Yamaha DTXpress/DTXplorer/DTXtreme

I don't know anything about the FD8, but I do have the Yamaha HH pedal
and know how that works.  If you have access to multimeter and measure
the resistance from the tip and ring to the sleeve then we should be
able to work out the differences.  The other option is for you to
dismantle it and trace out the circuit.

Keith.