MOTU 828x 28x30 Audio Interface with ThunderTechnology - Manual (Page 41)

M O T U A U D I O S E T U P
41
Operation at 4x sample rates (176.4 or 192kHz)
At the 4x sample rates (176.4 or 192kHz),
operation of the 828x is restricted, due to the
higher audio bandwidth demands, as follows:
■
All digital I/O is disabled (there is no ADAT
optical, TOSLink or S/PDIF input/output).
■ The 828x provides 8 channels of analog input
and 8 channels of analog output, simultaneously.
■ The stereo return bus, as described in “Return
Assign” on page 43, can only be assigned to one of
the four available analog output pairs.
■
The headphone output can only be assigned to
one of the four available analog output pairs.
■
The Main Outs can only be assigned to one of
the four available analog output pairs.
Clock Source
The Clock Source determines the digital audio
clock that the 828x will use as its time base. For a
complete explanation of synchronization issues,
see “Making sync connections” on page 32. The
following sections briefly discuss each clock source
setting.
Internal
Use the Internal setting when you want the 828x to
operate under its own digital audio clock. For
example, you may be in a situation where all you
are doing is playing tracks off hard disk in your
digital audio software on the computer. In a
situation like this, you most often don’t need to
reference an external clock of any kind.
Another example is transferring a mix to DAT. You
can operate the 828x system on its internal clock,
and then slave the DAT deck to the 828x via the S/
PDIF connection (usually DAT decks slave to their
S/DIF input when you choose the S/PDIF input as
their record source) or via the 828x’s word clock
output (if your DAT deck has a word clock input).
If you would like help determining if this is the
proper clock setting for your situation, see
“Making sync connections” on page 32.
Word Clock In
The Word Clock In setting refers to the Word Clock
In BNC connector on the 828x rear panel.
Choosing this setting allows the 828x to slave to an
external word clock source, such as the word clock
output from a digital mixer or another 828x.
S/PDIF
The S/PDIF clock source setting refers to the
S/PDIF RCA input jack on the 828x. This setting
allows the 828x to slave to another S/PDIF device.
Use this setting whenever you are recording input
from a DAT deck or other S/PDIF device into the
828x. It is not necessary in the opposite direction
(when you are transferring from the 828x to the
DAT machine).
For further details about this setting, see “Syncing
S/PDIF devices” on page 34.
ADAT Optical A / B
The ADAT optical clock source settings ( ADAT
Optical A and ADAT Optical B ) refer to the clock
provided by the 828x’s two optical inputs, when
either one is connected to another optical device.
These two settings only appear in the Clock Source
menu when their corresponding optical bank input
is enabled and set to the
ADAT Optical format, as
explained in “Optical input/output” on page 43.
This setting can be used to resolve the 828x directly
to the optical input connection. Most of the time,
you can set up a better operating scenario that uses
one of the other synchronization options.
However, there may be occasions when you have an
optical device that has no way of synchronizing
digitally to the 828x or an external synchronizer. In