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

[Phrazemaster]

I'm excited! Just got the mic to a local machine shop and they are going to bore the base for the Amphenol connector...gonna be a little bit trick, if it turns out right, because I'm having them bury the Amphenol into the base a lot like the XLR connector is. It's gonna be a little pricey, but should have it back in a week. I'll post photos if it comes out great! And then it might be something to consider as an option for Chunger's bodies; to have this kind of base mod for the Amphenol.

Mike

Edit: include pic

 

[Phrazemaster]

Ok couple questions. First, this is dumb, but I have to ask - my studio is in another city and I haven't been there in a while.

The bottom of the mic has a screw base. Does this fit into mic shockmounts that have a screw base? Or is the screw base at the bottom of the mic just to screw on the bell? I'm asking because I had spec'ed the machine shop to remove about 1/4" thinking I didn't want it to stick out, but maybe if it serves a useful purpose like fitting into a neumann shock mount with screw on, I'll have them not cut off the last 1/4" of the screw base. I need to let them know asap, so if anyone has a quick answer I would be most grateful.

Second, I have a question about the wiring of the switches. I went through the d269 tutorial, and it all made sense except there are a couple of images referencing bridging of C1-C10, which I believe we have already done in the DU67 up to that point. Is there some other bridging here that I'm not catching due to my eyesight/misreading of the pic/schematic?

I'm including one of 2 of those pix here; Dan - is this an additional bridging necessary for the DU67?

Thanks a lot folks!

Mike


PS I had a run-in with some conformal coating the other night. I thought after making the high-z section it would make sense to use some brush-on conformal coating. Well, it was thick. WAAY too thick in the bottle and I ended up making a big mess of my high-z....ended up having to scrape it all off...lesson learned: use conformal coating thinner!

Is anyone else using conformal coating on their high-z section? I had picked up some Q-Dope but now I'm not sure if I'm gonna buy the thinner and reapply it...traumatized...

 

[poctop]

Ok couple questions. First, this is dumb, but I have to ask - my studio is in another city and I haven't been there in a while.

The bottom of the mic has a screw base. Does this fit into mic shockmounts that have a screw base? Or is the screw base at the bottom of the mic just to screw on the bell? I'm asking because I had spec'ed the machine shop to remove about 1/4" thinking I didn't want it to stick out, but maybe if it serves a useful purpose like fitting into a neumann shock mount with screw on, I'll have them not cut off the last 1/4" of the screw base. I need to let them know asap, so if anyone has a quick answer I would be most grateful.

Second, I have a question about the wiring of the switches. I went through the d269 tutorial, and it all made sense except there are a couple of images referencing bridging of C1-C10, which I believe we have already done in the DU67 up to that point. Is there some other bridging here that I'm not catching due to my eyesight/misreading of the pic/schematic?

I'm including one of 2 of those pix here; Dan - is this an additional bridging necessary for the DU67?

Thanks a lot folks!

Mike


PS I had a run-in with some conformal coating the other night. I thought after making the high-z section it would make sense to use some brush-on conformal coating. Well, it was thick. WAAY too thick in the bottle and I ended up making a big mess of my high-z....ended up having to scrape it all off...lesson learned: use conformal coating thinner!

Is anyone else using conformal coating on their high-z section? I had picked up some Q-Dope but now I'm not sure if I'm gonna buy the thinner and reapply it...traumatized...

Not sure why you used conformal coating on the H-Z section but this is DIY after all,  I understand that they use to at certain time , but i did not and had no issue with noise.

as per the bridging they are many ways to do it but the principle will stay the same in the 269 thread i have done it a bit diefferenly but the connection overall is the same wich is  that the top of C1, C10 and R8 need to floating connect to the grid of the tube as well as the front diaphragme and the switch pin 1 of te pattern switch. and this is for the D-U67 only there is some subtility in the 269C mic
you can use the turret point as a bridging aid or you could float all the connection straight to it , using the turret wil allow to connect the front diaphragme easier i always leve a little bit of the lead of the resistor when i do that to allow a solder point for the other wire that will come in

see the picture atached, and see the yelow line are the actual phsical connection that need to be made , the gray line is just the same thing
hope this helps,
Best,
DAn,

PS I also notice that the reference in the text on the picture is referering the wrong resistor it is R8 not R6 i corrected the picture in the pictorial  of the 269B thread where you took the picture from , 
the PCB is correct.

