Syncing Word Clock Devices; Syncing Large Systems - MOTU 828mkII User Manual

SYNCING WORD CLOCK DEVICES

The 828mkII word clock connectors allow you to
synchronize it with a wide variety of other word
clock-equipped devices.
For standard word clock sync, you need to choose
an audio clock master (as explained in "Be sure to
choose a digital audio clock master" on page 22).
In the simplest case, you have two devices and one
is the word clock master and the other is the slave
as shown below in Figure 3-18 and Figure 3-19.
Master
Word clock OUT
Word clock IN
Slave
Figure 3-18: Slaving another digital audio device to the 828mkII via
word clock. For the 828mkII clock source, choose any source besides
word clock, as it is not advisable to chain word clock.
MOTU Digital Timepiece universal synchronizer
Audio
clock
Master
Word clock OUT
Word clock IN
Slave
Figure 3-19: Slaving the 828mkII to word clock. For the 828mkII clock
source, choose 'Word Clock In' .
Don't chain word clock
If you have three or more digital audio devices that
you need to synchronize, avoid chaining their word
clock connections (OUT to IN, OUT to IN, etc.), as
this causes problems. Instead, use a dedicated
synchronizer like the Digital Timepiece or a word
clock distribution device of some kind.
Slaving to 2x and 1/2x word clock
All MOTU FireWire audio interfaces that support
96 kHz operation (including the 828mkII and 896)
have the ability to slave to a word clock signal
running at either twice or half their current clock
I N S T A L L I N G T H E 8 2 8 M K I I H A R D W A R E
rate. For example, the 828mkII could be running at
96 kHz while slaving to a 48 kHz word clock signal
from a MOTU Digital Timepiece. Similarly, the
828mkII could run at 88.2 kHz and slave to
44.1 kHz word clock. Conversely, the 828mkII
could run at 48 kHz and slave to a 96 kHz word
clock signal. In all of these cases, the front panel
clock LEDs flash both sample rates to indicate that
the 828mkII is slaving to word clock at either twice
or half its own clock rate. But if the 828mkII is
running at 96 kHz, it cannot slave to word clock
running at 44.1 kHz.
828mkII
Remember, the word clock signal must be one of
the following:
the same as the 828mkII clock
■
Other device
twice the 828mkII clock
■
half of the 828mkII clock
■

SYNCING LARGE SYSTEMS

If you are connecting the 828mkII to a lot of other
digital audio gear, get a Digital Timepiece. It can
synchronize a wide variety of devices, and it offers
sample accurate synchronization for devices that
support it, such as ADATs. You will also be able to
control everything from the transport controls of
828mkII
your audio software. If you have even more devices
than a single Digital Timepiece can support,
consider a word clock distribution device, such as
the Aardvark Aard Sync™ video-to-word clock
converter. Products like this offer multiple word
clock outputs and an extremely low-jitter clock.
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