The AC/P1 from Mazda is an audio output triode. The short-path design was originated by Cosmos Valves in 1925. The company amalgamation took place in 1928.
Face view: the anode is opened out to the side to provide extra radiating area for anode cooling.
The single grid support with narrow loops within the anode.
A closer view of short-path construction. The grid/cathode spacing is small and this increases the mutual conductance of the valve. The insulated heater can be seen on the left.
The balloon envelope is 58 mm in diameter and, excluding the B4 base pins, is 111 mm tall.
Reference: Data Type AC/P1 was first introduced in 1928. See also1928 adverts.
