anyone have a good link explaining how to install an expression pedal jack so that when nothing is plugged into the jack, the parameter will be controlled by the knob/pot?

i want to put an expression pedal jack on my boss ch1 super chorus to control speed, to get some univibe-esque sounds. I still want to be able to use the speed knob when no expression pedal is plugged in though, and i don't want to have to switch it.

personal insite and links welcome. thanks!

good idea anyone