Appsys ProAudio ADX-32A, User Manual

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ADX-32A / ADX-64A-PRO
9. Wordclock synchronization
9.1. General concept
For all devices within a digital audio system, it is required to share a common clock. This ensures
that data processing on all channels and on all devices is done at the same rate. Without a
common clock, the individual clocks would drift apart with time due to small skew between even
crystal clocks. This means that number of samples generated by one device would differ from
the number of samples expected by another, leading to drop-outs and crackles.
To prevent this, one device (usually the mix console) operates at the clock master. All other
devices operate in slave mode, using the clock signal generated by the master rather than their
own clock. Several ways exist to distribute the clock signal from the master to the slaves, as
described below.
NOTE: ADAT Multicore Extenders do not need a clock to operate. However, the embedded
clocks within ADAT signals are transmitted, and with the ADX-64A-PRO, a dedicated (separate)
clock can also be transmitted.
9.2. Wordclock synchronization over ADAT
Any ADAT signal can be used for wordclock synchronization as it carries an embedded clock
signal. The master clock device outputs ADAT streams with the master clock timing embedded,
and all slaves can extract the embedded wordclock from the stream. Please refer to your
equipment's manual to ensure the appropriate wordclock source setting of the device.
If ADAT synchronization is used, no additional wordclock cabling is required.
Use the "local loopback” feature (see 8.2. Transmission direction (ADAT 1-4) to break
out additional ADAT signal outputs which can be used as wordclock source. An ex-
ample configuration using ADAT sync is shown under
10.2. Digital 24/8 multicore
(Wordclock-Sync over ADAT) .
9.3. Wordclock synchronization over coaxial cable
For larger installations, it is often not convenient to use ADAT for wordclock synchronization. In
such cases, the wordclock can be transmitted over a dedicated (separate) wordclock connection,
usually a 75 ohms coaxial cable with BNC connectors, terminated with 75 ohms at both ends.
The master clock device generates the wordclock signal and is distributed by means of a daisy-
chained coaxial cable to all slave devices.
The ADX-64A-PRO supports the distribution of a dedicated wordclock signal over
Cat5 cables. This means that you do not need a separate coaxial cable along with
your Cat5 cabling. For details, see 8.4. Channel 5 mode selection (ADAT or Word-
clock) . An example configuration is shown under 10.3. Digital 40/16 multicore (Word -
clock-Sync over dedicated coaxial cable) .
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