When ordering these from bluedo.com, I only ordered one International Voltage Converter (i.e. convert safely from UK power source), which I'm currently just using for the remote control docking station. Haven't set up the RF extender yet. Do I need another Voltage Converter for the US extender too or can I just use an adapter so that it plugs in? Don't want to risk putting it in without one in case it blows?!