GroupDIY

Project Specific Discussions => Microphones => Topic started by: poctop on March 12, 2012, 11:26:36 PM

Title: Neumann Vintage U87 Clone : Build Thread.
Post by: poctop on March 12, 2012, 11:26:36 PM
D-U87 Build Thread

Let's get those Electron flowing.
All of the info: http://www.groupdiy.com/index.php?topic=49675.0 (http://www.groupdiy.com/index.php?topic=49675.0)
Picture Provided By Chunger :)

Mouser Cart including all options ( 60M and 68M included also 2 different PN  for 2K2 resistance)
important note :The BOM already contained alternate part number for the 2.2K (delete whatever is not available at the moment and also there is both the 60M and the 68M listed in there for you to decide both will work fine
just delete from your order the one you wont take,  the 68M is less expensive !


Most Recent BOM here :
http://www.mouser.com/ProjectManager/ProjectDetail.aspx?AccessID=1AD602D54E

Sound Sample Provided By Chunger and Exhaustive Build thread   here http://www.groupdiy.com/index.php?topic=49389.60 (http://www.groupdiy.com/index.php?topic=49389.60)


Demonstrative Video Provided By Peterson Goodwyn at DIY Recording Equipment and Matthew Jenkins.  :)
http://youtu.be/DtNH46jpwJo



Build Demonstration
http://www.vintagemicrophonepcbkit.com/Neumann%20U87%20Build.htm

Large PCB version in SYT-5 mic body
(https://io.groupdiy.com/file/gdiy-2017/u/39511/58d1402a01fad.jpg)

(https://io.groupdiy.com/file/gdiy-2017/u/39511/58d1402a01fd3.jpg)

Taper Version in BM-600 Type mic Body
(https://io.groupdiy.com/file/gdiy-2017/u/39511/58d1402a01fe5.jpg)

(https://io.groupdiy.com/file/gdiy-2017/u/39511/58d1402a01ff6.jpg)

(https://io.groupdiy.com/file/gdiy-2017/u/39511/58d1402a02008.jpg)



Microphone Body and accessories Available Here :http://www.groupdiy.com/index.php?topic=50015.0 (http://www.groupdiy.com/index.php?topic=50015.0)

The Original Version Contains Polystyrene Filter Cap,  as this is an option not included in the BOM it may be ordered  via the webstore

Styro Kit includes
1 X 10pf Styroflex/630V
1 X 220pf Styroflex/630V
2 X 470pf Styroflex/630V ,
1 X 560pf Styroflex/630V ,

Read This First : Assembly Instruction , Excel BOM and Tips For Assembly and  Important Considerations Here: https://io.groupdiy.com/file/gdiy-2017/u/39511/58d1402a02019.xlsx






this will fit the Aurycle Micropone the MXL or any tapper standard Fet Mic Body
This is a Combo Set (2 Boards)
BOM , Layout ,Schem, ..... For this project,

Tutorial Document Thanks to UDO on how to wire the behringer B2 Pro switch board Here:

 https://io.groupdiy.com/file/gdiy-2017/u/39511/58d1402a0202b.pdf


How to make it in a behringer B2 thank to jasonallenh

https://www.dropbox.com/s/zm4eexpvpmhwab2/USING%20THE%20AMERICAN%20B2%20FOR%20DANYs%20U87.pdf?dl=0

B1 Reference Voltage and Schematic https://io.groupdiy.com/file/gdiy-2017/u/39511/58d1402a02050.pdf

B2 Reference Voltage and Schematic https://io.groupdiy.com/file/gdiy-2017/u/39511/58d1402a02062.pdf


Here a Fantastic FET Behavior Calculator ( Thanks To Matador)
http://www.musicalsparks.com/images/curve_tracer/jfet_bias.php (http://www.musicalsparks.com/images/curve_tracer/jfet_bias.php)

Important note :calibration resistor R11 is not Included in  the Bom as it is specific for each  FET.
use the potentiomter in the BOM to determine R11 Value.
Consider having those on hand the value of R11 Will be approximatively
Ranging from 7k to 12k


The new version of the Board include the Pot or resistor Package much easier
   
Mouser Cart including all options ( 60M and 68M included also 2 different PN  for 2K2 resistance)
important note :The BOM already contained alternate part number for the 2.2K (delete whatever is not available at the moment and also there is both the 60M and the 68M listed in there for you to decide both will work fine
just delete from your order the one you wont take,  the 68M is less expensive !


Most Recent BOM here :
http://www.mouser.com/ProjectManager/ProjectDetail.aspx?AccessID=1AD602D54E

(https://io.groupdiy.com/file/gdiy-2017/u/39511/58d1402a02074)

Dimension Here : https://io.groupdiy.com/file/gdiy-2017/u/39511/58d1402a02085.doc

Needed For this Project is a K87 Type Capsule With isolated backplate.

Best suited Capsule for this Project for this project: K87i by Peluso and can be found here :
 http://www.pelusomicrophonelab.com/parts/Capsules.html (http://www.pelusomicrophonelab.com/parts/Capsules.html)
(https://io.groupdiy.com/file/gdiy-2017/u/39511/58d1402a02096)
Best suited Capsule for this Project  The RK-87 by Microphone Parts and can be found here :
http://microphone-parts.com/rk87-microphone-capsule/ (http://microphone-parts.com/rk87-microphone-capsule/)
http://microphone-parts.com/faq/ (http://microphone-parts.com/faq/)
(https://io.groupdiy.com/file/gdiy-2017/u/39511/58d1402a020a7)

Best suited Capsule for this Project for this project: K87 by TSKGUY and can be found here :
http://www.groupdiy.com/index.php?topic=49859.0 (http://www.groupdiy.com/index.php?topic=49859.0)
(https://io.groupdiy.com/file/gdiy-2017/u/39511/58d1402a020b6)

capsule connection the  Proper Way to make sure front is front and back is back:
  Side A (https://io.groupdiy.com/file/gdiy-2017/u/39511/58d1402a020ca.jpg)
  Side B (https://io.groupdiy.com/file/gdiy-2017/u/39511/58d1402a020dc.jpg)
 (https://io.groupdiy.com/file/gdiy-2017/u/39511/58d1402a020ed.gif)


See by your self Here Thanks To John Peluso :):  Frequency Response Test from John Peluso (K87-PK87i) : https://io.groupdiy.com/file/gdiy-2017/u/39511/58d1402a020fd (https://io.groupdiy.com/file/gdiy-2017/u/39511/58d1402a020fd)
http://www.pelusomicrophonelab.com/parts/Capsules.html (http://www.pelusomicrophonelab.com/parts/Capsules.html)

Here are the best suited transformers for this project :

New T13 From Tab-Funkenwerk The T13 was designed specially for the u87 circuit by Tab-FunkenWerk

http://www.tab-funkenwerk.com/id133.html (http://www.tab-funkenwerk.com/id133.html)


CM2480 from Cinemag http://cinemag.biz/mic_output/mic_output.html (http://cinemag.biz/mic_output/mic_output.html)
(https://io.groupdiy.com/file/gdiy-2017/u/39511/58d1402a0211d.jpg)

New Peluso T87 Specialy designed for this application
(https://io.groupdiy.com/file/gdiy-2017/u/39511/58d1402a02130.gif)

More Info here  : http://www.groupdiy.com/index.php?topic=47350.300

How To measure FET Idss By Matador https://io.groupdiy.com/file/gdiy-2017/u/39511/58d1402a02141.jpg

FET Biasing Method By ZapNSpark : https://io.groupdiy.com/file/gdiy-2017/u/39511/58d1402a02152.pdf

Reference Version 16 Schematic: https://io.groupdiy.com/file/gdiy-2017/u/39511/58d1402a02163.jpg

Manual and Version 21 Schemo : https://io.groupdiy.com/file/gdiy-2017/u/39511/58d1402a02175.pdf

Tuning Hint : http://www.groupdiy.com/index.php?topic=47350.340

To Bias Fet, make sure you install R6 backward in reference to the silk screen like this:
this is Valid for Large Version and Taper Version do not do this for the Blue PCB version
(https://io.groupdiy.com/file/gdiy-2017/u/39511/58d1402a02187.jpg)
(https://io.groupdiy.com/file/gdiy-2017/u/39511/58d1402a0219a.jpg)

Tuning Thread : http://repforums.prosoundweb.com/index.php/topic,11630.0.html (http://repforums.prosoundweb.com/index.php/topic,11630.0.html)

Precious Info on how to use a scope to Bias a Fet (Thanks To Matador) http://www.groupdiy.com/index.php?topic=46109.40

Here is a software based oscilloscope for those interested :
https://io.groupdiy.com/file/gdiy-2017/u/39511/58d0281993732.exe

Here a List of suggested Mic Bodies ( Thanks To ChuckD )

All Switches
Behringer B-2 Pro 
MXL 2010               
Filter and Pad Only
Aurycle A460
MCA SP1 
CAD GXL2400
Carvin CM87S
No switches:
Gauge ECM 87
Nady SCM 900


Cheers Dan,
Title: Re: Neumann U87 vintage circuit build thread
Post by: Blue Jinn on March 13, 2012, 01:32:34 AM
Is it possible to amend this thread with that thread? There is a wealth of information over there in among the 'I'll take two' (including my own ....) posts!
Title: Re: Neumann U87 vintage circuit build thread
Post by: Hank Dussen on March 13, 2012, 05:52:54 AM
Someone out there who can make us a transformer closer to the original?
Title: Re: Neumann U87 vintage circuit build thread
Post by: HellfireStudios on March 13, 2012, 10:37:59 AM
I was wondering, since my 2480 is already engaged to another design, if there are any other transformers that could be recommended for an authentic U87 sound (Peluso makes some Neumann copies, but which one?).
Poctop, which transformer would you choose out of the two you've used? BTW, what is a 090415 transformer (manufacturer, price, website, etc.)? Better yet which mic would you suspect works better for vocals out of the two you have built?
I knew I wanted a U-87 for vox, but I know I can't turn down a better sound, IF it's just as versatile and performs just as well over a wide variety of applications.
I guess what I'm asking is, does the "API" U87 still sound like a U87? Is the change subtle or drastic? Is it like running a U87 through a different preamp, or are they totally different beasts?

One last thing. Are there any cap preferences on this circuit yet? I'm still on the fence about this part. I'd normally use Illinois caps, but I know tants are the standard for that circuit (despite their eventual drift). I'm sure the BOM caps are sufficient, but not sure which type will give me an authentic sound and long-term reliabilty (hence my concern for the tants). Thanks for your time.
Sorry so many questions, but someone's gotta ask...

-James-
Title: Re: Neumann U87 vintage circuit build thread
Post by: poctop on March 13, 2012, 11:12:41 AM
I knew I wanted a U-87 for vox, but I know I can't turn down a better sound, IF it's just as versatile and performs just as well over a wide variety of applications.
I guess what I'm asking is, does the "API" U87 still sound like a U87? Is the change subtle or drastic? Is it like running a U87 through a different preamp, or are they totally different beasts?

One last thing. Are there any cap preferences on this circuit yet? I'm still on the fence about this part. I'd normally use Illinois caps, but I know tants are the standard for that circuit (despite their eventual drift). I'm sure the BOM caps are sufficient, but not sure which type will give me an authentic sound and long-term reliabilty (hence my concern for the tants). Thanks for your time.
Sorry so many questions, but someone's gotta ask...

-James-

So Far, I have done a Total replica of one as this date with the original capsule K87 and the original transformer 090415
and then the results is incredible the only difference i can make is the tiny lost of high's due to the worn out capsule ,  i have used the tantalum all the way and the polystyrene as the original,  if you put tant in there dont worry about the life of these there is a lot of old u87 working out there. ;) if you look in the BOM there only the 10pf  polystyrne that is not on the BOM but all other option are mentionned,
the other one was based on the peluso and 2480 it a bit  less dirty than the original because of the very dirty 09415 but with more punch to it , however the 09415 is not readiliy available and might be pricy unless you want to try reaching neumann with this :-X, nothing is imposible ;D  i wish i had some suggestions here for alternative with the trannie i just went on the 2480 because there good and cheap.

If anyone would like to suggest some specific trannies i'd love to have them in your mics too, 
I think Marik makes one that suits the u87 ?,
peluso ? thinks he does the bv8 only.
Ioaudio ?  good candidate  ;D

So at this point i can't wait to hear some opinion out there.
that will problably explains it better :)
as for wich one is best then your ear shall decide.

Hope this Helps,












Title: Re: Neumann U87 vintage circuit build thread
Post by: poctop on March 13, 2012, 11:25:18 AM
Someone out there who can make us a transformer closer to the original?

I Wish 8),
Title: Re: Neumann U87 vintage circuit build thread
Post by: Marcocet on March 13, 2012, 04:17:48 PM
Okay:

I ordered Peluso K87i capsules for my mics. However there are only three wires coming off them - the centers of the capsules and one tag on the front for the capsule body. What about the rear body? Did peluso just forget to put a tag on the back? Is it safe to just solder a wire to one of the tension screws? That seems like madness to me, but then again that's what the tag on the front is connected to so it should prob be fine.

Thoughts?

Thanks
Title: Re: Neumann U87 vintage circuit build thread
Post by: poctop on March 13, 2012, 05:10:16 PM
Okay:

I ordered Peluso K87i capsules for my mics. However there are only three wires coming off them - the centers of the capsules and one tag on the front for the capsule body. What about the rear body? Did peluso just forget to put a tag on the back? Is it safe to just solder a wire to one of the tension screws? That seems like madness to me, but then again that's what the tag on the front is connected to so it should prob be fine.

Thoughts?

Thanks

I dont remember exactely how i dod get mine or ended solder-screw a screw on the backplate ,

just to make things right drop him an email at

[email protected]

and let us know please ,

hope this helps,

Title: Re: Neumann U87 vintage circuit build thread
Post by: poctop on March 13, 2012, 05:14:04 PM
I sent also an email to make sure with the capsule..

I will keep you posted ,
D,
Title: Re: Neumann U87 vintage circuit build thread
Post by: poctop on March 13, 2012, 05:31:15 PM
The Answer is the front backplate tab already on the capsule is for the front capsule so this is how you recognize the front ,
the (back) backplate will connect via a tab that you need to supply ( Peluso Wisher will be providede one) and attached to the mounting saddle connection so it will make contact will the back backplate,
Hope this helps,
Dan,
Title: Re: Neumann U87 vintage circuit build thread
Post by: poctop on March 13, 2012, 05:35:18 PM
To Mention here

Regarding the Peluso Event Jobs Done, each of you that signed up will get contacted with the final price   

John Mentionned also intersting transfo to try for this project, his own brewed BV11T and T14    if your intetested drop him an email,  the cinemag is a good starter but i will be testing those soon,
 ;D
cheers,
D

Title: Re: Neumann U87 vintage circuit build thread
Post by: Blue Jinn on March 13, 2012, 11:23:31 PM
I ran into a few threads that couldn't identify the u87 transformer spec. then another thread on a Neumann forum which identified as a BV13, but couldn't find any info on that.  Other threads say the cinemag 10:1 is 'in the ballpark." So does anyone know what the specs are on the transformer?
Title: Re: Neumann U87 vintage circuit build thread
Post by: poctop on March 14, 2012, 03:16:38 PM
the specification on the mouser web site is wrong if you look at the data sheet the 68M is like this,
it should be all fine 1/4 W and dimension too,
Title: Re: Neumann U87 vintage circuit build thread
Post by: wtmnmf on March 14, 2012, 04:47:21 PM
the specification on the mouser web site is wrong if you look at the data sheet the 68M is like this,
it should be all fine 1/4 W and dimension too,

How about that 750W 60M resistor?  ;D   

Been noticing a ton of errors on Mouser recently...
Title: Re: Neumann U87 vintage circuit build thread
Post by: poctop on March 14, 2012, 05:45:32 PM
Its seems that AMI funkenwork might have the magic transformer ,

I am working on it very hard now, :P

 let you know
Title: Re: Neumann U87 vintage circuit build thread
Post by: poctop on March 14, 2012, 05:46:48 PM
so seems that the original tran is BV13 and the BV90415  is the succesor with core grounding ,

if anyone has info on those let me know,

thanks,
dan.,
Title: Re: Neumann U87 vintage circuit build thread
Post by: poctop on March 14, 2012, 06:33:42 PM
New Scoop

just receive an email from Tabfunkenwerk they are just to realese the new T13 wich is designed as a direct replacement of the u87 transfo,  email i received below ;D ;D

Hi Dany,

Thanks for enquiring about BV13’s!  We are about to add a new item to our website which is our T13 transformer.  It is built on the same platform as our T14 transformer but with the ratio and impedance necessary as a drop in replacement for U87’s and U87 DIY projects.  I don’t have a picture of it yet but I will be adding it to the site soon. 
The price will be the same as our T14 transformer, $95 plus shipping.  I think Oliver has a few available from the first production run that he made but I will check with him to see.

