GZ34

The GZ34 (5AR4) is a full-wave indirectly-heated rectifier developed by Mullard, capable of delivering up to 250mA with a relatively low voltage drop (~15V under full load). Its indirectly-heated cathode provides a slow, controlled warm-up that functions as a built-in soft-start for the power supply, gradually bringing B+ voltage up to operating level and extending the life of other tubes in the circuit. The GZ34's combination of high current capability and low voltage drop makes it the most capable of the common audio rectifiers. Mullard f32 and f33 coded fat-base versions from the Blackburn factory are the most prized, followed by Philips Heerlen and Amperex production.