Tap Tempo / Expression Pedal Jack

[MarshallPlexi]

How does a person wire a jack to be both a tap tempo and an expression jack? I've seen this done on several delays etc. The JHS Panther Cub comes to mind.

[Ripthorn]

This will likely require microcontroller logic to sense what is going on. An expression pedal typically takes a 5V (or whatever the microcontroller logic level is) in on a TRS connection and returns a voltage between 0 and that voltage. From there, the microcontroller interprets that as a bin in its ADC. For the tap tempo, you would need to do something clever, like use a standard TS cable, sense that the ring is shorted, and declare that it is in tap tempo mode. Then your tap tempo switch would take the tip as voltage in while having the microcontroller monitor that pin and watch for when the voltage drops (tap shunts the voltage to ground). I don't know how a typical external tap tempo switch is wired, but you could use these concepts to write the code and wire up the circuit to work as you want, it just requires knowing what your tap tempo switch and expression pedal are producing for the microcontroller to monitor.