Whirlwind PA-1 Personal Headphone Monitor, Stereo/Mono Selector Switch, Parallel XLR and TRS Jacks, Volume and Balance Control Knobs

The Whirlwind PA-1 is a high quality, portable stereo 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.

The PA-1 accepts line level inputs and will monitor both separate balanced left and right feeds and unbalanced stereo signals on a single connector. Each channel has a female XLR and a 1/4" TRS jack that are parallel wired with pin 2 wired to tip, pin 3 wired to ring and pin 1 connected to shield. This feature allows for loop through operation with commonly available adapter cables. The input mode select switch changes the input wiring from balanced left and right to unbalanced stereo.

The XLR and 1/4" jacks are all paralleled together in unbalanced stereo mode. After the input hardware the audio can be attenuated by 20 dB by applying the pad. Signals are then routed to balanced buffers and the stereo gain circuit. Volume is controlled by a dual gang potentiometer, which provides a gain range of -60 to +15 dBm of gain. The volume control has an audio type taper from the 9 o'clock to 3 o'clock positions with larger amounts of gain and cut at the extremes (above 3 o'clock and below 9 o'clock). The stereo signals then go through a standard audio taper pan potentiometer, for balancing the signal in the two earpieces. The stereo/mono switch, when in mono, allows the PA-1 to be used as a two mix monitor . In mono mode, the pan pot serves as a mix control adjusting the blend of the two input sources in both ears.

The output drivers of the PA-1 are capable of delivering high sound pressure levels with low impedance headphones. Turn the volume control down before putting on headphones to prevent accidental ear damage. Both 1/4" and 1/8" jacks are available on the PA-1 for use with all types of headphones. The PA-1 is powered by 2 nine volt batteries or the supplied PS-24 wall power supply. When using the PS-24, the batteries are automatically disconnected.