1. Set the EFX send and channel level controls to an appropriate level.
  2. Press the EFX CUE button (located above the CTRL RM volume control), and you will hear the channels signal through the EFX send.

Note: Because the EFX send is affected by each channels level control, you have to turn the level control to the appropriate setting in order to hear channel signal through the EFX send. When multiple channels are in use, simply set one EFX send level controls to an appropriate setting, and turn the remaining channels EFX send level control to the far left, then you will only hear the channel on headphones through EFX CUE button.