The 6Q7 and 6Q7G are 8-pin octal duplex-diode high-mu triode vacuum tubes introduced by RCA in the mid-1930s. Designed for multi-function service in superheterodyne radio receivers, they combine two signal diodes for detection and automatic volume control (AVC) with a high-mu triode section for audio preamplification in a single envelope. The standard 6Q7 features a metal envelope for integral shielding, while the 6Q7G utilizes a classic ST-12 shoulder glass envelope. Both feature a top grid cap for high isolation on the triode control grid, operate on a 6.3V heater, and fit standard 8-pin octal sockets. Available NOS and tested used.