User Manual

HARDWARE INSTALLATION
41
Be sure to choose a digital audio clock master
When you transfer digital audio between two
devices, their audio clocks must be in phase with
one another — or phase-locked. Otherwise, you’ll
hear clicks, pops, and distortion in the audio — or
perhaps no audio at all.
Figure 4-6: When transferring audio, two devices must have phase-
locked audio clocks to prevent clicks, pops or other artifacts.
There are two ways to achieve phase lock: slave one
device to the other, or slave both devices to a third
master clock. If you have three or more digital
audio devices, you need to slave them all to a single
master audio clock.
Figure 4-7: To keep the your MOTU interface phased-locked with
other digital audio devices connected to it, choose a clock master.
Also remember that audio phase lock can be
achieved independently of timecode (location).
For example, one device can be the timecode
master while another is the audio clock master, but
only one device can be the audio clock master. If
you set things up with this rule in mind, you’ll have
trouble-free audio transfers with your MOTU
hardware.
SYNCING OPTICAL DEVICES
There are several ways to sync an optical device
with the 24Ai or 24Ao:
A. Resolve the other device to the 24Ao
B. Resolve the 24Ai to the other device
C. Resolve both devices to a word clock source
For A, choose Internal (or anything other than
Optical) as the clock mode in the Device tab (item
#13 on page 14). Then configure the other device
to resolve to its optical input.
For B, choose Optical as the clock mode (item #13
on page 14), and configure the other device to
resolve to its own internal clock.
For C, choose Word C lock as the clock mode for the
24Ai or 24Ao (item #13 on page 14), and resolve
the other device to its word clock input.
SYNCING WORD CLOCK DEVICES
The word clock connectors on your MOTU device
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 41).
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 4-8 and Figure 4-9.
Figure 4-8: Slaving another digital audio device to your MOTU device
(a 24Ai in this example) via word clock. For the 24Ai clock source,
choose any source besides word clock, as it is not advisable to chain
word clock.
Not phase-locked Phase-locked
Device A
Device B
Master
Slave
Master
Slave Slave
Master
Slave
Word clock OUT
Word clock IN
Other device
24Ai