When selecting a Red 4Pre/8Pre/16Line or RedNet PCIe/PCIeR interface as the input and output device in System Preferences > Sound on Mac OS X, a message stating 'This device has no input/output controls' will be displayed at the bottom of the screen for both tabs:
This is normal behaviour. The input/outputs levels on the Red 4Pre/8Pre/8Line/16Line can be controlled via RedNet Control and/or the front panel, the level coming into/out of the RedNet PCIe/PCIeR card is fixed.
In addition to this, the speaker icon in the Menu Bar will be greyed out if you have this icon enabled and visible.