Neumann Vintage U87 Clone : Build Thread.

[TillM]

Hey,
this is my first post.
I'm from germany, so I hope, that you understand everything I write.
I've build this fantastic Mic some weeks ago.
I enjoyed this experience very much and first want to thank all people who make this happen.
My Mic works but i've a problem when I record the mic.
I use logic and when i press the record button the waveforms look normal.
When the recording stops, I got this.

As you can see, i got trouble with the negative phase.
I hope you can help me with my problem.

 

[ln76d]

As long as you do not write in German, everything is understandable
If microphone sounds ok, much more probable is bad placement of microphone or unmatched to source.
For high SPL I have seen many similar situations with dynamic microphones, especially on snare and mostly at the bottom / springs.

 

[TillM]

The microphone sounds okay
As you said, this negative wave forms I mostly get when i'm hitting the snare.
The thing is, why i'm wondering, when I use my Neumann TLM 102 as mono overhead mic, then the wave forms look normal.
That's why i'm wondering, because the with my DIY U87 the waveform looks like on the picture.

 

[ln76d]

Assuming that your build is close to original unit, comparing it to TLM102 is 122dB VS 144dB for max SPL.

 

[TillM]

okay ...so at the end, everything seams normal.
I played a bit with the Bias.
I take the mic beside my drum, press record and play, than take a screw and adjust the bias.
The problem was, as the wave form was perfect for me (positive and negative phase) my multimeter shows me 1,5v.
10 Volt less than in the shematics.
So I turn the bias back to 11,5v. With very percussive instruments the Waveform looks like this.
The weird think is, that when I record in Logic the waveform looks "normal" as long as i press the recording button.
When I stop the recording button, the waveform turns into the weird form.
For me, without any plugins the Snare sounds a bit compressed when I place the mic as overhead.
But voice recording sounds beautiful.
I never used a original Neumann U87 so I've no comparison.
But as you guys said, everything seams normal.

 

[ln76d]

That "compression" is when the circuit can't handle too much SPL.
It's normal - so now you know, that you need to look for different microphone for OH
Also waveform shape at the recording and after is nothing which you should worry about.
I had similar situations in other programs runing it on win7.


After a while - there's also possibility that your microphone preamp can't handle too much SPL and it's overdrived.
Worth to check.

 

[JessJackson]

Hey,
this is my first post.
I'm from germany, so I hope, that you understand everything I write.
I've build this fantastic Mic some weeks ago.
I enjoyed this experience very much and first want to thank all people who make this happen.
My Mic works but i've a problem when I record the mic.
I use logic and when i press the record button the waveforms look normal.
When the recording stops, I got this.

As you can see, i got trouble with the negative phase.
I hope you can help me with my problem.

looks like DC Offset. First thing i would check is the bias perfectly and make sure the TX outputs is correct phase.

 

[granger.frederic]

asymmetrical waveform is abnormal
possible solutions , most to lesser probable :
-bad biasing or bad Jfet , check biasing with a scope and signal injection
-bad source capacitor c8, change it
-bad capsule , try with another or a 80pf capacitor with signal injection, clean it , change it or look foward
-bad polarization resistor(s)  check all voltages with a static voltmeter , clean or change it
-leaking or bad negative feedback capacitors c3 , c5 , c6 or c9  or even c1 , c2 , change it
-bad c7 , check dc after with signal sinus injection , change it
-bad c6, c7 ,L1 , L2 change or remove
-bad output transformer

regards

 

[TillM]

asymmetrical waveform is abnormal
possible solutions , most to lesser probable :
-bad biasing or bad Jfet , check biasing with a scope and signal injection
-bad source capacitor c8, change it
-bad capsule , try with another or a 80pf capacitor with signal injection, clean it , change it or look foward
-bad polarization resistor(s)  check all voltages with a static voltmeter , clean or change it
-leaking or bad negative feedback capacitors c3 , c5 , c6 or c9  or even c1 , c2 , change it
-bad c7 , check dc after with signal sinus injection , change it
-bad c6, c7 ,L1 , L2 change or remove
-bad output transformer

regards

Thanks for the Replay.
I'll check it.
Capsule is from Peluso K87 and the output transformer from AMI.
My first hope is, that it is just bad biasing, because i don't have a scope.
Your list is perfect, thank you very much.

 

[ln76d]

asymmetrical waveform is abnormal
possible solutions , most to lesser probable :
-bad biasing or bad Jfet , check biasing with a scope and signal injection
-bad source capacitor c8, change it
-bad capsule , try with another or a 80pf capacitor with signal injection, clean it , change it or look foward
-bad polarization resistor(s)  check all voltages with a static voltmeter , clean or change it
-leaking or bad negative feedback capacitors c3 , c5 , c6 or c9  or even c1 , c2 , change it
-bad c7 , check dc after with signal sinus injection , change it
-bad c6, c7 ,L1 , L2 change or remove
-bad output transformer

regards

Overall:
-bad microphone




How do you explain similar results with a dynamic microphone?
Exactly when recording snare.

