The 40B2 tube, also known as a 6L6GC, is a beam power pentode vacuum tube. It is most often used as an audio power amplifier in electric guitar amplifiers, public address systems, and other audio applications. It was introduced by RCA in July 1936 and was adopted as a replacement for the underperforming 6L6GC. It was designed to have similar characteristics to the 6L6 but with improved power, higher efficiency, and better sound quality. It is capable of producing up to 33 watts of power. The 40B2 has a diode cathode cap, an indirectly heated oxide coating, a long plate structure, and uses a beam plate that can allow a greater plate voltage than the 6L6GC. Its characteristics are ideal for high power audio circuits and make it ideal for use in guitar amplifiers.