Neumann Vintage U87 Clone : Build Thread.

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Pip said:
Arkenberg said:
Matt55 said:
Hi Arkenberg,

Im not sure if you have read my posts above but maybe we are having the same problem. I just get like constant noise and crackling through the mic.

I tested every resistor and the FET and all my voltages appear fine, biased up fine also. The capsule is also wired correctly.

In my build its either a cold solder (which seems unlikely) or a busted component, most probably one of the capcitors but its hard to check because my DMM wont measure capacitance.

Just to ask, are you using the Styrenes from dany? Just wondering maybe they are bad? I cant test them currently as I have nothing to measure them.

Thanks,

  Matt
Matt
I am using the styrenes from Dany.  I built two microphones and one worked great and the other one just was popping. Then I grabbed a bad cable and shorted the good mic. I fixed that by replacing the L1/L2 but now it pops as well.
It might be the caps but I also have no way to test them. I guess I can replace one by one. I guess I might also have to order more of dany's styrenes to troubleshoot.
Thanks for the Info
Jonathon

Yes check all caps that is a likely source especially if you went with the Polystyrene caps as they hate heat and solvents so you have to be really careful when soldering and cleaning. I dont think an ESR meter is all that helpful with DIY but an LDC meter is invaluable. Lastly how closely matched are you R18 and R19 as these need to be really close, like 3 decimal places close. Read Chungers build thread again as it is really spot on.
I am about to replace the caps and see what happens. R18&R19 I matched.
 
Hey guys, I'm having trouble with biasing my circuit. I think its possible that I settled on a Jfet that isn't optimal for the circuit, because whenever I try to measure the IDSS of any particular Jfet I get 0.16mA??  Eventually I just soldered one in to see if I could make it work but I cant seem to get the clipping symmetrical in my O-scope.  It seems unlikely to me that every Jfet I try would all have the exact same IDSS since most people have some variation. So maybe I'm trying to measure them incorrectly? I took a picture of how I'm measuring so maybe someone can spot my mistake. Thanks in advance for taking time to help a beginner!

Update: I tried an older multimeter that my dad had, and for some reason I was able to get idss values that made more sense. I had about 3 that were around 9.25 idss but now that meter isnt giving a value anymore. It just reads 0.00? I feel like I must be doing something kind of wierd. Any insight would still be appreciated!
 

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Hello folks,
just wanted to post about a picture and some sound clips I did comparing my U87 build with Dany's 87M PCB,  Peluso 87i capsule, and Cinemag CM 13113 transformer... What a gem this mic is (I will be building another very soon for matched pair) and how it sounds compared to my Neumann U87ai...
The clips are of a Martin D28 (just riffin') recorded straight into a RME Fireface 800 and then through a Redd 47 into RS124 VariMu into the RME FF800.

https://www.dropbox.com/sh/6kfjhmbvfrusaqh/AADEC732p8ufoBFqcP2khvJpa?dl=0
 

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OrganizedKonfusion said:
Hey guys, I'm having trouble with biasing my circuit. I think its possible that I settled on a Jfet that isn't optimal for the circuit, because whenever I try to measure the IDSS of any particular Jfet I get 0.16mA?? ...

The measuring method picture you posted looks right. But with that meter, I believe you need the red meter lead to be plugged in to the socket marked "400mA". Remember you're measuring the current through the fet. Check the meter manual - I may be wrong. I think that Dad's meter was probably giving something closer to the true value. If his meter is old then maybe the battery just needs changing. Build a small circuit with just a battery and resistor and check that the current flowing in it is correct - use Ohm's Law to work out what current reading you should see on the meter. When you're sure you've got a reliable meter go back to testing the fets.

Let us know how you get on.
 
Krumlee said:
The measuring method picture you posted looks right. But with that meter, I believe you need the red meter lead to be plugged in to the socket marked "400mA". Remember you're measuring the current through the fet. Check the meter manual - I may be wrong. I think that Dad's meter was probably giving something closer to the true value. If his meter is old then maybe the battery just needs changing. Build a small circuit with just a battery and resistor and check that the current flowing in it is correct - use Ohm's Law to work out what current reading you should see on the meter. When you're sure you've got a reliable meter go back to testing the fets.

