The Russound P125 2-Channel Dual Source 125w Amplifier Volume And Balance Allows For Control At The Component Instead Of Volume Control Or Keypad A/B Speaker Switching Easily Toggles Output Between Two Sets Of Speakers Or Zones Signal Sensing Inputs Automatic Turn On/Off And Switching To Second Source Bridgeable - Delivers Higher Output For Use With A Subwoofer Or Outdoor Speakers A Speaker-Level Input Can Be Connected And Assigned As Either The Primary Or Secondary Source