The PS1A is an ac power supply that provides phantom power to one or two Shure condenser microphones. The PS1A can be used with either balanced or unbalanced low-impedance microphone inputs, and is designed to handle both microphone- and line-level signals. It features extremely low noise, hum and RF susceptibility. The PS1A will operate over a wide range of ac voltages, and provides short-circuit-proof operation.