53KU Cossor CV378 KB/K GZ37 ST fat shape pair audio rectifiers clean top large getter tested 100%

Description

The GZ37 aka 53KU is an indirectly heated full wave rectifier and together with the U52 the 53KU and GZ37 are the most sought after valves here at AM.

Looking at the Cossor 53KU there are two separate valve in one envelope

Cossor started production of the 53KU circa 1958

Pair of Cossor CV378 KB/K for sale here feature grey ribbed plate with large getter located in the middle of envelope.

Brown base.

A well engineered valve that lasts longer than any other counterpart, delivering excellent rectification.

Clean top and in great shape.

Both come with Cossor boxes

Tested with AVO VCM 163 with A1=A2 100% emission