It is suggested that you set up your audio levels for unity gain using peak levels. To do this put the unit in bypass mode:
Press SYSTEM and select AUDIO menu.
Scroll to Audio Output and select Analog or Digital.
Press SYSTEM again and select the Modes menu.
Scroll to Modes: Bypass and make sure the assignment is Bypass (the default setting).
Press the front panel BYPASS button. The button will light to indicate that bypass is engaged.
Press EDIT, scroll to Meters Assign and select Output.
(page 1-7 in manual).

Next, set your MPX 1 meters to monitor inlevels:
Set the rear panel Input button to the appropriate position for balanced (+4) or unbalanced (-10) operation.
Press EDIT and scroll to the Meters assign parameter. Make sure that the meter assignment is Input (the default setting).
Press SYSTEM.
Select the Audio menu and scroll to the Input/Clck screen.
Select the desired input mode. (page 1-6 in manual).

Make sure your console faders are set for unity. Run audio through the unit and use the front panel output knob to set the level on your console. Set your levels (using peak levels) so that you are getting the same level out as you are sending in.