Neumann Vintage U87 Clone : Build Thread.

[dacapitan]

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

ah, that would also be my problem then haha! With the sine tone generator Is it OK to use the software sound card oscilloscope or is it best to use a real one too?

 

[poctop]

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

ah, that would also be my problem then haha! With the sine tone generator Is it OK to use the software sound card oscilloscope or is it best to use a real one too?

if you continue doing DIY , you should get one ,
D

 

[poctop]

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

Thanks For the kind word,
i do have those in kits in the webstore if needed,
yes 10pf is pretty hard to find these days,
Best,
Dan,

 

[Rocinante]

Dan,
I was actually trying to avoid your store cause I know once I go to purchase the polys I'll feel compelled to keep adding other items (like the d-u47 pcbs or the d-12 or the d-u67...) and therefore forced to build another amazing microphone.
Oh well...

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

Thanks For the kind word,
i do have those in kits in the webstore if needed,
yes 10pf is pretty hard to find these days,
Best,
Dan,

 

[dacapitan]

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

ah, that would also be my problem then haha! With the sine tone generator Is it OK to use the software sound card oscilloscope or is it best to use a real one too?

if you continue doing DIY , you should get one ,
D

I am still waiting for my capsules, which should be here next week some time, and not having the budget to own a scope/signal generator at the moment, and not having one on hand I just decided to give this a go with what I have on hand

powered the mic with 48v and I trimmed the drain to 11.5 and I am now also able to push the scope to levels where it clips - I must say it is quite a tricky to get the clipping symmetry - 11.5v actually isn't far off - maybe its just my "chewing gum and sticky tape" signal generator and scope setup that makes it harder? I noticed that when I push it I get these little "teeth" on the edge of the wave form? is that a problem and does this look generally ok in terms of symmetry?

 

[dacapitan]

I received my capsules and the one mic is working great - I did some tracking with it and it sounds absolutely amazing, so I am very pleased  ;D

I am having a problem with my second one, since  first calibration and power on - the FET keeps blowing when I trim the drain voltage to 11.5VDC. I have replaced it a few times now.

Something that I have noticed which may be completely unrelated (I have no clue) - is, with my working mic is when the drain voltage is 11.5V the source leg is around 2.5VDC. But, with my problematic Mic, when the drain gets to 11.5V the source leg is at over 4VDC, the drain leg stays at 11.5VDC for about half a minute and then it drops to 4v (same as source leg) and it cant be trimed higher than 7v - where the drain and source measure 7v at this point, and I have to replace the FET.

I took voltage readings according to the schematic, below are the results:

Problem Mic:
R18 - 46.1VDC (shematic: 46.6VDC)
R19 - 46.1VDC (shematic: 46.6VDC)
Zener 24 -  22.98VDC (shematic: 23.6VDC)
R12, R14, C10 - 19.28VDC (shematic: 20.62VDC)
C5 - 39.7VDC (shematic: 40VDC)
FC - 39.7VDC (shematic: 40VDC)


Working Mic:
R18 - 46.6VDC (shematic: 46.6VDC)
R19 - 46.1VDC (shematic: 46.6VDC)
Zener - 24 22.88VDC (shematic: 23.6VDC)
R12, R14, C10 - 20.96VDC shematic: 20.62VDC)
C5 - 42VDC (shematic: 40VDC)
FC - 39.7VDC (shematic: 40VDC)

Capsule and Transformer were not connected when this happened, I have Tried disconnecting the switch board too but I still get that high 4V voltage at the source, so I quickly trim it down before I have to replace it again. I really have no clue how to trouble shoot this and get to the bottom of this, any help would be much appreciated I am very willing to learn and follow instructions, I would really appreciate some help as I am stuck with this

 

[spacecho]

Hello Danny,

Thanks for a great project!

I've searched all of the forum threads and your website for the 'schematic ' / wiring diagram and i can't seem to find it anywhere?
You once had a build pictorial that seems to be missing also?

I'm a little confused when it comes to wiring the switches - i.e: which pins correspond to which polar pattern etc...
Furthermore - different versions of your circuit board seem to contradict the photo build pictorials that are our there on the net
i.e. the green boards of the chunger build seem to be back to front, compared to a build with the blue boards?

Could you point me to the relevant schematic / wiring diagram?

Also - in lieu of a schematic, could you verify the 'pinout' on the pCB for the 'XLR' connector?
The build doc says Pin 1 Hot, Pin 2 Cold, Pin 3 Ground?

I assumed (without a schematic or wiring diagram to go by) that pad 1,2,3 on the PCB would correspond to Pin 1,2,3 (GND,Hot,Cold) on the XLR.

I'm asking, because i wired up the mic and powered it up successfully (fet is at 11.5v) and i seem to have a working FIG8, but weak Cardiod / Omni.
I'm trying to determine if the switch PCB is wired wrong, or the XLR socket, or both?

 

[dacapitan]

Hello Danny,

Thanks for a great project!

I've searched all of the forum threads and your website for the 'schematic ' / wiring diagram and i can't seem to find it anywhere?
You once had a build pictorial that seems to be missing also?

