Wetzel microphone on the bench

Here's a nice little tube mic for restoration. The manufacturer is Joachim Wetzel of Liepzig and looks to date from the 50s or 60s.

It is currently undergoing a recap and the capsule will be reskinned. The head amp is based on an ECC83, with two triode gain stages. There's something funny going on with this one. The power supply voltages are somewhat low, and it seems like the old diode rectifiers are causing problems. More on this later.