User`s guide

INSTALLING THE 828MKII HARDWARE
33
Using multiple interfaces under Mac OS 9
All connected MOTU FireWire interfaces get their
clock from whatever you choose from the Clock
Source menu in the MOTU FireWire Audio
Console. When you connect multiple MOTU
FireWire interfaces, all of their respective sync
sources are displayed in the menu as shown below
in Figure 3-22.
Figure 3-22: In Mac OS 9, all MOTU FireWire audio interfaces get their
clock from a single master sync source on any connected 828mkII (or
other MOTU FireWire interface). After you choose a source from this
menu, the entire system, including all connected 828mkIIs, synchro-
nizes to it.
Under Mac OS 9, Each FireWire interface in the
system gets its clock from the Audio Wire cable
connection (unless it is the master clock itself).
There is no need to make word clock connections
between multiple FireWire interfaces.
Using multiple interfaces under Mac OS X
Mac OS X provides a more advanced, flexible
driver model that allows multiple CoreAudio
drivers to be active at one time, accessed by
multiple applications simultaneously. For example,
under Mac OS X, you can run both FireWire and
PCI audio interfaces at the same time, accessing all
of their inputs and outputs from your host audio
application — or even multiple applications —
simultaneously.
A by-product of this more flexible model is that
multiple devices must be externally synchronized
to one another in order to remain resolved to each
another. Without external synchronization, the
audio streams going to each interface might drift
with respect to one another. For example, the audio
tracks playing back through the 828mkII might
drift out of sync with the audio tracks playing back
through your 2408mk3 PCI interface.
Synchronizing them to each other externally
ensures that they remain as tightly and
continuously phase-locked as if they were
operating as one unified interface.
To resolve two 828mkII FireWire interfaces with
each other, choose one as the word clock master
and then slave the second interface to the first, as
shown in Figure 3-20 on page 32. For three
interfaces, you can probably get away with daisy-
chaining them via their word clock connectors, but
this may not always produce the most reliable
results. For three or more devices, a word clock
distribution device is highly recommended. In this
case, the distribution box is the master, and all
FireWire interfaces slave directly to it (instead of to
each other).
Connecting an 828
Yo u can add an original MOTU 828 to the end of a
FireWire daisy chain (because the 828 has only one
FireWire port), or you can mix and match multiple
828’s with other MOTU FireWire interfaces using a
standard FireWire hub. Up to four interfaces can be
combined on one FireWire bus.
Operating multiple FireWire interfaces at high
sample rates
Four MOTU FireWire interfaces can operate at
44.1 or 48kHz on a single FireWire bus. At the high
samples rates (88.2 or 96kHz), you can operate no
more than two FireWire interfaces on a single
FireWire bus.
Adding additional interfaces with a second
FireWire bus
Third-party FireWire bus expansion products in
the form of a cardbus (“PC card”) adaptor or PCI
card allow you to add a second FireWire bus to
your computer. In may be possible to add
!828 Manual/Mac Page 33 Tuesday, May 27, 2003 1:45 PM