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

skidmorebay said:

Solved my problem - broken wire between the two PCB's (A to AA) . Back in business.
JS

Click to expand...

Another one Down ,
8)
Dan

Another "official" track, 47fet clone with Thiersch M7 capsule:

https://www.youtube.com/watch?v=c0KooOUYV7o&index=11&list=PLkaemF17IwDLnW4JyPK-n2RhjsmEqUhIv

Nice. 

How much treble lift?

I wasn't there at the mixing,so I'm not sure, the raw version is pretty nice also.

micaddict said:

Nice. 

How much treble lift?

Click to expand...

ive been tinkering away on a build here, hk47 capsule and cinemag transformer so looking forward to hearing it!

only problem is i haven't got it going yet.

triple checked my soldering and components but still no luck

at the moment i can get sound out of it (however thin) when i first switch on phantom but a few seconds later it cuts out and wont give me any more sound.... any thoughts?

You may want to make sure that you have the leg of R2 resistor in the top hole.. I messed that up once and if I recall had a similar issue.

Eric

yeh i have r2 going into the the no R+ hole

Hi All,
I have 3 questions I am hoping someone can assist 
1) I exposed part of the trace on the pcb when pulling the 3.6 to add the 6.8 - Is this really, really bad? (Third solder point down from top left in photo)

2) I was going to jumper where the bias goes. Ok to just use the wire cutoff from the styrocap?

3) I have 3 mini jumpers, (2) 2c header, (1) 3c header, and 1 turret to pin leftover. Did I miss something??

Image for question #2

Image for Question #3

Which cap value should be changed if I want to reduce the highs? (9k area) the styro 33pf, or the 2200pf one?

On the original Neumann schematic that has transformer U1, p/n 90 331, this is the wiring:

RT = pin 1 on U47fet PCB
BR = pin 2 on U47fet PCB
VI = pin 3 on U47fet PCB
BL = pin 4 on U47fet PCB
WS is shorted to WS*
GE is shorted to GN* (ignore switch S3)

Here are the wiring details I figured out for the AMI T49 transformer and poctop's T49 adapter PCB. I have confirmed the following to work properly in my own build.

See AMI's T49 schematic attached. On my transformers, A-B does measure at higher resistance on a multimeter--around 658 ohms. C-D does measure at lower resistance--around 15 ohms.

To read the chart, use this legend:
U47fet PCB pin => wire color => AMI T49 pin

1 => brown => A "capacitor"
2 => red => B "ground"
3 => yellow => D "xlr pin 3"
4 => orange => C "xlr pin 2"

The Cinemag CM-13101 wire colors are the same and should work, but I have not confirmed that the wiring is correct as above, as I do not own one.

Next are the photos for the AMI T49 adapter PCB and how it is mounted in the GT-2B body. I had to drill and tap one hole in each rail to mount the board. My advice: don't bother using a tap. Use self-tapping M2 screws. The tap thread is so fine and the metal so mushy that it basically was useless.

The transformer is huge, so it is necessary to sandwich the rails between the PCB and the transformer.

Photo showing the rails sandwiched between the T49 and the adapter PCB:

Now on to a totally different topic:

I researched DPDT switches that would fit the 2x3 2.54mm x 2.54mm grid labeled "Pad" that is an optional replacement for the s1a and s1b 1x3 2.54mm male headers and found that the NKK "ultra-miniature" switches will work.

Of the NKK switch designs, their slide switch is the shortest vertically:

http://nkk.com/documents/products/illuminated_slide/ss/ssnonilluminated.pdf

The part number I chose is SS22SDP2 and is available at Mouser, Digikey, and Allied Electric.

For the 1x2 2.54mm male header labeled "LC (Low Cut)" there are two options for a switch:

1) Buy the SPDT NKK SS12SDP2 and cut one leg off. The body is somewhat large for the spot, so it will overlap onto the space for the trimmer (where the jumper is).

2) Erg Components makes an ingenious little slide switch with a tiny footprint exactly for the purpose of replacing 1x2 jumpers.

Allied Electric is the only USA carrier that stocks them so far, as Erg is a British company:

http://www.alliedelec.com/erg-jsa4-01-go/70746110/

Attached is the photo of the tiny NKK "ultra-miniature" switches. They fit perfectly. Given how much space is inside the GT-2B body, I could have ordered the 9mm tall ultra-miniature toggle or rocker switches that NKK also makes.

There are some resistors marked as 1/2W in BOM (6K8, 100K, 4K7, 470K, 47K....). Can I safely use 1/4W metal film resistors instead?

Bump...

yes you can ,
D,

Hey just a question

Are those yellow caps on the board of good quality or do they not matter so much ? also Is this a Class-A circuit ?
Im quite interested in making a U47 this one looks quite nice

Hey all, Just wondering, can this mic be built for £500 ?

Thanks