Here is the page (https://old.alembicguitars.com/support/SVC_F1X_voltage.html) that shows the jumper settings for various voltages.
Changing the voltage setting jumpers on the F-1X preamp.
F-1X_jumperlocation.jpg
F-1X_100Vm.jpg
F-1X_120Vm.jpg
F-1X_220Vm.jpg
F-1X_240Vm.jpg