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

[Delta Sigma]

Hi, thanks. My schematic reading skills are far from good. I am already in contact with Moby ( great help, amazing  dude) but I thought of asking somebody that has already installed in this kit. If it’s not too much trouble of course. Thanks again.

I understand your reasoning. Which PCB set did you order? AMI or Max K? The AMI PCB is shorter; the Max K PCB takes up almost the entire internal area as Max's transformer is PCB mount.

 

[Purplenoise]

I understand your reasoning. Which PCB set did you order? AMI or Max K? The AMI PCB is shorter; the Max K PCB takes up almost the entire internal area as Max's transformer is PCB mount.

Hi, thanks for responding. I have Dan’s pcb from vintage microphones with the extra small pcb for bv12 mounting. I believe though this is just for mounting and the bv12 connects straight to the main pcb. Thanks again.

 

[Delta Sigma]

You have a small PCB for just the transformer? That's good! That'll make it easier to mount your Moby BV.12. I'll check my notes today and you can compare to the markigns on your PCB.

 

[Moby]

You have a small PCB for just the transformer? That's good! That'll make it easier to mount your Moby BV.12. I'll check my notes today and you can compare to the markigns on your PCB.

Hey Delta Sigma, do you want me to send you my wiring guide so you can compare and confirm it?

 

[Delta Sigma]

Hi, thanks for responding. I have Dan’s pcb from vintage microphones with the extra small pcb for bv12 mounting. I believe though this is just for mounting and the bv12 connects straight to the main pcb. Thanks again.

It looks like Dany's PCB numbers the transformer leads in the same order they're shown on the schematic. The confusing part will be the duplicate colours. I have the spool numbers marked on the schematic so you'll have to refer to them. You'll have to confirm with an ohm meter to identify correct leads.

In other words, one of the two greens on spool 2 will have continuity with one of the whites. When you identify which green/white they are PCB pads 9 & 10. The remaining spool 2 green is pad 3 and the remaining spool 2 white is pad 12.

I tried snapping a picture of my PCB but the pads weren't visible under the transformer. I'd have to pull it apart and I don't have time right now.

 

[Purplenoise]

It looks like Dany's PCB numbers the transformer leads in the same order they're shown on the schematic. The confusing part will be the duplicate colours. I have the spool numbers marked on the schematic so you'll have to refer to them. You'll have to confirm with an ohm meter to identify correct leads.

In other words, one of the two greens on spool 2 will have continuity with one of the whites. When you identify which green/white they are PCB pads 9 & 10. The remaining spool 2 green is pad 3 and the remaining spool 2 white is pad 12.

I tried snapping a picture of my PCB but the pads weren't visible under the transformer. I'd have to pull it apart and I don't have time right now.

Thank you so much for taking the time to share this info, I really appreciate it. This is very helpful. When I have everything down and working properly  I’ll take and post pics. Between this and mobys info I believe I can come up with a solid connection. Thanks again to you and Moby for your time and expertise

 

[emrr]

Delta Sigma's color chart looks right to me.  The Moby and the current Neumann both follow those color codes. 

 

[Purplenoise]

Delta Sigma's color chart looks right to me.  The Moby and the current Neumann both follow those color codes.

Thank you so much, one more question. Do the black wires from bv12 go to pad 7 on pcb? Thanks

 

[Moby]

Thank you so much, one more question. Do the black wires from bv12 go to pad 7 on pcb? Thanks

Black wires are shield and it has to be on ground

 

[Delta Sigma]

A little update on my 67 with a Beesneez capsule and Moby transformer. I felt the change was quite significant but I had only had time to use it at home in an untreated room. I finally fired used it at a friend's studio and we were all blown away.

I have built an M49, 251 and EF47 as well and they all have places where they shine (esp the 47 and 251). If I could only have one of the four mics though, it would have to be the 67. I'm so happy with it now.

 

[xarolium]

Hi there,

I finally finished my U67 build and it seems to work except that i can't set 210VDC on the plate. I only have 193VDC the pot full CCW. I use EF806S Tube. Could it be why i can't set 210VDC ?

No problem with the Heather .

Thank you for your help
Best regards,
xarolium

 

[Delta Sigma]

Hi there,

I finally finished my U67 build and it seems to work except that i can't set 210VDC on the plate. I only have 193VDC the pot full CCW. I use EF806S Tube. Could it be why i can't set 210VDC ?

