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

[Murdock]

I’m also interested in this topic. Maybe we should start a separate thread about it.

 

[rock soderstrom]

I’m also interested in this topic. Maybe we should start a separate thread about it.

Good idea I plan to test it in the next weeks.

 

[klem]

Can anyone speak to what version or revision number or year, etc Dan's u67 PCBs are?
E.g., in searching U87 thread, I see those PCBs are reflective of Neumann's revision 16 + phantom power filtering from revision 21 + battery meter omitted.

 

[doqmemory]

Can anyone speak to what version or revision number or year, etc Dan's u67 PCBs are?
E.g., in searching U87 thread, I see those PCBs are reflective of Neumann's revision 16 + phantom power filtering from revision 21 + battery meter omitted.

The schematic used is shown on the first page.

 

[klem]

the schematics on the first page show dany's re-drawings, and there's no mention of what year or version in the thread AFAIK (and yes, i've both searched and read the entire 93 pages). in the build folder, indeed linked on first page, there are a few historical documents of years ranging from 1960, 63, 66... i do see a mic-side only schematic from neumann dated 1960, but no original psu schematic. i've no idea if PSU design changed over time. since different features were introduced in its original lifespan, and given dan blended multiple versions into the 87 PCBs, i was just curious about the history of these PCBs. short of retracing dany's schematics to the mic side one in the build folder (which still wouldn't help clear up PSU side), i thought simply asking in the build thread would be a better use of time. so, could you clarify any further? am i missing something basic that your reply seems to suggest?

 

[doqmemory]

the schematics on the first page show dany's re-drawings, and there's no mention of what year or version in the thread AFAIK (and yes, i've both searched and read the entire 93 pages). in the build folder, indeed linked on first page, there are a few historical documents of years ranging from 1960, 63, 66... i do see a mic-side only schematic from neumann dated 1960, but no original psu schematic. i've no idea if PSU design changed over time. since different features were introduced in its original lifespan, and given dan blended multiple versions into the 87 PCBs, i was just curious about the history of these PCBs. short of retracing dany's schematics to the mic side one in the build folder (which still wouldn't help clear up PSU side), i thought simply asking in the build thread would be a better use of time. so, could you clarify any further? am i missing something basic that your reply seems to suggest?

The first post has the mic schematic right above the Neumann schematic. Not sure what else you want. If you want some sort of history of the U67 circuit versions and what one this represents, then no, that is not discussed in this thread, as far as I can remember.

 

[dmp]

An early u67 mic schematic does not have c17. I don't know of other differences. I've only seen one psu schematic.

 

[C12VR]

I've gone through and rechecked the ground scheme, tidying up some points, but I still have an annoying buzz on the signal. It's neither high frequency hiss nor 60 or 120hz AC noise. it sounds like stratocaster pickup buzz. What could this be? I notice that it gets worse, not better, when the 10db pad is engaged. Faulty polystyrene cap? Any ideas would be appreciated.

 

[vitopower]

That’s great to hear. The wimas don’t really matter for sound but I went back to the red ones cause I thought it sounded a little harsh compared to my first...maybe just paranoia haha.
I have tried many coupling caps and I ended up with the 1839 for the first and an Illinois electrolytic for the second ( I wanted to keep it as close to the reissue...the Illinois I think sounds better than the nichicon). The best and smoother cap was two wet tantalum 1uf 150v in series but I had some noise and I took them out. One of them was leaky I think.
Something else to try is a thin piece of foam in the headbasket, 3mm 30ppi or 3mm 60ppi. They sell those at air filter supplies. Brings the response even closer to a 67 which has a smaller and 3 layer headbasket.

I noticed a little hardness/edginess in the high end like a few posters have mentioned and will give this a try... but this is open cell foam. Are you putting it inside the headbasket, and if so, wouldn't you be concerned about it storing moisture and eventually shedding on the capsule?

 

[Whoops]

I've gone through and rechecked the ground scheme, tidying up some points, but I still have an annoying buzz on the signal. It's neither high frequency hiss nor 60 or 120hz AC noise. it sounds like stratocaster pickup buzz. What could this be? I notice that it gets worse, not better, when the 10db pad is engaged. Faulty polystyrene cap? Any ideas would be appreciated.

