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

[JamieOxford]

Hello, I'm repairing an early STAM U-47 FET for a friend and it turns out it uses these DU47FETi PCBs and what looks like the 3U capsules mentioned here.

It's having some problems with popping every 5-10 seconds (it sounds like the phantom power is disconnecting continuously so I'm assuming it's a bad capacitor or component). Does anyone have any experience with this?

The circuit on the mic looks slightly modded to accommodate the lack of pad and HPF as well.

Please find a few photos attached. Thanks!

I've replaced R1, C1, C2 & C3 on the STAM which has reduced the amount of popping but the pops are still happening and I'm now not getting anything from the capsule. (I think the polarisation voltage is too low for any output but not sure where to go next.) I've traced a voltage drop at T3/R9 and a transient pop (negative voltage) at R9/T5 but not sure what could be causing it as the circuit is very interconnected. Can anyone help with suggestions of what the cause might be? (I've attached the original FET47 schematic which is almost identical)
Thanks!

 

[globalpurpose]

Hi Guys!

I'm reporting back to HQ here with my finished D-U47fet build!
It has a Cinemag CM-13101 and for the moment an RK-47 capsule.

I must say that I am very impressed with this mic!
It has authority, detail and presence. Basically a really good mic.

It is absolutely not dark, probably due to the RK47, and still handles sibilance very well.
It gives the detail of the TLM 103, without being harsh or thin, and with much more authority and punch. I really like it.

My plan was to change the capsule to a Thiersch or original Neumann once it was operational, but now I'm not sure anymore..
I think the RK47 performs really well in this config, and I can imagine it will sound very good on acoustic guitar.
It will probably work great as vocal mic too in many situations.

So the new plan now is to build another one with a Neumann capsule and see if the difference is worth the money.

A big shout out to Poctop for making this wonderful kit, and to Chunger for making the GT-2B bodies available to us!

Best regards,
Michael

Hello , i know it s been a long time but i wanted to know if You did build another 47fet with Tiearsh or Neumann capsule ?? how did it compare ? also did You try other transfo ??? Have a great day