Syncing S/Pdif Devices - MOTU 1248 User Manual

Not phase-locked
Device A
Device B
Figure 4-18: 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 4-19: 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.

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 #14 on page 18) to resolve the 1248 to its
S/PDIF input.
H A R D W A R E I N S T A L L A T I O N
S/PDIF input with sample rate conversion
Phase-locked
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 53 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 #14
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
Master
(from the 1248), it will simply synchronize to the
clock provided by the 1248 S/PDIF signal.
SYNCING OPTICAL DEVICES
Slave
There are several ways to sync an optical device
with your MOTU interface:
A. Resolve the other device to your MOTU
interface
B. Resolve your MOTU interface to the other
device
C. Resolve both devices to a word clock source
For A, choose Internal (or anything other than
Optical) as the clock mode in the Device tab (item
#14 on page 18). Then configure the other device
to resolve to its optical input.
For B, choose Optical as the clock mode (item #14
on page 18), and configure the other device to
resolve to its own internal clock.
For C, choose Word Clock as the clock mode for the
24Ai or 24Ao (item #14 on page 18), and resolve
the other device to its word clock input.
59