I'm a little confused when it comes to wiring the switches - i.e: which pins correspond to which polar pattern etc...
Furthermore - different versions of your circuit board seem to contradict the photo build pictorials that are our there on the net
i.e. the green boards of the chunger build seem to be back to front, compared to a build with the blue boards?

Could you point me to the relevant schematic / wiring diagram?

Also - in lieu of a schematic, could you verify the 'pinout' on the pCB for the 'XLR' connector?
The build doc says Pin 1 Hot, Pin 2 Cold, Pin 3 Ground?

I assumed (without a schematic or wiring diagram to go by) that pad 1,2,3 on the PCB would correspond to Pin 1,2,3 (GND,Hot,Cold) on the XLR.

I'm asking, because i wired up the mic and powered it up successfully (fet is at 11.5v) and i seem to have a working FIG8, but weak Cardiod / Omni.
I'm trying to determine if the switch PCB is wired wrong, or the XLR socket, or both?

It sounds like you have the patterns wired to the wrong switch points....

Check that it is wired like this...

“OMN” - PAT 1

“CRD” - PAT 2

  “8” - PAT 3

XLR to PCB is

1-1 (GND)
2-2(HOT)
3-3(COLD)

I found the Schematic in the mic&mod build guide which uses the same boards.... http://p3796.phpnet.org/shop/tutoriels/U87DIYKIT/U87iDIYKit-Build-Guide-1.0.zip

This will also come in handy...
http://www.vintagemicrophonepcbkit.com/Neumann%20U87%20Build.htm

 

[spacecho]

Thanks for your reply 'dacapitan'

I checked my wiring, and it matches:

“OMN” - PAT 1
“CRD” - PAT 2
“8” - PAT 3
XLR to PCB is
1-1 (GND)
2-2(HOT)
3-3(COLD)

I did an extensive comparison with an original (early 70's) and fully serviced U87.

These were the differences:
My fig 8 pattern is similar volume, but muddy in the low end and missing high frequencies (dull), when compared to the original mic.

My Cardiod patter is slightly lower in volume, but muddy in the low end and missing high frequencies (dull), when compared to the original mic. In this mode, the rear capsule signal is louder than the original U87.

My Omni is much lower in volume, but it's freq response is much better, and very similar to the original. I rotated both mics 90 degrees (4 times) and found that they both sound similar in each position.

I guess i've figured out that my mic sounds really good (normal) in omni, but something is not right in the other positions.

If anyone had any suggestions of things to look for, it would be great to hear from you.

My mic is using a cinemag transformer and Eric H capsule.

Thanks in advance!

 

[tskguy]

It may be capsule related, 

Is the capsule wired correctly?? I assume by your description but its always good to ask. Do you have another test capsule to compare with?  It will rule out problems electronically

Eric

 

[dacapitan]

Thanks for your reply 'dacapitan'

I checked my wiring, and it matches:

“OMN” - PAT 1
“CRD” - PAT 2
“8” - PAT 3
XLR to PCB is
1-1 (GND)
2-2(HOT)
3-3(COLD)

I did an extensive comparison with an original (early 70's) and fully serviced U87.

These were the differences:
My fig 8 pattern is similar volume, but muddy in the low end and missing high frequencies (dull), when compared to the original mic.

My Cardiod patter is slightly lower in volume, but muddy in the low end and missing high frequencies (dull), when compared to the original mic. In this mode, the rear capsule signal is louder than the original U87.

My Omni is much lower in volume, but it's freq response is much better, and very similar to the original. I rotated both mics 90 degrees (4 times) and found that they both sound similar in each position.

I guess i've figured out that my mic sounds really good (normal) in omni, but something is not right in the other positions.

If anyone had any suggestions of things to look for, it would be great to hear from you.

My mic is using a cinemag transformer and Eric H capsule.

Thanks in advance!

I had the exact same problem you are experiencing and I thought it was the PCB switch wiring I had wrong, but I remember now it was actually the capsule wiring that I had wrong - that one is working  like a charm now.... all patterns should be fairly equal in volume and clarity. I'm still having trouble with my second one though (built a matched pair) - FET keeps blowing and I'm not sure why.

It may be capsule related, 

Is the capsule wired correctly?? I assume by your description but its always good to ask. Do you have another test capsule to compare with?  It will rule out problems electronically

Eric

Eric is actually right - the capsule is likely to be wired wrong. I had the same problem with my working mic, it was the capsule wiring that solved it. It helps to use a DMM  to and buzz out which is which wire is which plate, follow the build guide and PCB labeling accordingly - it can take some concentration and patience to get your head around which plate/wire corresponds to which PCB label - which makes it error prone too.  Good luck!

Eric - you don't by any chance, have some tips on what the problem could be on my one non-working  mic? Problem is posted a few posts up

 

[moprq]

I have a question about capsule wiring. I ended up having to screw the the back plate wire hire up on the capsule, most appeared to be screwed in near the saddle. Does it matter what hole I screwed it into as long as it's on the backplate, and if it's wrong how would I know?