So basically at the end it will look like this , notice the extra lenght of lead that i leave to solder the front Diaphragme and pattern switch pin 1

 

[Phrazemaster]

Thanks Dan. I will study this; I appreciate your explanation and updated photos.

Regarding the conformal coating, my understanding is, it's not so much about noise as long-term stability issues. Any moisture, dust, fingerprints, etc in the long-term can cause issues since it's such a high resistance and subject to minute contaminants. It was recommended to me by a neumann mic tech, Andreas Grosser, for a U47 build I am doing. I may leave it out in the end, but that was the thinking.

Any thoughts on the screw thread at the bottom of the mic...is this only for the bottom bell to connect to, or does this actually fit mic shock mounts with a screw thread?

Thanks all,

Mike

 

[poctop]

Thanks Dan. I will study this; I appreciate your explanation and updated photos.

Regarding the conformal coating, my understanding is, it's not so much about noise as long-term stability issues. Any moisture, dust, fingerprints, etc in the long-term can cause issues since it's such a high resistance and subject to minute contaminants. It was recommended to me by a neumann mic tech, Andreas Grosser, for a U47 build I am doing. I may leave it out in the end, but that was the thinking.

Any thoughts on the screw thread at the bottom of the mic...is this only for the bottom bell to connect to, or does this actually fit mic shock mounts with a screw thread?

Thanks all,

Mike

the standard shockmount that is supplied with the Syt-5 body is a press fit one ,
no screwing on this one , not sure if this helps,
Best,
DAn,

 

[Phrazemaster]

Hi Dan, thanks. Yes I have the press-fit shock mount that came with it. I was wondering if the screw base happened to fit standard neumann screw-fit shock mounts. Thx.

 

[Phrazemaster]

OK, I understand your explanation about the bridge. Where I'm unclear is in the actual black photo you posted. It seems there are connections going to points next to the turret point, but not the actual turret point - I'm confused. There are a couple of holes on the PCB marked with an * but as far as I can tell they are unused in your build photos but it seems there are connections going there in the black photo that are really supposed to go to the turret point.

There are not actually any wires supposed to go to the holes in the PCB marked *, right? This was just a best-effort way of showing the 3D connections of the bridge using a 2D photo...right?

See my attached photo. Thanks so much Dan...project is incredible!

 

[poctop]

OK, I understand your explanation about the bridge. Where I'm unclear is in the actual black photo you posted. It seems there are connections going to points next to the turret point, but not the actual turret point - I'm confused. There are a couple of holes on the PCB marked with an * but as far as I can tell they are unused in your build photos but it seems there are connections going there in the black photo that are really supposed to go to the turret point.

There are not actually any wires supposed to go to the holes in the PCB marked *, right? This was just a best-effort way of showing the 3D connections of the bridge using a 2D photo...right?

See my attached photo. Thanks so much Dan...project is incredible!

where you show the picture with the 2 pad hole that are not used it is correct because the top end of those component will float direclty to the tube grid- Turret point(R8)
you are not in a obligation to use the turret point if you send the top of R8 direclty to the grid as well but it will be usefull to connect later capsuile connection and pattern pin 1 connection as depicted in the overall connection document, 

Unused Right

Correct.

PS: the connection on the black picture is a representation of how the CAD software make the connection but it cannot interepret any floating connection.
The astrerisk on the pcb denote a floating connection up to the tube grid pin. 

Let me know if this makes sense, dont hesitate to question me if it isnt. 



Best,
Dan,

 

[Phrazemaster]

Hi Dan, beautiful answer - thanks! Yes your pictures are very clear!!! I thought I was going to have a terrible time with this project, but between your pix and the schemos, it was fairly easy!

I just lost my nerve a little when I was trying to interpret the CAD version - my mind is very literal sometimes so I was thinking that perhaps I had made a mistake.

