Neumann U67 Clone : D-U67 Tube Microphone Build Thread.

[Matt Nolan]

It can be useful when bringing up power supplies and checking internal mic connections, if you can find an old plug that is the same pinout as your valve, to solder up a dummy tube with it - high wattage resistor for the filament and lower wattage resistor for the anode-cathode path. Otherwise, just do lots of probing of voltages at every step of the way.

 

[mrerdat]

So now that I've gotten the grounding issues out of the way with the mic I'm now running into really strong RF issues at one particular studio. 

Doesn't matter where my new ground switch is toggled to, even though that affects buzz/hum.  I'm thinking that the solution might be to install R10, R11, and R12 in the PSU (pictured only in some but not all NU-67 schematics).  Is that correct?  Is the purpose of those resistors to block RF, or is it just a pad?

 

[fgan81]

Group Order SYT-5 Body.
I just started a new topic:
http://groupdiy.com/index.php?topic=63542.0

 

[vintagegear]

Hi

If I measure the 210 vdc on b+ .. I can only turn the potentiometer between 190 vdc and 200 vdc .. It won't go up too the 210vdc that's mentioned in the calibration !

What you guys think?

And even after the wiring transformer fix , I had to swap the audio + and - .. To be in phase ! Does this mean I wired something wrong in the mic?

Thx a lot

 

[TLRT]

Hi

If I measure the 210 vdc on b+ .. I can only turn the potentiometer between 190 vdc and 200 vdc .. It won't go up too the 210vdc that's mentioned in the calibration !

What you guys think?

And even after the wiring transformer fix , I had to swap the audio + and - .. To be in phase ! Does this mean I wired something wrong in the mic?

Thx a lot

I also could not get the 210V on B+ with the 56k resistors between the pot and the PCB - solution: try it with a lower rated resistor, I found that 36k is ideal(use at least 1W rated) to get the mic in proper phase just swap the cables, if the mic sounds OK, you don't need to worry.

 

[Phrazemaster]

Hi

If I measure the 210 vdc on b+ .. I can only turn the potentiometer between 190 vdc and 200 vdc .. It won't go up too the 210vdc that's mentioned in the calibration !

What you guys think?

And even after the wiring transformer fix , I had to swap the audio + and - .. To be in phase ! Does this mean I wired something wrong in the mic?

Thx a lot

I had to use a lower value resistor too.

Lots of guys had the polarity wrong so it's probably something in the pcb. Fix is what you did swapping the pin 2-3 wiring to the xlr.

 

[vintagegear]

Thanks for the info..

It worked with a 35kohm resistor! Thanks a lot!

One more question.. 

What about the low cut? I feel it's rather high.. Is it from 200hz down?
Too much low is cut off..

Can we change a value somewhere to make the low cut start around 100hz maybe?

I'll try taking the jumper out  to see if that is satisfying!

And can I tweak the circuit to make it less sibilant and less high end? Still a bit too bright in a way..

(ami t 67 +k6 beesneez)


Still the best mic I've ever had in my studio

Thx
Grts

 

[micaddict]

What about the low cut? I feel it's rather high.. Is it from 200hz down?
Too much low is cut off..

There are two low cuts.
One is at 30 or 40 Hz (depending what you measure). This one is on or off "permanently" (S2).
The other is at 200 Hz and  is switched on or off, on the body, below the basket.

And can I tweak the circuit to make it less sibilant and less high end? Still a bit too bright in a way..

If the build is executed properly (and with all parts functioning like they should) the very last thing a U67 should be is bright and sibilant.

 

[poctop]

Thanks for the info..

It worked with a 35kohm resistor! Thanks a lot!

One more question.. 

What about the low cut? I feel it's rather high.. Is it from 200hz down?
Too much low is cut off..

Can we change a value somewhere to make the low cut start around 100hz maybe?

I'll try taking the jumper out  to see if that is satisfying!

And can I tweak the circuit to make it less sibilant and less high end? Still a bit too bright in a way..

(ami t 67 +k6 beesneez)


Still the best mic I've ever had in my studio

Thx
Grts

have you been using the corected wiring for T67 in the firsta page of this thread,
let me know ,
Dan,

 

[micaddict]

Yup, that would have been my next post and question.

But Dan asked it before I did and you're in better hands with him anyway. 

I'll just say that I wouldn't know a condenser microphone that is a better sibilance killer than  the U67.
So don't rest before it does that.

 

[vintagegear]

Hi Dan

Yes I think so..  But maybe it confused me..

I did it like this..

4--- t44
10---t1010
12---t1212
5---t55
7---t77
1---t11

Maybe I took the right wiring scheme and applied the fix that would be stupid lol

Thx for the replies everybody

Grts

 

[poctop]

from page 1

this is the corrected AMI T67 wiring ,  ;D

Pad 5 ----->  mic pcb pad T1212
Pad 12 -------> mic pcb pad T55
Pad 1 --------> mic pcb pad T44
Pad 4 --------> mic pcb pad T11
Pad 7 --------> mic pcb pad T1010
Pad 10 ------> mic pcb Pad T77

 

[vintagegear]

Hi

Thanks for replying..
I am switching the wiring right now..

I was wondering why the valvo e80f isn't working like the ef86 in the mic?

I only get this weird static and no sound.. Any ideas?

 

[ln76d]

Hi

Thanks for replying..
I am switching the wiring right now..

I was wondering why the valvo e80f isn't working like the ef86 in the mic?

I only get this weird static and no sound.. Any ideas?

Bad tube, or wrong tube (do you have visibe label on the tube?).
Remember that E80F sucks more current than EF86. There could be need a  little adjust the circuit.
Also heater should be as spec. shows 6.3V.  Overheating or underheting not recommended.

 

[Phrazemaster]

Bad tube, or wrong tube (do you have visibe label on the tube?).
Remember that E80F sucks more current than EF86. There could be need a  little adjust the circuit.
Also heater should be as spec. shows 6.3V.  Overheating or underheting not recommended.

How do you KNOW so much?!

Thanks!!

 

[vintagegear]

Hi

Which tubes you think  works
best in this mic?

Or is the difference between brands hardly noticeable?

It was this tube I tried that didn't work properly..  Ill attach a pic

It's a larger tube.. Red markings valvo.. With gold pins

Thx

 

[TLRT]

Hi

Which tubes you think  works
best in this mic?

Or is the difference between brands hardly noticeable?

It was this tube I tried that didn't work properly..  Ill attach a pic

It's a larger tube.. Red markings valvo.. With gold pins

Thx

Most of the people will say Telefunken EF86/EF806S, I tried many of them the Teles are perfect, NOS Philips/Siemens are also great, and we have many NOS Tungsrams, the industrial/military versions are very good quality with very good noise levels(even compared to the Teles)

 

[ln76d]

Hi

Which tubes you think  works
best in this mic?

Or is the difference between brands hardly noticeable?

It was this tube I tried that didn't work properly..  Ill attach a pic

It's a larger tube.. Red markings valvo.. With gold pins

Thx

Attachement doesn't work.

Yes i know E80F very well
In my opinion it's much better than any EF86.
I tried it against EF806 and many different EF86 including Tele.
From what i know Valvo/Philips/Mullard are the same tube with different logo.

 

[Lordward]

Hello! I'm trying to figure out if the 3 switches in mic are on-off-on or on-on or both or neither....
Any clarification would be greatly appreciated!

DW

 

[ln76d]

Hello! I'm trying to figure out if the 3 switches in mic are on-off-on or on-on or both or neither....
Any clarification would be greatly appreciated!

DW

All three can be both type.