Software Setup; Playback From Itunes - Apogee Symphony I/O User Manual

Software Setup

Playback from iTunes

Note: Analog Outputs 1-2 will default to a level of -20dB. It is recommended to turn the level down all the way and
gradually bring it up when connecting speakers and playing audio for the first time.
If you are going to use an external monitor controller or console and would like Analog Outputs 1-2 to be at line-level
like the other outputs, you can either turn them up to 0dB by using the left-side front-panel encoder knob to select the
speaker icon and then using the right-side front-panel encoder knob to raise the level to 0dB. You could also do this in
the Apogee Maestro app by going to the Output tab, scrolling over to the right, and raising the level to 0dB with the
Main output's software knob or changing the output format from Speaker to Line.
With 'Symphony64 (ThunderBridge or PCI)' selected as your Mac's default audio input and output, open Apple iTunes
and play an audio selection. Using the front panel left hand encoder, select the speaker or headphone icon; use the
right hand encoder to adjust the playback level of the selected output.
Symphony I/O - User's Guide Page 34