Cant wait to try this one out,


Title: Re: Neumann U87 vintage circuit build thread
Post by: Marcocet on March 14, 2012, 07:27:20 PM
Awesome. Just finished one of mine with the cinemag and peluso capsule and it sounds great! Let me get the other one up and running and I'll shoot it out with my vintage u87.
Title: Re: Neumann U87 vintage circuit build thread
Post by: adeptusmajor on March 14, 2012, 08:28:20 PM
I don't suppose you inquired about a group buy for the T13 by chance, did you? :D
Title: Re: Neumann U87 vintage circuit build thread
Post by: poctop on March 14, 2012, 09:27:17 PM
Awesome. Just finished one of mine with the cinemag and peluso capsule and it sounds great! Let me get the other one up and running and I'll shoot it out with my vintage u87.

Great Marcocet  ;),  i really hope you enjoy the mike keep me posted as per your findings,
D.
Title: Re: Neumann U87 vintage circuit build thread
Post by: Hank Dussen on March 16, 2012, 06:17:48 AM
New Scoop

just receive an email from Tabfunkenwerk they are just to realese the new T13 wich is designed as a direct replacement of the u87 transfo,  email i received below ;D


Awesome!
Title: Re: Neumann U87 vintage circuit build thread
Post by: wthrelfall on March 16, 2012, 07:42:44 AM
Dany,

I'm trying to wire the Aurycle transformer to the board.  I have Black, Green, Red, White cables coming from the transformer, how do they connect to the board?  I don't understand what the TRFO abbreviations are (1 RT, 2 SW, 3 BL, 4 WS).
Hope you can help.

cheers.
Title: Re: Neumann U87 vintage circuit build thread
Post by: poctop on March 16, 2012, 09:07:46 AM
Dany,

I'm trying to wire the Aurycle transformer to the board.  I have Black, Green, Red, White cables coming from the transformer, how do they connect to the board?  I don't understand what the TRFO abbreviations are (1 RT, 2 SW, 3 BL, 4 WS).
Hope you can help.

cheers.
Aurycle Transformer lead connection to the U1621

RT = red from aurycle Transfo
SW = White from aurycle TRansfo
WS = Black from aurycle Transfo
BL = green from aurycle Transfo,

Just note that the Aurycle transformer is ultimately need to be replaced to get the full potential of the mike,

here is for the cinemag 2480 to u1621 if it can help anyone,
RT = red from cinemag 2480 Transfo
SW = brown from cinemag 2480 TRansfo
WS = yellow from cinemag 2480 Transfo
BL =  orange fromcinemag 2480 Transfo,
Title: Re: Neumann U87 vintage circuit build thread
Post by: wthrelfall on March 16, 2012, 09:21:41 AM
thanks dany.


Dany,

I'm trying to wire the Aurycle transformer to the board.  I have Black, Green, Red, White cables coming from the transformer, how do they connect to the board?  I don't understand what the TRFO abbreviations are (1 RT, 2 SW, 3 BL, 4 WS).
Hope you can help.

cheers.
Aurycle Transformer lead connection to the U1621

RT = red from aurycle Transfo
SW = White from aurycle TRansfo
WS = Black from aurycle Transfo
BL = green from aurycle Transfo,

Just note that the Aurycle transformer is ultimately need to be replaced to get the full potential of the mike,

here is for the cinemag 2480 to u1621 if it can help anyone,
RT = red from cinemag 2480 Transfo
SW = brown from cinemag 2480 TRansfo
WS = yellow from cinemag 2480 Transfo
BL =  orange fromcinemag 2480 Transfo,
Title: Re: Neumann U87 vintage circuit build thread
Post by: 0dbfs on March 16, 2012, 09:24:18 AM
New Scoop

just receive an email from Tabfunkenwerk they are just to realese the new T13 wich is designed as a direct replacement of the u87 transfo,  email i received below ;D ;D

Hi Dany,

Thanks for enquiring about BV13’s!  We are about to add a new item to our website which is our T13 transformer.  It is built on the same platform as our T14 transformer but with the ratio and impedance necessary as a drop in replacement for U87’s and U87 DIY projects.  I don’t have a picture of it yet but I will be adding it to the site soon. 
The price will be the same as our T14 transformer, $95 plus shipping.  I think Oliver has a few available from the first production run that he made but I will check with him to see.

Cant wait to try this one out,

That's awesome. I can use those for some KM54 style mic's that I'm working up :)

Cheers,
j
Title: Re: Neumann U87 vintage circuit build thread
Post by: wthrelfall on March 16, 2012, 11:49:51 AM
So, my first test reveals a very dark, quiet and bassy signal.  definately something not right.
I calibrated R11 without a 'scope as described, looking for 10.5v at the drain.  just to clarify, of the transistors legs, the drain is the closest to the side of the board, nearest R11?  I calibrate without the capsule connected (or the 50pf rear jumper cap)?  Anyway, with 10.5v i'm getting 4.46k across R11 (measured with one leg lifted), pretty far away from the expected 7k - 10k..
any thoughts?
Title: Re: Neumann U87 vintage circuit build thread
Post by: poctop on March 16, 2012, 12:27:36 PM
So, my first test reveals a very dark, quiet and bassy signal.  definately something not right.
I calibrated R11 without a 'scope as described, looking for 10.5v at the drain.  just to clarify, of the transistors legs, the drain is the closest to the side of the board, nearest R11?  I calibrate without the capsule connected (or the 50pf rear jumper cap)?  Anyway, with 10.5v i'm getting 4.46k across R11 (measured with one leg lifted), pretty far away from the expected 7k - 10k..
any thoughts?

I would say start with the basics,  the transistor drain is indeed the nearest from r11 , check the cap polarity check for cold solder on gnd plane connection to electrolytic capacitor, double check value and components with the meter when possibe , check for the voltage up to zener you should have 24V there , double check C7 polarity, wich side of the legs have you been lifting out the gnd side ?. measure R11 unconnected . is it possible for you to inject a sine tone in the mik to check on how you FET Bias pot is behaving . what is your setup transfo for now, have you double checked your transfo connection ? check all connection A-AA B-BB G-GG C-CC , i never attempted anything with the Aurycle aurycle traffo yet it is not intended here. ,. is the capsule intact any abnormality on he capsule if you look very closely those cheap chinese capsule sometimes arrives DOA (dead on arrival ) that is why i dont use them at all, hope this helps, also Check the capsule connection at FC     Cap= capsule and Bdy= Backplate  check for solder bridge look at schemo and check all connection in the circuit. last time i checked the Backplate Voltage it was arround 40V wich is not a really accurate reading because of impedance
D
Title: Re: Neumann U87 vintage circuit build thread
Post by: wtmnmf on March 16, 2012, 03:42:33 PM
New Scoop

just receive an email from Tabfunkenwerk they are just to realese the new T13 wich is designed as a direct replacement of the u87 transfo,  email i received below ;D ;D

Hi Dany,

Thanks for enquiring about BV13’s!  We are about to add a new item to our website which is our T13 transformer.  It is built on the same platform as our T14 transformer but with the ratio and impedance necessary as a drop in replacement for U87’s and U87 DIY projects.  I don’t have a picture of it yet but I will be adding it to the site soon. 
The price will be the same as our T14 transformer, $95 plus shipping.  I think Oliver has a few available from the first production run that he made but I will check with him to see.

Cant wait to try this one out,

Got an email today :  "We will have the T13’s in full stock around Wednesday of next week.  They will be $95 plus shipping."  :)
Title: Re: Neumann U87 vintage circuit build thread
Post by: wthrelfall on March 16, 2012, 03:48:07 PM
ok, had the capsule connections the wrong way around.  It's working so I made a comparison with my cheap valve mic and my Rode NT2, recording side by side..  This clone is way darker in tone to the others..  I like that.  when I compare them A/B it's quite shocking how much emphasis I can hear on the other mics.  I can't imagine a scenario when I wouldn't use the 100hz cut on the this clone, so much bottom end already there.  It's quieter than the valve mic, forgot to measure against the Rode.  I find it needs alot of gain to get a decent level, I mean alot.  is that normal dany?

on a technical note, the mic seems to be running nicely despite my R11 value of 4.4k, and I checked the voltage at the zener, it's around 15v.  Do you think this is maybe down to the different transformer I'm using? (the stock Aurycle transformer).


So, my first test reveals a very dark, quiet and bassy signal.  definately something not right.
I calibrated R11 without a 'scope as described, looking for 10.5v at the drain.  just to clarify, of the transistors legs, the drain is the closest to the side of the board, nearest R11?  I calibrate without the capsule connected (or the 50pf rear jumper cap)?  Anyway, with 10.5v i'm getting 4.46k across R11 (measured with one leg lifted), pretty far away from the expected 7k - 10k..
any thoughts?

I would say start with the basics,  the transistor drain is indeed the nearest from r11 , check the cap polarity check for cold solder on gnd plane connection to electrolytic capacitor, double check value and components with the meter when possibe , check for the voltage up to zener you should have 24V there , double check C7 polarity, wich side of the legs have you been lifting out the gnd side ?. measure R11 unconnected . is it possible for you to inject a sine tone in the mik to check on how you FET Bias pot is behaving . what is your setup transfo for now, have you double checked your transfo connection ? check all connection A-AA B-BB G-GG C-CC , i never attempted anything with the Aurycle aurycle traffo yet it is not intended here. ,. is the capsule intact any abnormality on he capsule if you look very closely those cheap chinese capsule sometimes arrives DOA (dead on arrival ) that is why i dont use them at all, hope this helps, also Check the capsule connection at FC     Cap= capsule and Bdy= Backplate  check for solder bridge look at schemo and check all connection in the circuit. last time i checked the Backplate Voltage it was arround 40V wich is not a really accurate reading because of impedance
D
Title: Re: Neumann U87 vintage circuit build thread
Post by: poctop on March 16, 2012, 04:55:11 PM
Quote
ok, had the capsule connections the wrong way around.  It's working so I made a comparison with my cheap valve mic and my Rode NT2, recording side by side..  This clone is way darker in tone to the others..  I like that.  when I compare them A/B it's quite shocking how much emphasis I can hear on the other mics.  I can't imagine a scenario when I wouldn't use the 100hz cut on the this clone, so much bottom end already there.  It's quieter than the valve mic, forgot to measure against the Rode.  I find it needs alot of gain to get a decent level, I mean alot.  is that normal dany?

on a technical note, the mic seems to be running nicely despite my R11 value of 4.4k, and I checked the voltage at the zener, it's around 15v.  Do you think this is maybe down to the different transformer I'm using? (the stock Aurycle transformer).

i am glad your case in going forward but there is definitely something going wrong i made measurement just a minute ago without the transformer attached and no capsule attached no cap jumper just the circuit and the xlr connection to the mike and i have a 22.69VDC on the top off the Zener can you measure if you have the 48VDC from the 2K2 resistor my guess is that the problem is in that area or the microphone pcb GND is not firm to the chassis verify a 0 ohm from gnd pin from the PCB to the Mic body it self , check  the zener orientation , the R11 value will make sense only if you can get the proper inital voltage , double check also if you would by mistake confused some resistor with the L1 and L2 inductor, at this point if you dont have the proper initial voltage reading your R11 resistor will probably make no sense ,  Since your capsule if probably not polarized with the proper voltage try to measure the voltage coming trough the front backplate = bdy pad on the mik it should be arround 39V DC,  it looks that something is not in place correctly. So this way you rule out the ,capsule and transformer. you should be able to get those 3 voltages to start with, then go from there ,
any new builder should check those initial voltage before connecting transfo or capsule.
Title: Re: Neumann U87 vintage circuit build thread
Post by: Matador on March 16, 2012, 05:24:54 PM
I find it needs alot of gain to get a decent level, I mean alot.  is that normal dany?

You have a low IDSS FET.  The higher the source resistance, the lower the gain.  Try another FET that gives you about 1V-1.5V on the source with 10V on the drain.
Title: Re: Neumann U87 vintage circuit build thread
Post by: wthrelfall on March 17, 2012, 02:37:30 PM
Quote
i am glad your case in going forward but there is definitely something going wrong i made measurement just a minute ago without the transformer attached and no capsule attached no cap jumper just the circuit and the xlr connection to the mike and i have a 22.69VDC on the top off the Zener can you measure if you have the 48VDC from the 2K2 resistor my guess is that the problem is in that area or the microphone pcb GND is not firm to the chassis verify a 0 ohm from gnd pin from the PCB to the Mic body it self , check  the zener orientation , the R11 value will make sense only if you can get the proper inital voltage , double check also if you would by mistake confused some resistor with the L1 and L2 inductor, at this point if you dont have the proper initial voltage reading your R11 resistor will probably make no sense ,  Since your capsule if probably not polarized with the proper voltage try to measure the voltage coming trough the front backplate = bdy pad on the mik it should be arround 39V DC,  it looks that something is not in place correctly. So this way you rule out the ,capsule and transformer. you should be able to get those 3 voltages to start with, then go from there ,
any new builder should check those initial voltage before connecting transfo or capsule.

I have nearly 48v from the 2k2, 46.1v actually.  L1 & L2 are correct (46.7v both).  15.55v on the Zener diode, and here's a thing - I have 15.55v on the top of R17, but 46.1v on the bottom.  I have double checked the resistor and replaced with one of exactly 56k, still reading 15.55v.
Yes, i'm getting 39v from front body pad.
Title: Re: Neumann U87 vintage circuit build thread
Post by: wthrelfall on March 17, 2012, 02:41:01 PM
I find it needs alot of gain to get a decent level, I mean alot.  is that normal dany?

You have a low IDSS FET.  The higher the source resistance, the lower the gain.  Try another FET that gives you about 1V-1.5V on the source with 10V on the drain.

if by source you mean the voltage on the leg on the opposite side from the drain, this is reading 2.4v.
Title: Re: Neumann U87 vintage circuit build thread
Post by: poctop on March 17, 2012, 04:49:10 PM
The big question is why on the Zener side you have 15V , is the Zener oriented properly is it a 15V zener ?
look in this net of Zener, C12, R14, R16, R12, C9 , and C7 connection to FET,  , this is the first thing to find out .

on the nod touching C10, R14, R12 you should have 20VDC, on the other hand of R12 drain Cal point at 11V,
Hope this helps, here attached a pic of the board for any visual pointer.
D

Title: Re: Neumann U87 vintage circuit build thread
Post by: wthrelfall on March 17, 2012, 06:17:10 PM
The big question is why on the Zener side you have 15V , is the Zener oriented properly is it a 15V zener ?
look in this net of Zener, C12, R14, R16, R12, C9 , and C7 connection to FET,  why is the zener not doing the job ?
this is the first thing to find out .

on the nod touching C10, R14, R12 you should have 20VDC, on the other hand of R12 drain Cal point at 11V,
Hope this helps, here attached a pic of the board for any visual pointer.
D

all the components are from your BOM and therefore should be correct.
I'm finding it a little hard to understand you, but certainly those voltages are very different.
Title: Re: Neumann U87 vintage circuit build thread
Post by: poctop on March 18, 2012, 12:15:57 AM

Quote
all the components are from your BOM and therefore should be correct.
I'm finding it a little hard to understand you, but certainly those voltages are very different.

Lets Try to put a 10K resistor for R11 and see what happens ?

Dan,
Title: Re: Neumann U87 vintage circuit build thread
Post by: Matador on March 18, 2012, 12:57:27 AM
I have nearly 48v from the 2k2, 46.1v actually.  L1 & L2 are correct (46.7v both).  15.55v on the Zener diode, and here's a thing - I have 15.55v on the top of R17, but 46.1v on the bottom.  I have double checked the resistor and replaced with one of exactly 56k, still reading 15.55v.
Yes, i'm getting 39v from front body pad.

The top of R17 and the voltage across the 2K2 are the same.

Your source resistance is 4K4, and you have 2.4V on the source, which means you are idling 0.5mA through the FET.

The U87 schematic assumes a 0.25mA idle point:  you need to adjust your resistors to match your FET.  You are reading 15.5V at the Zener because the 0.5mA is dropping across R17.  In this case, the Zener is doing nothing.

Here's what you need to do:  lower R17 until the Zener voltage raises to 24V.  Then, lower R14 until you get about a 3V drop across it (or about 21V at the "top" of the drain resistor R12).  Ohms Law says R12 should be about 6K (down from 10K) in this case.

Don't lower R17 too much though, as the Zener will take over and start dumping the phantom current to ground to keep the voltage at 24V (and this extra current will start dropping across the 2V2 resistors, which will then lower the capsule bias....).

Until you get the voltage at R12 up to 21V then setting the bias point is meaningless.  The output signal is developed across R12, and until the "top" of this voltage is up near 21V you won't be able to get any appreciable signal swing out of the circuit.

And this is the weakness of this circuit:  the entire topology must be tweaked around the individual FET. :(
Title: Re: Neumann U87 vintage circuit build thread
Post by: wthrelfall on March 18, 2012, 07:55:18 AM
excellent analysis Matador, I will be attempting this and shall come back here with good news I hope!



I have nearly 48v from the 2k2, 46.1v actually.  L1 & L2 are correct (46.7v both).  15.55v on the Zener diode, and here's a thing - I have 15.55v on the top of R17, but 46.1v on the bottom.  I have double checked the resistor and replaced with one of exactly 56k, still reading 15.55v.
Yes, i'm getting 39v from front body pad.

