I purchased in NZ a PC 10 with 230 V 50H 100W along with the Warfdale surround speakers. When I moved back to Canada to change the voltage input on the amplifier, which I also purchased in NZ, was a simple flip of a switch from the 240 V to 110V , however there is nothing like that on the back of my Warfdale subwoofer. What do I change on this 240 Voltage SW to make it work on the 110 Voltage here in Canada .