Let us know how you get on.

Thanks Krumlee, I'm not sure what's going on with my fluke meter but I tried the 400mA side before and that didn't do the trick either. After seeing how many of my Jfets were a fairly nominal Idss value I decided to try biasing my circuit again with the Jfet that I already installed and I was able to get some very symmetrical looking clipping on my scope. I also measured the voltage at the drain and got 11.22 V so I think I'm in the ballpark now.

Thanks for your help!
 
OrganizedKonfusion said:
Hey guys, I'm having trouble with biasing my circuit. I think its possible that I settled on a Jfet that isn't optimal for the circuit, because whenever I try to measure the IDSS of any particular Jfet I get 0.16mA??  Eventually I just soldered one in to see if I could make it work but I cant seem to get the clipping symmetrical in my O-scope.  It seems unlikely to me that every Jfet I try would all have the exact same IDSS since most people have some variation. So maybe I'm trying to measure them incorrectly? I took a picture of how I'm measuring so maybe someone can spot my mistake. Thanks in advance for taking time to help a beginner!

Update: I tried an older multimeter that my dad had, and for some reason I was able to get idss values that made more sense. I had about 3 that were around 9.25 idss but now that meter isnt giving a value anymore. It just reads 0.00? I feel like I must be doing something kind of wierd. Any insight would still be appreciated!
Had this same problem when I was choosing my jfet. It seems two of my multimeters worked well and then went dead. I found that I had blown the fuse in both of the multimeters. So I did some research and realized if you cross the leads while hooked up or touch the leads to the wrong legs of the jfet it will cause the fuse in the multimeter to blow.
 
Arkenberg said:
Had this same problem when I was choosing my jfet. It seems two of my multimeters worked well and then went dead. I found that I had blown the fuse in both of the multimeters. So I did some research and realized if you cross the leads while hooked up or touch the leads to the wrong legs of the jfet it will cause the fuse in the multimeter to blow.

Aha! I wondered if something like that was going on! Thank you so much!
 
Ok, so I finished my D87 and it works great in cardioid! The problem is with the the other two polar patterns...  :( in either one, I get alot of static noise that sounds like I've got my mic out in some strong winds. I still get signal from the capsule, it just sounds faint and drowned out by all the noise. Forgive my ignorance, but since the mic works in cardioid I would assume that the front and rear diaphragm connections are good and maybe the problem is with either the front back connection or the rear back connection? Could a bad solder joint cause sound like that? Any opinions would be greatly appreciated.

 
Ok, so I've followed a hunch and now I've got 2/3 polar patterns woking. I went in and tightened the saddle screw for front back and now I have the Cardioid and Figure 8 patterns totally functional.  The weird thing is that I went to check the Omni setting and now the noise is even worse for that setting and the saddle screw for rear back isnt loose like Front back was. I opened it up again and tried to tighten it a little bit but I doubt thats the problem this time. I think the saddle of the mount might be the culprit. Its a little wierd because it isn't totally level. The front half is lower than the back half. If I can't get it to work when I test it again I may try to swap out the saddle for one that is level.  I tried to take a picture so you can see what I mean but it was almost impossible to get my phone to focus on the saddle and its really dim in my place at night.  Any thoughts on the issue would still be appreciated.
 

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Hey,

My D-U87 is not working either with just pure noise as you describe in all polar patterns.

I also blew the fuse in my DMM when testing the FET's.

I am gueeing you got the Body from Chunger because my capsule mount is exaclty the same, half is stepped down lower than the other half and the capsule will not screw tightly onto the capsule holder...

I also need to get another capsule mount for my D-U47Fet because the mount that came with that was too small and wont fit the capsule :( I guess i need to email chunger and ask for the correct ones?

Thanks,

Matt
 
Matt, yeah I got the body from chunger, I also bought a different mount from him (that doesnt fit the body anymore) with an extra saddle so I have two others to try out. I'll let you know if swapping out the saddle fixes my problem. Are you getting any mic signal to come through at all or is it just noise?
 
Im just getting pure noise no signal in all patterns.

Everything I checked with the DMM is correct. Im using an Eric (TSKGUY) Capsule which people checked and is wired correctly. (There are some photos of my build a few posts back).

