6x8.,6fh8, 6fa7, 7591, 5u4

best vintage audio vacuum tubes, (valves) for tube preamps, tube amplifiers, phono stages, stereos, guitar amplifiers, microphones, recording studio equipment, radios, ham radios, jukebox; ge, rca, mullard, telefunken, western electric, sylvania, raytheon, westinghouse, tungsol, siemens, philips, valvo, marconi, brimar