U67 Build

[dmp]

This is from the 1963 manual ( I think the 1500 Hz must be a typo for 15kHz )
I have not seen another Neumann doc with a different spec.

 

[dmp]

White line is the measurement through the calibration input with S2 open

 

[RuudNL]

"I have not seen another Neumann doc with a different spec."
But I have!

 

[dmp]

Looks like that specifies -5dB to -9dB at 16kHz.
I guess builders can chose how to proceed. Adjusting C17 would modify the response.
The important thing is to measure the response!

 

[soliloqueen]

It's to compensate for the capsule, I think. Those capsules changed a lot in the early days

 

[Moby]

- Getting Moby's transformer through the rectangular hole was a little tricky because of the wire leads. I pushed one side in and then worked each wire though. The wires were close to too short and I had to extend one. If the wire leads were slightly longer it would fit better. I think a 'real' u67 has the connections lower, but I didn't want them under the metal core so I put them up higher.

Original U67 has a pertinax insulation boards between PCB and the transformer core. Yes, original PCB pins are close to the transformer and since my Bv.12 is a direct replacement I produce it with the leads lenght stated in the Bv.12 winding data. Sorry because you had to improvise.

 

[dmp]

It's to compensate for the capsule, I think. Those capsules changed a lot in the early days

My understanding is the capsule was designed with a high frequency boost that was attenuated by the amplifier to have lower noise. Overall flat frequency response. The manual excerpt I posted was 1963 and the later spec sheet was 1981.
Very reasonable that there would be some capsule variation. I'm trying some differences in C17 and will post the results later.

Original U67 has a pertinax insulation boards between PCB and the transformer core. Yes, original PCB pins are close to the transformer and since my Bv.12 is a direct replacement I produce it with the leads lenght stated in the Bv.12 winding data. Sorry because you had to improvise.

Ahh, interesting. So the wire leads and bobbin don't sit through the board. That would make it simpler.
My design is inspired by but not exact copy. Anyway it works.
And I meant no criticism about your transformer, it's performance is fantastic. Just a little improvisation to fit it into my board design.

 

[Okimy123]

I designed and got the first samples this week. No major mechanical problems yet.

I'd be interested in some boards as well

 

[studiosus]

I would be in for a pair too!

 

[Moby]

My understanding is the capsule was designed with a high frequency boost that was attenuated by the amplifier to have lower noise. Overall flat frequency response. The manual excerpt I posted was 1963 and the later spec sheet was 1981.
Very reasonable that there would be some capsule variation. I'm trying some differences in C17 and will post the results later.

Ahh, interesting. So the wire leads and bobbin don't sit through the board. That would make it simpler.
My design is inspired by but not exact copy. Anyway it works.
And I meant no criticism about your transformer, it's performance is fantastic. Just a little improvisation to fit it into my board design.

I think you did it mechanically the same way as the original but you excluded the pads for the TX leads. Transformer is "sitting" on the bottom PCB but leads are connected on the bottom side. Generally speaking those pads are right under the core but as I mentioned, core is insulated with small pertinax boards (30x10mm with hole for screw). Please take a look at the photo and see the pads position. Maybe you can revise the PCB to come closer to the original.
And I meant no criticism about your transformer, it's performance is fantastic. Just a little improvisation to fit it into my board design.
No hard feelings, I just wanted to explain the situation and the reason of the wire length.

 

[Moby]

Here is the Bv.12 with the small pertinax insulators.

 

[Drosselmeier]

i decided to try to make U67. Right now trying to find any possible bugs

 

[Drosselmeier]

conversion of the Chinese copy of U87Ai into "U67"

 

[Silas]

View attachment 119068View attachment 119069
View attachment 119070View attachment 119071

conversion of the Chinese copy of U87Ai into "U67"

looks great!
Nice that it has the right switching board too - was the Chinese AI very expensive?
they seem to range in pricing across the sites…

 

[Drosselmeier]

Thnx The microphone cost the owner about $630, free shipping to Moscow.

 

[soliloqueen]

Thnx The microphone cost the owner about $630, free shipping to Moscow.

You're not allowed to link to that directly here IIRC, only discussion

 

[Kelvin Zero]

Thnx The microphone cost the owner about $630, free shipping to Moscow.

You're not allowed to link to that directly here IIRC, only discussion

I suspect that may have been a warning rather than a promotion.
It looks like the owner may have originally purchased a fake rather than a clone

 

[Drosselmeier]

I suspect that may have been a warning rather than a promotion.
It looks like the owner may have originally purchased a fake rather than a clone

the owner specifically bought this fake u87 for conversion into a u67, everything was thought out

 

[MagnetoSound]

the owner specifically bought this fake u87 for conversion into a u67, everything was thought out

How would you describe the quality of the metalwork? In particular, of the connector housing at the base and of the side rails? Does it compare favourably to the original in terms of the machining and the materials? How about the headbasket to body connection pins and the general fit of the body components?

 

[Kelvin Zero]

the owner specifically bought this fake u87 for conversion into a u67, everything was thought out

Sorry, totaly misread that. That's not gonna be a cheap project then