dbx AFS224 Quickstart Guide - Manual (Page 4)

6. To exit the setup mode, press and hold the channel 1 MODE button. Hold this
button until the filter LEDs flash all the way across.
7. Press the BYPASS buttons so that they are both lit red (bypassed).
8. Press and hold the channel 1 TYPE button to select between dual mono or stereo
mode.
Note: You can tell which mode you are in by pressing any of the buttons. If the other
channel changes as well, the two channels are working in conjunction (stereo mode).
If not, the unit is in dual mono mode.