible signals are synched properly (e.g., synchronized ADATs), then
transferring all 24 tracks simultaneously will occur with single-sample accuracy.
H D
ARD ISK
One of the biggest limitations of hard disk recording is how to back up the huge
amounts of data generated by multitrack digital audio. With an ADAT-PCR or
similar interface, you can save audio to inexpensive, rugged ADAT-format
cassettes. Not only is this far less costly than using removable hard drives, they
are easy to exchange with other ADAT owners, and can be cloned to make
additional safety copies.
ADAT LX20 Reference Manual
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ORLD XAMPLE
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Chapter 11 - Applications
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