The Whirlwind PA-1 is a high output, low distortion, portable monitoring device suitable for critical listening in any professional audio environment. This headphone amplifier designed to deliver superior sonic accuracy in any audio monitoring application. High output level combined with very low distortion make the PA-1 suitable for critically listening to all professional audio sources in any environment. The PA-1 accepts both balanced and unbalanced stereo line level signals through paralleled XLR and 1/4” TRS inputs. A switch changes the input configuration from separate balanced stereo inputs to unbalanced TRS (ring-right/tip-left) for sources such as headphone jack outputs. Power is supplied by two nine volt batteries that load into easy access drawers or an external AC supply which is included.