Looking at the manual for a Diezel Schmidt, it seems to me that you should be able to use one of the function switch out puts on the PBC to do the switching you want. The key thing will be to make sure to use a TRS cable to run from the PBC function switch out to the Diezel External switching input. I’m guessing that one or the other of activating channel 3 and turning the effects loop on or off get the switching ‘signal’ on the tip of the TRS cable, the other function on the ring. So if you run a TRS cable from, say, the FuncSw 3-4 jack on the PBC to the Ch3/Loop jack on the Diezel, it should work. You’ll just need to check which of PBC function switches 3 or 4 control which function on your a Diezel.
