The 6DN7 is a 9-pin miniature dissimilar twin triode engineered specifically for vertical deflection oscillator and output stages in television receivers, and later adopted by audiophiles for single-ended headphone amplifiers and small power output stages. It houses two unequal sections in one noval envelope: Section 1 acts as a voltage amplifier/oscillator, while Section 2 functions as a heavy-duty power triode capable of delivering significant plate current. Operates on a 6.3V heater and fits standard 9-pin noval sockets. Available NOS and tested used.