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

[Tedrummerx]

Hey Dan, was there a specific switch you had in mind for the pad when you added that option on the pcb?

 

[poctop]

Hey Dan, was there a specific switch you had in mind for the pad when you added that option on the pcb?

not specifically I knew they were very limited space  , for a miniature dpdt package but it remains internal on the pcb or can be wired this is just an option) or you could wire your own  I beleive mouser have some dip type switches like these if you want intern or you can have one on the mic but not all are dpdt but defaults , So I decided to use the dual jumper config,
anyway my use of the Pad is very predictable so i dont mind taking the extra 2 seconds to configure the mic The jumper can be left inside on the other way so i dont have to worry about the jumper anymore, but the options remains,

Hope this helps,
Best,
DAn,

 

[Scrappersa]

Did anybody try fitting it into the MXL 550 type body? Or any other MXL body for that matter?

 

[mukole]

Did anybody try fitting it into the MXL 550 type body? Or any other MXL body for that matter?

I'm currently in the process of trying mine in an mxl 2006, I've bent the rails out to accomodate the boards, which i will also have
to redrill slightly and probably file off about 1mm either side for them to fit, the only real problem is i have an AMI t49 to go with it, and i'm having trouble
figuring how to get that in there, there isn't really enough space for it.

MXL state the diameter of this mic to be 50mm, but the actual body diameter is closer to 47mm so i think any mic with that kind of diameter is going to be
a tight fit.

Also I'm waiting for info from Oliver at AMI on how to use this transformer in the circuit, if anyone else has any info on this feel free to post it, I'm holding off hacking anything until i find out this info.

 

[poctop]

A= RT on pcb
B =BR on pcb
C =BL on pcb
D=  VI on pcb

Hope that helps,
Dan,

 

[mukole]

Thanks for that Dan,

I'll give it a go this evening,

I'm also curious though, there are 8 pins on the transformer, are only the outer pins used? or are the inner pins paired with the outer pins?

I notice there is windings attached to all of them, this is what was confusing me.

Thanks again,,

Mick

 

[poctop]

Thanks for that Dan,

I'll give it a go this evening,

I'm also curious though, there are 8 pins on the transformer, are only the outer pins used? or are the inner pins paired with the outer pins?

I notice there is windings attached to all of them, this is what was confusing me.

Thanks again,,

Mick

it is a dual bobin ? but it seems that the drwaing is wrong ,  the primary and the secondary must be wired in series ,,
i believe the scheme is that the primary is on one side pin and the secondary the other side then those pins would need to be tied up on each side,
Hope this helps ,
Dan,


edit: would you be able to take the dcr measurement between A and B you will find out at this moment ,
and if you have a chance that would be interesting to know the dcr resistance of the  primary and secondary once tied up, to get a starter on this one,
Thanks ,
Dan,

 

[mukole]

I believe it is a dual bobbin,

If i check it for DC ohms i get -

325.9ohms  -  A outer pin - C inner pin
7.6ohms  -  A inner pin - C outer pin
324.4ohms- B outer pin - D inner pin
7.6ohms  -  B inner pin  - D outer pin

if that makes any sense to you,
There is no continuity between any other combinations,

As i said i'm pretty confused about this transformer, I have 2 of them and they both read the same,

As to linking up the primary and secondary which pins do you suggest i use for WS,WS,GE and GN?

thanks in advance

 

[mukole]

OK, so if i bridge the inner pins of C and D i get a DC reading of 650ohm across the outer pins of A and B

and if I bridge the inner pins of A and B i get a DC reading of about 15 ohm across the outer pins of C and D

Is this useful? The other combinations wouldn't make sense because that would make it 1:1

 

[poctop]

OK, so if i bridge the inner pins of C and D i get a DC reading of 650ohm across the outer pins of A and B

and if I bridge the inner pins of A and B i get a DC reading of about 15 ohm across the outer pins of C and D

Is this useful? The other combinations wouldn't make sense because that would make it 1:1

Yes you got it  ,  My original was reading about 717ohm  and 15ohm  IIRC
Best,
dan,

 

[mukole]

