The Monoprice ss-pro 12 is a powerful and efficient dual source, audiophile grade speaker selector for up to 12 pairs of speakers. Featuring robust transformers, the ss-pro 12 allows you to play all 12 pairs of speakers at once without damaging the amplifier, and is able to withstand up to 300 watts peak of power per channel. A front panel a/b switch allows you to choose between two amplifier sources, and easily removable Snap in connectors make installation easy. A rotary switch located on the rear panel can be used to set the appropriate impedance based on the number of pair of speakers connected.