I tested every resistor and they all checked ok.

The only thing I can do is go over solders and replace the capacitors 1 by 1 and see if that fixes it...

Thing is I built 2xAML EZ1073's just before the mic which have many more solders and both worked without fault first time. I don't think its a solder issue...

Thanks,

Matt
 
Ok, well I switched out the saddle for my mount and it hasnt paid off. I have the noise back in figure 8 pattern and its still in Omni as well. This saddle mount was slightly thicker than the last so I drilled holes to line up with the capsule and then I drilled a little well so the saddle screws would sit a little deeper and thread into the capsule a bit more. Same problem.  I decided to try those patterns out with different combinations of low cut and pad engaged.  It seems like the switches do everything that they should. However, when I'm in figure 8 and the low cut is engaged the noise disapeers. I turned up my pre and was able to get a clean recording without any audible noise. I can only hear noise again if I really crank the pre. In omni when I engage the low cut I still have noise its just a little less present.  I think my next best guess is to check my wiring and switches for cold solder joints...

Correction: Noise disappears completely in figure 8 with low cut engaged.  Definitley going to take a look at my switches.
 
Hi guys,
just after a bit of help when reading the idss rating of a Jfet. I may've shorted the wrong to legs to together, would this Jfet be considered destroyed?
Thanks
 
Hey,

Like I said above I did this with 2 out of the 10 Jfets I bought. I retested them once I had replaced the fuse in my DMM and got a reading that seemed reasonable, but I put them 2 Jfets to the side and did not use them because, like you, I didnt know if that had damaged them or not...

Hopefully someone who knows more than me will come along and help :)

Thanks, Matt
 
Hi

I am busy trying to bias the FET of my D-87 v1.3 (blue pcb)build using Matadors method - http://groupdiy.com/index.php?topic=46109.40

The way I have it setup is using my soundcard and "Soundcard Oscilloscope" - I have a Line Out cable with an alligator clip on the Hot (2) Pin going to R6 (Installed backwards) and an  Alligator clip from Pin 1 to the Chassis of the Mic.

On the Line In Hot (2) Pin I have an alligator clip going to the Drain Leg of the FET on the mic. and from Pin 1 on the line in to the Mic Chassis.

I generate a signal a 1Khz and I see the Sine Wave on the Oscilloscope. I Increase the level from the signal generator and the output on my soundcard mixer but I cannot seem to get the signal to flatten at the top or bottom, I have also tried turning the Bias trimmer but that does not make any significant changes - I am not sure if the settings on the oscilloscope are wrong. I have never really used one before

I would appreciate it if you could please give me any advice as to what I might be doing wrong.

One thing I noticed was the level coming in to my sound card (from drain to scope) was very low
 
dacapitan said:
Hi

I am busy trying to bias the FET of my D-87 v1.3 (blue pcb)build using Matadors method - http://groupdiy.com/index.php?topic=46109.40

The way I have it setup is using my soundcard and "Soundcard Oscilloscope" - I have a Line Out cable with an alligator clip on the Hot (2) Pin going to R6 (Installed backwards) and an  Alligator clip from Pin 1 to the Chassis of the Mic.

On the Line In Hot (2) Pin I have an alligator clip going to the Drain Leg of the FET on the mic. and from Pin 1 on the line in to the Mic Chassis.

I generate a signal a 1Khz and I see the Sine Wave on the Oscilloscope. I Increase the level from the signal generator and the output on my soundcard mixer but I cannot seem to get the signal to flatten at the top or bottom, I have also tried turning the Bias trimmer but that does not make any significant changes - I am not sure if the settings on the oscilloscope are wrong. I have never really used one before

I would appreciate it if you could please give me any advice as to what I might be doing wrong.