The top of R17 and the voltage across the 2K2 are the same.

Your source resistance is 4K4, and you have 2.4V on the source, which means you are idling 0.5mA through the FET.

The U87 schematic assumes a 0.25mA idle point:  you need to adjust your resistors to match your FET.  You are reading 15.5V at the Zener because the 0.5mA is dropping across R17.  In this case, the Zener is doing nothing.

Here's what you need to do:  lower R17 until the Zener voltage raises to 24V.  Then, lower R14 until you get about a 3V drop across it (or about 21V at the "top" of the drain resistor R12).  Ohms Law says R12 should be about 6K (down from 10K) in this case.

Don't lower R17 too much though, as the Zener will take over and start dumping the phantom current to ground to keep the voltage at 24V (and this extra current will start dropping across the 2V2 resistors, which will then lower the capsule bias....).

Until you get the voltage at R12 up to 21V then setting the bias point is meaningless.  The output signal is developed across R12, and until the "top" of this voltage is up near 21V you won't be able to get any appreciable signal swing out of the circuit.

And this is the weakness of this circuit:  the entire topology must be tweaked around the individual FET. :(
Title: Re: Neumann U87 vintage circuit build thread
Post by: poctop on March 18, 2012, 10:29:22 AM
Hi Matador,

I have been initially using this FET here 512-2N3819
 http://ca.mouser.com/ProductDetail/Fairchild-Semiconductor/2N3819/?qs=sGAEpiMZZMutXGli8Ay4kAuOt55Alb1HdgBfgvzEKeQ%3d (http://ca.mouser.com/ProductDetail/Fairchild-Semiconductor/2N3819/?qs=sGAEpiMZZMutXGli8Ay4kAuOt55Alb1HdgBfgvzEKeQ%3d)

this is what i get from reading on the 3 mikes i have built so far,
Across R12  47K  i get about 10V wich would be arround 0.22ma ,
and accross R11 the 2.4 V from the Source of the FET so about .25ma.

i had to put replace the FET in the orginal BOM because the 512-2N3819 cam obsolete ,
the new FET in the BOM is http://ca.mouser.com/ProductDetail/Fairchild-Semiconductor/2N3819_D74Z/?qs=sGAEpiMZZMutXGli8Ay4kHKRdIvtrnJvJrjALq5IAXw%3d (http://ca.mouser.com/ProductDetail/Fairchild-Semiconductor/2N3819_D74Z/?qs=sGAEpiMZZMutXGli8Ay4kHKRdIvtrnJvJrjALq5IAXw%3d)

do you think the problem would be The FET itself,  i had checked all the spec and they are the same, i will order a bunchof those and try it out by myself then. i would like to catch anything before it is too late.

anyone has completed their build so far with any comments on this FET used,
any finished build out there ?

so i am really confused as why the idling current of whtrelfall is beeing 0.54ma hence calibration value so low, should be more like 10K  for 0.25ma . there is must be a simple reason for this to happen ?
just trying to help here.
Title: Re: Neumann U87 vintage circuit build thread
Post by: wthrelfall on March 18, 2012, 11:27:28 AM
Matador

I dropped R17 so I now have 23.5 volts at the zener (i can't get it exactly to 24v as I don't have a large range of resistors).  doesn't the voltage at R12 depend on the R11 value?  I mean as soon as I adjust R11 to bias the fet then R12 just tracks this voltage from the fet drain.  so I don't understand how I can get R12 to produce 21v if I'm going to then adjust R11 to bring the fet drain (and therefore R12) back to 10.5v.?
I'm clearly no expert when it comes to electronics but it seems for such a simple small circuit this is proving to be very difficult!


I have nearly 48v from the 2k2, 46.1v actually.  L1 & L2 are correct (46.7v both).  15.55v on the Zener diode, and here's a thing - I have 15.55v on the top of R17, but 46.1v on the bottom.  I have double checked the resistor and replaced with one of exactly 56k, still reading 15.55v.
Yes, i'm getting 39v from front body pad.

The top of R17 and the voltage across the 2K2 are the same.

Your source resistance is 4K4, and you have 2.4V on the source, which means you are idling 0.5mA through the FET.

The U87 schematic assumes a 0.25mA idle point:  you need to adjust your resistors to match your FET.  You are reading 15.5V at the Zener because the 0.5mA is dropping across R17.  In this case, the Zener is doing nothing.

Here's what you need to do:  lower R17 until the Zener voltage raises to 24V.  Then, lower R14 until you get about a 3V drop across it (or about 21V at the "top" of the drain resistor R12).  Ohms Law says R12 should be about 6K (down from 10K) in this case.

Don't lower R17 too much though, as the Zener will take over and start dumping the phantom current to ground to keep the voltage at 24V (and this extra current will start dropping across the 2V2 resistors, which will then lower the capsule bias....).

Until you get the voltage at R12 up to 21V then setting the bias point is meaningless.  The output signal is developed across R12, and until the "top" of this voltage is up near 21V you won't be able to get any appreciable signal swing out of the circuit.

And this is the weakness of this circuit:  the entire topology must be tweaked around the individual FET. :(
Title: Re: Neumann U87 vintage circuit build thread
Post by: KasperNyhus on March 18, 2012, 01:39:44 PM
Hi

This seems like a really noob question but I just can't figure out how to wire the peluso p-k87i capsule to the pcb.

First, is the peluso a dual isolated backplate capsule? I found that the screws on either side is electrinically connected... So I guess not... :)

Also found this quote:
"When the U 87Ai was introduced, the K67 was employed again, as there was no advantage perceived with using the split backplate."

http://recordinghacks.com/microphones/Neumann/U-87-Ai#ixzz1pUMxOm2D

So what wires should go to cap and bdy on the pcb if both backplates are the same?

I'm planning to use only card and omni as I have bought the german version of the mic bodys suited for the project - the "Fame" microphone which seem very good for the job btw...

Hope someone can clear up my messy understanding of the circuit!

Cheers,
Kasper
Title: Re: Neumann U87 vintage circuit build thread
Post by: poctop on March 18, 2012, 03:59:19 PM
in this case with the peluso capsule as the original K87  the 2 backplate front and back are isolated electrically this is guaranteed,

The Answer is the front backplate tab already on the capsule is for the front capsule so this is how you recognize the front , there actually on opposite side because of that  ;)
the (back) backplate will connect via a tab that you need to supply ( Peluso Wisher will be providede one) and attached to the mounting saddle connection so it will make contact will the back backplate only,

So the connection on the PCB are for FC = front capsule   (cap = capsule and bdy = backplate) and same for the back diaphragme  as the RC section on the PCB Cap= back capsule and bdy back backplate,
 
Hope this helps,
Dan,
Title: Re: Neumann U87 vintage circuit build thread
Post by: poctop on March 18, 2012, 04:15:12 PM
please also note that since the backplate are isolated the tab from the front backplate is on the other side of the capsule hence creating your confusion , if you check continuity between the 2 backplate it will be an open connection
just play with the capsule with your ohm meter set to continuity check and you will find out pretty quick.

Dan,
Title: Re: Neumann U87 vintage circuit build thread
Post by: lefilsdejack on March 18, 2012, 04:46:28 PM
Hi,
Please excuse my language if I make some english mistakes, I'm french, and I will try to do my best :)
First af all, congretulations for this great project!

I don't understand with what the soldering points "SW" and "RT" have to be link?
And do the "ground link" point need to be link with the mic body? and the "cground" point?

Thank you!
Title: Re: Neumann U87 vintage circuit build thread
Post by: poctop on March 18, 2012, 05:05:54 PM
Hi,
Please excuse my language if I make some english mistakes, I'm french, and I will try to do my best :)
First af all, congretulations for this great project!

I don't understand with what the soldering points "SW" and "RT" have to be link?
And do the "ground link" point need to be link with the mic body? and the "cground" point?

Thank you!

what transformer do you have for the project that will help alot for the configuration ?,  the PCB B1 needs to make a solid contact on the mic body via the screws and pad from the pcb mounting hole, you can verify that after installation with a 0 ohm between the mic body and cgnd ,  the cgnd pad was used with the original transfomer wich has a core grounding to it if your transfomer does not have a core grounding you just simply omit this pad,  the Gndlink was designed in case where the head basket is not grounded to the mic body properly.

Note also that the Color code is the german color code as used in the original schematic see page 1 of the white market thread for the schemo or here Reference: https://io.groupdiy.com/file/gdiy-2017/u/39511/58d0281993744 (https://io.groupdiy.com/file/gdiy-2017/u/39511/58d0281993744) rev 16 schemo


it will help figuring any transfomer configuration.
Hope this helps,
Title: Re: Neumann U87 vintage circuit build thread
Post by: lefilsdejack on March 18, 2012, 06:29:11 PM
I use the Cinemag transformer, so if I well understand what you said before, I don't have to connect those pads.
Thank you Dan!
Title: Re: Neumann U87 vintage circuit build thread
Post by: KasperNyhus on March 18, 2012, 07:06:19 PM
please also note that since the backplate are isolated the tab from the front backplate is on the other side of the capsule hence creating your confusion , if you check continuity between the 2 backplate it will be an open connection
just play with the capsule with your ohm meter set to continuity check and you will find out pretty quick.

Dan,

Thanks Dan!

Now I have figured it out... As you said a little time with my meter and it all made sense.

To be sure - and for the fun of it - I completely disassembled the stock "Fame" capsule. :)

In 30 min I have learned so much about capsules :)

Cheers
Title: Re: Neumann U87 vintage circuit build thread
Post by: poctop on March 18, 2012, 08:01:12 PM
LefilsJack and Kasper , Please keep us posted of your finding and sucess I hope :)

Dan,
Title: Re: Neumann U87 vintage circuit build thread
Post by: Matador on March 18, 2012, 08:04:46 PM
Matador

I dropped R17 so I now have 23.5 volts at the zener (i can't get it exactly to 24v as I don't have a large range of resistors).  doesn't the voltage at R12 depend on the R11 value?  I mean as soon as I adjust R11 to bias the fet then R12 just tracks this voltage from the fet drain.  so I don't understand how I can get R12 to produce 21v if I'm going to then adjust R11 to bring the fet drain (and therefore R12) back to 10.5v.?
I'm clearly no expert when it comes to electronics but it seems for such a simple small circuit this is proving to be very difficult!

The entire string of voltages depends on the Q point of the JFET.

Perhaps this is best explained by looking at the load line for this circuit (stolen from my other thread):

(http://www.musicalsparks.com/images/aurycle/2n3819_bias.jpg)

The default load line is in red, and the U87A intended bias point is the blue square on that load line (at about 10V on the drain).  Note that the slope of the load line is set by the drain and source resistors (and NOT the FET!).

But this plot assumes a nominal JFET:  the actual VGS that results in 10V at the drain (with 0.25mA IDS) varies quite a bit from device to device.  One can imagine that if you deleted all of the green lines the load line would not change, however the individual green line (representing the gate-source bias that intersects the blue box) would change from device to device.  This is what setting R11 does:  matches the bias so that the individual JFET idles at the design point.

However the implicit assumption here is that the U87 biasing string depends on the Zener keeping it's node at 24V!  It could be the original JFET's didn't pull much current.  However a modern 2N3819 can range anywhere from 2mA IDSS all the way up to 20mA!  That is a tremendous range for a single topology to cope with!

If you set R11 to maximum, then the drain voltage should be at maximum (the blue box is far to the right).  As you lower R11, the blue box will move along the red line to the left, and drain voltage should decrease as the idle current increases.  As R11 approaches zero the JFET will pinch-off and then the drain voltage will rapidly rise back up.

If you don't see this, then something else isn't correct in the wiring.

If you happen to have devices that have very high IDSS, then you won't be able to make R11 large enough with a 10K pot to move the idle current down into the intended range, because the device will be pulling too much current and dropping all of your voltage across R17!  If you take my plot, and move the top-most line (VGS=0V) up to 20mA (on my plot, it's about 12mA), you'll see that in order to drop the current back down to 0.25mA you'll need perhaps 4V gate-to-source bias, which would be 4V/0.25mA = 16Kohm!

Do you have perhaps a 25K pot to put in place?  Or you could also add a 10K resistor in series with the pot of you can perform the gymnastics on the board with your soldering iron.  I would also test 10 JFET's for IDSS and pick one that's on the lower end of the spectrum.

Hope that makes sense.
Title: Re: Neumann U87 vintage circuit build thread
Post by: wthrelfall on March 18, 2012, 08:21:46 PM
Matador,
Thanks again for another insightful post.  it will take me a little while to fully comprehend all this info, but quickly can I ask - what's the procedure for checking a fet's IDSS?  I can use a digital multimeter?

thanks.


Matador

I dropped R17 so I now have 23.5 volts at the zener (i can't get it exactly to 24v as I don't have a large range of resistors).  doesn't the voltage at R12 depend on the R11 value?  I mean as soon as I adjust R11 to bias the fet then R12 just tracks this voltage from the fet drain.  so I don't understand how I can get R12 to produce 21v if I'm going to then adjust R11 to bring the fet drain (and therefore R12) back to 10.5v.?
I'm clearly no expert when it comes to electronics but it seems for such a simple small circuit this is proving to be very difficult!

The entire string of voltages depends on the Q point of the JFET.

Perhaps this is best explained by looking at the load line for this circuit (stolen from my other thread):

(http://www.musicalsparks.com/images/aurycle/2n3819_bias.jpg)

The default load line is in red, and the U87A intended bias point is the blue square on that load line (at about 10V on the drain).  Note that the slope of the load line is set by the drain and source resistors (and NOT the FET!).

But this plot assumes a nominal JFET:  the actual VGS that results in 10V at the drain (with 0.25mA IDS) varies quite a bit from device to device.  One can imagine that if you deleted all of the green lines the load line would not change, however the individual green line (representing the gate-source bias that intersects the blue box) would change from device to device.  This is what setting R11 does:  matches the bias so that the individual JFET idles at the design point.

However the implicit assumption here is that the U87 biasing string depends on the Zener keeping it's node at 24V!  It could be the original JFET's didn't pull much current.  However a modern 2N3819 can range anywhere from 2mA IDSS all the way up to 20mA!  That is a tremendous range for a single topology to cope with!

If you set R11 to maximum, then the drain voltage should be at maximum (the blue box is far to the right).  As you lower R11, the blue box will move along the red line to the left, and drain voltage should decrease as the idle current increases.  As R11 approaches zero the JFET will pinch-off and then the drain voltage will rapidly rise back up.

If you don't see this, then something else isn't correct in the wiring.

If you happen to have devices that have very high IDSS, then you won't be able to make R11 large enough with a 10K pot to move the idle current down into the intended range, because the device will be pulling too much current and dropping all of your voltage across R17!  If you take my plot, and move the top-most line (VGS=0V) up to 20mA (on my plot, it's about 12mA), you'll see that in order to drop the current back down to 0.25mA you'll need perhaps 4V gate-to-source bias, which would be 4V/0.25mA = 16Kohm!

Do you have perhaps a 25K pot to put in place?  Or you could also add a 10K resistor in series with the pot of you can perform the gymnastics on the board with your soldering iron.  I would also test 10 JFET's for IDSS and pick one that's on the lower end of the spectrum.

Hope that makes sense.
Title: Re: Neumann U87 vintage circuit build thread
Post by: Matador on March 18, 2012, 08:39:56 PM
Put your DMM in current measuring mode.  Take a Jfet, short gate and source together, and connect to negative terminal of a 9V battery.  Connect one DMM probe to the drain, the other to the positive 9V battery terminal.  You should be able to read the IDSS on the meter.

If your meter can't measure current, then put a 10 ohm resistor (measure it first!) between the drain and the positive battery terminal, then read the voltage drop across the resistor and divide the voltage by the resistance you measured.
Title: Re: Neumann U87 vintage circuit build thread
Post by: poctop on March 18, 2012, 11:24:35 PM
Thanks Matador for your resourcefullness it very appreciated,  i guess stating that the FET drain should be set at 10.5V it is not a good thing,  like you said it is not all fet that will bias properly into those conditions ,  in my case problably luck i had those 3 FET ending up at the same voltage and idle current when set about there that is probably why i stated the 10.5V adjustments a bit to soon.

i have tried different method the scope the THD method and they would relate pretty well , i did include in the BOM a 25K pot for bias adjustment so there should be some margin there to set those conditions.

but i have to say that my prefered method is to inject a signal trough big RT and SW pad a 1K sine tone and while tweaking the pot i could easilly hear when the FET opens and distorts when it barely opens, i also could relate the behavior of the FET as i tweak the Pot and make sure everything is set properly , i encourage new builder to use the 1K tone method with the room capture software for a minimum thd  past the opening point as this method can be related to our earing it never missed for me,

again this is great info and i still learning great stuff there.
Dan,




Title: Re: Neumann U87 vintage circuit build thread
Post by: wthrelfall on March 19, 2012, 09:07:26 AM
Hi matador and Dany,

I've been reading with interest, but sadly I am unable to follow matador's post explaining the fet biasing theory, I'm afraid I just don't have a great understanding of mathematical theory - I'm a cycle mechanic, so I guess it's a bit like when I try to explain to my customers how the gears on a bike work, and they look at me blankly and scratch their heads  ;)  Yes, i've built a few mic pre's and compressors, but mostly kits, so gives you an idea of my level of (in) competence!


