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

[wave]

Hooked up mic. Adjusted to  -6.3 vdc.
At full could only get 202 vdc. ???

How long did you let the mic warm up? It took a few minutes before I was able to get the B+ to 210V.

I agree with this. I notice that with both of the tube mics I have built (DU67 and MK47) letting the PSU come up to temp yields much better results as far as dialing in the exact B+ and heater voltages. I usually let my mics warm up for about 15 min before I test voltage and apply signal (like singing into it)

Dave

 

[Winetree]

Let it warm up and got the voltage to +204vdc.
I think I'll try lowering the 56k resistor to raise the voltage a little.
Got the new tubes. Decided to go all the way.
N.O.S. Matched pair. Sound amazing.

 

[Marc Duchesne]

IMO wrote:
I have the beezneez 67 capsule and it sounds amazing! Tele EF86, IO audio transformer. I'm using the Chunger bday. Ill bring it to my other studio in the next day or so and give it a run against our vintage 67, but as i said earlier it sounds amazing. Just as i would expect the mic to sound. It has that quality that a SM7 has(but more HIFI) where they just sit in the mix with no eq

--- This is exactly my configuration, but with a NOS Amperex Bugle Boy EF86 tube. Just need to receive my beesneez 67... Can't wait...

 

[micaddict]

Ill bring it to my other studio in the next day or so and give it a run against our vintage 67

IMO, please post samples of that shootout.

 

[Jim50hertz]

I can't seem to find reference to the second set of jumpers, should I jumper both? I know one is for the internal 200Hz filter, what's the other for?

 

[poctop]

I can't seem to find reference to the second set of jumpers, should I jumper both? I know one is for the internal 200Hz filter, what's the other for?

IS is jumpered for default configuration , you will get more bass response and proximity with the jumper off,  the other jumper serves as soldering point for the low cut switching,
Best,
dan,

 

[Jim50hertz]

Thanks Dany 

 

[imo]

will  post sound samples as soon as i can. Been working at my studio

 

[micaddict]

To avoid possible confusion, 200 Hz is the corner frequency of the switchable high pass on the body of a U67.
The S2 jumper makes for a set 40 Hz (or 30 Hz depending how you measure) high pass or bass roll off. There's no switch for that one on the body.

 

[Jim50hertz]

Ok pcbs are stuffed, moving onto the PSUs this week and will be buying tubes.

A question, how critical is tube matching for a pair of D-U67s? 

 

[poctop]

seems like a good prospect fun.  i have some but tought l'd let you know,
http://www.ebay.ca/itm/ws/eBayISAPI.dll?ViewItem&item=140920342309&ssPageName=ADME:B:WNA:CA:1123
Best,
Dan,

 

[poctop]

Ok pcbs are stuffed, moving onto the PSUs this week and will be buying tubes.

A question, how critical is tube matching for a pair of D-U67s?

i guess the answer to this would be relative on sligth diff in gain ,emission, response Curve. from the tube at the same  operating conditions (H+ B+ma) , Microphone specifics ( noise, microphonics),
the capsule will also have to be very close in capacitance and tension as well  ,  those 2 element will interacts.  ,

just toughts,

Best
DAn.

 

 

[Jim50hertz]

Thanks Dany, I bid on those but missed out.  Snagged a matched pair from Germany.

 

[MikeFFG]

Thanks for clarifying the star ground, Dan.

I've completed my PSU and I'm getting around 214V for the B+ and around -16V at the heater. Going by dmp's great explanation above, I'm in the right ball park, now I just need to calibrate. I tried lowering the B+ voltage using the RTRIMPLATE, but the lowest it will go is 214V. Do I need to increase the value of the pot then?

I also tried raising the voltage for the heater to -15V (mic not connected), but the RTRIM H- doesn't do anything. Maybe my wiring is wrong? Please see the attached picture. Thanks everyone.

-Kevin

Hi someone responded that these seemed alright without a load attached...but I didn't see anyone say that it made sense that the H- not doing anything is correcT? I just want to verify this. I just finished my PSU build and I'm running B+ at 255 with the trim all the way up and H- at -16v...but the H- trim pot doesn't change it at all.  I've read the thread and know that the voltages are fine but just wanted to check on this point before I connect anything else!

I attached a pic of my build. Can't wait to finish the mic and get this tested out!

 

[poctop]

It is perfectly normal for the heater voltage to stay at -16v during pot adjustment with nô load cause the zener is actually eating up the différential

Once the mic with a tube is connected it Will drop down

Best
Dany.

 

[MikeFFG]

Okay thanks...

One more thing...I installed the Low cut and pattern switches backwards, and in the process of desoldering them, broke them. Does anyone have any Mouser part numbers or anything for them?? That'd be great!

 

[Tedrummerx]

Hey guys, I'm having a small issue with one of my u67s, maybe someone can possibly point me in the right direction. In cardioid, both mics seem to be functioning correctly: similar tone and level, both sound great. But on the troublesome mic, when I switch to omni or bi, the level drops significantly and the tone is much darker compared to the other mic. Let it be know, the first mic seems to be functioning just as it should in it's different modes. My first step was comparing the wiring and component placement of the working mic with the non working mic. Seems ok. Can anyone point me in any other direction that may cause my issue? thanks in advance! Capsules are beezneez, ami transformers, telefunken ef86 tubes off ebay.

 

[Jim50hertz]

Sounds like the rear diaphragm is not connected/not functioning.  Check your patterns switch connections and look for dry joints in this area.  It may be worth reversing your capsule connections to verify that both sides are functioning correctly in cardioid, eliminating this possibility.

 

[Tedrummerx]

Thanks Jim50hertz,
Ill try switching the sides and will report back. This has me worried because I noticed a slight issue with the backside of the capsule in the troublesome mic...I won't go into details unless I find this to be the problem and contact the manufacturer first. Thanks again.

 

[Tedrummerx]

update: so I swapped the capsule sides and it seems like that's my issue. Now in cardioid mode, there's significant less high end and about 20 db less.  :-\