Joachim Wetzel tube mic

[ruffrecords]

Hello Ian, thank you so much for your help.

I know that these microphones had different versions, and there were Hi-Z unbalanced out, like my mike, and there was also a balanced output versions with a transformer.
Could the second half of the ECC83 be used only for the balanced with transformer versions of the mic?

I can wire it that way, just need to get a proper transformer for it.

I recommend you get it working with the Hi-z output first. The you could try connecting  the output cap to the second cathode which will give you a low impedance output.

In the meanwhile, I discovered that when the transformer was rewinded the primaries and secondaries wire colors were swapped, so I changed the connections accordingly and the voltages are as follows.
The Heater voltage seems to be spot on now.

With mic connected to PSU (230VAC mains power):

B+
Ramps to 338V at power on and then settles at:
218VDC

Heater (tube heaters wired for 12V,  6,3V lamp in series with the heater out)
12.8V

That would explain all your previous symptoms. Looks like it should wok now.

Cheers

Ian

 

[Whoops]

The Mic output is connected to a 1M2 Log potenciometer that then has a female output jack

here are some pictures of the PSU after the recap job:

 

[Whoops]

I tested the microphone and it sounds fine.

Pluged the Hi-z unbalanced output to the Hi-Z input of my console.

In some places on the internet this mic is described as Omnidirectional, but it testing the mic it seems to me it's cardiod and not omni.
Also to achieve an omni polar pattern didn't 2 capsules had to be used?


I would like to replace the original mic cable, it's a 4 conductor unshielded cable (1 Heater,  2 Masse+ground, 3 B+,  4masse+ground), with a Shielded cable.
As the enclosure is made of plastic (only the panel is metal) I think I will shield and ground the plastic interior glueing copper foil and connecting it to ground (like it's done on guitars)
There's some residiual noise on the mic and that might help a litle bit to reduce the noise.

I would like also to modify the mic signal output , for a Low-Z balanced connection with an XLR.
What transformer could I use for this ?

thank you so much

 

[PRR]

I don't understand why the audio out is taken from the B+ terminal. ...

https://el34world.com/Forum/index.php?topic=24352.msg261650#msg261650

 

[rock soderstrom]

In case someone wants to buy such a mic, here is a link to an offer on ebay Kleinanzeigen/ germany.

Note the circuit diagram

https://www.ebay-kleinanzeigen.de/s...ampaign=socialbuttons&utm_content=app_android