The 1LA4 is a battery audio output valve. With a 27,000 Ω load the output can be up to 115 mW. The 1AL4 is high impedance pentode. It is a Loctal based valve and the 1A5G is the octal alternative.
The oval anode from the side.
The Type designation is etched into the top of the envelope in the traditional RCA octagon.
The wide glass tube envelope is 29 mm in diameter, and excluding the B8B base pins is 56 mm tall.
Reference: Data-sheet. Type 1LA4 was first introduced in 1940. See also1940 adverts.
