The Power Ace Voltage Doubler Y-Cable is a high quality voltage doubling adapter cable for effect pedals to combine two separate, isolated 5.5 x 2.1 mm power slots, e.g. 2 x 9 V to 18 V.
RockBoard Power Ace Voltage Doubler Y Cable, 2 x 2.1 x 5.5 mm barrel plug (series) to 2.1 x 5.5 mm barrel socket