The Black Magic 275 follows a tradition of lighter weight but none the less powerful, musical and accurate amplifier designs by Bob Carver. The Black Magic 275 incorporates Bob's latest high voltage power supply. Vacuum tubes are voltage amplifiers by nature. Bobs design, tracks the dynamic, reactive, variable impedance load that amplifiers actually encounter (2 to 30 ohms) when reproducing music and driving actual loudspeaker loads, increasing voltage in responce. This capacity to deliver wide voltage swings, provides a most musical and dynamic performance you would never expect from a 19 lb. amplifier. The avarage B+ or plate voltage within most tube amplifiers is 450V. This high voltage supply is the reason tube amplifiers seem so powerful and effortless for their modest power ratings, when compared to solid state transistors at maybe 70 volts. Bob designed the Black Magic 275 to operate at a powerful 685 volts B+. As Bob says, "it provides a nice wide voltage swing and lots of headroom, and the current is enough". The Black Magic 275 leverages the physics that make vacuum tube amplifiers sound great, and makes them sound even greater. 6550, KT88 and KT120 vacuum tube compatability offers a wide variety of vintage and new production tubes to experience and enjoy. The KT120 tubes we've chosen are extremely musical, with a sound that is musically exciting and detailed without being edgy. The KT120 Tung-Sol tube is tonally balanced throughout the entire music spectrum.