Synchronization - MOTU 8M User Manual

SYNCHRONIZATION

If you connect devices digitally to your MOTU
device, or if you need to synchronize your MOTU
device with an outside time reference such as word
clock, you must pay careful attention to the
synchronization connections and clock source
issues discussed in the next few sections.
Do you need to sync?
If you will be using only your MOTU device's
analog inputs and outputs (and none of its digital
I/O), and you don't need to resolve your system to
external word clock, you don't need to make any
sync connections. You can skip this section.
Situations that require synchronization
There are two general cases in which you will need
to resolve you MOTU device with other devices:
Synchronizing with other digital audio devices
■
so that their digital audio clocks are phase-locked
(as shown in Figure 4-9)
Resolving your MOTU device to an external
■
clock source
Networking multiple MOTU AVB interfaces
■
together
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 digital I/O features on your MOTU
device depends almost entirely on proper synchro-
nization. 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.
H A R D W A R E I N S T A L L A T I O N
Not phase-locked
Device A
Device B
Figure 4-9: 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 4-10: 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.
Phase-locked
Master
Slave
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