But I did manage to measure my 3 fet's.  they were 11.4ma, 10ma & 9.7ma.   Not sure if these figures are higher than 'normal'?  anyway, I installed the 9.7ma fet, and put all my resistors back to the original values specified on the BOM.  This time I installed a 50k pot at R11, and following matador's guidelines, I was able to verify that while reducing the resistance from maximum to minimum, the fet behaved as expected (with the sudden rise near the lowest resistance).  With the drain reading around 10.5v, the pot was giving 5K of resistance, and I'm getting 18.3v at the zener.  I swapped the pot out for a 5k1 resistor and tested the mic, and yes it sounds alot better, actually pretty good.  Signal is low, needs tons of gain for a decent level.  I also did as Dany asked and put a 10k resistor at R11 and tested it.  sounds pretty much the same as the 5k1, but the zener is getting over 20v.

I guess what is confusing me most is that the voltage's i'm getting are dramatically different from what Dany has measured on his.  24v at the zener - is this vitally important?  I know, it's got to do with the fet bias, just can't get my head around it.

I would like to attempt feeding a tone to the mic, but would need clearer instructions dany..

thanks for your patience guys  :-[



Put your DMM in current measuring mode.  Take a Jfet, short gate and source together, and connect to negative terminal of a 9V battery.  Connect one DMM probe to the drain, the other to the positive 9V battery terminal.  You should be able to read the IDSS on the meter.

If your meter can't measure current, then put a 10 ohm resistor (measure it first!) between the drain and the positive battery terminal, then read the voltage drop across the resistor and divide the voltage by the resistance you measured.
Title: Re: Neumann U87 vintage circuit build thread
Post by: benlindell on March 19, 2012, 09:22:41 AM
I guess what is confusing me most is that the voltage's i'm getting are dramatically different from what Dany has measured on his.  24v at the zener - is this vitally important?  I know, it's got to do with the fet bias, just can't get my head around it.

What is your source of phantom power? there's a chance it's not delivering enough power, most mics that require phantom can make do with such a wide range of voltage that the phantom power coming from you mic pre may not be exactly 48V to begin with.
Title: Re: Neumann U87 vintage circuit build thread
Post by: wthrelfall on March 19, 2012, 10:14:06 AM
I guess what is confusing me most is that the voltage's i'm getting are dramatically different from what Dany has measured on his.  24v at the zener - is this vitally important?  I know, it's got to do with the fet bias, just can't get my head around it.

What is your source of phantom power? there's a chance it's not delivering enough power, most mics that require phantom can make do with such a wide range of voltage that the phantom power coming from you mic pre may not be exactly 48V to begin with.

47v
Title: Re: Neumann U87 vintage circuit build thread
Post by: Matador on March 19, 2012, 11:15:55 AM
But I did manage to measure my 3 fet's.  they were 11.4ma, 10ma & 9.7ma.   Not sure if these figures are higher than 'normal'?  anyway, I installed the 9.7ma fet, and put all my resistors back to the original values specified on the BOM.  This time I installed a 50k pot at R11, and following matador's guidelines, I was able to verify that while reducing the resistance from maximum to minimum, the fet behaved as expected (with the sudden rise near the lowest resistance).  With the drain reading around 10.5v, the pot was giving 5K of resistance, and I'm getting 18.3v at the zener.  I swapped the pot out for a 5k1 resistor and tested the mic, and yes it sounds alot better, actually pretty good.  Signal is low, needs tons of gain for a decent level.  I also did as Dany asked and put a 10k resistor at R11 and tested it.  sounds pretty much the same as the 5k1, but the zener is getting over 20v.

You are very close!  The next step is replace R17 with a 50K pot, and start reducing it until the Zener voltage reaches 24V.  You shouldn't see a lot of modulation of the drain voltage, however your output swing before distortion will be better (assume a fixed 10.5V drain value for the chosen bias!).

The 10.5V value is not sacrosanct:  it was chosen basically because it's exactly half of 21V, which on the original U87 was selected as the "VDD" value.  For the JFET's being used, you aren't reaching 21V, so 10.5V is no longer "optimum", based solely on signal swing capability.

All of those currents you measured were in the datasheet ballpark of roughly middle between 2mA and 20mA, so don't worry too much.

As for gain:  what transformer did you end up using?  The gain of the circuit is (roughly) -R12/R11, which for R12=47K and R11 =5K is about 10.  And the step-down transformer will throw part of that back away:  for example a 10:1 Cinemag CM-2480 will reduce the overall gain of the circuit down to unity.  The original Neumann transformer was (I believe 7:1) which means the overall gain is only 3dB.  So unless you are close miking stuff with hot transients the mike is going to be on the quiet side.
Title: Re: Neumann U87 vintage circuit build thread
Post by: poctop on March 19, 2012, 04:35:28 PM
Anyone has any info on what the Aurycle transfomer is it has never been intented for this project anywhay but
if it has a ratio of 15:1 that would not help any cause here.

Title: Re: Neumann U87 vintage circuit build thread
Post by: poctop on March 19, 2012, 05:58:52 PM
Hi Wthrelfall ,  i hope this can help referencing things, i did a measurement here with original component value and without the FET installed  and No transformer installed and no capsule installed and No R11 installed and my reading at the Drain pad is 22.67V same as on the top of the Zener can you verify that,  if you dont have that then something went wrong during stuffing. i measure the FET i did installed for IDss (Thanks to Matador )
and i have a 10.4ma IDss,

Hope this helps,
Dany,


Title: Re: Neumann U87 vintage circuit build thread
Post by: Matador on March 19, 2012, 06:07:27 PM
Anyone has any info on what the Aurycle transfomer is it has never been intented for this project anywhay but
if it has a ratio of 15:1 that would not help any cause here.

The Aurycle site contradicts itself:  it says 2:1 (which makes sense with a PNP follower in that circuit).  But another page says 10:1 so who knows....
Title: Re: Neumann U87 vintage circuit build thread
Post by: poctop on March 19, 2012, 08:49:28 PM
Tuning Pointers. Hope this helps :)

with nothing connected to the  Front Capsule nor Rear Capsule ( important )For the sine Tone Method and THD Method : use the big RT and SW Pad on the board,  RT + ,SW -
feed it 0db (0.775VAC) at 1Khz and tweak the pot , if using your Daw as sine tone ,you should be able to hear what come from the mike with headphone or something you need to be able to ear separtely what come from the mike,  tweak the pot fully in 1 way and then fully the other way you should ear the sounds come louder and then get to almost dissapear, what you need to do is to tweak just after it becomes louder and there is no more Fizz in the sounds, you will clearly ear fizzing when the FET opens, just a bit past this point is the good approximative Bias, if you go too Far the Signal will becomes fizzy again but more subtile past this point.( easier to see on a scope) At this point the method is the same for using the Room capture demo software with the THD Meter you only use the THD Meter as an indicator , when the FET opens the Meter goes up at near 25-30% THD so you can clearly see what happening the more you tweak past the opening point the Less THD on the Meter until your reach about 0.4% thd that is fine. if you go too far the THD will slowly rise backup as the fizz in the sounds as the sine symmetry seen in a scope meter, doing it a couple of times is good pratice and you can actually verify your method with the ending drain Voltage if the ending voltage makes sense.

Hope this helps,
Dany,
 
Title: Re: Neumann U87 vintage circuit build thread
Post by: poctop on March 19, 2012, 09:52:09 PM
Quote
However the implicit assumption here is that the U87 biasing string depends on the Zener keeping it's node at 24V!  It could be the original JFET's didn't pull much current.  However a modern 2N3819 can range anywhere from 2mA IDSS all the way up to 20mA!  That is a tremendous range for a single topology to cope with!


i tought the the use of the zener here was to keep the node just above the breakdown Knees at about 22V to keep the curent in the linear Portion To stabilize the Voltage without pulling too much of current for no reason.   :-\
Dan,
Title: Re: Neumann U87 vintage circuit build thread
Post by: poctop on March 19, 2012, 10:15:41 PM
I just received some other boards if someone would like to give it a shot.
Dan,

Title: Re: Neumann U87 vintage circuit build thread
Post by: wthrelfall on March 20, 2012, 09:02:19 AM
Dany

I removed the transformer connections, and the connections to the capsule, and also removed the fet and R11.  original bom components elsewhere.  Here are my voltages:

Phantom power is 48.6v

top of L1 - 48.6v
top of L2 - 45.9v
top of R18 - 48.6v
top of R19 - 45v
bottom of R17 - 45v
top of R17 - 23.18v
Zener 23.17v
FET drain pad 23.15v
FET source pad 0.089v
top of R12 23.15v
top of R13 42.4v
top of R14 23.14v
top of R8 41.8v


What is R9 & R10 doing?  I got 0v there..

Title: Re: Neumann U87 vintage circuit build thread
Post by: HellfireStudios on March 20, 2012, 09:30:18 AM
Has anyone tried the 1.5-2.2 pF across the the Gate and Drain of the FET yet? This supposedly makes newer 2N3819's closer to the old ones (there was a reference to black magic in the post I read).
If a cap is implemented in this way, would biasing be carried out in the same manner? Any other circuit considerations? Thanks for all the info contributed so far.

Here's the original post: I don't know who to quote here, but you know who you are...

Hi Dan,
Did you measured amp specs via test input? There is Neumann U87i specification at page 8:
 http://www.neumann.com/download.php?download=copi0042.PDF
I had a problem to meet frequency response specs, as well as THD specs. 
After some research I found simple way to tune the circuit to original specs by adding 1.5-2.2pF capacitor between Gate and Drain of FET. Why so? I think that modern 2N3819 FETs have much lower reverse capacitance than original ones from 70s.
Hope it can help in U87 black magic.
Title: Re: Neumann U87 vintage circuit build thread
Post by: wthrelfall on March 20, 2012, 09:58:27 AM
Ok, so I put the 25k pot on R11 and the 50K pot on R17.
With the fet drain set at 10.5v by R11 (1.67k), I adjust R17 to give me 23.17v at the Zener (turned right down to 65 ohm!!). 
I experiment with some other combinations, and I find that with R17 adjusted to a point where the zener hits 23.17'ish it then begins to be ineffective.  at that point the FET reads 17.66v with R11 @ 4.64k. 



But I did manage to measure my 3 fet's.  they were 11.4ma, 10ma & 9.7ma.   Not sure if these figures are higher than 'normal'?  anyway, I installed the 9.7ma fet, and put all my resistors back to the original values specified on the BOM.  This time I installed a 50k pot at R11, and following matador's guidelines, I was able to verify that while reducing the resistance from maximum to minimum, the fet behaved as expected (with the sudden rise near the lowest resistance).  With the drain reading around 10.5v, the pot was giving 5K of resistance, and I'm getting 18.3v at the zener.  I swapped the pot out for a 5k1 resistor and tested the mic, and yes it sounds alot better, actually pretty good.  Signal is low, needs tons of gain for a decent level.  I also did as Dany asked and put a 10k resistor at R11 and tested it.  sounds pretty much the same as the 5k1, but the zener is getting over 20v.

You are very close!  The next step is replace R17 with a 50K pot, and start reducing it until the Zener voltage reaches 24V.  You shouldn't see a lot of modulation of the drain voltage, however your output swing before distortion will be better (assume a fixed 10.5V drain value for the chosen bias!).

The 10.5V value is not sacrosanct:  it was chosen basically because it's exactly half of 21V, which on the original U87 was selected as the "VDD" value.  For the JFET's being used, you aren't reaching 21V, so 10.5V is no longer "optimum", based solely on signal swing capability.

All of those currents you measured were in the datasheet ballpark of roughly middle between 2mA and 20mA, so don't worry too much.

As for gain:  what transformer did you end up using?  The gain of the circuit is (roughly) -R12/R11, which for R12=47K and R11 =5K is about 10.  And the step-down transformer will throw part of that back away:  for example a 10:1 Cinemag CM-2480 will reduce the overall gain of the circuit down to unity.  The original Neumann transformer was (I believe 7:1) which means the overall gain is only 3dB.  So unless you are close miking stuff with hot transients the mike is going to be on the quiet side.
Title: Re: Neumann U87 vintage circuit build thread
Post by: tskguy on March 20, 2012, 10:43:54 AM
Hi all,

I just ordered some of these boards..Looks like a fun project! I am going to use this as a test bed for some capsule design. Anyway I found this and thought it was interesting read.
http://recordinghacks.com/microphones/Neumann/U-87-Ai


Title: Re: Neumann U87 vintage circuit build thread
Post by: Matador on March 20, 2012, 10:56:55 AM
Dany

I removed the transformer connections, and the connections to the capsule, and also removed the fet and R11.  original bom components elsewhere.  Here are my voltages:

Phantom power is 48.6v

top of L1 - 48.6v
top of L2 - 45.9v
top of R18 - 48.6v
top of R19 - 45v
bottom of R17 - 45v
top of R17 - 23.18v
Zener 23.17v
FET drain pad 23.15v
FET source pad 0.089v
top of R12 23.15v
top of R13 42.4v
top of R14 23.14v
top of R8 41.8v


What is R9 & R10 doing?  I got 0v there..

All of that looks correct.  You are pulling 0.32mA through R17 because the Zener is sinking current to keep the node "top of R17" at it's breakdown voltage.  Once the Zener is regulating, R17 does nothing as the system acts like a constant current source (the Zener will change it's internal impedance to keep the voltage across it at 23.14V, making R17 "do nothing" as it's adjusted). 

The idea is that you turn R17 down until the Zener just starts regulating.  Once this happens, you re-adjust R11 until you get 10.5V at the drain, then check the Zener voltage to make sure it hasn't changed, and if it dropped, you lower R17 a little bit more, and iterate through the process.  Something like this:

1) Raise R11 and R17 to maximum.
2) Stick in your FET
3) If the Zener node is not 23.14V, lower R17 until it just hits 23.14V
4) Lower R11 until you see 10.5V
5) If the Zener node is not 23.14V, go back to step 3

After several of these sequences you should be able to get both conditions met, at least for that FET, and that Zener.  You can then remove the pots and substitute the closest values that you have if you want to.

R9 and R10 are there to provide an AC ground point for the capsule backplate.  C5 will not allow DC current flow through these two resistors, so your meter will not register a voltage there.
Title: Re: Neumann U87 vintage circuit build thread
Post by: wthrelfall on March 20, 2012, 11:29:30 AM
Yes, that process is basically what I've been doing, over and over again and now my boards are losing pads due to the number of parts being changed.  I was feeling like I was getting 'good' numbers, and successfully got the sine input and tweaked it for 'sound' as well as for volts.  so feeling confident, i plugged in the capsule and tested the mic...  Now it's noisier and still ridiculously quiet.  I need at least 60 - 70db of gain to get a usable signal but then it's so noisy it's unusable.


Dany

I removed the transformer connections, and the connections to the capsule, and also removed the fet and R11.  original bom components elsewhere.  Here are my voltages:

Phantom power is 48.6v

top of L1 - 48.6v
top of L2 - 45.9v
top of R18 - 48.6v
top of R19 - 45v
bottom of R17 - 45v
top of R17 - 23.18v
Zener 23.17v
FET drain pad 23.15v
FET source pad 0.089v
top of R12 23.15v
top of R13 42.4v
top of R14 23.14v
top of R8 41.8v


What is R9 & R10 doing?  I got 0v there..

All of that looks correct.  You are pulling 0.32mA through R17 because the Zener is sinking current to keep the node "top of R17" at it's breakdown voltage.  Once the Zener is regulating, R17 does nothing as the system acts like a constant current source (the Zener will change it's internal impedance to keep the voltage across it at 23.14V, making R17 "do nothing" as it's adjusted). 

The idea is that you turn R17 down until the Zener just starts regulating.  Once this happens, you re-adjust R11 until you get 10.5V at the drain, then check the Zener voltage to make sure it hasn't changed, and if it dropped, you lower R17 a little bit more, and iterate through the process.  Something like this:

1) Raise R11 and R17 to maximum.
2) Stick in your FET
3) If the Zener node is not 23.14V, lower R17 until it just hits 23.14V
4) Lower R11 until you see 10.5V
5) If the Zener node is not 23.14V, go back to step 3

After several of these sequences you should be able to get both conditions met, at least for that FET, and that Zener.  You can then remove the pots and substitute the closest values that you have if you want to.

R9 and R10 are there to provide an AC ground point for the capsule backplate.  C5 will not allow DC current flow through these two resistors, so your meter will not register a voltage there.
Title: Re: Neumann U87 vintage circuit build thread
Post by: Matador on March 20, 2012, 12:21:35 PM
Make sure you scrub the area around the capsule connections with isopropyl alcohol to get rid of solder flux:  the board can't be "too clean" in this regard.  The more you solder around this area (like where the gate of the JFET connects), the more flux splatter you have.  The high impedance nodes see any leakage paths and can cause noise like you are describing.