But I'm happy to report I got the whole floating bridge and temporary capsule setup! I'm waiting on a capsule from BeesKneez, and some machining, and then I can get the party really started!

Thanks again for a super project!! I used premium components so I think this going to come out great!

Mike

 

[poctop]

Hi Dan, beautiful answer - thanks! Yes your pictures are very clear!!! I thought I was going to have a terrible time with this project, but between your pix and the schemos, it was fairly easy!

I just lost my nerve a little when I was trying to interpret the CAD version - my mind is very literal sometimes so I was thinking that perhaps I had made a mistake.

But I'm happy to report I got the whole floating bridge and temporary capsule setup! I'm waiting on a capsule from BeesKneez, and some machining, and then I can get the party really started!

Thanks again for a super project!! I used premium components so I think this going to come out great!

Mike

Thanks For Nice word,  I too am like that, when i get something to accomplish i make sure i understand it all and all the details that comes with it,
Keep me posted,

Best,
dAn ,

 

[Studio Mollan]

Hi guys.
I'm just about to finish the first of my four u67. I have an issue with the psu. I blew a couple of fuses trying to power it up. The 250v pilot just flashes and then it's gone. After disconnecting the 210v transformer from the pcb the fuse won't brake. Getting 20v from the other transformer.
There's 0,9ohm resistance between one of the 210v inputs on the psu and 0v. Is that right? It's the same on all of my four psu pcbs. I've double checked all the components and the wiring/soldering.
Triad 210v tranny in series, bridging violet/gray on primary and red/orange on secondary. 250v/2w pilot light.
I'm in Europe (230v) and I'm using the spec 0,1a fuse. Microphone not connected.
/
Emil

 

[poctop]

Hi guys.
I'm just about to finish the first of my four u67. I have an issue with the psu. I blew a couple of fuses trying to power it up. The 250v pilot just flashes and then it's gone. After disconnecting the 210v transformer from the pcb the fuse won't brake. Getting 20v from the other transformer.
There's 0,9ohm resistance between one of the 210v inputs on the psu and 0v. Is that right? It's the same on all of my four psu pcbs. I've double checked all the components and the wiring/soldering.
Triad 210v tranny in series, bridging violet/gray on primary and red/orange on secondary. 250v/2w pilot light.
I'm in Europe (230v) and I'm using the spec 0,1a fuse. Microphone not connected.
/
Emil

yes this is correct if you look at the PSU schemo on page 1 one leg of the secondary 230VAC is tied to ground, and the other one at the half phase rect diode,  did you try another fuse like 0.2A or 0.3A , sometime the fuse is not slow blow enough or not slow blow at all,  and there a smal inrush current at startup, is you pilot direclty wired to AC or the current involved in the pilot lamp is counted in ,

Hope this helps,
Best,
DAn,

 

[Studio Mollan]

Hi guys.
I'm just about to finish the first of my four u67. I have an issue with the psu. I blew a couple of fuses trying to power it up. The 250v pilot just flashes and then it's gone. After disconnecting the 210v transformer from the pcb the fuse won't brake. Getting 20v from the other transformer.
There's 0,9ohm resistance between one of the 210v inputs on the psu and 0v. Is that right? It's the same on all of my four psu pcbs. I've double checked all the components and the wiring/soldering.
Triad 210v tranny in series, bridging violet/gray on primary and red/orange on secondary. 250v/2w pilot light.
I'm in Europe (230v) and I'm using the spec 0,1a fuse. Microphone not connected.
/
Emil

yes this is correct if you look at the PSU schemo on page 1 one leg of the secondary 230VAC is tied to ground, and the other one at the half phase rect diode,  did you try another fuse like 0.2A or 0.3A , sometime the fuse is not slow blow enough or not slow blow at all,  and there a smal inrush current at startup, is you pilot direclty wired to AC or the current involved in the pilot lamp is counted in ,

Hope this helps,
Best,
DAn,

Hi dan and thansk for replying!
I have not tried a larger fuse yet but i will this evening. Tje pilot is drawing from the fuse yes. Its inside the IEC.
/
Emil

 

[Studio Mollan]

I'm excited! Just got the mic to a local machine shop and they are going to bore the base for the Amphenol connector...gonna be a little bit trick, if it turns out right, because I'm having them bury the Amphenol into the base a lot like the XLR connector is. It's gonna be a little pricey, but should have it back in a week. I'll post photos if it comes out great! And then it might be something to consider as an option for Chunger's bodies; to have this kind of base mod for the Amphenol.