No problem with the Heather .

Thank you for your help
Best regards,
xarolium

The power supply is designed for a wide range of wall voltages, components and loads (mic amp tubes) but it does not catch all. You're drawing more current than expected (not necessarily a bad thing) so the voltage drops on your power supply resistors R1 and R3 is too much so that when you turn your pot in series with R3, your drop is still too much.

Depending on how much current you're drawing, you could change the values of R1 and R3. The easiest way to do this is put resistors in parallel with R1 and R3. Choose resistors larger in value to start like 10k and 15k and see if you can dial in the voltage you need.

Make sure you re-check voltages as you tube burns in.

 

[xarolium]

The power supply is designed for a wide range of wall voltages, components and loads (mic amp tubes) but it does not catch all. You're drawing more current than expected (not necessarily a bad thing) so the voltage drops on your power supply resistors R1 and R3 is too much so that when you turn your pot in series with R3, your drop is still too much.

Depending on how much current you're drawing, you could change the values of R1 and R3. The easiest way to do this is put resistors in parallel with R1 and R3. Choose resistors larger in value to start like 10k and 15k and see if you can dial in the voltage you need.

Make sure you re-check voltages as you tube burns in.

Thank you for your fast replay. I will try it tomorrow.

After spent 2 hours testing my U67, i notified a very small background noise when polarity is Cardio. Like fire . Nothing appear when Omni or 8.
Any idea where this noise come from ?

Best regards,
Vincent

 

[Delta Sigma]

Thank you for your fast replay. I will try it tomorrow.

After spent 2 hours testing my U67, i notified a very small background noise when polarity is Cardio. Like fire . Nothing appear when Omni or 8.
Any idea where this noise come from ?

Best regards,
Vincent

I believe that in cardioid, the pattern switch is open . This means the rear diaphragm is floating. If you have any oil from your fingers, leftover flux, etc anywhere in the rear diaphragm section there could be noise from the rear diaphragm.

Careful cleaning with alcohol around styroflex caps if you used them.

 

[xarolium]

I believe that in cardioid, the pattern switch is open . This means the rear diaphragm is floating. If you have any oil from your fingers, leftover flux, etc anywhere in the rear diaphragm section there could be noise from the rear diaphragm.

Careful cleaning with alcohol around styroflex caps if you used them.

Thank you, i will do it

 

[xarolium]

After replacing the 56K resistor in series with the Plate potentiometer with a 39K i can reach the 210VDC.
I notified that background noise is far now but still a little present.
I will try with a better preamp maybe it comes from my very cheap preamp i use for my test.

Thank you for your reply

 

[Moby]

After replacing the 56K resistor in series with the Plate potentiometer with a 39K i can reach the 210VDC.
I notified that background noise is far now but still a little present.
I will try with a better preamp maybe it comes from my very cheap preamp i use for my test.

Thank you for your reply

  Don't forget to give tube some time to burn in. I usuaually burn in the tube for at least 48h . After that you can expect (not always) significant noise improvement.

 

[xarolium]

  Don't forget to give tube some time to burn in. I usuaually burn in the tube for at least 48h . After that you can expect (not always) significant noise improvement.

What do you mean by "burn the tube".
You think let the Mic plugged with PSU on ?

 

[Purplenoise]

Ok, build finished and calibrated. Original k870 capsule, Moby bv12 and a really nice Amperex bugle boy tube. Dead quiet and gorgeous sounding. On Monday I’ll shoot it out with a U67 reissue.
I run into an issue with the psu transformer until I realized it should be wired differently than what the instructions indicate. Primary 1 and 3 should be jumped as well as 2 and 4.
Thanks a ton to the members helping me out with the bv12 wiring and also Dan for such an awesome kit. Cheers.

 

[Avgatzeblouz]

Ok, build finished and calibrated. Original k870 capsule, Moby bv12 and a really nice Amperex bugle boy tube. Dead quiet and gorgeous sounding. On Monday I’ll shoot it out with a U67 reissue.
I run into an issue with the psu transformer until I realized it should be wired differently than what the instructions indicate. Primary 1 and 3 should be jumped as well as 2 and 4.
Thanks a ton to the members helping me out with the bv12 wiring and also Dan for such an awesome kit. Cheers.

Awesome ! Let us know about the shootout and don't be shy to post audio examples !