On-Stage HA4000 4-Channel Pro Headphone Amplifier,BlackThe 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