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TECHNICAL INFORMATION
3.2 DIGITAL CONNECTIONS AND SYNCRONIZATION
3.2.1 ADAT Optical Lightpipe
ADAT is an industry standard abbreviation for the ADAT Lightpipe protocol, which transfers eight tracks in
a single fiber optic cable. Supported sample rates are 44.1 kHz and 48 kHz.
When you are utilizing the eight DigiMax 96K preamplifiers and converting to the digital optical output,
connect one ADAT optical cable from the ADAT output on the back of the DigiMax 96K to the ADAT optical
input on your digital audio interface, workstation or digital mixer.
To synchronize your system to the DigiMax 96K's internal clock, set your other device to receive external
word clock via its ADAT optical input. You may need to consult your device's user manual for instructions on
how to do so.
3.2.2 BNC Sync and Word Clock
When using multiple devices connected through digital audio formats like S/PDIF, AES/EBU, ADAT or
TDIF, it is necessary to synchronize them to a single word clock generator. Word clock is used to keep a
perfectly timed and constant bit rate between all synced devices to avoid data errors. A word clock generator
creates digital pulses that contain no other data (i.e. audio). These pulses clock the internal oscillators of
each device and are essential to avoid frequency drift.
A word clock signal is bundled with the audio data in the ADAT Lightpipe protocol; however, many engineers
prefer to keep word clock sync and audio separate from each other.
This is where BNC word clock
connections come into play and the DigiMax 96K has a BNC word clock input for just this purpose. You will
find BNC cables used to deliver dedicated word clock in many quality studios and broadcast facilities
worldwide. BNC cables are rugged, lock into position, and can carry clock signals much farther than the
standard optical cable. A BNC word clock cable is a 75 Ω, shielded coaxial cable with standard 'twist-lock'
Please note: BNC cables are made in several impedances. The DigiMax
BNC-type connections on each end.
96K requires an impedance of 75
Ω
to achieve consistent sync.
To synchronize the DigiMax 96K via BNC word clock, you will need to run a BNC word clock cable from the
BNC word clock output of your external device to the BNC word clock input of your DigiMax 96K. From the
front panel of your DigiMax 96K, select external sync using the clock button.
3.2.3 Master/Slave and Multiple Digital Devices
Whether you are using the ADAT output of the DigiMax 96K to generate word clock or you are using the
BNC word clock output of another device as your word clock generator, it is necessary to denote one device
as the "master" word clock device to which all other digital devices are synced or "slaved". The DigiMax
96K should perform equally well as a master or a slave in most cases, although syncing it to a lesser quality
clock source may affect performance. Not all word clock generators are created equal. The general
approach is to determine which device has the best clock from which to reference and to designate that device
as the word clock master. This is done with careful listening and A/B testing.
Once you've determined which device is to be your Master clock, you will need to sync the remaining digital
devices either through series or parallel distribution or some combination thereof. Of course, if your digital
device chain only consists of one master and one slave, syncing the two is as simple as connecting a 75 Ω
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| PreSonus 2007
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