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Rectifier Hum

Posted by datman on March 13, 2017 at 19:24:08:
I recently tried an experiment with my amp. I substituted a NOS Mullard GZ34 for a 5U4GB. Where there was NO noise or hum with the 5U4GB, the GZ34 hums. I have two of them and substituted one GZ34 for the other GZ34. The hum decreased but did not go away. I Thought full wave rectifiers are interchangeable as long as the voltage differences are accounted for.

My problem is that while it hums, I like the sound of the GZ34. Any ideas what might be causing this?