The RU-PA518 features two modes of operation: stereo and bridged mono. Depending on the mode of operation, the RU-PA518 can deliver from 5 to more than 18 watts of RMS power at the output. In stereo mode, each of the two inputs feeds its respective left or right output. Front-panel level controls set the gain for both left and right channels. When the rear-panel switch is set to the bridge mode, the two inputs (A and B) are mixed together and fed to the output. In either the stereo or mono mode,...