User Guide

HARDWARE INSTALLATION
37
SETUP FOR MULTIPLE INTERFACES
It is possible to connect multiple MOTU interfaces
directly to your host computer through multiple
USB (and Thunderbolt) ports. However, there are
several disadvantages to using any of these direct
connection schemes:
■ The audio interfaces will not be clocked to one
another and may be susceptible to drift, unless you
use external word clock connections (if available).
You are better off using the AVB network
connections shown on pages 34-36. In this setup,
the interfaces are very tightly synchronized with
each other (measured in pico seconds) through
their network connections.
■ You will not be able to route audio directly from
one audio interface to another. You are better off
using the AVB network connections shown on
pages 34-36, which allows you to route audio
streams (hundreds at a time) directly among
interfaces with near-zero latency.
Connecting multiple interfaces using
Thunderbolt
If you have other MOTU AVB interfaces with
Thunderbolt connectivity (1248, 8M, 16A, 112D,
624 or 8A) and your host computer has two or
more Thunderbolt ports, you can connect one
interface to each port, either directly or at the end
of a Thunderbolt daisy chain (on either port or
both ports).
Connecting multiple interfaces using
Thunderbolt and USB
Another way to operate multiple interfaces on the
same host computer is to connect the first interface
to a Thunderbolt port and the second to a USB 3.0
(or 2.0) port.
Multiple interfaces and USB
When connected through USB, the 624 operates as
a USB 3.0 device, unless it is connected to a
USB 2.0 port. USB 2.0 provides enough bus speed
for several USB 2.0 devices, but due to the 624’s
high-performance requirements for real-time
operation and low latency timing, we recommend
the following:
■ Try to use USB 3.0 whenever possible.
■ If your computer has USB 2.0 ports, do not
connect more than two units to your computer’s
USB 2.0 ports.
■ When two 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 clock synchronization
with other interfaces connected to the same
computer. You can use optical or AVB to achieve
clock synchronization.
Multiple AVB Ethernet audio interfaces
When operating 624 as an AVB Ethernet audio
interface (“AVB Ethernet audio interface setup” on
page 34), multiple AVB audio interfaces can be
connected using a MOTU AVB Switch (or any 3rd-
party AVB switch), and the Mac can see all of them
through their AVB connection. For example, you
could connect an Avid S3 console to the Mac, and
then connect a MOTU 624 to the S3’s extra
network port (which is a built-in switch). The Mac
can see both 624 and S3 for audio I/O. For best
results in this scenario, be sure to use OS X 10.11
(El Capitan) or later. See “Syncing multiple AVB
audio interfaces connected to a Mac” on page 47.
Mixing and matching audio interfaces
You can mix and match MOTU audio interfaces.
For example, you could connect a 624 through
Thunderbolt and another MOTU audio interface,
such as the Stage-B16, through USB 2.0.