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

[LarryChicken]

Just finished my U47fet today. It sounds great. Didn't get to do much testing with it other than some vocals but the midrange is so present and I feel like instruments will sit in the mix nicely.

I am using an old SE Z-2200 as a doner mic along with an RK47 from Microphone-parts and a Peluso BV8p transformer. I'm not sure if this is the transformer but as previously mentioned, I'm not 100% on the bass output. It just seems a bit thin. I guess I may have to go to AMI for their t49.

 

[poctop]

I'm not sure if this is the transformer but as previously mentioned, I'm not 100% on the bass output. It just seems a bit thin. I guess I may have to go to AMI for their t49.

Try reducing the Value of C1 to something like 1000pf-500pf to see,
Let me know
Dan,

 

[Scrappersa]

Oh man. I'm having massive issues with my build. I'm using the ami t49 transformer. No audio is passing but when I short the transformer by touching a pin with my finger, it starts making crazy popping sounds and occasionally I can hear my voice for a split second but it quickly fades out. I keep checking everything over and the only thing I'm unsure of is my transformer wiring. In your diagram Dan, a and b and c and d are reversed from what's actually printed on the transformer. I've tried switching it around but I'm the same issue. Could It be that I haven't usea jumper on any of the pad or lc pads? I can post some pictures tonight but where would you guys start looking?

 

[poctop]

The traffo is from pin view in the image but that should not change the a b c d on the transformer right , I will have T49 Shortly here and i will make sure it is the correct connection Can you measure the resistance between A-B and C-D that will tell whats what.

so the transfo connection would be

A- to  RT
B- to BR
C--to BL
D- to VI


Do you mean that the info on the website is wrong again  ,  so you primary is C and D

 

[skidmorebay]

Sorry to interrupt the troubleshooting...

Dan asked me how I liked the mic and how it sounded. Here's some info on that, at least for a mic with the components I used (Neumann K47 and AMI Fet47 transformer):

It seems to have big low end (but it's not woofy sounding), and it's got a little bit of a high frequency lift but it's not edgy.

The two large-diaphragm condensers I have are a Peluso 2247 and a Neumann M149. I have also used a Shure KSM44 a lot. Compared to the Peluso 2247, I think it has a cleaner, less colored sound. I think I like it better on acoustic guitar because of that. The low end is a lot tighter also. The M149 is a very bright and powerful mic. This mic is a lot mellower than that, but I think that is going to make me like it more on some sources. It's not as brash in the mid-range either. Compared to the KSM44, I would say that this mic is way warmer.

This is based on just a short time using the Fet 47. I haven't had a chance to put it in front of a bass cabinet or kick drum yet.

It was definitely a great project to take on as my first microphone build. The most exciting part for me has been to see that I can build a high-quality mic myself, for a lot less money.

 

[Scrappersa]

 

[Scrappersa]

I have all of my connections wired as:

A- to  RT
B- to BR
C--to BL
D- to VI

I also took out the trim pot and bridged the connection. Replaced R6 with a 6.8k resistor. I'm not getting any signal except occasionally this weird popping thing happens where it makes a really loud clipping pounding sound over and over again until I turn off the mic. It's almost as if it's building up energy and then finally starts popping. Maybe a grounding issue? I checked all of my transistors and they seem to be in the right place. The polarity of all of the caps are good too. Hopefully my pictures are clear enough but let me know if you guys need to see anything else. I've been working on this all day and can't seem to get to the bottom of this.

 

[skidmorebay]

I also took out the trim pot and bridged the connection. Replaced R6 with a 6.8k resistor. I'm not getting any signal except occasionally this weird popping thing happens where it makes a really loud clipping pounding sound over and over again until I turn off the mic. It's almost as if it's building up energy and then finally starts popping. Maybe a grounding issue? I checked all of my transistors and they seem to be in the right place. The polarity of all of the caps are good too. Hopefully my pictures are clear enough but let me know if you guys need to see anything else. I've been working on this all day and can't seem to get to the bottom of this.

I wonder if the problem is with your capsule. I'm not sure how this works, but I've read on this thread that some people checked their circuit with a small capacitor in place of the capsule. I think that would allow you to trace the circuit with an oscilloscope and tone generator, if I understand it right.
Anyone care to explain how that would work?