The U87 circuit is definitely not high gain in any case. ;). My Aurycle mikes need 50-60dB when used several feet back from quieter sources.
Title: Re: Neumann U87 vintage circuit build thread
Post by: Matador on March 20, 2012, 01:46:36 PM
Thinking about this some more:  there is a duality with this circuit due to the capsule bias.  We can maximize gain by finding higher gm transistors and hand selecting higher IDSS from our stash.  We could then lower the drain resistor and probably squeeze another 25dB out of the circuit.  I can see why the 2SK170 is a popular mike JFET as it has 10 times the transconductance of the 2N3819. But those concerned about needing too much gain (and not recording highly dynamic sources that need lots of input headroom) might want to try this JFET in this circuit.

But the more current we pull from the phantom supply, the lower our capsule bias, which increases noise and reduces sensitivity, which ultimately steals back gain.
Title: Re: Neumann U87 vintage circuit build thread
Post by: HellfireStudios on March 20, 2012, 01:55:05 PM
My Carvin CM-87S only has switches for pad and low-cut. I was wondering if there were any suggestions for mounting a switch inside the mic with this PCB.
On the mic's original PCB, there was a place to put a DPDT switch for the low-cut.  My original plan was to add a switch on the PCB, and replace the low-cut on the exterior with a pattern selector switch. Could this be adapted to work with the new PCB?
I would hate to have to add a relay system just for pattern switching, unless the geniuses on this forum can figure out a way to add a relay without replacing the 3-pin XLR with what I'm guessing is at least 5-pin.
If this is the only plausible solution, are there any suggestions on relays that will fit and work reliably?
Sorry about all the questions. My head is swimming with the 15 or so electronic projects I'm trying to finalize so I can order the goods. As the old saying goes, "Design twice, order once."
Title: Re: Neumann U87 vintage circuit build thread
Post by: wthrelfall on March 20, 2012, 05:12:21 PM
Matador,
That seems like a good idea.  Could the aurycle transformer be adding considerable noise or be giving a lower gain?  I'm going to get a cm-2480 and a Peluso capsule so I think this should make some marginal improvements.  I'm also going to build up the Aurycle board using your ideas and BOM from your other thread, see how that sounds..  Have you used and heard what the stock Aurycle components sound like?  big differences using your BOM?

cheers.

Make sure you scrub the area around the capsule connections with isopropyl alcohol to get rid of solder flux:  the board can't be "too clean" in this regard.  The more you solder around this area (like where the gate of the JFET connects), the more flux splatter you have.  The high impedance nodes see any leakage paths and can cause noise like you are describing.

The U87 circuit is definitely not high gain in any case. ;). My Aurycle mikes need 50-60dB when used several feet back from quieter sources.
Title: Re: Neumann U87 vintage circuit build thread
Post by: Matador on March 20, 2012, 05:28:03 PM
Matador,
That seems like a good idea.  Could the aurycle transformer be adding considerable noise or be giving a lower gain?  I'm going to get a cm-2480 and a Peluso capsule so I think this should make some marginal improvements.  I'm also going to build up the Aurycle board using your ideas and BOM from your other thread, see how that sounds..  Have you used and heard what the stock Aurycle components sound like?  big differences using your BOM?

Wait...you are using the stock Aurycle transformer with the poctop's boards?
Title: Re: Neumann U87 vintage circuit build thread
Post by: Matador on March 20, 2012, 05:42:53 PM
Nevermind, you already said you were earlier in the thread.

We need to confirm that the transformer supplied with the Aurycle kit is indeed a 10:1.  The exact same mike from MXL (2001?) comes with a 2:1 transformer which is common for circuits that contain the PNP follower stage (as the 2:1 is cheaper).

If Aurycle is giving out 2:1 transformers, this would explain why the mike output is messed up, as the U87 common drain stage would be immensely loaded down.  If the mike was plugged into a pre with a 600ohm input impedance, this would look to the JFET stage like a 2K4 load, which means that 95% of the signal would be thrown away.
Title: Re: Neumann U87 vintage circuit build thread
Post by: wthrelfall on March 21, 2012, 05:30:07 AM
Any way I can check the transformer ratio?


Nevermind, you already said you were earlier in the thread.

We need to confirm that the transformer supplied with the Aurycle kit is indeed a 10:1.  The exact same mike from MXL (2001?) comes with a 2:1 transformer which is common for circuits that contain the PNP follower stage (as the 2:1 is cheaper).

If Aurycle is giving out 2:1 transformers, this would explain why the mike output is messed up, as the U87 common drain stage would be immensely loaded down.  If the mike was plugged into a pre with a 600ohm input impedance, this would look to the JFET stage like a 2K4 load, which means that 95% of the signal would be thrown away.
Title: Re: Neumann U87 vintage circuit build thread
Post by: wthrelfall on March 21, 2012, 08:21:23 AM
Cleaned up the boards, still noisy.  Here's a screen grab of the noise profile of the mic with the capsule disconnected, with 54db of gain.
Title: Re: Neumann U87 vintage circuit build thread
Post by: wthrelfall on March 21, 2012, 08:49:54 AM
Here's another, with transformer disconnected, same gain.  (not sure if this actually confirms if the tx is noisy, is the circuit now incomplete?)
Title: Re: Neumann U87 vintage circuit build thread
Post by: Matador on March 21, 2012, 10:43:38 AM
Here's another, with transformer disconnected, same gain.  (not sure if this actually confirms if the tx is noisy, is the circuit now incomplete?)

What point in the circuit are you measuring from in both cases?  From the output of the drain?  After the coupling cap?  From the XLR output?

How well matched are the phantom 2k21 resistors?  Were they the exact same value?
Title: Re: Neumann U87 vintage circuit build thread
Post by: wthrelfall on March 21, 2012, 10:53:08 AM
measuring from the xlr output.
can't recall the exact measurements, but this was my voltage readings taken earlier
top of L1 - 48.6v
top of L2 - 45.9v
top of R18 - 48.6v
top of R19 - 45v



Here's another, with transformer disconnected, same gain.  (not sure if this actually confirms if the tx is noisy, is the circuit now incomplete?)

What point in the circuit are you measuring from in both cases?  From the output of the drain?  After the coupling cap?  From the XLR output?

How well matched are the phantom 2k21 resistors?  Were they the exact same value?
Title: Re: Neumann U87 vintage circuit build thread
Post by: Matador on March 21, 2012, 01:43:55 PM
measuring from the xlr output.
can't recall the exact measurements, but this was my voltage readings taken earlier
top of L1 - 48.6v
top of L2 - 45.9v
top of R18 - 48.6v
top of R19 - 45v

That doesn't look right:  you should be pulling phantom current equally through R18 and R19, which means the common nodes on the "top" of these resistors should be the same.  This is why R18 and R19 are specified to be closely matched (to within 0.1 ohms or better).

The voltages you show above mean that there is a 2.7V drop across the transformer, which means there is DC current flowing through the secondary, which is going to be 50Hz hum city.

There's only two things that can explain this:  either of R18 or R19 is not the correct 2K21 ohm value, or the secondary may have a short to ground. 

It seems that most of your woes center around this Aurycle iron. ;)  When you disconnect the transformer, do your "top of R18/R19" voltages re-equalize?
Title: Re: Neumann U87 vintage circuit build thread
Post by: poctop on March 21, 2012, 03:21:20 PM
The Resistance Matching is in the considerations Excel on the first page of the Thread 0.4% Matching here some from the Docs.

Do you have your mic PCB in a sheilded environement ( Mic body Arround the PCB to GND)  when you do those test  ? the circuit sensitive to RF you will hear it even more with the capsule in ,

Here are from the BOM: 




Title: Re: Neumann U87 vintage circuit build thread
Post by: poctop on March 21, 2012, 04:05:57 PM
There some conditions to this project also, as there is not supposed to be chinese component when finished  ;) except for the Body  ???

Dan,
Title: Re: Neumann U87 vintage circuit build thread
Post by: Marcocet on March 21, 2012, 10:38:46 PM
Okay, my mic's working great! Checked all the voltages today and they're dead on.

There's only one quirk I can't get my head around: I'm using the Aurycle body, as of now unpainted, and if I over tighten the bottom ring the signal will die. it always comes back when I loosen it a bit, and I can't figure out where it's shorting. No matter how much I play with it I can't get it to cut out unless I tighten that bottom ring. It'll take some playing with I suppose...

Also, if you're using the Aurycle body keep in mind that you have to reverse the wires to the low-cut switch. The pad wires are correct.

As far as the Peluso capsules: be carefull getting them out of the packaging. One of mine slid right out, but the other one required a bit of prying, which ended up with me damaging the backplate. I was planning to use them as cardioid only anyway but it's still a bit of an annoyance.
Title: Re: Neumann U87 vintage circuit build thread
Post by: HellfireStudios on March 21, 2012, 10:50:20 PM
I asked Peluso about the BV11T mentioned in poctop's email, as I was unable to find it on his website. He said it was on the site, and costs $85. The only x-former that fits that description is the BV11P. Is this the transformer I'm looking for?
Title: Re: Neumann U87 vintage circuit build thread
Post by: wthrelfall on March 22, 2012, 05:19:16 AM
R18 & R19 are an exact match, 2.2k.  I followed the instructions exactly.


measuring from the xlr output.
can't recall the exact measurements, but this was my voltage readings taken earlier
top of L1 - 48.6v
top of L2 - 45.9v
top of R18 - 48.6v
top of R19 - 45v

That doesn't look right:  you should be pulling phantom current equally through R18 and R19, which means the common nodes on the "top" of these resistors should be the same.  This is why R18 and R19 are specified to be closely matched (to within 0.1 ohms or better).

The voltages you show above mean that there is a 2.7V drop across the transformer, which means there is DC current flowing through the secondary, which is going to be 50Hz hum city.

There's only two things that can explain this:  either of R18 or R19 is not the correct 2K21 ohm value, or the secondary may have a short to ground. 

It seems that most of your woes center around this Aurycle iron. ;)  When you disconnect the transformer, do your "top of R18/R19" voltages re-equalize?
Title: Re: Neumann U87 vintage circuit build thread
Post by: Matador on March 22, 2012, 10:40:09 AM
R18 & R19 are an exact match, 2.2k.  I followed the instructions exactly.

Yeah, I figured as much, given the tremendous difference in voltage.  That really couldn't be explained by a resistor mismatch (of even several hundred ohms), unless you were trying to pull a tremendous amount of current from the phantom supply.

Did you try re-measuring the R18/R19 voltages after the transformer is disconnected?
Title: Re: Neumann U87 vintage circuit build thread
Post by: wthrelfall on March 22, 2012, 02:09:06 PM
Yes, same voltages with and without the tx..


R18 & R19 are an exact match, 2.2k.  I followed the instructions exactly.

Yeah, I figured as much, given the tremendous difference in voltage.  That really couldn't be explained by a resistor mismatch (of even several hundred ohms), unless you were trying to pull a tremendous amount of current from the phantom supply.

Did you try re-measuring the R18/R19 voltages after the transformer is disconnected?
Title: Re: Neumann U87 vintage circuit build thread
Post by: MagnetoSound on March 22, 2012, 05:30:29 PM
Quote
There's only two things that can explain this:  either of R18 or R19 is not the correct 2K21 ohm value, or the secondary may have a short to ground.

Or there may be a problem with one leg of the phantom supply upstream.

Title: Re: Neumann U87 vintage circuit build thread
Post by: poctop on March 22, 2012, 05:46:48 PM
Wthrelfall your initial Voltage that you have posted are fine,  dont forget that we are using a 10% tolerance inductor and some 5% resistor , and the most important is the current divider in 2K2 pair,  my voltage here shows some little difference but are pretty damn close and the mic is working like charm ,  you are all good with what you have for now i think you just need to stick the proper traffo in there and you will  be fine.  keep on the good work.
Title: Re: Neumann U87 vintage circuit build thread
Post by: wthrelfall on March 22, 2012, 07:01:37 PM
Yeah Dany, I've got a transformer and peluso capsule on order, hopefully it'll make the difference!


Wthrelfall your initial Voltage that you have posted are fine,  dont forget that we are using a 10% tolerance inductor and some 5% resistor , and the most important is the current divider in 2K2 pair,  my voltage here shows some little difference but are pretty damn close and the mic is working like charm ,  you are all good with what you have for now i think you just need to stick the proper traffo in there and you will  be fine.  keep on the good work.
Title: Re: Neumann U87 vintage circuit build thread
Post by: poctop on March 22, 2012, 11:07:43 PM
The diode you have is 5% also So 22.8V is just Fine, it may vary a little,  22.8 to 25.2V

This are all what you need

Quote
top of L1 - 48.6v
top of L2 - 45.9v
top of R18 - 48.6v
top of R19 - 45v
bottom of R17 - 45v
top of R17 - 23.18v
Zener 23.17v
FET drain pad 23.15v
FET source pad 0.089v
top of R12 23.15v
top of R13 42.4v
top of R14 23.14v
top of R8 41.8v


Keep Rockin  8)
Title: Re: Neumann U87 vintage circuit build thread
Post by: poctop on March 23, 2012, 01:39:03 AM
R18 & R19 are an exact match, 2.2k.  I followed the instructions exactly.


measuring from the xlr output.
can't recall the exact measurements, but this was my voltage readings taken earlier
top of L1 - 48.6v
top of L2 - 45.9v
top of R18 - 48.6v
top of R19 - 45v

That doesn't look right:  you should be pulling phantom current equally through R18 and R19, which means the common nodes on the "top" of these resistors should be the same.  This is why R18 and R19 are specified to be closely matched (to within 0.1 ohms or better).

The voltages you show above mean that there is a 2.7V drop across the transformer, which means there is DC current flowing through the secondary, which is going to be 50Hz hum city.

There's only two things that can explain this:  either of R18 or R19 is not the correct 2K21 ohm value, or the secondary may have a short to ground. 

It seems that most of your woes center around this Aurycle iron. ;)  When you disconnect the transformer, do your "top of R18/R19" voltages re-equalize?


I think i know why you are confused  ;) There is nothing wrong with your Phantom Power , When you say on top of resistor that does not relate onto the top the of R2 in the schematic ,  this is why your are confused , and the board is designed this way. if you are carefull on putting the resistor in the right way ( on the Bigger circle on the PCB) you should have the same voltage on top(top of board) of the 2 inductor 48V ish. And the top (top off the board) of the 2.2K resistor should be a bit diffent because  (top off the board) is actually after the current divider.  as for the regulation the Zener will decide how much is a Voltage drop across R17 it is the remainer of the Zener Differiential,  and Then the 10-15V ish on the Drain has you tweak it and about 20V after the Zener. dont get confused as if the schematics is a map of the boards,

So everything is Correct Voltage Side Wise  :)
Hope this helps ,

 





Title: Re: Neumann U87 vintage circuit build thread
Post by: poctop on March 23, 2012, 01:47:49 AM
Okay, my mic's working great! Checked all the voltages today and they're dead on.

There's only one quirk I can't get my head around: I'm using the Aurycle body, as of now unpainted, and if I over tighten the bottom ring the signal will die. it always comes back when I loosen it a bit, and I can't figure out where it's shorting. No matter how much I play with it I can't get it to cut out unless I tighten that bottom ring. It'll take some playing with I suppose...

Also, if you're using the Aurycle body keep in mind that you have to reverse the wires to the low-cut switch. The pad wires are correct.

As far as the Peluso capsules: be carefull getting them out of the packaging. One of mine slid right out, but the other one required a bit of prying, which ended up with me damaging the backplate. I was planning to use them as cardioid only anyway but it's still a bit of an annoyance.


Have you followed the instructions for the potentiomter if you let it in, in certain case you may have to file the edge a bit to make sure you a re not stressing anything in the Aurycle mic ,  i have one here and i can use a boa tool and screw it to death.

Hope this helps,

dan,
Title: Re: Neumann U87 vintage circuit build thread
Post by: poctop on March 23, 2012, 09:01:54 AM
All order shipped today,
Dany,  :)
Title: Re: Neumann U87 vintage circuit build thread
Post by: Marcocet on March 23, 2012, 10:38:58 AM
Have you followed the instructions for the potentiomter if you let it in, in certain case you may have to file the edge a bit to make sure you a re not stressing anything in the Aurycle mic ,  i have one here and i can use a boa tool and screw it to death.

Hope this helps,

dan,

Yeah, the pots have been replaced with resistors and the bodies have been painted so there's no electrical connection except for the edges, but it's still happening. And only on one mic. Super weird, right? I'll check it out more thoroughly today.

-marc alan
Title: Re: Neumann U87 vintage circuit build thread
Post by: stanz on March 23, 2012, 10:49:21 AM
Okay, my mic's working great! Checked all the voltages today and they're dead on.

There's only one quirk I can't get my head around: I'm using the Aurycle body, as of now unpainted, and if I over tighten the bottom ring the signal will die. it always comes back when I loosen it a bit, and I can't figure out where it's shorting. No matter how much I play with it I can't get it to cut out unless I tighten that bottom ring. It'll take some playing with I suppose...


