It is possible to use Apple's keyboard volume buttons to adjust levels in smaller increments. Here's how:
Note: First select the Apogee device in Mac System Preferences > Sound > Output.
To adjust the volume in large increments:
- Press the Apple keyboard buttons F11 and F12
To adjust the volume in smaller increments
- Hold the SHIFT + OPTION buttons as you press the F11 or F12 buttons.
See this article on how to select between controlling the speaker or headphone output volume control on your Apogee device: Keyboard Volume Control: Selecting Speaker or Headphone