Sensibly equivalent¶ to:
The 6SK7 is a variable μ pentode for RF and IF amplifiers in superhet receivers. Essentially the S stands for single ended so the 6K7 had a top cap and this later development did not.
The gain of the device being controlled by a negative voltage derived from rectifying the final IF signal. In this way strong signals do not overload the receive chain because the various controlled stages have their gain reduced.
The 12SK7 had identical characteristics apart from the heater. The 12.6 Volt heater being used directly across a vehicle battery.
The thin metal tube envelope is 25 mm in diameter and, excluding the IO base pins, is 51 mm tall.
References: Datasheet, 1040 & 1043. Type 6SK7 was first introduced in 1938.
Absolute Maximum Operating Conditions¶
Updated February 28, 2013.