 

[granger.frederic]

waouh !
thanks ln76d , helps a lot  ???
you're really an expert ...

dynamic is dynamic and static is static
even with a dynamic you shouldn't have that kind of waveform , look again

he said that he had a symmetrical waveform with his tlm102

a snare with an appropriate mic should look more or less like this :

 

[ln76d]

I can not compete with your Magnificence all Wise - no one can!

I know how looks typical waveform of properly recorded snare and you do not have to strain.
BTW it's weak from your side that you can't normally carry a conversation...

Check again max SPL for TLM102 and compare for example.
Recording chain isn't only microphone and your waveform.
I didn't said i have all the snares captured that way.
Put a drummer with a hand like a hammer and some microphones can't handle that, some preamps can't handle that - especially with fixed gain or gain set not properly etc.

To OP - you could try different preamp in the same situation.

 

[granger.frederic]

you're kidding , i posted a checklist of probable issues to help a member and you took a sarcastic tone :

I can not compete with your Magnificence all Wise - no one can!

I know how looks typical waveform of properly recorded snare and you do not have to strain.
BTW it's weak from your side that you can't normally carry a conversation...

and :

" Overall:
-bad microphone

"

i don't take it for a personal attack because, usually ,  someone becomes sarcastic in reply,  when he lacks of knowledge...

i add that you were personally happy when i helped you for some measurements in another topic , and that TillM thanked me as well , so why would i deviate to unfriendly tone ?

 

[ln76d]

Fred!

the written word, as you can see has its limits, even if using  emoticons.
My intentions were quite different, it had to be joke (even if weak) and definitely not sarcastic - much more in friendly atmosphere.
I didn't wrote that you are wrong, that it has no sense etc.
I didn't comment it at all in meritorical matter.
It have lot of sense, especially when you listed most of the circuit
Please remember from now, that if i'll be disagreeing with you it wouldn't be sarcastic and will be clearly stated.
I don't have any need to be sarcastic here on gdiy and sorry if someone ever could read my words that way - i love dry jokes and i have really stupid sense of humor.
I asked you also about dynamic microphones with the same symptoms, and even if dynamic is dynamic and static is static - i had these results when i recorded tracks and i know few others similar recordings, because am mixing not only tracks recorded by me.
I never denied your knowledge, even if i disagree with something, so please
don't use "you're really an expert ..." and "lacks of knowledge..."  because i'm not against you - rather I'm hoping for productive discussion in friendly atmosphere
than proving own right.
It's everything clear and ok now??

Back to the topic - before i would look inside the circuit - first i would check everything else in recording chain, use different preamp etc.

 

[granger.frederic]

Fred!

the written word, as you can see has its limits, even if using  emoticons.
My intentions were quite different, it had to be joke (even if weak) and definitely not sarcastic - much more in friendly atmosphere.
I didn't wrote that you are wrong, that it has no sense etc.
I didn't comment it at all in meritorical matter.
It have lot of sense, especially when you listed most of the circuit
Please remember from now, that if i'll be disagreeing with you it wouldn't be sarcastic and will be clearly stated.
I don't have any need to be sarcastic here on gdiy and sorry if someone ever could read my words that way - i love dry jokes and i have really stupid sense of humor.
I asked you also about dynamic microphones with the same symptoms, and even if dynamic is dynamic and static is static - i had these results when i recorded tracks and i know few others similar recordings, because am mixing not only tracks recorded by me.
I never denied your knowledge, even if i disagree with something, so please
don't use "you're really an expert ..." and "lacks of knowledge..."  because i'm not against you - rather I'm hoping for productive discussion in friendly atmosphere
than proving own right.
It's everything clear and ok now??

Back to the topic - before i would look inside the circuit - first i would check everything else in recording chain, use different preamp etc.

make sense to me
sorry for the misunderstanding

 

[TillM]

Well guys, i don't want the discussion in that way
I'm thankful for your help @ln76d and granger.frederic

I'll check the circuit when I've the time.
First of all I'll check my mic with a oscilloscope.
My multimeter is not the best, so I need a better one.
The funny thing is, when I record voice or guitar, a get a symmetrical wave form.
Only on percussive instruments, like snare or hand clapping, I get these weird wave forms.
The thing that makes me wonder is, that on percussive instruments the x-phase waveform gets cut and negative phase looks like on the picture.
I hope a oscilloscope will help.
If not, i'll check the circuit and change the jfet.

 

[storres1]

Hi Guys!
I am building my mic and want to give it a more accentuated high end (10kHz and up), as well as a stronger overall output. Anyone have any ideas on how to go about this?
-Simone

 

[ln76d]

Change C6 220pF for 150pF or 100pF.
Wan't more low end? Change C5 to 100nF.
There's not much too change to get higher output level.

 

[micaddict]

Well, you could go for the -ai version instead.

But you'll sacrifice headroom for higher output. 
Tone, too.
Well, tha't's the consensus anyway.

What preamp do you use?
And EQ?

 

[storres1]

Thank you  ln76d! Is the theory that the lower the value of the C6, the more high end?

Hmm okay, yeah that's what I was afraid of. I don't wanna loose headroom. we use a 1073 pre-amp and just EQ in pro tools.