We recommend a regulated power supply rather than a switching power supply. While a switching power supply will work, it often produces noise that will interfere with your radio's receiver. The SR-955HPC, SR-655HPC & SR-447HPC2 need a 20 amp supply. Our SR-497HPC should have a 25 amp power supply. The SR-94HPC needs a 12 amp power supply, and the SR-25MC requires 5 amps at a minimum.