RExxx series of Telefunken is a direct-heated triode tube
that almost using in radio receiver of 40’s and 50’s era.
Include RE034, RE052, RE054, RE062, RE064, RE065, RE072d, RE074, RE084, RE102, RE109, RE112, RE114, RE122, RE124, RE134, RE144, RE152t, RE154, RE184, RE209, RE210, RE212, RE228, RE234, RE304, RE352, RE354, RE404, RE454, RE504, RE604, RE614.
Most of them produce really good sound in audio system.
Telefunken also have option and indicate with suffix like “k” mean low noise
such as RE084 & RE084k / EF804 & EF804k / EF12 & EF12k.
I just found another suffix “UX” with RE144 tube.
It is RE144 in UX4 base like 2A3 or 300B tube and use vertical plate like general tube.
Come with information & characteristic curve.
Compare with regular RE144 in B4 base.
Filament glow in the dark.
Will using in next preamplifier parafeed with line output transformer.
Cheers !!!