The A15 from Hivac was called the All-Stage valve and was designed to be used in all stages of a receiver. The design utilised the work of Harries on critical distance valves.
Nice idea but not as effective as using valves optimised for particular stages. Overall not a commercial success.
The wide pinch.
Looking up from the base. The insulated heater wires and the lead to the cathode are easily seen. The wide diameter anode comes from the critical distance research.
The top of the valve with the multiple wire grids.
The cathode has rounded ends and flat sides.
The mass of grid wires. The notch and peen method of fixing the wire to the support can be seen in the foreground.
The classic envelope is 46 mm in diameter and, excluding the IO base pins, is 115 mm tall.
References: Data & 1043. Type A15 was first introduced in 1937. See also1937 adverts.
