EL509 / EL519 / 6KG6 / PL509 / PL519
The EL509 and EL519 series and their 40 V filament variants, the PL509 and PL519 are beam power tetrodes designed for use in linear transmission equipment. The 519 or PL519 are simply more powerful. Even today they are still produced due to their demand and excellent performance in transmitting equipment but, naturally, they have also been used with great success in AUDIO frequency, we remember the mythical and esoteric E.A.R. productions.