Neumann U 47 Clone - A DIY Bachelor Thesis

But i thought that the dropping resistor is serially connected to the heater resistance. And because this thing is broken and has a infinit resistance all the voltage is measured at this point. (Hard to translate)

What tube are you using?

If it is Andreas's FET solution 108VDC at the 5 of the tube is way high it should be between 35-40VDC!

Is the 29 OHM resistor still referencing ground correctly?

the 1780 Ohm resistor must be soldered between 5 pin on the tube socket, and pin 3 on the basis socket of the microphone ( on pin 3 : 105вольт comes from the power supply) . If the resistor 1780 Ohms is connected otherwise -  it will not work. 

Zottel said:

But i thought that the dropping resistor is serially connected to the heater resistance. And because this thing is broken and has a infinit resistance all the voltage is measured at this point. (Hard to translate)

Click to expand...

Yes, that is right. If the heater is broken, then it is drawing no current and you will measure a high voltage at the dropping resistor - same voltage at both ends?

So yes Andreas told me that the heater is broken. 

Not sure what to do now. I tried everything! All seems very fine! I guess i will try to place a normal resistor, with the resistance value of the heater, between the two tube pins so I can check the voltage.

(All this stuff would be no problem if there wouldnt be a strict timeline for my thesis  :-\ )

Today I used some 5 Watt resistors to create a 930 Ohm replacement for the heater of the tube. With this one I wanted to make sure that everything was working fine. So in case I get a new tube it won’t be my fault if it breaks.  :

So strangely everything looks fine! The dropping resistor drops the voltage it should and I was able to measure a heater pin Voltage at the tubesocket of about 36.8 Volt.

Your 1,78 kOhm resistor is connected to pin5 or pin 6 of tube socket? It is very important!

Connected to pin 5. This was done with andreas advice.

Hey guys,

today i got a new tube from andreas. Checked everything and this is what happens when i turn on the mic:
https://dl.dropboxusercontent.com/u/56430716/humming.mp3

The Volt's at the tube measure right. Everything looks fine.  :'(

Zottel said:

Hey guys,

today i got a new tube from andreas. Checked everything and this is what happens when i turn on the mic:
https://dl.dropboxusercontent.com/u/56430716/humming.mp3

The Volt's at the tube measure right. Everything looks fine.  :'(

Click to expand...

Is the mic fully assembled, head-grille and all, or is some of it open?

I’m an idiot. When I started it for the first time, it was fully assembled. There was no sound so I turned it off after 10 seconds (prevent damage  ). Unscrewed all of the parts and measured the voltage whilst still listening to the output. When the hum began I was completely confused. Searching for a problem that didn’t exist. After some cigarettes I realised… “Dude… put on the fucking enclosure and try it again. The tube needs some time to power up!”  :

It’s a crazy thing! Sometimes I worry too much about the stuff I do.  :
Its working! 

What a great project! I'm glad it works!

Howdily doodily neighborinos!

I went to Berlin to record some A/B files. You can download them via my dropbox link:
https://dl.dropboxusercontent.com/u/56430716/AB%20DIY%20U47.rar

If you’d like to guess which microphone is the original U47 and which one is mine… Do it! 
I think there are some differences, some might have its origin in the mic placement differences, some might be caused from the mic itself. A/B are changed. So if you think the file “Drum A” might be the real U47 don’t think it will be the same at the guitar, etc.  . Levels are matched via Impulses. Some pictures:





If you don’t know it: There is a cool tool to to ABX Test. Just google foobar2000 ABX. if your doing it with this software you could send me your results. The only requirement i have: please use headphones if youd like to submit your results

Anyway, if you just like to have some fun with the files. Feel free 

Hello,

I read about your project. it is very interesting.

I myself have compiled a clone U47 with tube 408a (parallel) and nuvistor (13.6 V) - both playing perfectly, but the problem is a bit of heat (nuvistor not such consumption watts as VF14 or two 408a).

I listen to your test. I think this:

U47 played here:
Acustic G - Track A
Piano - Track B
Vocals - Track B
drums - Track B

Of course I could be wrong.

Only quick listening on the headphones:

U47:
Git A
Drums B
Piano A
Vocals A

I will verify that in a free time ;D

I think I'll post the solving next weekend.

Could be interesting what kind of feeling you guys have. Why do you think the one file is a U47 and the other is my Mic?

bro just post what mic is the recordings. no one wants that gearslutz guessing games on here!

Jesse

no wait! I want to do a gues....... 

Hi Zottel, could you please  resize your photos to a way smaller size? On a mobile device even with WLAN it lasts for minutes to load those XXXL photos! During this time the IOS browser is blocked, so one cannot follow your interesting thread here without a huge delay.

Thanks a lot!

cheers