Using The Ad-1000 With Adat Systems - Apogee AD-1000 Operating Manual

AD-1000 Operating Manual
General notes on ADAT Recording
The AD-1000 has the ability to output the ADAT digital format (on Toslink Optical) allowing you to bypass the
A/D converters in the ADAT recorder and get the legendary Apogee sound on ADAT. The following pages con-
tain information on how to accomplish this in a number of different ways. There are, however, some basic con-
cepts that need to be understood first.
The most common questions revolve around the fact that the AD-1000 is a two channel device and the ADAT
is an eight track recorder. You will notice that the AD-1000 has only one optical output (and one optical input)
and the ADAT has the same number and type of optical connectors. When in ADAT mode (power switch to
"ADAT"), the ADAT transmitter in the AD-1000 transmits eight channels of information which is just the origi-
nal two channels (left and right) duplicated four times. If you were to put all eight tracks of an ADAT into
"input," you will see four pairs of information with the left channel of the AD-1000 going to tracks 1, 3, 5 and
7 of the ADAT and the right channel of the AD-1000 going to tracks 2, 4, 6 and 8 of the ADAT. Thus, you can
record onto tracks 3 and 8, or 5 and 6, or 1 and 4, or 7 and 8, and so on. This of course, begs the question of
"How do you record four different channels worth of music simultaneously on to four tracks of the ADAT"
(assuming that you have two AD-1000s)? Unfortunately, you can't. At least not on one ADAT. Remember, the
AD-1000 is only a two channel device and there is only one connector, so there is no way to get those other
channels into the ADAT. You can connect as many AD-1000s as you wish to that many ADATs (see diagram on
"Using Multiple AD-1000s") and record lots of tracks simultaneously, but only two channels per ADAT.
Obviously, you can go back and overdub on the remaining tracks.
This brings up the question of using multiple ADATs controlled by a BRC (Big Remote Controller). Recording on
to a single ADAT (with no BRC) is easy (see note on "Recording Without a BRC"– later in this section). Any time
a BRC enters the picture, even with a single ADAT, sync must be provided to (or from) the BRC. For digital
equipment to communicate properly, all the gear must be running synchronously, that is they must all have their
clocks lined up so that they do exactly the same things at exactly the same time. The BRC provides sync infor-
mation to the ADAT; therefore if the AD-1000 is providing a signal to the ADAT, the BRC must have the same
timing (clocking) information as the AD-1000. Imagine having two different drummers in two different rooms
playing the same song. They are both providing a beat (clock) to the song, but in order for the song to work
they have to play together, therefore it is necessary to provide both of them with the same information (sync)
and they need to be able to hear each other. Digital audio gear must all be "playing together" to work prop-
erly. A separate timing signal (usually Word Clock or video sync) is used to accomplish this. Usually one piece
of gear is designated the Master and everything else "slaves" to this master clock. The AD-1000 is remarkable
in that it can either be a "master" or a "slave" depending on the requirements. Please see notes on "Recording
With a BRC."
The last (hopefully) question that needs to be addressed is "How does the AD-1000 receive ADAT?" That's easy
– it doesn't. Remember that ADAT is an eight channel format and the AD-1000 is a two channel device. The
basic AD-1000 cannot decode this information and make anything sensible of it, nor does it have a way to "pass
it through" so the AD-1000 cannot be hooked up in the ADAT optical loop. (The special version AD1K-ADT can
decode this information and convert it to AES/EBU format two channels at a time. See later in this section.) It
is recommended that the AD-1000 be connected (via optical) only to the particular ADAT being recorded onto.
The optical input on a standard AD-1000 is not an ADAT input.
The AD-1000 will output AES "black" (Audio Black – clock signal with no data) from the AES output when in
ADAT mode. The ADAT format is a 16-bit format. That is, it records with 16-bit resolution per track. The AD-
1000 is a 20-bit converter and can output 20-bit data even in ADAT mode. The AD-1000 gives you three choic-
es for output resolution – 16, UV16, and 20 (16-bit triangular dithered output, 16-bit UV22 processed output,
and unprocessed 20-bit output, respectively). With a 20-bit output, the ADAT will truncate (cut off) the "extra"
4 bits, which obviously is not the way to go, so you are left with a choice of "UV or not UV?" We generally rec-
ommend that the UV process not be used twice on a signal that remains in the digital domain (does not become
analog again) and we recommend against doing any digital signal processing after the signal has been UV
encoded (please see UV22 Caveats page 49).
Page 36