6R7 Double diode triode, verschillende merken
The 6R7 is a double diode triode. The 6R7 was designed for radio receiver use and in the classic superhet broadcast receiver, such a valve would provide signal and AGC rectification, followed by the voltage amplifier triode to feed the output stage.
In the 1940s the 6R7 was re-designed into a single-ended version without the top cap, this is the 6SR7. The 'S' indicates a single-ended version.
The thin metal tube envelope is 25 mm in diameter, and excluding the IO base pins, is 62 mm tall.
The 6R7 was first introduced in 1936.