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

[Jim50hertz]

Not compared to a real one  ;D

Figure on around €800-1200 or so per mic, depending on capsule/transformer/tube/PSU enclosure/cable choices.

Worth it?

Yes 8)

 

[micaddict]

Best ever LDC mic design.
Does that count? :

 

[G-Sun]

Not compared to a real one  ;D

Yes, indeed

Figure on around €800-1200 or so per mic, depending on capsule/transformer/tube/PSU enclosure/cable choices.

Worth it?

Yes 8)

Good, yet still costly compared to a D-U87 or something right?

Best ever LDC mic design.
Does that count? :

Absolutely

How about difficulty and number of vendors needed?

 

[JessJackson]

Tested, sounds great with this wiring and capsule... much much better, no de-essing needed. still bright and open and smooth, probably helped by the coupling cap type.

Still 5-6db down from vintage u67 here. smh. Not the end of the world for now though. All voltages seem good. except from r10-r11 and r12-r13 very odd.

B+ (210v)
H (-6.3v)
R12 - R13 (+49.7v)
R10 - R11 (-1.83v)
Plate (+84v)

 

[0dbfs]

R12/13 @ 49V. Is that the backplate node? Lower voltage there would decrease sensitivity wouldn't it?

Thx,
jb

 

[JessJackson]

R12/13 @ 49V. Is that the backplate node? Lower voltage there would decrease sensitivity wouldn't it?

Thx,
jb

yeah exactly. It should be 59v which should continue on to remain 59v at the capsule. I'm pretty sure this is my reason for decreased output / sensitivity but my b+ is 210v exactly measured at the mic.

Can someone else measure the same point on your mics please? my bias seem ok at the top end -1.8v

Cheers

Jesse

 

[poctop]

R12/13 @ 49V. Is that the backplate node? Lower voltage there would decrease sensitivity wouldn't it?

Thx,
jb

yeah exactly. It should be 59v which should continue on to remain 59v at the capsule. I'm pretty sure this is my reason for decreased output / sensitivity but my b+ is 210v exactly measured at the mic.

Can someone else measure the same point on your mics please? my bias seem ok at the top end -1.8v

Cheers

Jesse

great news Jess ,  did you check your polarisation divider to see if they match ,
Let me know,
Dany,

 

[micaddict]

Tested, sounds great with this wiring and capsule... much much better, no de-essing needed. still bright and open and smooth, probably helped by the coupling cap type.

Good news!

Still 5-6db down from vintage u67 here.

IME the tube alone could account for that.
They vary a lot.


Henk

 

[dmp]

R12 - R13 (+49.7v)

The impedance of your multimeter can cause the voltage at this point to drop noticeably, if the meter impedance is on the order of 1-10 Mohm.

 

[dmp]

So a quick calc, neglecting the -1.8v at the end of the divider

v ~=210*(2.2M)/(2.2M+2.2M+3.3M) = 60

When you measure this, the impedance of the meter is in parallel with R12 to ground

v ~=210*(Rm||2.2M)/(Rm||2.2M+2.2M+3.3M)

I did this in a spreadsheet and if the meter impedance is 7M, the voltage drops to 49v

If you use a lower impedance meter the voltage would drop even more.

 

[JessJackson]

So a quick calc, neglecting the -1.8v at the end of the divider

v ~=210*(2.2M)/(2.2M+2.2M+3.3M) = 60

When you measure this, the impedance of the meter is in parallel with R12 to ground

v ~=210*(Rm||2.2M)/(Rm||2.2M+2.2M+3.3M)

I did this in a spreadsheet and if the meter impedance is 7M, the voltage drops to 49v

If you use a lower impedance meter the voltage would drop even more.

Thanks brother! Really appreciate these calculations although I am actually using a fluke 115 multimeter which states a rated max impedance of 30meg but I've tested 40meg resistors on it no problem.

So where does this leave me?

Cheers.

Jesse

 

[dmp]

With 30 Mohm, the voltage will only drop a couple volts. Not sure why the voltage is low. Could a resistor be wrong?
You might have to start pulling components to figure out the problem.

 

[baadc0de]

Quick question from the side.. has anyone tested both ioaudio and Oliver's transformer offerings and could weigh in if there is a significant difference between the two?

 

[JessJackson]

With 30 Mohm, the voltage will only drop a couple volts. Not sure why the voltage is low. Could a resistor be wrong?
You might have to start pulling components to figure out the problem.

Thanks bro, I'm going to run some more voltage tests in a moment when i get a minute to open it up

Jesse

 

[wave]

Quick question from the side.. has anyone tested both ioaudio and Oliver's transformer offerings and could weigh in if there is a significant difference between the two?

Tskguy and I have done this and we both thought they were very similar. That being said IMO ioaudio's trafo is slightly less saturated in the bottom.


Dave

 

[kaguenpituak]

It is posible to modify  to have a little less brightness? Only a little.. Thanks

 

[kaguenpituak]

I have a problem , I have a lot of interferences around 6-8k .. with the u87 and u47 (diy) not have. How I can remove? thanks

 

[poctop]

I have a problem , I have a lot of interferences around 6-8k .. with the u87 and u47 (diy) not have. How I can remove? thanks

what kind of capsule did you put in,  interference ? if using AMI T67 hoping you have made the proper wiring correction,
as recommended ,
best,
dAn,

 

[kaguenpituak]

I have 2 units, one with peluso k67 and another with mparts 67. The interference is caused by a lift (elevator).. in my u47 diy is less listenable, and not listenable in my u87.. I have conected the t67 correctly Thanks

 

[poctop]

I have 2 units, one with peluso k67 and another with mparts 67. The interference is caused by a lift (elevator).. in my u47 diy is less listenable, and not listenable in my u87.. I have conected the t67 correctly Thanks

wich one is problematic ?