User Manual

HARDWARE INSTALLATION
48
SYNCING S/PDIF DEVICES
The 1248 provides RCA (coax) S/PDIF digital
input and output. Your 1248 and the other S/PDIF
device will sync to each other by way of the S/PDIF
connection itself. One device is the master, and the
other device is the slave.
Syncing the 1248 to its S/PDIF input
When you transfer audio from the S/PDIF device
into the 1248, choose S/PDIF as the clock source
(item #13 on page 18) to resolve the 1248 to its
S/PDIF input.
S/PDIF input with sample rate conversion
The 1248 S/PDIF input provides sample rate
conversion, which allows you to record any S/PDIF
signal up to 96 kHz, even when the 1248 is resolved
to other clock sources besides S/PDIF. See “S/PDIF
with sample rate conversion” on page 43 for more
information.
Syncing another S/PDIF device to the 1248
When transferring audio from the 1248 to another
S/PDIF device, set the 1248’s clock mode (item #13
on page 18) to any source other than S/PDIF.
Doing so makes the 1248 the clock master. When
the other device records (or receives) S/PDIF audio
(from the 1248), it will simply synchronize to the
clock provided by the 1248 S/PDIF signal.
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 47).
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 4-11 and Figure 4-12.
Figure 4-11: 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.
Figure 4-12: 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 front panel
LCD. See “Settings menu” on page 59.
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.
Master
Slave
Word clock OUT
Word clock IN
Other device
1248
Audio
clock
Master
Slave
Word clock master device
Word clock OUT
Word clock IN
1248