Syncing Word Clock Devices; Syncing To Smpte Time Code (Ltc) - MOTU 1248 User Manual

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 58).
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 4-20 and Figure 4-21.
Master
Word clock OUT
Word clock IN
Slave
Figure 4-20: Slaving another digital audio device to your MOTU
device (a 1248 in this example) via word clock. For the 1248 clock
source, choose any source besides word clock, as it is not advisable to
chain word clock.
Word clock master device
Audio
clock
Master
Word clock OUT
Word clock IN
Slave
Figure 4-21: Slaving your MOTU device (a 1248 in this example) to
word clock. For the 1248 clock source, choose 'Word Clock In' .
Daisy-chaining word clock
If necessary, you can daisy-chain several word
clock devices together. When doing so, connect
WORD CLOCK OUT from the first (master)
device to the WORD CLOCK IN on the second
device. Then connect its WORD CLOCK THRU
port to the next device's WORD CLOCK IN port,
and so on. On your MOTU interface, use its
WORD CLOCK OUT port and change its
operation from OUT to THRU in the Device tab of
the MOTU Pro Audio Control web app (item #16
on 18).
60
If you have more than four word clock devices that
you need to synchronize, avoid chaining their word
clock connections. Instead, use a word clock
distribution device of some kind.
Word clock is not needed for AVB networking
When working with multiple MOTU AVB
interfaces on an AVB network, synchronization is
handled by AVB, so no word clock connections are
necessary. See the next section for details.

SYNCING TO SMPTE TIME CODE (LTC)

The Clock Mode menu (item #14 on page 18)
1248
provides the ability to resolve to SMPTE time code
(Longitudinal Time Code, referred to as LTC) from
any specified analog or digital input.
When you choose the LTC clock mode setting, the
Other device
audio phase lock engine in your MOTU interface
resolves to the incoming time code. (See below for
how to specify the time code input.) This ensures
that audio passing through the interface remains
resolved to time code and won't drift over time, as
long as the audio is coming from other sources that
are also resolved to the same time code. This also
ensures that audio recorded by DAW host software
on a connected computer, or audio playing back
from the DAW, will remain resolved to time code
and won't drift over time, even when restarting or
1248
cueing the source time code.
☛
Depending on the stability of the incoming
time code, it may take a few seconds for your
interface to lock to the time code. The more stable
the incoming time code, the faster the lock-up
time.
SMPTE time code (LTC) settings
There are several settings for the time code features
in your MOTU interface. In the web app, go to the
Device tab (page 19) and scroll to the LTC Setup
section, shown below.
H A R D W A R E I N S T A L L A T I O N