MOTU PCI-424, Руководство пользователя

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I N S T A L L I N G T H E P C I - 4 2 4 H A R D W A R E
37
MAKE SYNC CONNECTIONS
Synchronization between the PCI-424 system and
the devices connected to it is critical, even if you
don’t plan to synchronize your PCI-424 system
with an outside time reference such as SMPTE time
code. While there are dozens of ways to
synchronize the system, the next few pages discuss
common recommended setups.
Do you need to synchronize the PCI-424?
If you will be using only analog inputs and outputs,
and you have no plans to synchronize your
PCI-424 system to SMPTE time code, you don’t
need to make any sync connections, and you can
skip the rest of this chapter. Open the PCI Audio
Console Window and set the
Clock Source
setting
to Internal as shown below in Figure 4-15. For
details, see chapter 6, “MOTU PCI Audio Console”
(page 63).
Figure 4-15: You can run the PCI-424 system under its own internal
clock when it has no digital audio connections and you are not
synchronizing the PCI-424 system to SMPTE time code or video.
Situations that require synchronization
There are three general cases in which you will
need to synchronize the PCI-424 system with other
devices:
■
The 2408mk3 or other interface is connected to
other digital audio devices, and their digital audio
clocks need to be
phase-locked (as shown in
Figure 4-16).
■
You need to resolve (synchronize) the PCI-424
system to SMPTE time code and/or video.
■
Both of the above.
Synchronization is essential for digital I/O
Synchronization is critical in any audio system, but
it is especially important when you are transferring
audio between digital audio devices. Your success
in using the PCI-424 system depends almost
entirely on proper synchronization. The following
sections guide you through several recommended
scenarios.
Choosing 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 4-16: When transferring audio, two devices must have
phased-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 4-17: To maintain phase-lock between the PCI-424 system and
other digital audio devices connected to it, choose a clock master.
Also remember that audio phase lock can be
achieved independently of time code (location).
For example, one device can be the time code
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.
Not phase-locked Phase-locked
Device A
Device B
Master
Slave
Master
Slave Slave