Hey! You'll need to make or buy a mini (1/8") to banana jack adaptor. To make one take a one side of a 1/8" cable and attach (twist, solder, crimp, wire nut, etc) the copper wire in the middle of the 1/8" cable to a banana plug. The 1/8" cable will have two separate wires inside of it, the signal in the middle and the 'ground' on the outside. If the 'ground' wire touches the signal wire, the adaptor won't work. You will need to attach the ground wire to your synth some where, however. If your synth doesn't have a banana jack ground connection, try connecting the ground wire to a metal screw on the chassis.