 

[dacapitan]

I have a question about capsule wiring. I ended up having to screw the the back plate wire hire up on the capsule, most appeared to be screwed in near the saddle. Does it matter what hole I screwed it into as long as it's on the backplate, and if it's wrong how would I know?

It shouldn't be a problem - using the saddle screws allows the wire to be shorter, closer to the holes and use less screws

As long as it's the correct plate to pcb.

If it's wrong you would hear it's wrong, you can use a DMM to buzz out which screw or wire is which plate

 

[spacecho]

Thanks for your replies, and thanks to Eric for getting in touch via p.m.

I did some more investigating.

My wiring appears to be correct:

FD - front diaphram
FBK - front backplane (brass ring)

RD - rear diaphram
RBK - reak backplane (brass ring)

i checked each wire individually.
I also checked for shorts - the front and back brass rings are 'isolated'. Each diaphragm is 'isolated' from its own brass ring.

My voltages seem to match the schematic:
11.5 v at fet
40v at FD
23.1v (instead of 23.6v) at zener

My pad / phase and pattern switches are wired correctly (as per the 'micandmod' build guide) - i can't seem to find the build guide or a schematic on Dany's site or anywhere here at Gdiy. I am using the 'blue boards'. they appear to be different to the 'green' boards in the chunger build.

I did more listening and recording:
The different polar patterns all have different volume:

Fig 8 loudest,
Cardiod medium
Omni softest

They also sound different:

Fig 8 - muddy /bassy no hi end
Cardiod - as above
Omni - open and balanced sound (similar to original u87)

If anyone can point me to the correct 'schematic / build guide' for the 'Blue 2 piece PCB' it would be appreciated. As it stands, all i had to go on for the build, was the excel found on Dany's site. I don't know if the designations on the parts list match the PCB.
It seems that this excel has errors: (it says to connect pin 1 to hot?)

if anyone has any suggestions for things i can check, i'd love to hear from you.

 

[Arkenberg]

Well gets I have finally finished my two match set of u87's it took forever and a lot of trial and error. Mostly I have found that I was horrible at soldiering! After fixing my cold soldier joints the Mics are finished!

 

[xWESTWOODx]

Hi there,

I just finished building this mic. I'm getting sound and all the switches seem to be working. The only issue I'm getting is a lot of white noise. Any suggestions as to what could be causing this and where I should look? I'm new to this whole diy process and this is my first project.

Thanks,

Mat

 

[atticmike]

Anybody here selling beesneez / high quality bodies for the project? And capsules of course.

I also have an unopened iphone 6s plus I'd trade in as well

 

[Pip]

Hi there,

I just finished building this mic. I'm getting sound and all the switches seem to be working. The only issue I'm getting is a lot of white noise. Any suggestions as to what could be causing this and where I should look? I'm new to this whole diy process and this is my first project.

Thanks,

Mat

What capsule are you using? Make sure all your PC Boards are as clean as they can be especially near the high impedance connections. Also do a search in this thread there is a lot of info.

 

[xWESTWOODx]

Thanks for the reply Pip.

'm using the peluso k87i capsule. I'll try giving the PC board a good clean again and see if that helps. I tried doing a search in the forum for other comments/documentation, but I can't seem to find anything. Any recommendations on what I should be searching for?

Thanks again for all the help,

Mat

 

[dacapitan]

Im still having a problem with my mic and have been finding it hard to get any real troubleshooting help here, if anyone could please help me through this, I would really appreciate it, as I don't know what the problem is or how to go about solving it.

since  first calibration and power on - the FET keeps blowing when I trim the drain voltage to 11.5VDC. I have replaced it a few times now.

Something that I have noticed which may be completely unrelated  - is, with my working mic is when the drain voltage is 11.5V the source leg is around 2.5VDC. But, with my problematic Mic, when the drain gets to 11.5V the source leg is at over 4VDC, the drain leg stays at 11.5VDC for about half a minute and then it drops to 4v (same as source leg) and it cant be trimed higher than 7v - where the drain and source measure 7v at this point, and I have to replace the FET.

I took voltage readings according to the schematic, below are the results:

Problem Mic:
R18 - 46.1VDC (shematic: 46.6VDC)
R19 - 46.1VDC (shematic: 46.6VDC)
Zener 24 -  22.98VDC (shematic: 23.6VDC)
R12, R14, C10 - 19.28VDC (shematic: 20.62VDC)
C5 - 39.7VDC (shematic: 40VDC)
FC - 39.7VDC (shematic: 40VDC)


Working Mic:
R18 - 46.6VDC (shematic: 46.6VDC)
R19 - 46.1VDC (shematic: 46.6VDC)
Zener - 24 22.88VDC (shematic: 23.6VDC)
R12, R14, C10 - 20.96VDC shematic: 20.62VDC)
C5 - 42VDC (shematic: 40VDC)
FC - 39.7VDC (shematic: 40VDC)

Capsule and Transformer were not connected when this happened, I have Tried disconnecting the switch board too but I still get that high 4V voltage at the source, so I quickly trim it down before I have to replace it again.