OK, so if i bridge the inner pins of C and D i get a DC reading of 650ohm across the outer pins of A and B

and if I bridge the inner pins of A and B i get a DC reading of about 15 ohm across the outer pins of C and D

Is this useful? The other combinations wouldn't make sense because that would make it 1:1

OK, you lost me a little on that drawing,
I tried bridging the centre pins A-B and C-D, using the outer pins put 1 volt AC at 1000hz  into A and B and got 0.132 out of C and D,
in reverse this was about 7.6 volts, I'm not sure if this is right, Its supposed to be 10:1 isn't it?
Maybe there's some loss?

 

[mukole]

OK, so if i bridge the inner pins of C and D i get a DC reading of 650ohm across the outer pins of A and B

and if I bridge the inner pins of A and B i get a DC reading of about 15 ohm across the outer pins of C and D

Is this useful? The other combinations wouldn't make sense because that would make it 1:1

Yes you got it  ,  My original was reading about 717ohm  and 15ohm  IIRC
Best,
dan,

Awesome, thanks for your help, I'll let you know how it goes

 

[mukole]

I'm out at the moment, but I'll give that a try when I get home, I'm pretty sure that will give a 1:1 ratio though,

There is a 7.6ohm winding and a 325ohm on each bobbin, and the bobbins run from A to C and B to D.

So I'm pretty sure this would put one of each winding in series on both bobbins,

I'll let you know,

Thanks again

 

[poctop]

OK, so if i bridge the inner pins of C and D i get a DC reading of 650ohm across the outer pins of A and B

and if I bridge the inner pins of A and B i get a DC reading of about 15 ohm across the outer pins of C and D

Is this useful? The other combinations wouldn't make sense because that would make it 1:1

OK, you lost me a little on that drawing,
I tried bridging the centre pins A-B and C-D, using the outer pins put 1 volt AC at 1000hz  into A and B and got 0.132 out of C and D,
in reverse this was about 7.6 volts, I'm not sure if this is right, Its supposed to be 10:1 isn't it?
Maybe there's some loss?

At this point the official drawing from oliver will be needed,  to make sure it is not an odd ball one ,
forget about my last post i think it did not make sense i and i removed it , need to sleep
but i am the impression my first pic was right, i attached it again ,  8:1 would be what we have here,
so let confirm this with  Oliver,

 

[mukole]

Thanks for you help Dan, I've emailed Oliver

Mick

 

[Scrappersa]

Thanks for you help Dan, I've emailed Oliver

Mick

Post what he says! I think I'm going for one of their transformers and will probably end up running into the same problems. Haha


And for anybody else who missed my post, did anybody successfully fit the pcb and a transformer into the MXL 550?

 

[Marik]

Are you sampling Mark's transformer (the Samar audio)?

It is on my wish list  ,  Actually I have asked Mark to supply some info in the thread ,
Keep ya posted,

Hey Folks,

Thank you for your interest! I am completely swamped with "post AES" catching up. Give me a couple days and I will post the pics, dimensions, and specs.

Best, M

 

[poctop]

OK, so if i bridge the inner pins of C and D i get a DC reading of 650ohm across the outer pins of A and B

and if I bridge the inner pins of A and B i get a DC reading of about 15 ohm across the outer pins of C and D

Is this useful? The other combinations wouldn't make sense because that would make it 1:1

OK, you lost me a little on that drawing,
I tried bridging the centre pins A-B and C-D, using the outer pins put 1 volt AC at 1000hz  into A and B and got 0.132 out of C and D,
in reverse this was about 7.6 volts, I'm not sure if this is right, Its supposed to be 10:1 isn't it?
Maybe there's some loss?

I would not actually see another way in regards to this drawing here but 8:1 would make the more sense to me  , make sure to ask oliver about the ratio.
Best,
DAn,

 

[mukole]

Just an update,

Oliver has confirmed that this is the correct wiring,
He said the ratio is approximately 9:1 and the inductance values the same as the
FET47 transformer.

Also he's going to get us a drawing in the next day or 2

 

[mukole]

And here's the updated spec sheet