6AT6

Duodiode and High-Mu Triode Multi-Unit Tube, integrating two independent signal diodes sharing a common cathode with a high-gain triode voltage amplifier. Operating from a 6.3V heater, it serves as the complete AM detector, automatic volume control (AVC) loop, and primary audio pre-amplifier in vintage desktop radios, housed in a standard 7-pin miniature glass envelope (T-5.5 bulb).