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

[kingkorg]

How does this have a Supercardiod pattern? It seems it is just connected to just the front of a standard k47 capsule. Does the lower polarization voltage change the pattern? Or is the body characteristics important?
I have a dead shure 52a that I am thinking I could retrofit with the round pcb version.

K47 is by nature super or hypercardioid. It's tricky to determine which one of these it exactly is, they are very close, but it most certainly isn't cardioid.

 

[dmp]

K47 is by nature super or hypercardioid. It's tricky to determine which one of these it exactly is, they are very close, but it most certainly isn't cardioid.

I was assuming the front and back of a k47 were cardioid because I thought the regular u47 'cardioid' pattern was a real cardioid. But the regular U47 always was super/hypercarioid? The 'cardioid' pattern shown here has a rear lobe (near bottom on the blue Gotham sales sheet).
The spec sheet for the FET47 shows a really strong rear lobe on page 9 (i.e. super/hyper cardioid).
Is there any difference between 'cardioid' setting on a U47 and the pattern of the FET47?

 

[kingkorg]

The spec sheet clearly shows super/hypercardioid response. Even thought the mic is classified as a cardioid. The same goes for the tube version. It's because the through holes on the k47 capsule that make it progressively more directional towards the high frequencies. You can play with a continuous pattern selector on a 47 type mic to get it more towards cardioid, but then you step into murky waters. Something i touched upon in this thread. You electronically fight it's physisical pattern response.

https://groupdiy.com/threads/why-you-should-never-use-multi-pattern-mics.81157/

 

[dmp]

Makes sense - thanks

 

[aaronmc]

Has anyone used the Beesneez BV-11 transformer in this build? I am trying to determine the proper wiring for this transformer.

I wired the transformer similar to this diagram: https://www.mobytransformers.com/_files/ugd/692932_25ea5f4fa2a440f3aad6ccb6bcf96389.pdf

Measuring resistance for BL/VL I get 15.6 ohms, for BR/RT I get 1.157k ohm.

I noticed that the output is ~7db less than my D-U87 build and (comparatively) seems to roll off around 50hz. I do have the beesneez m7 capsule in the microphone so perhaps the rolloff is just the capsule. Is this to be expected?

 

[globalpurpose]

Hello , do You know when the D47fet pcb will be back in stock again ? Akemashite Omedetto !!!

 

[c1184701]

I'm building a fet47 in a BM800 body (using the pcbs in mihi_fuchs' thread) and I have just been installing the keystone turret terminals. I have used the same ones in the BOM on page 1 of this thread, but I was surprised to find that they have continuity from end to end. Is this normal? I thought the idea was to keep the high impedance connections away from the pcb. Here are the ones I got from Mouser:

Keystone 11218 at Mouser

 

[johnsonic]

You should have continuity from end to end. The isolation happens by the teflon bit being the part that sits in the pcb itself (no conductive surface is directly touching the PCB).

 

[c1184701]

You should have continuity from end to end. The isolation happens by the teflon bit being the part that sits in the pcb itself (no conductive surface is directly touching the PCB).

I'm not sure I understand. If there is continuity from the turret all the way through to the far end of the pin, how can there be any isolation? The pin gets soldered to the pcb, so now the turret has continuity with the pcb.

 

[johnsonic]

Take a look at how they sit. in the PCB here: Telefunken ELA M 251 Clone Tube Microphone Build Thread (D-Ela M 251E)

Specifically - this image: https://proxy.imagearchive.com/8a7/8a721c3ce0cd186197432cee71d482e2.jpg

 

[c1184701]

Take a look at how they sit. in the PCB here: Telefunken ELA M 251 Clone Tube Microphone Build Thread (D-Ela M 251E)

Specifically - this image: https://proxy.imagearchive.com/8a7/8a721c3ce0cd186197432cee71d482e2.jpg

Aha, thanks John that makes sense! So the pcb should have holes the right diameter to push-fit the teflon part through.

