Making Sync Connections - MOTU 828 Mk III Hybrid User Manual

MAKING SYNC CONNECTIONS

If you connect devices digitally to the 828mk3, or if
you need to synchronize the 828mk3 with an
outside time reference such as SMPTE timecode,
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 828mk3?
If you will be using only the 828mk3's analog
inputs and outputs (and none of its digital I/O),
and you have no plans to synchronize your 828mk3
system to SMPTE timecode, you don't need to
make any sync connections. You can skip this
section and proceed to "MOTU Audio Console" on
page 35,where you'll open MOTU Audio Console
to confirm that the Clock Source setting is Internal
as shown below.
Figure 4-14: You can run the 828mk3 under its own internal clock
when it has no digital audio connections and you are not synchroniz-
ing the 828mk3 system to an external time reference such as
timecode.
Situations that require synchronization
There are three general cases in which you will
need to resolve the 828mk3 with other devices:
Synchronizing the 828mk3 with other digital
■
audio devices so that their digital audio clocks are
phase-locked (as shown in Figure 4-15)
Resolving the 828mk3 system to SMPTE
■
timecode from a video deck, analog multi-track,
etc.
Both of the above
■
28
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 828mk3'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.
Not phase-locked
Device A
Device B
Figure 4-15: 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.
Master
Slave Slave
Figure 4-16: To keep the 828mk3 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 the 828mk3.
I N S T A L L I N G T H E 8 2 8 M K 3 H A R D W A R E
Phase-locked
Master
Slave