6L6G

The 6L6G is a vacuum tube in the 6L6 family, a beam-power tetrode used for audio power amplification. The “G” suffix denotes a glass-encased variant, as opposed to earlier metal versions. It was commonly used in mid-20th-century audio and radio equipment, including guitar amplifiers and hi-fi amplifiers, where it served as a power output stage device.

Construction and operation: The 6L6G comprises a thermionic cathode, control grid, screen grid, and a suppressor/beam arrangement inside a glass envelope. It is heated by a 6.3-volt supply and is designed to operate with relatively high plate voltages and appropriate bias to deliver audio power into loudspeaker loads. As a beam tetrode, it uses beam-forming plates to improve efficiency and regulate secondary emission.

Applications and legacy: The 6L6G is part of the classic 6L6 family that powered many amplifiers from the 1940s through the 1960s. It has since been superseded in most new designs by higher-rated variants such as the 6L6GC, but remains common in vintage gear and among tube enthusiasts. Manufacturers historically included RCA, Sylvania, GE, and Mullard; today, the 6L6G is mostly found as NOS stock or in reissued form, while modern players typically use 6L6GC or other modern equivalents. When replacing tubes in vintage equipment, matching and proper bias are important to preserve performance and protect the amplifier.