Is it possible tightening it is flexing the support rails, thus flexing the PCB or XLR connector and causing something to become open (as opposed to something shorting)?

A bit wire with a bit of insulation exposed?
Title: Re: Neumann U87 vintage circuit build thread
Post by: poctop on March 24, 2012, 09:14:58 AM
I think That would make sense, well i hope. ;D
Title: Re: Neumann U87 vintage circuit build thread
Post by: Marcocet on March 24, 2012, 09:31:02 PM
Yep, it's just one of them that's being a problem. I only get to work on the things intermitantly but I should be able to put together a full report on the things soon. For now here's a pic! (Also it's on my new diy blog for the studio. I've built a lot of stuff we use, so I figured it's time to start documenting it. http://strangeweathercustom.wordpress.com (http://strangeweathercustom.wordpress.com)

(http://strangeweathercustom.files.wordpress.com/2012/03/photo-e1332469395496.jpg?w=480&h=642)
Title: Re: Neumann U87 vintage circuit build thread
Post by: kante1603 on March 24, 2012, 10:32:00 PM
Woah-red!Now that´s brave,nice!
Udo ;)
Title: Re: Neumann U87 vintage circuit build thread
Post by: poctop on March 25, 2012, 12:08:46 PM
Yep, it's just one of them that's being a problem. I only get to work on the things intermitantly but I should be able to put together a full report on the things soon. For now here's a pic! (Also it's on my new diy blog for the studio. I've built a lot of stuff we use, so I figured it's time to start documenting it. http://strangeweathercustom.wordpress.com (http://strangeweathercustom.wordpress.com)

(http://strangeweathercustom.files.wordpress.com/2012/03/photo-e1332469395496.jpg?w=480&h=642)

this look nice a pair, congrats ,  for the one that squezze you may wnat to stilck your DMV on pin 1 and 2 or 3 and stick it to the XLR while yo are tightening it you may find if you have a short at a certain point when squezzing , hope this helps,
Again thanks for sharing  ;D
Title: Re: Neumann U87 vintage circuit build thread
Post by: HellfireStudios on March 26, 2012, 04:03:07 PM
Boards just arrived. They look great. Thanks.

Does anyone know what SPDT (on-off-on) switch will fit on the new PCB (preferably in place of the connector at the bottom of board two) for the pattern selector?
The Mountain sub-miniature, right-angle, pc-mount switch (Mouser# 2MS3T2B2M6QE) might fit the bill, but I'm not sure whether the overall length of .79" might incur interference from the transformer housing. Mouser# 633-G13AP is a sure-fire fit, but it maxes out at .4 VA and 28VAC/DC. Would this work, or is it too underspec'd? Any suggestions would be greatly appreciated.

-James-
Title: Re: Neumann U87 vintage circuit build thread
Post by: KasperNyhus on March 26, 2012, 05:05:05 PM
Hi guys

I can't figure out exactly how to calibrate R11.

I have a scope and use my soundcard as tone generator

I have tried to inject a 1k sine into the FC cap spot (without the capsule) but where do I put the ground leg from the soundcard - its a balanced signal but I only need the hot and the ground wire, right? Is the FC Bdy the spot for the ground wire?
And the test probe of course goes to the drain of the transistor but where to put the ground leg from the test probe?

Can someone please tell me - really slow - how to use a scope for calibrating these microphones

Sorry for being such a noob

/Kasper
Title: Re: Neumann U87 vintage circuit build thread
Post by: poctop on March 26, 2012, 05:08:46 PM
Tuning Pointers. Hope this helps

with nothing connected to the  Front Capsule nor Rear Capsule ( important )For the sine Tone Method and THD Method : use the big RT and SW Pad on the board,  RT + ,SW -
feed it 0db (0.775VAC) at 1Khz and tweak the pot , if using your Daw as sine tone ,you should be able to hear what come from the mike with headphone or something you need to be able to ear separtely what come from the mike,  tweak the pot fully in 1 way and then fully the other way you should ear the sounds come louder and then get to almost dissapear, what you need to do is to tweak just after it becomes louder and there is no more Fizz in the sounds, you will clearly ear fizzing when the FET opens, just a bit past this point is the good approximative Bias, if you go too Far the Signal will becomes fizzy again but more subtile past this point.( easier to see on a scope) At this point the method is the same for using the Room capture demo software with the THD Meter you only use the THD Meter as an indicator , when the FET opens the Meter goes up at near 25-30% THD so you can clearly see what happening the more you tweak past the opening point the Less THD on the Meter until your reach about 0.4% thd that is fine. if you go too far the THD will slowly rise backup as the fizz in the sounds as the sine symmetry seen in a scope meter, doing it a couple of times is good pratice and you can actually verify your method with the ending drain Voltage if the ending voltage makes sense.

Hope this helps,
Dany,
Title: Re: Neumann U87 vintage circuit build thread
Post by: poctop on March 26, 2012, 05:12:55 PM
Hi guys

I can't figure out exactly how to calibrate R11.

I have a scope and use my soundcard as tone generator

I have tried to inject a 1k sine into the FC cap spot (without the capsule) but where do I put the ground leg from the soundcard - its a balanced signal but I only need the hot and the ground wire, right? Is the FC Bdy the spot for the ground wire?
And the test probe of course goes to the drain of the transistor but where to put the ground leg from the test probe?

Can someone please tell me - really slow - how to use a scope for calibrating these microphones

Sorry for being such a noob

/Kasper

Relating My previous post you can set the scope,  the goals is to see the sine loosing its symetry on the top, happens when you hit the FET opening and then tweak until the lower portion of the sine wave looses it's symetry and then you back off the number of turn in the middle of that, so lets say 5 turn from loosing sym on top to loosing sym on bottom you would back off 2.5 turn from the bottom symetry shift.

please use the RT(+) and SW(gnd) pad for the sine tone calibration , you actally need to monitor the outup of the mic rather than the Drain Voltage, you will need your mic plugged in to a preamp also. and you can also use the Room cature program to Measure THD from the mic output wich i find more precise.

Dany,
Title: Re: Neumann U87 vintage circuit build thread
Post by: KasperNyhus on March 26, 2012, 05:24:02 PM
Hi guys

I can't figure out exactly how to calibrate R11.

I have a scope and use my soundcard as tone generator

I have tried to inject a 1k sine into the FC cap spot (without the capsule) but where do I put the ground leg from the soundcard - its a balanced signal but I only need the hot and the ground wire, right? Is the FC Bdy the spot for the ground wire?
And the test probe of course goes to the drain of the transistor but where to put the ground leg from the test probe?

Can someone please tell me - really slow - how to use a scope for calibrating these microphones

Sorry for being such a noob

/Kasper

Relating My previous post you can set the scope,  the goals is to see the sine loosing its symetry on the top, happens when you hit the FET opening and then tweak until the lower portion of the sine wave looses it's symetry and then you back off the number of turn in the middle of that, so lets say 5 turn from loosing sym on top to loosing sym on bottom you would back off 2.5 turn from the bottom symetry shift.

please use the RT(+) and SW(gnd) pad for the sine tone calibration , you actally need to monitor the outup of the mic rather than the Drain Voltage, you will need your mic plugged in to a preamp also. and you can also use the Room cature program to Measure THD from the mic output wich i find more precise.

Dany,
Thanks Dany I'll try that

But if I need to monitor the mic output I guess I need the trafo? still waiting for my cinemag...
Title: Re: Neumann U87 vintage circuit build thread
Post by: poctop on March 26, 2012, 05:32:54 PM
I do have to mention that the SW(gnd) and the RT pad are the bigger pad one on the PCB 1 , not to be confused with the traffo pad
D
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: poctop on March 26, 2012, 08:31:39 PM
The T13 From Tab-Funkenwerk is arrived  ;D

(https://io.groupdiy.com/file/gdiy-2017/u/39511/58d028199375e)

http://www.tab-funkenwerk.com/id133.html (http://www.tab-funkenwerk.com/id133.html)
Title: Re: Neumann U87 vintage circuit build thread
Post by: berkleystudios on March 27, 2012, 02:02:22 AM
Boards just arrived. They look great. Thanks.

Does anyone know what SPDT (on-off-on) switch will fit on the new PCB (preferably in place of the connector at the bottom of board two) for the pattern selector?
The Mountain sub-miniature, right-angle, pc-mount switch (Mouser# 2MS3T2B2M6QE) might fit the bill, but I'm not sure whether the overall length of .79" might incur interference from the transformer housing. Mouser# 633-G13AP is a sure-fire fit, but it maxes out at .4 VA and 28VAC/DC. Would this work, or is it too underspec'd? Any suggestions would be greatly appreciated.

-James-

would also like to know this. planning on modding the a460 body to use it as multi-pat.
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: trancedental on March 27, 2012, 08:25:44 AM
Are there any suitable transformers & capsules made in or even available in Europe for this project? Shipping & customs / handling fees from the US / Canada is working out expensive >:(

Someone in Europe must still be able to manufacture these items nowadays?  8)
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: HellfireStudios on March 27, 2012, 02:51:30 PM
Are there any suitable transformers & capsules made in or even available in Europe for this project? Shipping & customs / handling fees from the US / Canada is working out expensive >:(

Someone in Europe must still be able to manufacture these items nowadays?  8)

Sowter might make a transformer (you should look for around a 10:1 ratio). I couldn't even venture a guess at capsules (other than the obvious and expensive Nueumann, AKG, and BLUE). Sorry I can't be of more help.
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: HellfireStudios on March 27, 2012, 03:03:55 PM
berkleystudios, the Apex 460 is a killer platform for mic modding, mainly C12-style designs, but the head basket is too far off for the U-87 sound. The head basket on the U-87, much like the U-47, is integral to the sound of the mic. The options listed elsewhere for this mod are much more suited to the task at hand. I'm using a Carvin CM87S (comes with case, shock, power supply, cable- $130) and the only thing I dislike is the lack of a pattern switch on the outside of the mic. There are plenty of other options that may fit you a little better, but they will all work better that the 460.
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: berkleystudios on March 27, 2012, 06:53:04 PM
berkleystudios, the Apex 460 is a killer platform for mic modding, mainly C12-style designs, but the head basket is too far off for the U-87 sound. The head basket on the U-87, much like the U-47, is integral to the sound of the mic. The options listed elsewhere for this mod are much more suited to the task at hand. I'm using a Carvin CM87S (comes with case, shock, power supply, cable- $130) and the only thing I dislike is the lack of a pattern switch on the outside of the mic. There are plenty of other options that may fit you a little better, but they will all work better that the 460.
oh no not an apex 460, an a460. u87 style diy mike kit.
http://www.diymic.com/

i have build one, just ordered a second since im building 2. would like it to be multi pattern though.... would it be as simple as drilling a whole and installing a switch to the board at the proper points?
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: HellfireStudios on March 27, 2012, 08:14:57 PM
Sort of...

On a lot of other mics, the switch would have to be mounted internally (on a PCB or subframe). As for the outside switch access, the easiest place to accomodate a switch is where two outer parts come together. Like the headbasket and body sleeve.
The problem with this mic style is that there is a plastic disc directly under the headbasket baseplate (with inconviently placed screws as well). This makes "just add a switch" difficult.
I intend to use a 7-pin mic cable and required jacks to allow relay-based switching at the dedicated phantom power supply that came with my mic.
If your mic doesn't come with a power supply, you could build a dedicated polar pattern/7-pin to 3-pin XLR conversion box with a transformer sized for the relay(s) you choose (usually 5-24 volts).
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: stanz on March 27, 2012, 09:39:39 PM
***delete***
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: lefilsdejack on March 28, 2012, 02:49:23 AM
Hi everybody,
I just finished my first U87. I builded it with the Peluso K87i cap and the Cinemag CM2480 ytransformer.
I tried it yersteday on a vocal session at the studio. And it sound great! I tried it with a DIY SSL preamp, a DIY API preamp, and a UA LA610. Really really great with the Universal Audio.
I build it on a Behringer B2-Pro body, the pcb don't screw on the body at the exact place so I had to fix it like I could. But no problem.
Here are photos of the mic with the painting.
I have to give one thousant thanks to Dany (ploctop) for his help on my building, all the answers he gave to my questions, and his project!
Hope all of you will have as pleasure as I have with this mic and with the building step.
Sorry if I made english mistakes, this is not my native language.
Have a good day.

(http://[URL=http://www.imagup.com/data/1147582198.html][IMG]http://data.imagup.com/11/1147582197.JPG)[/URL][/img]
(http://[URL=http://www.imagup.com/data/1147582917.html][IMG]http://data.imagup.com/12/1147582917.JPG)[/URL][/img]
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: lefilsdejack on March 28, 2012, 02:50:31 AM
Sorry for the links!
(http://data.imagup.com/12/1147582917.JPG) (http://www.imagup.com/data/1147582917.html)
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: lefilsdejack on March 28, 2012, 02:51:39 AM
(http://data.imagup.com/11/1147582197.JPG) (http://www.imagup.com/data/1147582198.html)
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: kante1603 on March 28, 2012, 04:56:00 PM
Hi,

any inside pics please?
I'm especially interested in how you mounted the transformer as well as how you did the switch arrangement (have bought the B2 too but not opened yet,just curious about it).

Thank you,

Udo. :)
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: mrcase on March 29, 2012, 02:39:27 AM
loog great! how did you get rid of the stupid behringer engraving? or did you just paint it and its still there?
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: lefilsdejack on March 29, 2012, 03:18:26 AM
Hi,

for kante,
 I will try to take other photos of the inside. The pcb is just in place with a little cord, I have to make new holes in the pcb to fix it. The transformer just sit between the pcb and the XLR connector, it isn't fixed but don't move at all.
For the switch, if you take a look at the B2 head of the mic, you will see that there are 6 pins wich connect the head to the body. You will use 4 of them for the capsule, so the 2 others can be use for the low cut or the pad. For the other one and the polarity switch, you have to put cables. I don't connected them to the switch and prefer open the mic for changing the polarity of the mic (I use cardioide 90% of the time)  If you find another solution, I'm open to it!

for mrcase,
 for the Behringer engraving, I used a metalic mastic, a dough (excuse me if I don't find the fine word) for obstruct it.
If you don't understand, in France this mastic could be named "sintofer" (it is the brand name I think), and it is used for stripe on car's body. So you put it on the engraving (it dry really fast), you sand it with very small sand paper, perhaps you will have to make those two steps a second time, and finally just have to paint it (with a spray for me).

Hope this help you.

Have a good day.

Adrien
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: HellfireStudios on March 29, 2012, 03:30:13 AM
mrcase, the easiest way to remove the stamped logos is to fill it with epoxy (kneaded type works best for me, but requires more paint to look totally smooth). On the cheap side, Mighty Putty comes to mind. There is an equivalent (more expensive) available at ACE Hardware stores that is grey.
Just overfill the logos, and wait for it to cure. Sand flush (down to 220 grit), and finish with desired color. Be patient with dry times and everything should turn out fine.
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: kante1603 on March 29, 2012, 04:24:04 AM
loog great! how did you get rid of the stupid behringer engraving? or did you just paint it and its still there?
mrcase, the easiest way to remove the stamped logos is to fill it with epoxy (kneaded type works best for me, but requires more paint to look totally smooth). On the cheap side, Mighty Putty comes to mind. There is an equivalent (more expensive) available at ACE Hardware stores that is grey.
Just overfill the logos, and wait for it to cure. Sand flush (down to 220 grit), and finish with desired color. Be patient with dry times and everything should turn out fine.

Hi,

I have done that with 2K glue (for metall connections),worked superfine on a t-bone mic with really deep engravings.
BTW:The B2 I bought is not engraved,just painted,so pretty easy to handle.

Cheers,

Udo.
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: mrcase on March 29, 2012, 04:32:04 AM
Great info! Thanks all. what kind of paint would you recommend? and should I sand the whole body as a preparation for the painting process?

sincerely yours
mrcase  ;)
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: mrcase on March 29, 2012, 04:34:21 AM


I have done that with 2K glue (for metall connections),worked superfine on a t-bone mic with really deep engravings.
BTW:The B2 I bought is not engraved,just painted,so pretty easy to handle.

Cheers,

Udo.

strange. mine has a quite deep engraving - I bought mine used. did you buy yours new?
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: kante1603 on March 29, 2012, 04:49:30 AM
Hi,

for kante,
 I will try to take other photos of the inside. The pcb is just in place with a little cord, I have to make new holes in the pcb to fix it. The transformer just sit between the pcb and the XLR connector, it isn't fixed but don't move at all.
For the switch, if you take a look at the B2 head of the mic, you will see that there are 6 pins wich connect the head to the body. You will use 4 of them for the capsule, so the 2 others can be use for the low cut or the pad. For the other one and the polarity switch, you have to put cables. I don't connected them to the switch and prefer open the mic for changing the polarity of the mic (I use cardioide 90% of the time)  If you find another solution, I'm open to it!
Hi Adrien!

thank you for the fast reply.
As said I haven't opened the mic yet,but I want to use the switches from the outside as "normal".
Concerning your mounting solutions of the pcb as well as for the transformer I must say that I'm not lucky with it(thinking of the possibility of parts moving inside a condenser mic makes me very very nervous).
Let's see how this works out when I open up mine,I'm sure there are some things doable a "better"way,hahaha.... :)

Have fun,

Udo.
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: kante1603 on March 29, 2012, 04:52:17 AM
strange. mine has a quite deep engraving - I bought mine used. did you buy yours new?
Hi,

yes,bought mine 3 days ago at Thomann germany,definitely not engraved!

