The 76 is a classic 5-pin UX-base medium-mu single triode vacuum tube introduced in the 1930s for voltage amplification, detector service, and local oscillator applications in early radio receivers. Electrically identical to the earlier 56 tube, it updates the heater specification to a standard 6.3V rating. Designed with an ST-12 shoulder glass envelope, it provides linear audio amplification and reliable RF performance in vintage circuits. The 76 serves as the 5-pin predecessor to later 8-pin octal types such as the 6P5 and 6J5. Available NOS and tested used.