 

[Scrappersa]

I would be happy to try it with a cap in place. What value would you guys suggest?

 

[Scrappersa]

I also took out the trim pot and bridged the connection. Replaced R6 with a 6.8k resistor. I'm not getting any signal except occasionally this weird popping thing happens where it makes a really loud clipping pounding sound over and over again until I turn off the mic. It's almost as if it's building up energy and then finally starts popping. Maybe a grounding issue? I checked all of my transistors and they seem to be in the right place. The polarity of all of the caps are good too. Hopefully my pictures are clear enough but let me know if you guys need to see anything else. I've been working on this all day and can't seem to get to the bottom of this.

I wonder if the problem is with your capsule. I'm not sure how this works, but I've read on this thread that some people checked their circuit with a small capacitor in place of the capsule. I think that would allow you to trace the circuit with an oscilloscope and tone generator, if I understand it right.
Anyone care to explain how that would work?

Does it look like my transformer is hooked up correctly?

 

[poctop]

I also took out the trim pot and bridged the connection. Replaced R6 with a 6.8k resistor. I'm not getting any signal except occasionally this weird popping thing happens where it makes a really loud clipping pounding sound over and over again until I turn off the mic. It's almost as if it's building up energy and then finally starts popping. Maybe a grounding issue? I checked all of my transistors and they seem to be in the right place. The polarity of all of the caps are good too. Hopefully my pictures are clear enough but let me know if you guys need to see anything else. I've been working on this all day and can't seem to get to the bottom of this.

I wonder if the problem is with your capsule. I'm not sure how this works, but I've read on this thread that some people checked their circuit with a small capacitor in place of the capsule. I think that would allow you to trace the circuit with an oscilloscope and tone generator, if I understand it right.
Anyone care to explain how that would work?

Does it look like my transformer is hooked up correctly?

Make sure your link A to F are Solid continuity , that might be your problem here ,  remove the capsule and check all the schematic reference voltage that is usually the way to start  troubleshooting ,  relating the reading you sent me A B primary 648 ohm and secondary C D 15 ohm is correct so the infomation above is correct . double check also the polarity of tantalum cap they are polarized also. Check you that you have a proper ground from F to the mic body and then pin 1 also .
from the picture also it could be a cold solder joint ,  just a tip for the future, on soldering,  try to use less solder and focus on what the solder does when the proper temperature is reached just put a touch on it and if you see the solder penetrating in the pad and form a nice little cone then this will help your future build garantueed you'll see when experience come in  also from the picture make sure you dont have pad or connection from the pcb touching the rail this will do it bad.

hang i there ,
Best,
dan,




Hope this helps,
Dan,

 

[poctop]

Just finished my U47fet today. It sounds great. Didn't get to do much testing with it other than some vocals but the midrange is so present and I feel like instruments will sit in the mix nicely.

I am using an old SE Z-2200 as a doner mic along with an RK47 from Microphone-parts and a Peluso BV8p transformer. I'm not sure if this is the transformer but as previously mentioned, I'm not 100% on the bass output. It just seems a bit thin. I guess I may have to go to AMI for their t49.

This is a very nice example of a super clean build super nice work,  try reducing C1 to 500pf to see if it will react better with your transformer combination.
Congrats.

 

[kante1603]

from the picture also it could be a cold solder joint ,  just a tip for the future, on soldering,  try to use less solder and focus on what the solder does when the proper temperature is reached just put a touch on it and if you see the solder penetrating in the pad and form a nice little cone then this will help your future build garantueed you'll see when experience come in  also from the picture make sure you dont have pad or connection from the pcb touching the rail this will do it bad.

hang i there ,
Best,
dan,




Hope this helps,
Dan,

+1 on this!
In the first pic it looks like nearly none of the solder joints have been hot enough or better said the solder did not "flow".Some joints also have a certain amount of dirt on their top.You should really keep your solder iron tip as clean as possible.
Zooming in seems to show a lot of residual flux,not good for a build of this kind!

Udo.