Cheers,

Udo.
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: pavthefiddler on March 29, 2012, 04:54:43 AM
strange. mine has a quite deep engraving - I bought mine used. did you buy yours new?

Yeah I bought mine new just now and there's no engraving, just paint. But I used B2 maybe 8 years ago or so and I remember it had quite deep engravings.
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: kante1603 on March 29, 2012, 05:55:28 AM
Great info! Thanks all. what kind of paint would you recommend? and should I sand the whole body as a preparation for the painting process?

sincerely yours
mrcase  ;)
Hi,

I have done my "T-Bone"(containing max´s MK47 of course ;D) as follows:
*Filled the engravings with 2k glue for metall connections and let it dry well
*Sanded the whole body and controlled the formerly engraved parts with my figer tips
*Cleaned it to get rid of any dust and fat parts
*Used a 1K primer (spray) first
*Put "Hammerite" laquer on it to give it a vintage look
*Let it dry very well before proceeding assembly

I should mention that it is very important not to put any laquer on the top and bottom parts where the metall tube is touching the head basket and the bottom part!This would destroy the propper shielding against rf.Simply measure from head to bottom after assembly,your DMM reading should end up very close to 0 ohms.

Have fun,

Udo.
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: poctop on March 29, 2012, 08:06:57 AM
I really recommend the aurycle 460 body or the MxL type as they are a perfect fit but well this is diy after all ;D
Dan,
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: HellfireStudios on March 29, 2012, 10:24:47 AM
Great info! Thanks all. what kind of paint would you recommend? and should I sand the whole body as a preparation for the painting process?

sincerely yours
mrcase  ;)

Hammered finish paint tends to be one of the stronger paints. Self-etching primer isn't a bad idea beforehand either. You should google search how to paint/bake the finish on DIY guitar effects pedals. It is supposed to make the paint even tougher.
Sand the body down, in increasing grits on the engraved bits, and with 220 grit on the rest. Prime, paint, bake, label(optional), and clear coat as many times as needed with baking in between coats. There is a lot to it, but it looks great when done right.
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: saxmonster on March 29, 2012, 03:56:48 PM
The black wire at the top of the microphone Aurcycle 460 between the pad and the high pass gets connected to what on new boards?  Does it get connected to the ground link or Cground? 

I also connected the xlr wires like this hopefully this is right.  I don't do this everyday.

red = hot
white = cold
black = ground

When I start to check the bias of the mic I don't have the capsule in right?

I need to look back in the treads and find out how to do it again.  But i do plug it into a mic cable hook up to a preamp with phantom power right?

thanks
-Scott
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: saxmonster on March 29, 2012, 05:18:03 PM
Ok So I read the fet and adjusted the r11 to 10.53 volts from 10.8.  The R11 value goes from 15.77 - 15.92 resistance on my DMM each time it seems to be different.  Could be me i guess.  What resistor should i buy to replace the pot?   My zener is reading 22.82.  The overall phantom power reads 46.3 volts.  I guess this is why my numbers are a little off. 

Questions is should I go ahead and install John P capsule.  Is it ok to do this without hurting it?

Secondly what resister should I use to replace the R11 pot
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: poctop on March 29, 2012, 05:32:43 PM
Ok So I read the fet and adjusted the r11 to 10.53 volts from 10.8.  The R11 value goes from 15.77 - 15.92 resistance on my DMM each time it seems to be different.  Could be me i guess.  What resistor should i buy to replace the pot?   My zener is reading 22.82.  The overall phantom power reads 46.3 volts.  I guess this is why my numbers are a little off. 

Adjust the pot to get about 11V on the drain pad if you dont have any other way as a sine tone or scope, you can leave the pot inside if you already solder it to the board,  if not then the resistance from the Pot to replace with a specific resistance must be measured completely out off circuit this is why your meter is confused.

Questions is should I go ahead and install John P capsule.  Is it ok to do this without hurting it?

I would make sure all the voltage are right before installing the capsule,  you should get about 40V from the (bdy) pad on the (FC)  connection
the really best way to tune the FET is with an input signal in , 
Secondly what resister should I use to replace the R11 pot
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: poctop on March 29, 2012, 05:33:07 PM
The black wire at the top of the microphone Aurcycle 460 between the pad and the high pass gets connected to what on new boards?  Does it get connected to the ground link or Cground? 

I also connected the xlr wires like this hopefully this is right.  I don't do this everyday.

red = hot
white = cold
black = ground

This is Correct

When I start to check the bias of the mic I don't have the capsule in right?

I need to look back in the treads and find out how to do it again.  But i do plug it into a mic cable hook up to a preamp with phantom power right?

thanks
-Scott
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: poctop on March 29, 2012, 05:34:19 PM
The black wire at the top of the microphone Aurcycle 460 between the pad and the high pass gets connected to what on new boards?  Does it get connected to the ground link or Cground? 

I also connected the xlr wires like this hopefully this is right.  I don't do this everyday.

red = hot
white = cold
black = ground
This is Correct

It may Vary from mic to mike ,  the best is hot = pin 2   cold =pin 3 GND pin 1 with this you never get it wrong unless you are in the middle of the 60's


When I start to check the bias of the mic I don't have the capsule in right?

I need to look back in the treads and find out how to do it again.  But i do plug it into a mic cable hook up to a preamp with phantom power right?

thanks
-Scott
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: poctop on March 29, 2012, 05:37:21 PM
Quote
The black wire at the top of the microphone Aurcycle 460 between the pad and the high pass gets connected to what on new boards?  Does it get connected to the ground link or Cground? 

Is this black wire the Mic basket ground or mic body grnd or simply grnd ,  if it is you can connect to Gndlink,
GndLink are at the same level of gnrd,   one is designed for Traffo core Gnrd and the other one for linkin mic Body parts to grnd if needed,

Dan,
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: saxmonster on March 29, 2012, 05:50:42 PM
Do I pull the gold tape off of the backplate/body of John's Capsule.  Its in the way of the screw holes.  I can push the screws threw the tape but I think it should come off.  Just wanna make sure. 

Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: poctop on March 29, 2012, 06:02:52 PM
Dont Remove the Tap in any case ,

just use sharp tool pointy to pierce it and then screw ,  refer to thread for the capsule mounting ,
D
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: Marcocet on March 29, 2012, 06:28:07 PM
Fair warning: If you are using the aurycle mic bodies (or prob many others) do NOT store the microphone in the box it came in. I opened up one of mine to enact a quick repair and the capsule was already thoroughly covered in foam dust. Luckily most of it came off with some careful and distant use of canned air, but there's still more than I'd like. Stupid foam...
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: JamesW on March 29, 2012, 07:28:21 PM
Is there away of selecting a good sounding fet out of the circuit? Is there any thing we learn from the Idss like high current good low current bad?
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: saxmonster on March 29, 2012, 07:38:53 PM
ok i got it working but the is a low ground loop type hum that changes as you move the mic around near things, it this a grounding issue?  i dont have the case on yet as i would have to shave the side of the pot to fit it.  Where do i start to trouble shoot. 

Thanks Scott



Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: poctop on March 29, 2012, 07:43:37 PM
ok i got it working but the is a low ground loop type hum that changes as you move the mic around near things, it this a grounding issue?  i dont have the case on yet as i would have to shave the side of the pot to fit it.  Where do i start to trouble shoot. 

Thanks Scott

if you dont have the body of the mic you dont have RF isolator , so  that is normal ,  the body and the basket at ground is your protection,

Dan,
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: saxmonster on March 29, 2012, 08:54:35 PM
Ok got the body on and everything fits together and works great however when I tighten to much or too little it seems as if the phantom power turns off or gets shorted.  The mic doesn't work at it optimum level.  I think someone wrote about this a way back or on the original thread I will have to got back and trouble shoot this.  Other than that it sounds great.  I will put some sax through it tomorrow and upload some sound clips. 


This thing is awesome thanks alot DAN, you the MAN!!!!!!!!!

Now I must find a cool color does home depot sell Neuman grey? hahahah but in a hammered looked?

Thanks again Dan for everything!!!!!!


-Scott


Will try to get some pics up tonight.
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: saxmonster on March 29, 2012, 10:42:14 PM
B1
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: saxmonster on March 29, 2012, 10:42:59 PM
B1
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: saxmonster on March 29, 2012, 10:44:15 PM
B2
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: saxmonster on March 29, 2012, 10:46:39 PM
B2

No Matter which way I wire the LC the switch on the mic is still backwards any ideas?  I just left it off for now its the one with the black electrical tape on it.

Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: saxmonster on March 29, 2012, 11:08:17 PM
Some Short Demos

Please don't laugh as I kinda rushed to do these.  But this is a project I am working on.  I am still working on mic placement and mixing but this gives you an idea of what the mic sounds like compared to an AKG c414, the older kind from the 90's.  I am running both Mics through Slenderchap's  Eee-Zee 1073 clone.  With just a touch of waves C1 compressor.  And true verb for the mix demos.  Like I said still have a lot to learn and figure out mixing, reverbs and mic placements.  Since I was doing everything myself in different rooms I was running around like crazy so there are a few pitch issues but you get the idea. Be gentle.

U87 Clone Dry

http://www.ehornstudios.com/media/U87%20Clone%20Dry.aif

U87 Clone Mix

http://www.ehornstudios.com/media/U87%20Clone%20Mix.aif

C414 Dry

http://www.ehornstudios.com/media/C414%20Dry.aif

C414  Mix

http://www.ehornstudios.com/media/C414%20Mix.aif

Let me know what you think of the U87.  I already have some conclusions.

Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: poctop on March 30, 2012, 07:58:49 AM
Hey Saxmonster full Congrats ,  ;D I am glad you made it ,
D
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: HellfireStudios on March 30, 2012, 10:52:37 AM
Fair warning: If you are using the aurycle mic bodies (or prob many others) do NOT store the microphone in the box it came in. I opened up one of mine to enact a quick repair and the capsule was already thoroughly covered in foam dust. Luckily most of it came off with some careful and distant use of canned air, but there's still more than I'd like. Stupid foam...

This seems to be a common trait with foam-shocked boxes and flightcases. The capsules's polarization will actually electrically attract the broken-off foam bits to the diaphram. Although the logic behind using a material that both protects and damages a mic at the same time is beyond me, you can take preventative measures against it's detrimental effects. Simplest option would be the plastic bag your mic, hopefully, came in (or another similar-sized bag). Fancier, and more expensive, options are cloth-based bags (velvet looks great) or a whole seperate velvet-lined box that goes inside the flightcase (this seems to be a popular option in the expensive mic world). You could also wrap the foam from the box (the mic came in) in velvet and use the box as you did before.

I think I've spent enough time off topic. On with building...
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: Marcocet on March 30, 2012, 03:28:31 PM
Ok got the body on and everything fits together and works great however when I tighten to much or too little it seems as if the phantom power turns off or gets shorted.  The mic doesn't work at it optimum level.  I think someone wrote about this a way back or on the original thread I will have to got back and trouble shoot this. 

I had the same problem and it turned out to be something intermittent in the low cut switch assembly. When the switch was pushed up towards the capsule it would somehow turn off the mic. Must have been a short, but before I could locate it any more specifically it fixed itself. It's been working fine since then.

Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: berkleystudios on March 30, 2012, 04:29:55 PM
sax-
 personally i think the 414 sits better in that mix, the u87 makes it stick out a little odd. but stand alone i prefer the u87.
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: poctop on March 30, 2012, 06:36:30 PM
Hey Saxmonster i am not sure about the mix since i am not a mix guru but when i hear the sounds of the U1621 i really have the impression that i am in the room with you  8)

cheers ,

dan,
 
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: kante1603 on March 30, 2012, 07:11:13 PM
B2

No Matter which way I wire the LC the switch on the mic is still backwards any ideas?  I just left it off for now its the one with the black electrical tape on it.
@saxmonster:

Hi,

do you mean the lc function is set to "off" when switched to "in" and vice versa?
Please do a continuity check:Switch to "in" and look if your (now or still) loose wires do have continuity or not.
I can not see exactly the wiring directly on the switch in your photo,but I guess it´s just open condition then.
If so you can swap the outer (white?) wire on the switch(!) to the opposite side to get a "closed" condition.
The running order of the wires connected on the pcb doesn´t matter;It´s just a matter of the switch being closed or open.
Don´t know this specific switch,but I bet it´s just that simple.

Hope to have helped,

Udo.
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: saxmonster on March 30, 2012, 07:47:57 PM
Kante
That's what it was I pulled the white wire off of the switch and put it on the other side of the red one and now it works.  Fine.
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: kante1603 on March 30, 2012, 08:01:54 PM
Cool,nice to hear,have fun,

Udo. ;)
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: Hank Dussen on March 31, 2012, 06:53:47 AM
Anybody here has been able to contact AMI Tab Funkenwerk here?
From my regular mail account all my mails were returned as spam.
And they didn't respond to my Gmail account...
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: poctop on March 31, 2012, 08:41:20 AM
Try that ,

[email protected]
D
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: wthrelfall on March 31, 2012, 08:51:17 AM
I've got the use of a 'scope so decided to calibrate the FET according to Matador's post.  Problem is, when I measure the signal on the drain of the FET, the waveform doesn't really resemble a sine wave anymore, and doesn't respond to R11 calibration the way it should (ie. with the waveform flattening out as amplitude is increased).  I checked my sine wave source on the scope and it's perfectly symmetrical and normal.  Attached is a photo of the waveform I get at the FET drain.
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: wtmnmf on March 31, 2012, 08:53:08 AM
Anybody here has been able to contact AMI Tab Funkenwerk here?
From my regular mail account all my mails were returned as spam.
And they didn't respond to my Gmail account...

They had a problem with their host.   Should be fixed now.
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: wthrelfall on March 31, 2012, 08:55:01 AM
I've got the use of a 'scope so decided to calibrate the FET according to Matador's post.  Problem is, when I measure the signal on the drain of the FET, the waveform doesn't really resemble a sine wave anymore, and doesn't respond to R11 calibration the way it should (ie. with the waveform flattening out as amplitude is increased).  I checked my sine wave source on the scope and it's perfectly symmetrical and normal.  Attached is a photo of the waveform I get at the FET drain.

and another one with the time zoomed out.
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: bezen4uk on March 31, 2012, 09:17:54 AM
Hi,
There is oscillation.
You need probe with compensation.
Or  measure at transformer out
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: poctop on March 31, 2012, 10:32:04 AM
I've got the use of a 'scope so decided to calibrate the FET according to Matador's post.  Problem is, when I measure the signal on the drain of the FET, the waveform doesn't really resemble a sine wave anymore, and doesn't respond to R11 calibration the way it should (ie. with the waveform flattening out as amplitude is increased).  I checked my sine wave source on the scope and it's perfectly symmetrical and normal.  Attached is a photo of the waveform I get at the FET drain.

and another one with the time zoomed out.

have you consider the THD method with the Room capture demo software or the earing method to see how it behave first when you inject the sine tone,  first you could see how it works at a fix voltage to see if the circuits works, let say at 11V to the drain and try it out.
if your are not familiar with the scope sometime the trick is to get the proper level of signal to actually see hat will happen when you twaek the FET if you have too much signal you wont see anything ,  you also have to connect you probe ground to the mic Body or pin 1

hope this helps,

Dany,
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: saxmonster on March 31, 2012, 02:08:13 PM
sax-
 personally i think the 414 sits better in that mix, the u87 makes it stick out a little odd. but stand alone i prefer the u87.
[/quote

I agree and I think the u87clone has the better sound I will just have to tuck it into the mix a little better. May be a little eq here and there.  Like I said earlier, basically i just popped it in and raised the level untill it sounded somewhat ok.  I was in a rush. But now that i know its the better mic I will do some more tests and comparisons.

Thanks
scott
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: tskguy on March 31, 2012, 04:35:43 PM
Poctop,

I sent a paypal payment for a  set of your U87 boards. Its ben about 2weeks and I was wonderin if I should start to worry.
Thanks,
Eric
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: Matador on March 31, 2012, 04:36:51 PM
Attached is a photo of the waveform I get at the FET drain.
...
and another one with the time zoomed out.

Is it a high impedance probe?
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: wthrelfall on March 31, 2012, 04:55:47 PM
No, I don't think so.

Attached is a photo of the waveform I get at the FET drain.
...
and another one with the time zoomed out.

