MOTU 828x 28x30 Audio Interface with ThunderTechnology - Manual (Page 35)

I N S T A L L I N G T H E 8 2 8 X H A R D W A R E
35
SYNCING WORD CLOCK DEVICES
The 828x word clock connectors 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 32).
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 4-17 and Figure 4-18.
Figure 4-17: Slaving another digital audio device to the 828x via
word clock. For the 828x clock source, choose any source besides
word clock, as it is not advisable to chain word clock.
Figure 4-18: Slaving the 828x to word clock. For the 828x clock source,
choose ‘Word Clock In’.
Don’t chain word clock
If you have three or more digital audio devices that
you need to synchronize, avoid chaining their word
clock connections (OUT to IN, OUT to IN, etc.), as
this causes problems. Instead, use a word clock
distribution device of some kind.
Forcing a 1x word out rate
The 828x can generate a word clock output signal
that either matches the current system clock rate
(any rate between 44.1 and 192kHz) or the
corresponding 1x rate. For example, if the 828x is
operating at 192kHz, you can choose to generate a
word out rate of 48kHz. For details on how to make
this word clock output setting, see “Word Out” on
page 44.
CONNECTING MULTIPLE 828X INTERFACES
It is possible to connect two or more 828x
interfaces to your host computer, and you can mix
and match the 828x with other audio interfaces. All
connected interfaces will appear as audio I/O
devices in any host audio software that supports
multiple devices, such as Digital Performer.
Connecting multiple 828x interfaces using
Thunderbolt
If your host computer has two or more
Thunderbolt ports, you can connect one 828x
interface to each port, either directly or at the end
of a Thunderbolt daisy chain (on either port or
both ports).
Connecting multiple 828x interfaces using
Thunderbolt and USB
Another way to operate multiple 828x interfaces on
the same host computer is to connect the first 828x
to a Thunderbolt port and the second to a USB 2.0
(or 3.0) port.
Multiple interfaces and USB
When connected through USB, the 828x operates
as a USB 2.0 device, even when connected to a
USB 3.0 port. USB 2.0 provides enough bus speed
for several USB 2.0 devices, but due to the 828x’s
high-performance requirements for real-time
operation and low latency timing, we recommend
the following:
■
Do not connect more than two 828x units to
your computer’s USB 2.0 or 3.0 port(s).
■ When two 828x units are connected with
USB 2.0, don’t connect other USB 2.0 or 3. 0
devices, such as external hard drives.
■ For best results, establish word clock synchroni-
zation with other interfaces connected to the same
computer.
Master
Slave
Word clock OUT
Word clock IN
Other device
828x
Audio
clock
Master
Slave
Word clock master device
Word clock OUT
Word clock IN
828x