The 6K11 is a triple triode in a single envelope. Two triodes (2 and 3) are high μ types similar to the triodes in the 12AX7 and the third triode is similar to the 12AU7 and is medium μ with a higher anode current.
The Westinghouse name. Behind the star on the glass is triode two.
The central section has copper grid supports and is the medium μ triode.
The dome carries the Type designation and USA. The layout of the triodes can be seen from the top mica.
The wide glass tube envelope is 28 mm in diameter and, excluding the B12C base pins, is 36 mm tall.
Reference: Data-sheet. Type 6K11 was first introduced in 1960. See also1960 adverts.
