Sensibly equivalent¶ to:
The KT81 is the first M-OV kinkless tetrode audio power valve with a pressed glass foot. We can not find details of how it performed in the market place, but it was not a valve produced for many years. The KT81 appeared in 1947 and by 1951 this valve was being described as an obsolescent Type.
Produced by M-OV this example is branded Osram and our other KT81 exhibit is branded Marconi.
The detail photograph shows the M-OV identification on the envelope.
The wide glass tube envelope is 31 mm in diameter and, excluding the B8B base pins, is 68 mm tall.
References: 4018 & 1040. Type KT81 was first introduced in 1947.
Absolute Maximum Operating Conditions¶
Updated January 13, 2013. shape:wide.glass.tube construction:all.glass type:beam.tetrode age:1940.1950 base:b8b heater:6.3v pins:8 pin:1.h pin:2.a pin:3.g2 pin:4.ic pin:5.ic pin:6.g1 pin:7.k pin:8.h