Sensibly equivalent¶ to:
The 12SL7GT is a medium impedance double triode with high gain, it has separate cathodes and was designed for use as AF voltage amplifiers, phase splitters and where required as a cascade amplifier of very high gain.
The base cap is certainly featuring the Brimar name, BVA and Made in England, however, the lozenge on the glass looks much like an RCA product.
The 6SL7GT differs only in the fact that the heater is rated for 6.3 Volt operation.
Side view of the anodes.
The twin anodes with extended sides for fixing to the supports and adding extra radiating area for cooling up to one Watt per anode.
The wide glass tube envelope is 28 mm in diameter and, excluding the IO base pins, is 63 mm tall.
References: Data-sheet, 1043 & 1040.
Absolute Maximum Operating Conditions¶
Updated September 26, 2018. shape:wide.glass.tube construction:pinch type:double.triode age:1940.1950 base:io heater:12.6v pins:8 pin:1.g1 pin:2.a pin:3.k pin:4.g1 pin:5.a pin:6.k pin:7.h pin:8.h