The implementation is not correct in the pcbs I am working on unfortunately. They have regular solder pads for the turrets, just big enough for the pin part. I think the designer intended for them to be soldered in, which defeats the whole purpose.

I could remove the ones I have already soldered in, and drill out the holes to fit them in properly. Are there any general guidelines for how far above the pcb the high-impedance connections should sit? I have already trimmed the pins on most of my keystones, so I will have to use the turret end for the connection. Once the teflon is seated properly the turret will only be a mm or so above the pcb, do you think this will still be effective?

 

[johnsonic]

I think some of them ARE meant to have the turrets make connection with the traces in the PCB (the matachung C12 comes to mind), but I've usually seen those as the thicker gauge, no teflon. Went back to the beginning of this thread to see Dany's build photos, and it looks like there's only one turret with a million components soldered to it? There is a pad surrounding it but it looks like it's big enough to take that teflon piece, probably not meant to be soldered to the board. Would steer clear of modifying boards by drilling them out.

Not familiar with this circuit and haven't built it, just putting my 2¢ out there!

 

[EarthTone]

From ShuaiYin; I inquired about buying 47FET style and they have this. I will be buying one or two. This will be cool to install the Poctop build in! I wonder which will fit better the rounded or square PCB? Anyone know? I did not receive photos of the inside of the case/pcb mounts.

 

[ROC127]

I recently got AMI's FET 47 transformer and it came with green, red, black, and white wires. Does anyone happen to know the corresponding pads on Dan's pcb? Thank you for any help.

 

[egroys]

From ShuaiYin; I inquired about buying 47FET style and they have this. I will be buying one or two. This will be cool to install the Poctop build in! I wonder which will fit better the rounded or square PCB? Anyone know? I did not receive photos of the inside of the case/pcb mounts.

Nice!! How can I get my hands on one (or two) of these? And I would love to know about which PCB as well!

 

[EarthTone]

@egroys You may be interested in the group buy they are putting together in the "Round PCB" version thread here: D47 Fet New Body Style PCB now available The PCB is available from Dan here: Vintagemicrophonepcbkit.com On the "order" page it is the "round pcb" version.

Along these lines, is there a separate build thread for the round PCB version? There are some different component placements and the addition of a switch PCB. For myself and others who will build this version, it would be awesome to have a set of pictures of the completed boards and how they all connect together for reference as we finish them and hook everything up. Could someone (or @poctop ) please post a few pics of the completed round version? I want to see how everything connects together on a working unit, just in case I make a mistake... I'm sure others would appreciate having reference pictures as well.

Thanks! Can't wait to build two of these fet47's. Just ordered the components! Very excited.

This is the project I am referencing, just for clarity's sake.

Thank you Dan!

 

[TLRT]

I will post pics next week about the pcb's(Dany asked me)

 

[egroys]

Is anyone using the Moby 09331 tx?
Thoughts between his and Cinemag?

 

[EarthTone]

Great @TLRT

@egroys I called Cinemag today and bought 2x cm-13101's. I haven't heard enough about Moby to want to give it a shot yet but I have heard they are very good. Cinemag is in a lot of gear I trust and they replicated the 47FET transformer exactly. They have some in stock right now so you don't have to wait. Their waiting list can be quite long and I wanted to get started. I think Moby is not Stateside. If you get one of those let us know how it goes!

 

[egroys]

Great @TLRT

@egroys I called Cinemag today and bought 2x cm-13101's. I haven't heard enough about Moby to want to give it a shot yet but I have heard they are very good. Cinemag is in a lot of gear I trust and they replicated the 47FET transformer exactly. They have some in stock right now so you don't have to wait. Their waiting list can be quite long and I wanted to get started. I think Moby is not Stateside. If you get one of those let us know how it goes!

Cinemag is great but many folks here raved about Moby’s trafos so I followed ans am using them in my 67 and 49 pairs. They are absolutely delicious, though unlike others here, I haven’t A/B’d. I guess, in summary, Moby has access to some materials that more accurately replicate vintage German delights. Maybe @Moby can chime in?