Mike

Edit: include pic

I have done the exact same thing on mine. Had a friend of mine do it at work. I'm very happy with the looks and feel of it.
/
Emil

 

[Phrazemaster]

Cool Emil!

Maybe post a pic?  8)

 

[Studio Mollan]

Cool Emil!

Maybe post a pic?  8)

Hi!
Here's a pic of the mic with the binder mounted. I did like you and drilled a hole and fixed a stop screw to guide the connector. It's a bit tricky to get the microphone side connector to sit tight. I drilled another hole throught the mic and inserted another screw to hold it in place, high enough so it's not visibe with the body mounted.

I have a problem you guys can probably help me with: I cant get 210v to the mic. It stays at ca 196v.
I cant get 210v to the mic. A lower value resistor in series with the pot?
/
Emil

 

[Studio Mollan]

Cool Emil!

Maybe post a pic?  8)

Here's another pic.

 

[Phrazemaster]

Emil yours is even cooler than mine will be! I have a binder at the PSU, but went for the Amphenol for the mic itself. It's small... But I think it will be better than the xlr...

Thx for sharing!

Mike

 

[Studio Mollan]

Hi guys.
I'm just about to finish the first of my four u67. I have an issue with the psu. I blew a couple of fuses trying to power it up. The 250v pilot just flashes and then it's gone. After disconnecting the 210v transformer from the pcb the fuse won't brake. Getting 20v from the other transformer.
There's 0,9ohm resistance between one of the 210v inputs on the psu and 0v. Is that right? It's the same on all of my four psu pcbs. I've double checked all the components and the wiring/soldering.
Triad 210v tranny in series, bridging violet/gray on primary and red/orange on secondary. 250v/2w pilot light.
I'm in Europe (230v) and I'm using the spec 0,1a fuse. Microphone not connected.
/
Emil

yes this is correct if you look at the PSU schemo on page 1 one leg of the secondary 230VAC is tied to ground, and the other one at the half phase rect diode,  did you try another fuse like 0.2A or 0.3A , sometime the fuse is not slow blow enough or not slow blow at all,  and there a smal inrush current at startup, is you pilot direclty wired to AC or the current involved in the pilot lamp is counted in ,

Hope this helps,
Best,
DAn,

First 67 up and running. Everything seems to work and no noise. Will get it going in the studio ASAP for feedback.
I ended up paralleling the 56k resistor in series with the 210v adjust pot with another 56k, = 28k. Seems to work better here.

 

[poctop]

Hi guys.
I'm just about to finish the first of my four u67. I have an issue with the psu. I blew a couple of fuses trying to power it up. The 250v pilot just flashes and then it's gone. After disconnecting the 210v transformer from the pcb the fuse won't brake. Getting 20v from the other transformer.
There's 0,9ohm resistance between one of the 210v inputs on the psu and 0v. Is that right? It's the same on all of my four psu pcbs. I've double checked all the components and the wiring/soldering.
Triad 210v tranny in series, bridging violet/gray on primary and red/orange on secondary. 250v/2w pilot light.
I'm in Europe (230v) and I'm using the spec 0,1a fuse. Microphone not connected.
/
Emil

yes this is correct if you look at the PSU schemo on page 1 one leg of the secondary 230VAC is tied to ground, and the other one at the half phase rect diode,  did you try another fuse like 0.2A or 0.3A , sometime the fuse is not slow blow enough or not slow blow at all,  and there a smal inrush current at startup, is you pilot direclty wired to AC or the current involved in the pilot lamp is counted in ,

Hope this helps,
Best,
DAn,

First 67 up and running. Everything seems to work and no noise. Will get it going in the studio ASAP for feedback.
I ended up paralleling the 56k resistor in series with the 210v adjust pot with another 56k, = 28k. Seems to work better here.

Great News,

Let me know how the story ends up  ,
Best,
DAn