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

[Greenie]

What is the correct psu for the U67, I have at the moment 3 pcbs for 3 u67 builds but they alle seem to be different?

 

[EarthTone]

What is the correct psu for the U67, I have at the moment 3 pcbs for 3 u67 builds but they alle seem to be different?

Dany’s boards are usually green and have his name on them.

 

[dmp]

The upper left is from Poctop, the upper right is VAMIsound (find on FB)
Never seen bottom before

 

[Greenie]

What I am wondering about is if there one schematics for a U67, or if the Psu follows the build, that is called a U67, but isn't? Since the three pictured PSU's are so different, but meant for the one mic?

 

[dmp]

Compare to the Neumann schematic if you want it the same.

 

[Whoops]

What I am wondering about is if there one schematics for a U67, or if the Psu follows the build, that is called a U67, but isn't? Since the three pictured PSU's are so different, but meant for the one mic?

There’s many different ways to “skin a cat”.
From an operational point of view you just have to feed the mic the correct voltages. The original circuit was designed more than 60 years ago so there’s many different circuits nowadays that could achieve the same thing.
Some people seem to like the sound of the mic with the original PSU circuit.

Like dmp said, follow the original schematic and check which is similar

 

[egroys]

So I wired my Moby transformer as instructed on the spec sheet and my polarity is inverted.
Is it OK to simply flip pins 2&3 in the PSU output or what is best?

 

[Moby]

So I wired my Moby transformer as instructed on the spec sheet and my polarity is inverted.
Is it OK to simply flip pins 2&3 in the PSU output or what is best?

Yes, you can flip them at the PSU or inside the microphone side.

 

[egroys]

Yes, you can flip them at the PSU or inside the microphone side.

Thanks, @Moby! Is this normal?
My Cinemag in my 87 is exhibiting the same behavior and I have it wired to spec...

 

[Moby]

Thanks, @Moby! Is this normal?
My Cinemag in my 87 is exhibiting the same behavior and I have it wired to spec...

I don't know. Really. I'm not the designer of the PCB. Luckily, only two wires has to be swapped.

 

[egroys]

I don't know. Really. I'm not the designer of the PCB. Luckily, only two wires has to be swapped.

Thank you! @poctop can you comment on this?

 

[Greenie]

On the vintagemicrophonepcbkit for the U67 there is a part called "c17str1". What could that be, it's polarized?

 

[ratrace]

On the vintagemicrophonepcbkit for the U67 there is a part called "c17str1". What could that be, it's polarized?

it is styroflex (100pf) , you can buy it from vintagemicrophonepcbkit.

 

[EarthTone]

On the vintagemicrophonepcbkit for the U67 there is a part called "c17str1". What could that be, it's polarized?

The above answer is correct and to answer the polarization question regarding that part: No. That part is not polarized and you need to buy it from Dan when you order the pcb kit from his website vintagemicpcb.com

 

[Greenie]

Thanks I did, it just has the pluss sign on the board. Got me a bit confused.

 

[EarthTone]

Thanks I did, it just has the pluss sign on the board. Got me a bit confused.

Really? On the spot for the styro cap? Plus signs can also be voltage divider indicators or if it is theoretically possible to use a tantalum capacitor in that location, then you would want to know the polarization on the board since those caps are polarized. I would consult with the author of the PCB if you have uncertainties. Is!’t there a killer step by step guide for this build with pictures? I have read it before. Should clarify any foggy steps I’d imagine.

 

[Greenie]

Really? On the spot for the styro cap? Plus signs can also be voltage divider indicators or if it is theoretically possible to use a tantalum capacitor in that location, then you would want to know the polarization on the board since those caps are polarized. I would consult with the author of the PCB if you have uncertainties. Is!’t there a killer step by step guide for this build with pictures? I have read it before. Should clarify any foggy steps I’d imagine.

I bought this pcb many years back, maybe it changed?

 

[dmp]

Thanks I did, it just has the pluss sign on the board. Got me a bit confused.

The (+) sign tells you which side of the capacitor has higher voltage (in this case it is high, B+). The part footprint in the design software simply had a polarization symbol. It is information, no more no less. It is not telling you what kind of cap to use, other than to use use a cap rated to withstand 120 VDC.
You could use a film, ceramic, or polystyrene, as long as it is rated at greater than 120v.
If you want the paint-by-numbers answer to follow the crowd, use the polystyrene. Avoid heating it too much as they are more fragile to heat than other types.

 

[aharmonson]

Hi I'm running into the following issue(s),

All around there is a lot of white noise and ground hum. I'm only getting a solid signal from one side of the figure 8 setting, otherwise the signal is weak all around. The high pass and pad switches seem to be working fine. The heater and B+ voltages checked out fine.

 

[egroys]

I just moved into a new studio so I recalibrated my PSUs to match the higher voltage here. I have a power conditioner (for my rack) and I anm averaging between 121-125v whereas my previous studio was 115-119v.

I’m curious how the fluctuations in my new space affect my mics and if this is something I should consider when setting heater and polarization. Is it a good idea to use a UPS with automatic voltage regulation or is that overkill?
Thank you in advance!