 

[poctop]

I would recommend this solder to all my friends, as well this might help you with soldering in the future , just the best stuff i have ever encountered in this world
perfect for mic building
Hope this helps,
Dan,

 

[LarryChicken]

Just finished my U47fet today. It sounds great. Didn't get to do much testing with it other than some vocals but the midrange is so present and I feel like instruments will sit in the mix nicely.

I am using an old SE Z-2200 as a doner mic along with an RK47 from Microphone-parts and a Peluso BV8p transformer. I'm not sure if this is the transformer but as previously mentioned, I'm not 100% on the bass output. It just seems a bit thin. I guess I may have to go to AMI for their t49.

Just an update here. The lack of bass was due to the fact that the steel of my transformer was touching the side of the metal holder at the bottom of the mic. This must have changed the frequency response and introduced some excess distortion in the signal. So I wrapped the trans in electrical tape and the mic now sounds great.

As far as the sound is concerned I can say that this mic will sound good on SOME types of vocals but not all. This is mainly a factor of the high frequencies being rolled off by the k47 type capsule. Leave vocal duties to the k67-based mics. But where this mic shines is literally everything else. Every instrument I put it in front of is translated in a clean, and present form. There are no extraneous frequencies, only a natural transcription of how it sounds in real life. Speaking from limited expeirience, I've never heard a better recording of my acoustic guitar. The mid range is so richly captured that it's almost too good to be true. And the bass response is full, focused and muddiness does not exist (which is why it's used for bass instruments, I suppose). Maybe I'm just in the honeymoon phase but I really can't see myself leaving this mic in its case every session like I did before the upgrade. I can't wait to try it on guitar amps, bass amps, drum room, and even classical intruments.

Thanks to Dan for the great work on the PCB and all the help along the way.

 

[Scrappersa]

I also took out the trim pot and bridged the connection. Replaced R6 with a 6.8k resistor. I'm not getting any signal except occasionally this weird popping thing happens where it makes a really loud clipping pounding sound over and over again until I turn off the mic. It's almost as if it's building up energy and then finally starts popping. Maybe a grounding issue? I checked all of my transistors and they seem to be in the right place. The polarity of all of the caps are good too. Hopefully my pictures are clear enough but let me know if you guys need to see anything else. I've been working on this all day and can't seem to get to the bottom of this.

I wonder if the problem is with your capsule. I'm not sure how this works, but I've read on this thread that some people checked their circuit with a small capacitor in place of the capsule. I think that would allow you to trace the circuit with an oscilloscope and tone generator, if I understand it right.
Anyone care to explain how that would work?

Does it look like my transformer is hooked up correctly?

Make sure your link A to F are Solid continuity , that might be your problem here ,  remove the capsule and check all the schematic reference voltage that is usually the way to start  troubleshooting ,  relating the reading you sent me A B primary 648 ohm and secondary C D 15 ohm is correct so the infomation above is correct . double check also the polarity of tantalum cap they are polarized also. Check you that you have a proper ground from F to the mic body and then pin 1 also .
from the picture also it could be a cold solder joint ,  just a tip for the future, on soldering,  try to use less solder and focus on what the solder does when the proper temperature is reached just put a touch on it and if you see the solder penetrating in the pad and form a nice little cone then this will help your future build garantueed you'll see when experience come in  also from the picture make sure you dont have pad or connection from the pcb touching the rail this will do it bad.

hang i there ,
Best,
dan,




Hope this helps,
Dan,

Thanks for the help guys. It is now working due to my wonderful and amazing friend Nathan.

 

[poctop]

Thanks for the help guys. It is now working due to my wonderful and amazing friend Nathan.

Can you let us know what was the issue as it could help others as well, 

Congrats to you and Nathan for both your perseverance,
Best,
Dan

 

[poctop]

Be reminded that the U47FET is SuperCardiod and not Cardiod that contributes to make it sounds very focused and tight but with a nice low end and also Special

Best,
Dan,

 

[Scrappersa]

I am completely embarrassed but it was my horrible soldering. I need to get a nicer soldering iron and to learn how to properly do it.

I had a session today and used your FET47 with a Peluso 47 capsule on the outside of the kick and an RE20 on the inside. Man, it was absolutely incredible. I love the combination. Thank you for the wonderful design.

 

[kante1603]

Congrats,

nice to hear you got it up and working!

Cheers,

Udo.