Instead of using the ES-8's back panel CTL output jacks, or if you have already used all CTL jacks for other functions, it's possible to program the ES-8 to utilize one of it's on-board Loop switches to change your amp's channel (two channels max.)
Here are the steps:
1. Connect a 1/4" TRS cable from the CTL 1/2 jack, under the ES-8's EXT CTL
section, to your amp's channel selector footswitch jack.
2. Select the ES-8 preset that you want to use to set up amp channel switching on
one of the 8 available Loop switches.
3. Press “Edit” Button repeatedly to bring up the CTL/EXP menu and press “Enter”.
4. Use the arrow keys to get to “Number8” and press “Enter”.
5. Set FUNCTION (FUNC) to “off” with the – and + keys – This will stop the normal
operation of Switch Number 8 (Only in this Patch).
6. Press the DISPLAY/EXIT button.
7. Press the Left/Right Arrow buttons until you get to the ASSIGN 1 screen.
8. Press ENTER.
9. Press (+/-) to turn the Switch (SW) parameter ON.
10. Press the Left/Right Arrow buttons to select Source (SRC)
11. Press (+/-) to select NUM5.
12. Press the Left/Right Arrow buttons to select MODE (MOD).
13. Press (+/-) to select Toggle (TGL).
14. Press the Left/Right Arrow buttons to select Category (CATE).
15. Press (+/-) to select External Control (E.CTL).
16. Press the Left/Right Arrow buttons to select TARGET.
17. Press (+/-) to select CTL1.
18. Press WRITE three times.