4 Channel Mini Mixer. Expand Main Mixer When Low on Channels. Individual Level Controls. Compact Design. Low Noise Operation. A professional 4 channel line level mixer- designed to mix down 4 stereo line level signals. Can be used alongside an existing mixer to increase channels if desired. The four stereo inputs and one stereo output are via RCA connections. Each input has its own level control. This is a passive mixer so no batteries or external power supply are required.