The 6J7 (available in metal, 6J7G, and 6J7GT glass variants) is a classic sharp-cutoff pentode vacuum tube introduced in the mid-1930s. Designed for low-level audio voltage amplification, high-gain RF/IF amplifier stages, and detector service, it features a top grid cap to minimize grid-to-plate capacitance and noise pick-up. Extremely popular in early radio receivers and high-gain preamplifier stages, it operates on a 6.3V heater and utilizes an 8-pin octal base. Available NOS and tested used.