When using effects pedals with stereo outputs, it's necessary to configure either Loop 7 or 8 to a stereo configuration instead of mono.
To do this:
1. Press EDIT.
2. Press Right Arrow to get to PREFERENCES.
3. Press ENTER.
4. Press Right Arrow to get to either Loop 7 RETURN, or once more for Loop 8
RETURN.
5. Press ENTER.
6. Use Right Arrow to change the display from MONO to STEREO.
7. Press DISPLAY/EDIT four times to get back to the ES-8's home
screen.