Sensibly equivalent¶ to:
256 A256 C-56 CV611 ER56 G-56 PH256 PH56 VT-56
The Type 56 is an indirectly heated audio triode on an American UX5 base. The later Type 76 is the same valve but with a 6.3 Volt heater.
The electrodes seen in close-up. The blackened anode obscures the grid, but the spacing of the wire can be seen from the notches in the wire supports as they protrude above the mica. The cathode tube is round and matched the anode, this suggests that the grid will also be formed as a spiral.
Many thanks to Simon Balderson for donating these images and valve details.
The classic envelope is 39 mm in diameter, and excluding the UX4 base pins is 90 mm tall.
References: Data-sheet & 3002. Type 56 was first introduced in 1932.
Absolute Maximum Operating Conditions¶
Updated February 15, 2013. shape:classic construction:pinch type:triode age:1930.1940 base:ux5 heater:2.5v pins:5 pin:1.h pin:2.a pin:3.g1 pin:4.k pin:5.h