MOTU 896mk3, Руководство пользователя

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I N S T A L L I N G T H E 8 9 6 M K 3 H A R D W A R E
21
MAKING SYNC CONNECTIONS
If you connect devices digitally to the 896mk3, or if
you need to synchronize the 896mk3 with an
outside time reference such as SMPTE time code,
you must pay careful attention to the synchroni-
zation connections and clock source issues
discussed in the next few sections.
Do you need to synchronize the 896mk3?
If you will be using only the 896mk3’s analog
inputs and outputs (and none of its digital I/O),
and you have no plans to synchronize your 896mk3
system to SMPTE time code or other external clock
source, you don’t need to make any sync
connections. You can skip this section and proceed
to chapter 4, “Installing the 896mk3 Mac Software”
(page 33). After you install the 896mk3 software,
you’ll open MOTU Audio Setup and set the
Clock
Source setting to Internal as shown below. For
details, see chapter 5, “MOTU Audio Setup”
(page 35).
Figure 3-5: You can run the 896mk3 under its own internal clock
when it has no digital audio connections and you are not synchroniz-
ing the 896mk3 system to an external time reference such as SMPTE
time code.
Situations that require synchronization
There are three general cases in which you will
need to resolve the 896mk3 with other devices:
■
Synchronizing the 896mk3 with other digital
audio devices so that their digital audio clocks are
phase-locked (as shown in Figure 3-6)
■
Slaving the 896mk3 system to SMPTE time code
from a video deck, analog multi-track, etc.
■
Both of the above
Synchronization is critical for clean 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 896mk3’s digital I/O features depends
almost entirely on proper synchronization. The
following sections guide you through several
recommended scenarios.
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 3-6: 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 3-7: To keep the 896mk3 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 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 with the 896mk3.
Not phase-locked Phase-locked
Device A
Device B
Master
Slave
Master
Slave Slave