I also have a Warm Audio U67 clone (uses the same exact circuit as the U67) with the same behaviour, it might be the same problem that you’re having or not.
I still didn’t find the reason for this, but if I do I will let you know

Keep us posted also

 

[Purplenoise]

I noticed a little hardness/edginess in the high end like a few posters have mentioned and will give this a try... but this is open cell foam. Are you putting it inside the headbasket, and if so, wouldn't you be concerned about it storing moisture and eventually shedding on the capsule?

I have it on the inside. It took some tries to cut it in the right shape and size. It doesn’t look like it will start to disintegrate over time but…only time will tell

 

[jakearoo]

I’m getting correct voltages in my power supply until I hook up the mic. Then my b+ disappears in the power supply and is not on the mic either. Is it my cables?

 

[TLRT]

I’m getting correct voltages in my power supply until I hook up the mic. Then my b+ disappears in the power supply and is not on the mic either. Is it my cables?

You should have 210V with approx 200-230k load resistor, not without mic.

 

[jakearoo]

You should have 210V with approx 200-230k load resistor, not without mic.

Unloaded, my readings are -16VDCat H- and 250VDC at B+

I plugin my mic without tube and it reads 0.12 volts B+ so almost 0.

 

[TLRT]

Unloaded, my readings are -16VDCat H- and 250VDC at B+

I plugin my mic without tube and it reads 0.12 volts B+ so almost 0.

You have a short to gnd somewhere

 

[jakearoo]

You have a short to gnd somewhere

Thank you. I will look back at my work. I made the same mistake on two mics with the same readings. So I’m missing something easy. Maybe the cables

 

[jakearoo]

Want to hire someone in the states to look at my two 67’s to see why they are shorting to ground. If you can or you know of anyone message me.

 

[JeffKall]

Thank you. I will look back at my work. I made the same mistake on two mics with the same readings. So I’m missing something easy. Maybe the cables

Hi, jakearoo …
We are DIY soulmates …

I built two of Dan’s (poctop) D-67’s powered by two of Matador’s Universal Tube PSU’s without issue …


But I also built two of Dan’s D-EF47’s also powered by Matador Universal Tube PSU’s …

With a 180K 1W dummy load … the Universal PSU’s operate perfectly supplying ALL voltages to spec …

But when I connect the D-EF47’s to the Universal PSU they pull my POLAR/PTRN Selector switch leg to 0V effective locking the D-EF47’s in CARDIOD (which is not a bad thing) …

What are the odds of shorting my PTRN voltage leg to GRND in TWO D-EF47’s ???

Aside from this PTRN issue … the D-67’s and the D-EF47’s all sound amazing (thank you, Dan !) …

I hope someone can solve this WIERD mystery for BOTH of us …

PS … unloaded all of my 7 pin cables supplied the PTRN voltage to the female microphone connector .. it only disappears when I connect the D-EF47’s !

Best Regards !

 

[jakearoo]

Hi, jakearoo …
We are DIY soulmates …

I built two of Dan’s (poctop) D-67’s powered by two of Matador’s Universal Tube PSU’s without issue …


But I also built two of Dan’s D-EF47’s also powered by Matador Universal Tube PSU’s …

With a 180K 1W dummy load … the Universal PSU’s operate perfectly supplying ALL voltages to spec …

But when I connect the D-EF47’s to the Universal PSU they pull my POLAR/PTRN Selector switch leg to 0V effective locking the D-EF47’s in CARDIOD (which is not a bad thing) …

What are the odds of shorting my PTRN voltage leg to GRND in TWO D-EF47’s ???

Aside from this PTRN issue … the D-67’s and the D-EF47’s all sound amazing (thank you, Dan !) …

I hope someone can solve this WIERD mystery for BOTH of us …

PS … unloaded all of my 7 pin cables supplied the PTRN voltage to the female microphone connector .. it only disappears when I connect the D-EF47’s !

Best Regards !

Yes I know these mics are amazing. I built one 3 years ago and regret selling it. Now I’m building two and can live in cardioid mode and still be happy.

 

[joshjoshjosh]

Hey! Just signed up and already have a good excuse to chime in
I just picked up a D67 from someone that was built but not working. I basically just reflowed all the solder points and its working (and sounding amazing) when the polar pattern is set to cardioid. When i switch it to omni or bi-polar, i'm getting large amounts of distortion, with the signal still coming through. I'm a synth building hobbiest and this is the first time i've tried working on a mic. TBH i don't really understand how the circuitry works regarding the rear capsule and its relation to the polar patterns. Anything obvious i should be looking at before going through the schematic and start swapping parts?

any guidance would be appreciated!