Asus Crosshair V Formula/ThunderBolt - Manual (Page 167)

ROG Crosshair V Formula 4-33
Audio.output
Click the corresponding box to select from Speakers, Headphones, and SPDIF-Out
for the output device. Click each button directly to configure the related settings.
Headphone Settings
Click Headphone and select Headphone Settings to do the gain adjustment.
Select the gain tuning according to your headphone impedance.
A wrong gain tuning setting may damage your headphone. Select a proper gain
according to your headphone specification.
Only audio output from the front panel via the AAFP cable supports the
headphone gain tuning function.