Neumann U47FET Clone: D-U47 FET Microphone Project PCB Build thread

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micaddict said:
It sits pretty high in the original and there's a theory why that is.

I'll see if I can post the picture I have in mind.

...we have been having that debate over at realgearonline.com, as to whether the height of the capsule mount in the U47 was deliberate and if so, for what purpose...do the rumors it was designed to limit plosives/sibilance have any historical basis?...so I decided to reach out to a few "experts" and here's what they had to say about it...

Here's Klaus Heyne's thoughts on the positioning of the U47 capsule:

"The U47 capsule mount is at the end of a stiff rubber column whose height and material properties need to be an ideal compromise between elasticity (shock absorption) and stiffness (preventing the capsule to whiplash against the inside of the head basket after a shock). Making it shorter gets you into the territory of the C12 and its capsule mount problem: heavy subsonic Trittschall-transmission. The whole thing transmits too much at 20 hz and below when triggered with even the smallest external excitement.

The secondary, and probably unintended (positive) consequence of the column length Neumann chose is this: the higher you place the capsule inside the basket, the father away it gets from two parallel and reflective surfaces-the basket wall and the base plate-and the closer it gets to the domed (and diffractive) top.

Here is an experiment I have made a few times to understand the real-world consequences of an acoustical obstacle placed close to a diaphragm: mount the same CK12 capsule, once in a C12 (no obstacle in front of the front diaphragm) and then in a C24 (a nasty support bar crossing right through the middle of the front diaphragm): I cannot hear an difference.

That leads me to believe that the small circular weld connecting the U47's cylindrical basket with the domed portion of the basket must be quite negligible, acoustically.

I speculate that the capsule's proximity to the support/weld was known, considered, and found to be not a fatal flaw for the overall head design."



...I then got a response from David Bock :

"Nothing Neumann did, or does, is unintentional.

Even when they use series reg on re-issue U67 psu's (!!!!!), or internal switching psu on fet mics. Tells you everything.
Remember, they used to RUN the microphone world."



...And Toni Roger Fishman of Telefunken had this to say:

"The internal capsule mount has changed form the original design. The first 200 U47 had a mesh surround that was like a divider that split the head grill I will look for some photos and try to post them but this is very rare and hard to find as so many mics have been modified. This (pic below) is the real way it was to be set up but why they changed to what we see today would take much research to figure out.

The height is slightly shorter in the original and taller in the later units. It would be interesting to do some test with modified capsule mounts and heights. We may be willing to look into some tests as I've always wanted to make the earlier mount available to those that needed the parts to restore the fist 200 units to stock."
 

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Some pics of my build.  Alctron GT-2B body, Advanced Audio AK47 capsule, AMI T49 transformer
 

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Neumann returned my call today with pricing for what I asked for in the K47 capsule.

Their response was part #514753 at a cost of $587.86 USD.... but the message was choppy and I'm not even sure she understood clearly what part I was asking for.


I also didn't realize that the rear diaphragm wasn't sputtered?  That kind of kills the idea I had but would still be viable for this kit.
 
It would be very interesting to get on and compare it to some of the offerings out there, but at that price...  Depending on shipping, that is about the cost of the whole thing with Tskguy's capsule.  I'd love to know, but that is hard to justify.
Patrick

 
What about grounding?

  The XLR pin1 can be in electric contact with the body where the XLR connector is set..
  The PCB can be in electric contact with the body via the screws...
  The PCB can be in electric contact with the body via a wire that is connected to XLR's pin1..

Should all these connections be made ?
 
MicDaddy said:
Neumann returned my call today with pricing for what I asked for in the K47 capsule.

Their response was part #514753 at a cost of $587.86 USD.... but the message was choppy and I'm not even sure she understood clearly what part I was asking for.


I also didn't realize that the rear diaphragm wasn't sputtered?  That kind of kills the idea I had but would still be viable for this kit.

the Capsule that is not Sputtered on 1 side should be the K49 capsule , Since one of the side did not meet the machining spec for gaping distance for the backplate it is not sputtered , this is the capsule you will find in a tlm49 and style,
a K47 capsule should be on both side 100% sure,  in the case of the K49 it is a perfect match for this project beeingt only hypercardiod mic , but the price seems odd to me for a K47 Capsule,
Dan,
 
saint gillis said:
What about grounding?

  The XLR pin1 can be in electric contact with the body where the XLR connector is set..
  The PCB can be in electric contact with the body via the screws...
  The PCB can be in electric contact with the body via a wire that is connected to XLR's pin1..

Should all these connections be made ?

