RCA INPUT AND OUTPUT: Stereo mixer features 4 channels of RCA input and 1 channel of RCA output for ease of use, which is the best choice for headphones and speakers. STEREO MIXER: Stereo sound mixer mixes 4 stereo sound signals, mixing sound signals from mixed instruments, CD players, tape players, computers, cell phones, tablets to speakers and headphones. ULTRA LOW NOISE: 4 channel line mixer delivers better sound quality even at maximum output electrical frequencies, providing excellent sound performance. EXCELLENT DESIGN: Stereo sound mixer has 3.5mm stereo interface. The shell is made of high quality aluminum alloy, which is sturdy and durable. 4 SEPARATE VOLUME CONTROLS: Each channel of the sound mixer has its own independent volume control to adjust the volume as needed, making it very convenient to use.