The On-Stage HA4000 Four-Channel Headphone Amplifier in Black accepts one stereo input and makes the audio available to four separate stereo headphone outputs, each with its own volume control. Up to four people can listen simultaneously to a single audio source and independently adjust their headphone volume. It allows the listeners to hear the mix during recording or broadcast. The amp is meant for recording and audio playback applications. It delivers 20dB max gain per channel, plus 22dB max output level, a minimum of 10-ohm output impedance in each channel, 1000KO unbalanced input impedance, a 1/4-inch TRS stereo output connector, and a 1/4-inch TRS stereo input connector. The amp is compact yet powerful and delivers superior sound with low noise throughout the full-volume spectrum.