The ARX Ear Driver is an ultra compact Headphone monitoring breakout box, allowing you to independently adjust the audio levels of up to 4 sets of headphones. Internally, stereo true Class AB amplifiers drive the headphones, for pristine audio reproduction Expanded Input Options As well as Left and Right 6.5mm (1/4") jack inputs, there is also a stereo Mini jack input, making the unit usable with any portable media player. Inserting a 6.5mm/1/4" into the Left Input only will Mono all Outputs for added flexibility.