System Configuration : I/O Setup : Editing Paths : Restoring Default Paths and Path Names

Restoring Default Paths and Path Names
You can restore I/O Setup paths to their default state at any time. You may want to restore defaults if, for example, you replace or add an audio interface to your system.
To restore default paths and path names:
1 Choose Setup > I/O.
2 Click the Input, Output, Insert, or Bus tab to display the corresponding path type.
3 Click Default. Pro Tools does the following:
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Creates new default paths up to the capacity of your system’s available physical I/O and resources.
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Resets path names to the default path names (see Default Path Names). These default path names appear in track Input and Output Path selectors.
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Option-click (Mac) or Alt-click (Windows) the Default button to set all pages of I/O Setup to the default settings.
4 Click OK to save changes and close the I/O Setup.