PCB Gnd will always have Gnd connection trough screw to chassis unless plastic screw are used  ;)
then you need to make sure xlr pin 1 is to mic chassis as well,
Best,
Dan,


 
I'm asking because I'm fighting with a strange body to set everything together inside..
I should avoid ground loops I suppose?

  So XLR's pin1 always connected to the body, 2 options :
1 :  PCB to ground via the srews
2 : PCB to ground via a wire to XLR's pin1

  But not both at the same time right?
 
saint gillis said:
I'm asking because I'm fighting with a strange body to set everything together inside..
I should avoid ground loops I suppose?

  So XLR's pin1 always connected to the body, 2 options :
1 :  PCB to ground via the srews
2 : PCB to ground via a wire to XLR's pin1

  But not both at the same time right?

PCB to mic chassis via screw  and XLR pin 1 to mic chassis via pcb xlr pin 1 pad and you will be fine ,
Best,
dAN,
 
poctop said:
MicDaddy said:
Neumann returned my call today with pricing for what I asked for in the K47 capsule.

Their response was part #514753 at a cost of $587.86 USD.... but the message was choppy and I'm not even sure she understood clearly what part I was asking for.


I also didn't realize that the rear diaphragm wasn't sputtered?  That kind of kills the idea I had but would still be viable for this kit.

the Capsule that is not Sputtered on 1 side should be the K49 capsule , Since one of the side did not meet the machining spec for gaping distance for the backplate it is not sputtered , this is the capsule you will find in a tlm49 and style,
a K47 capsule should be on both side 100% sure,  in the case of the K49 it is a perfect match for this project beeingt only hypercardiod mic , but the price seems odd to me for a K47 Capsule,
Dan,

I would say it's the other way around, sort of.
In any case the number 49 alone would indicate two sides active, because of all the patterns in an M49.

Last I heard the double sided capsule was called K47/49 and the single sided one K47fet.
 
micaddict said:
poctop said:
MicDaddy said:
Neumann returned my call today with pricing for what I asked for in the K47 capsule.

Their response was part #514753 at a cost of $587.86 USD.... but the message was choppy and I'm not even sure she understood clearly what part I was asking for.


I also didn't realize that the rear diaphragm wasn't sputtered?  That kind of kills the idea I had but would still be viable for this kit.

the Capsule that is not Sputtered on 1 side should be the K49 capsule , Since one of the side did not meet the machining spec for gaping distance for the backplate it is not sputtered , this is the capsule you will find in a tlm49 and style,
a K47 capsule should be on both side 100% sure,  in the case of the K49 it is a perfect match for this project beeingt only hypercardiod mic , but the price seems odd to me for a K47 Capsule,
Dan,

I would say it's the other way around, sort of.
In any case the number 49 alone would indicate two sides active, because of all the patterns in an M49.

Last I heard the double sided capsule was called K47/49 and the single sided one K47fet.

I had actually a neumann capsule for reskin here, Yes I do Reskin here but not for the public yet but it is coming.... the box was labelled K49 capsule and the backside was not sputtered,
well,  maybe that was the box but this is how i undestand it.  Gold rules...... :)
Best,
Dan,
 
saint gillis said:
And if I can't connect pcb to chassis via screws..
can I  connect XLR pin1 to chassis via the XLR connector himself and connect pcb ground to XLR pin1 ?

Yes you can ,
Best,
DAn,
 
saint gillis said:
But in this case I should make sure there's no contact of the pcb to the chassis right?
(I know, it sounds stupid, but.. you know what it is ...)

Dont worry about the ground loop for now as the  , it is another topics,
just hooked it up and start from there, the essence here is that the mic chassis acts as a " star groud point"
best,
Dan,

 
You make me doubt !

I need to connect the XLR ground connector to the chassis or on the GND pad on the PCB?  'Cause the PCB are in contact with the body with the screws... I'm lost

And I have an another question : The turret connect some components to the ground, but the turret don't touch the PCB because of the white protection... It's normal?
 
acdc-angus said:
You make me doubt !

I need to connect the XLR ground connector to the chassis or on the GND pad on the PCB?  'Cause the PCB are in contact with the body with the screws... I'm lost

usually the xlr connector pin 1 goes to pcb xlr pad , so you will ground it from there

And I have an another question : The turret connect some components to the ground, but the turret don't touch the PCB because of the white protection... It's normal?
it does not connect to ground it the turrets serves a support to isolate the pcb from those connection but they are part of the circuit ,
 
That's my built (in progress) I waiting wires from Chunger :

The capsule RK7 from Microphone-parts and the T.Bone SCT700 used for Donor Body

11.jpg
13.jpg


Both side

23.jpg
24.jpg


The headbasket before and after

gtrhrthr.jpg


Previous capsule and Tube PCB

19.jpg
 
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