System Configuration : I/O Setup : Configuring Hardware in I/O Setup : Routing a Pro Tools Output Pair to Multiple Destinations

Routing a Pro Tools Output Pair to Multiple Destinations
Pro Tools channel pairs can be routed to multiple outputs on an audio interface through the I/O Setup. For example, if you assign both Analog 1–2 and Analog 3–4 interface outputs to Pro Tools Output pair 1–2, when you send a signal to Pro Tools Outputs 1–2, that signal will be routed simultaneously to both pairs of output ports on your audio interface.
This lets you send the same signal (such as a stereo pair, a stem mix, or a multichannel mix) to multiple destinations (such as multiple mastering devices).
The only limit to output choices is the number of outputs available in your system.
Pro Tools outputs pairs can also be routed to multiple audio interface outputs in the Hardware Setup.
To route a Pro Tools output channel pair to multiple audio interface output ports:
1 Choose Setup > I/O.
2 Click the Output tab.
3 Click the Output selector for an interface channel pair, just below an audio interface icon.
4 From the pop-up menu, select a physical port pair (such as Analog 1–2) to route to the corresponding Pro Tools channel pair (such as A 1–2) in the Path Name column on the left.
5 Start-click (Windows) or Control-click (Mac) the same Output selector and select an additional output pair from the same pop-up menu.
The output name updates with a plus sign (“+”) before it to indicate that multiple output ports are selected. In the pop-up menu, each physical port pair assigned to that Pro Tools output pair is indicated by a check mark.
6 Repeat the above steps to select additional output destinations.
7 Click OK to save changes and close the I/O Setup.