The castle BEC comes preset at 5.1 volts. I set mine to 6.0 since I dont have HV servos. Yes you need the usb connector to program at a different voltage. I have the field card which is very nice. I can program the speedo's in the field without the need of a computer, and hook up to the computer and run the computer software threw the card. The BEC will need to be programmed from the computer. Its the same software interface as the speedo's. Im sure someone you know has castle stuff, or the LHS can do it. Most of them around me will help people out and program their stuff for free.