Sennheiser HD 800 Over Headphone with HDVD 800 Headphone Amplifier Bundle contains (1) of Sennheiser HD 800 Over-Ear Circum-Aural Dynamic Headphone and (1) of Sennheiser HDVD 800 Headphone Amplifier with DAC Sennheiser HD 800 headphones have been specifically engineered to replicate the basic acoustic conditions of natural hearing Sennheiser HDVD 800 is a premium performance headphone amplifier with built in digital to analog converter Connectivity technology : Jack stereo  (6,3 mm)