One thing I noticed was the level coming in to my sound card (from drain to scope) was very low

you don't need to install the R6 backward on the blue pcb ( the only model you don't need to) , so surely that will help out ,
basically you have to inject signal just before the FET coupling cap ,
I strongly recommend using a real sinetone generator to do this it is more convenient and you need to puh the signal quite hard ,
the first time you bias a 87 is can be tricky with the scope method as you are looking for a precise point of symmetry so you can experiment with a little befor getting use to it,  I recommend to set the drain vltage at 11.5V to start and test the mic and afterwards bias it more precisely with it ,
Hope this helps,
Dan,
 
Hey guys
Boy I love this mic.
So much I'm about to build another.
I have the pcbs already but am trying to source the polys, specifically the 10pf.
Has anyone found a distrubuter in the States  that has them?
Thanks
Dylan
 
poctop said:
dacapitan said:
Hi

I am busy trying to bias the FET of my D-87 v1.3 (blue pcb)build using Matadors method - http://groupdiy.com/index.php?topic=46109.40

The way I have it setup is using my soundcard and "Soundcard Oscilloscope" - I have a Line Out cable with an alligator clip on the Hot (2) Pin going to R6 (Installed backwards) and an  Alligator clip from Pin 1 to the Chassis of the Mic.

On the Line In Hot (2) Pin I have an alligator clip going to the Drain Leg of the FET on the mic. and from Pin 1 on the line in to the Mic Chassis.

I generate a signal a 1Khz and I see the Sine Wave on the Oscilloscope. I Increase the level from the signal generator and the output on my soundcard mixer but I cannot seem to get the signal to flatten at the top or bottom, I have also tried turning the Bias trimmer but that does not make any significant changes - I am not sure if the settings on the oscilloscope are wrong. I have never really used one before

I would appreciate it if you could please give me any advice as to what I might be doing wrong.

One thing I noticed was the level coming in to my sound card (from drain to scope) was very low

you don't need to install the R6 backward on the blue pcb ( the only model you don't need to) , so surely that will help out ,
basically you have to inject signal just before the FET coupling cap ,
I strongly recommend using a real sinetone generator to do this it is more convenient and you need to puh the signal quite hard ,
the first time you bias a 87 is can be tricky with the scope method as you are looking for a precise point of symmetry so you can experiment with a little befor getting use to it,  I recommend to set the drain vltage at 11.5V to start and test the mic and afterwards bias it more precisely with it ,
Hope this helps,
Dan,

OK, I dont have a real Sinetone generator, so I'll have to see if I can rent one from somewhere - Is it OK to use the software sound card oscilloscope or is it best to use a real one too? This might sound like a stupid question, but does all of this biasing and voltage calibration need to be done with the mic receiving 48V phantom power?
 
dacapitan said:
poctop said:
dacapitan said:
Hi

I am busy trying to bias the FET of my D-87 v1.3 (blue pcb)build using Matadors method - http://groupdiy.com/index.php?topic=46109.40

The way I have it setup is using my soundcard and "Soundcard Oscilloscope" - I have a Line Out cable with an alligator clip on the Hot (2) Pin going to R6 (Installed backwards) and an  Alligator clip from Pin 1 to the Chassis of the Mic.

On the Line In Hot (2) Pin I have an alligator clip going to the Drain Leg of the FET on the mic. and from Pin 1 on the line in to the Mic Chassis.

I generate a signal a 1Khz and I see the Sine Wave on the Oscilloscope. I Increase the level from the signal generator and the output on my soundcard mixer but I cannot seem to get the signal to flatten at the top or bottom, I have also tried turning the Bias trimmer but that does not make any significant changes - I am not sure if the settings on the oscilloscope are wrong. I have never really used one before

I would appreciate it if you could please give me any advice as to what I might be doing wrong.

One thing I noticed was the level coming in to my sound card (from drain to scope) was very low

you don't need to install the R6 backward on the blue pcb ( the only model you don't need to) , so surely that will help out ,
basically you have to inject signal just before the FET coupling cap ,
I strongly recommend using a real sinetone generator to do this it is more convenient and you need to puh the signal quite hard ,
the first time you bias a 87 is can be tricky with the scope method as you are looking for a precise point of symmetry so you can experiment with a little befor getting use to it,  I recommend to set the drain vltage at 11.5V to start and test the mic and afterwards bias it more precisely with it ,
Hope this helps,
Dan,

OK, I dont have a real Sinetone generator, so I'll have to see if I can rent one from somewhere. This might sound like a stupid question, but does all of this biasing and voltage calibration need to be done with the mic receiving 48V phantom power?

yes , because then the circuit is not powered
so nothing at all will happen ,
D
 

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