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Old 16th Oct 2019, 1:06 pm   #8
GrimJosef
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Join Date: Sep 2007
Location: Oxfordshire, UK.
Posts: 4,310
Default Re: GZ34 - recommended brands?

Yes. The forward voltage drop in rectifiers is one of the more dramatic differences between them. If we check the Philips data for their GZ34 here http://www.r-type.org/pdfs/gz34.pdf then we find that the results measured in 1952 (5th page of the PDF) indicate a 30V drop at 300mA but by 1958 (the next page) that's become just 18V. And that's supposed to be the 'same' valve from a single manufacturer ! I've come across Quad II amps that have had Russian directly heated rectifiers substituted for the original GZ32. These are not so different from a 5R4 which drops 75V at 300mA !

Cheers,

GJ
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