You don't mention your current requirements? However, since you mention USB you need to keep in mind that if this 5 volt USB source is from a home PC the ports are limited in the 5 volt current they can provide. You really don't want to overload or accidently short a USB ports 5 volt power. Also, if this is a low current +12 / -12 volt application and you are using a home computer, there should be + / - 12 volts available from the power supply.