Is it a high impedance probe?
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: wave on April 01, 2012, 11:43:34 AM
Some Short Demos

Please don't laugh as I kinda rushed to do these.  But this is a project I am working on.  I am still working on mic placement and mixing but this gives you an idea of what the mic sounds like compared to an AKG c414, the older kind from the 90's.  I am running both Mics through Slenderchap's  Eee-Zee 1073 clone.  With just a touch of waves C1 compressor.  And true verb for the mix demos.  Like I said still have a lot to learn and figure out mixing, reverbs and mic placements.  Since I was doing everything myself in different rooms I was running around like crazy so there are a few pitch issues but you get the idea. Be gentle.

U87 Clone Dry

http://www.ehornstudios.com/media/U87%20Clone%20Dry.aif

U87 Clone Mix

http://www.ehornstudios.com/media/U87%20Clone%20Mix.aif

C414 Dry

http://www.ehornstudios.com/media/C414%20Dry.aif

C414  Mix

http://www.ehornstudios.com/media/C414%20Mix.aif

Let me know what you think of the U87.  I already have some conclusions.

Well we all have opinions so...
I like the sound of the U87 by itself over the 414 for sure. There's a nice presence and depth to it. I can understand what berkeleystudios was saying about how the 87 track sticks out a little in the mix but I prefer the sound of it. I personally like the rawness of the track. The 414 seems a little too polished for me. Just my 2¢.

Dave
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: KasperNyhus on April 01, 2012, 03:20:28 PM
I've got the use of a 'scope so decided to calibrate the FET according to Matador's post.  Problem is, when I measure the signal on the drain of the FET, the waveform doesn't really resemble a sine wave anymore, and doesn't respond to R11 calibration the way it should (ie. with the waveform flattening out as amplitude is increased).  I checked my sine wave source on the scope and it's perfectly symmetrical and normal.  Attached is a photo of the waveform I get at the FET drain.

and another one with the time zoomed out.

Have you tried to activate the PAD? That made my sine curve act as it should... But I don't know why...?
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: saxmonster on April 01, 2012, 08:46:05 PM
Figured out more stuff,

On the tightening problem, the sound would go in and out.  I messed with the transformer and I think it was hitting the bare ground wire on the xlr inputs in the transformer box of the 460case.  I fully insulated the transformer covering the ground wire with electrical tape and now it doesn't do it any more. Success!!!!!!!


I also found out that my akg C414 is louder when I swap it with the u87 clone.  I keep the same gain and just switch the xlr cable between the mics.  Why is the c414 louder?  I know they are different mics but the c414 just has a higher out put.  It that because of the differences in the transformer?


Also does anyone know where I can find a 15.6k ohm resistor?  Everywhere I look it seems that I have to buy them in bulk or they are not a stocked item.  I checked all of the usual places.  Can I get a different one.  Maybe a 15.4 or 15.8 would work?  How close do I have to be or does it have to be exact?  Also do I get a 1.4watt resister?  I can paypal someone in the usa if you want to send some to me.  They can be shipped through a letter in the mail right?

Thanks guys



Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: poctop on April 01, 2012, 09:15:23 PM
Figured out more stuff,

On the tightening problem, the sound would go in and out.  I messed with the transformer and I think it was hitting the bare ground wire on the xlr inputs in the transformer box of the 460case.  I fully insulated the transformer covering the ground wire with electrical tape and now it doesn't do it any more. Success!!!!!!!


I also found out that my akg C414 is louder when I swap it with the u87 clone.  I keep the same gain and just switch the xlr cable between the mics.  Why is the c414 louder?  I know they are different mics but the c414 just has a higher out put.  It that because of the differences in the transformer?


Also does anyone know where I can find a 15.6k ohm resistor?  Everywhere I look it seems that I have to buy them in bulk or they are not a stocked item.  I checked all of the usual places.  Can I get a different one.  Maybe a 15.4 or 15.8 would work?  How close do I have to be or does it have to be exact?  Also do I get a 1.4watt resister?  I can paypal someone in the usa if you want to send some to me.  They can be shipped through a letter in the mail right?

Thanks guys

There is nothing stoppping you from leaving the pot inside the mic,   and also when you measure the pot Value did you measured it out of the board completely or at least lifted the leg in contact with the (Source) pin of the FET ? because it will affect the reading by the DMM this is important  ;) as for the gain of the mic this is perfectely normal as the U87 circuit is not high gain like the 414

Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: saxmonster on April 01, 2012, 10:17:53 PM
Yes the resistance was the same in or out of the board.  It didn't matter.  I wanna put in a real resistor cause the pot is pretty beat up from shaving it to fit and its really not sitting in there good cause of the short legs and now that its been re-soldered I just wanna replace it with something sturdy.

-Scott 
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: HellfireStudios on April 02, 2012, 09:46:31 AM
Saxmonster, you could put two resistors in series whose values added up to the pot's value (maybe 2-7.8k resistors).
Just in case the question arises, series wiring is where you take one lead from both resistors, twist them together, and solder. Then, you would put the two remaining leads in the PCB holes for the original resistor (it might be easier the other way around with this mic).

Series wiring:

----[R1]----[R2]----
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: kante1603 on April 02, 2012, 04:17:27 PM
Output level on a U87 (1980)

Hello,

I did some search on the net,for those who are interested or concerned about a "lowish" output level check this:

A U87 from 1980 is specified for a sensitivity of 8mV/Pa +/-1bB.This equals arround -40dBu.
A Shure C414 (B**) is at 23mV/Pa,therefore arround -30bBu (for those who must compare apples to oranges ;D).
A nowadays U87Ai is specified even at 28mV/Pa what equals -29dBu.

So-compared to a modern U87-expect to dial in some 10 dB more gain.No biggie for even a standard nowadays mic preamp.
This all given at propper load and so forth.....
I think we can expect this when using the right parts etc.,I´ve ordered T13 and John Peluso´s capsule.
Just some "numbers" to give you an idea.

For those who want to go a bit in-depth here´s a good site from germany (you can switch to an english version on top of the page):

http://www.sengpielaudio.com/Rechner-sensitivity.htm

Have fun with your builds,

Udo ;)

Edit:I forgot to mention that the highest output level on switchable pattern microphones is normally in cardioid mode while omni is lowest!
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: dirtyhanfri on April 02, 2012, 04:55:44 PM
Got my boards today, Thanks!
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: saxmonster on April 03, 2012, 08:01:00 PM
Question.

If I need a resistor of 15.65 Kohms for this project can i use this one.

http://search.digikey.com/us/en/products/MFR-25FBF-15R8/15.8XBK-ND/4143

It has a 1% tolerence which if i subtract that I get 15.64kohm.  If I have to order 5 of them one has to be pretty close to that.  what do you think?  If not I will try to find two resistor at half the value.

Thanks
Scott
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: kpearsall on April 04, 2012, 02:51:41 AM
saxmonster, the resistor you're needing is a 15,650 ohm resistor but the one you posted a link to is 15.8 ohm. Nope won't work!

This is the same resistor series with the proper value.
http://search.digikey.com/us/en/products/MFR-25FBF-15K8/15.8KXBK-ND/13256

Hope that helps :)
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: kante1603 on April 04, 2012, 03:06:01 AM
saxmonster, the resistor you're needing is a 15,650 ohm resistor but the one you posted a link to is 15.8 ohm. Nope won't work!
kpearsal is right!
Do some search for resistor in E192,there is a value at 15,6k if you want to get closer.Don´t know where to buy them in the usa because Im in germany,sorry.

Udo.
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: saxmonster on April 04, 2012, 07:22:42 AM
I think the link above is wrong as it says 15.8 again.

getting closer

anyways, found this buts it only 100 mwatt will this work even though its not a 1/4watt?

http://ca.mouser.com/ProductDetail/Vishay-Dale/RN55C1562BRE6/?qs=NVJATC80C4%2fyLVR6unXY27%2fCIyKgzlEmBi3LQ5AHdOc%3d

thanks
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: kante1603 on April 04, 2012, 07:32:05 AM
I think the link above is wrong as it says 15.8
The link seems right,it says 15,8 k(=Kilo!!!) ohms,your first search ended at 15,8 ohms which is a thousand times lower.
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: saxmonster on April 04, 2012, 07:54:21 AM
Hahahah I see what I did.  I'm an idiot. Details details details.
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: 0dbfs on April 04, 2012, 11:21:05 AM
Stocking up on parts for building four of these. I've now got AMI T13's in stock as well as Peluso's P-k87i's and of course four sets of Dany's PCB's. Just ordered four Aurycle kits.

I am planning to use a jumper in the mic to switch the patterns as needed and wire up the pad/hpf on the switches.
Next is the mouser order and I see that it is currently at what appears to be rev4. I'll review the parts included/specified and add in a couple parts for other projects :)
Looking forward to listening to more music through these!
Thanks Dany!

Best,
jonathan
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: poctop on April 04, 2012, 03:41:08 PM
Stocking up on parts for building four of these. I've now got AMI T13's in stock as well as Peluso's P-k87i's and of course four sets of Dany's PCB's. Just ordered four Aurycle kits.

I am planning to use a jumper in the mic to switch the patterns as needed and wire up the pad/hpf on the switches.
Next is the mouser order and I see that it is currently at what appears to be rev4. I'll review the parts included/specified and add in a couple parts for other projects :)
Looking forward to listening to more music through these!
Thanks Dany!

Best,
jonathan

OK DOKE , great news here ,  keep us posted , your feedback will be very appreciated ,

Dan,
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: poctop on April 04, 2012, 11:00:56 PM
Stocking up on parts for building four of these. I've now got AMI T13's in stock as well as Peluso's P-k87i's and of course four sets of Dany's PCB's. Just ordered four Aurycle kits.

I am planning to use a jumper in the mic to switch the patterns as needed and wire up the pad/hpf on the switches.
Next is the mouser order and I see that it is currently at what appears to be rev4. I'll review the parts included/specified and add in a couple parts for other projects :)
Looking forward to listening to more music through these!
Thanks Dany!

Best,
jonathan

For the BOM revision all i added from original is

All Cap option are in the BOM have a look to designation for the option
only the 10pf polystyrene is not in the Bom the default is the Mica

revisions
1) sub part for 2.2 in case not in stock for the vishay
2) sub for 60M for 68M
3) 2 extra Cap for testing and bypass 51pf

the best is to choose option in mouser in deleting what you dont need.

Hope this helps,
D ;D
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: berkleystudios on April 04, 2012, 11:07:02 PM
Stocking up on parts for building four of these. I've now got AMI T13's in stock as well as Peluso's P-k87i's and of course four sets of Dany's PCB's. Just ordered four Aurycle kits.

I am planning to use a jumper in the mic to switch the patterns as needed and wire up the pad/hpf on the switches.
Next is the mouser order and I see that it is currently at what appears to be rev4. I'll review the parts included/specified and add in a couple parts for other projects :)
Looking forward to listening to more music through these!
Thanks Dany!

Best,
jonathan

For the BOM revision all i added from original is

All Cap option are in the BOM have a look to designation for the option
only the 10pf polystyrene is not in the Bom the default is the Mica

revisions
1) sub part for 2.2 in case not in stock for the vishay
2) sub for 60M for 68M
3) 2 extra Cap for testing and bypass 51pf

the best is to choose option in mouser in deleting what you dont need.

Hope this helps,
D ;D

why is the 10pf not in the BOM? is that the only part i need to add?
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: poctop on April 04, 2012, 11:13:15 PM
Stocking up on parts for building four of these. I've now got AMI T13's in stock as well as Peluso's P-k87i's and of course four sets of Dany's PCB's. Just ordered four Aurycle kits.

I am planning to use a jumper in the mic to switch the patterns as needed and wire up the pad/hpf on the switches.
Next is the mouser order and I see that it is currently at what appears to be rev4. I'll review the parts included/specified and add in a couple parts for other projects :)
Looking forward to listening to more music through these!
Thanks Dany!

Best,
jonathan

For the BOM revision all i added from original is

All Cap option are in the BOM have a look to designation for the option
only the 10pf polystyrene is not in the Bom the default is the Mica

revisions
1) sub part for 2.2 in case not in stock for the vishay
2) sub for 60M for 68M
3) 2 extra Cap for testing and bypass 51pf

the best is to choose option in mouser in deleting what you dont need.

Hope this helps,
D ;D

why is the 10pf not in the BOM? is that the only part i need to add?

The 10pf  is in the BOM but it is Mica not PolyST,

D
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: berkleystudios on April 04, 2012, 11:24:10 PM
awesome. thanks D. cant wait to finish these for my studio!
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: saxmonster on April 06, 2012, 10:58:50 AM
Paint job is now complete.

Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: poctop on April 06, 2012, 11:09:22 AM
Hey Congrats Saxmonster ,   i Really like the sound of this baby and it is nicely painted as well ,   

Have some nice recording sesssions,

Dan,
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: kante1603 on April 06, 2012, 05:33:38 PM
For those who want to go the "B2Pro"-way....

Cheers,

Udo.

Edit:I forgot to mention that you must re-label the pattern switch (swap cardioid and figure eight!!!) on the mic housing!
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: mrcase on April 06, 2012, 05:36:24 PM
great! thx! just waiting for the capsules to try this out!
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: kante1603 on April 06, 2012, 05:46:37 PM
great! thx! just waiting for the capsules to try this out!
You´re welcome.
I´m still waiting for my T13s and capsules too,so I´m stuck with it at the moment.Will post more when the parts are here.
Have fun,

Udo ;)
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: Marcocet on April 06, 2012, 07:30:38 PM
A client used the mic on vocals yesterday and really liked it. It got chosen over a number of other mics. Actually in the end we used the u87 clone and a RCA 77dx blended together. Wasn't my session so I don't have too many details, but I heard good things.

Just got a pair of original transformers. Looks like I'll be building another pair of these :)
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: wthrelfall on April 07, 2012, 11:57:34 AM
Got my Peluso K87i capsule and BV11 transformer at last. 
I'm confused as to what physically is the "backplate" and "capsule", can anyone enlighten me?  Also, there are 3 cables coming from the peluso, but 4 pad's on the pcb.. 
thanks in advance.
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: saxmonster on April 07, 2012, 12:29:24 PM
The side with the two wires on it is the front side that is so you can tell the difference.  Leave the tape on the capsule too.  Once the capsule is on the holder you can poke a hole through the tape and screw in the wire for the back backplate. Also Cap = Membrane front and back side.

Incase anyone wants to know the over all price for this clone I spent $384.46 dollars on everything.  Not bad at all compared to the actual cost of a U87, hahahahahah  what is that about a 10th of the cost of a real u87?   HAHHAHHAHAH  Great project Dan Thanks again.


Any one try a different transformer yet compared to the cinemag?  Any difference?


-Scott

Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: wthrelfall on April 07, 2012, 02:51:19 PM
great, but it doesn't explain the fact there's only 3 wires but 4 pads...  what about the rear connections?


The side with the two wires on it is the front side that is so you can tell the difference.  Leave the tape on the capsule too.  Once the capsule is on the holder you can poke a hole through the tape and screw in the wire for the back backplate. Also Cap = Membrane front and back side.

Incase anyone wants to know the over all price for this clone I spent $384.46 dollars on everything.  Not bad at all compared to the actual cost of a U87, hahahahahah  what is that about a 10th of the cost of a real u87?   HAHHAHHAHAH  Great project Dan Thanks again.


Any one try a different transformer yet compared to the cinemag?  Any difference?


-Scott
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: Marcocet on April 07, 2012, 05:53:56 PM
great, but it doesn't explain the fact there's only 3 wires but 4 pads...  what about the rear connections?

He did, but let me make it a little clearer.

Any condenser capsule has two major parts: The membrane and the backplate. When the membrane moves with changes in air pressure and the backplate stays still the difference between them creates an electrical signal that is analogous to the sound in the room. Many microphones have two membranes, one for the front and one for the back. This allows you to create varying polar patterns by blending the two signals.

The early U87 mics used a dual isolated backplate design. This means that each membrane has its own individual backplate. Hence the four pads on the pcb (front membrane, front backplate, rear membrane, rear backplate). The peluso capsules come with an easy solder tag along the rim to help you identify the front of the capsule. Connecting a wire to that tag will connect it to the front side backplate.

The fourth wire needs to be attached to the rear side backplate, which is electrically connected to the rear side of the rim of the microphone. If you'll notice, the capsule has three pairs of what looks like mounting holes around the outside of the rim. Two of them are spaced to hold the capsule to its mount, but the third ones are just there. You need to make an electrical connection between the one towards the rear of the capsule and the fourth pad on the PCB. I did it by putting a screw in to that hole and soldering a wire to it. It's as simple as that. A solder pad and shorter screw would have been more elegant, but the screws supplied with the capsule will work fine. Just keep in mind that the solder will not hold to the screw, so if you bang the mic around a lot it could eventually come loose.

If somebody else who has theirs handy could post some photos I'm sure they'd be appreciated.
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: kante1603 on April 07, 2012, 06:03:55 PM
great, but it doesn't explain the fact there's only 3 wires but 4 pads...  what about the rear connections?
@Scott:
Could you please post a pic of the capsule wiring?Some guys here seem to be very confused about this,and a picture says more than words...
I would have posted one if I had the capsule (still waiting for it...),therefore will take a while if you can not do it.

Best regards from germany,

Udo. ::)

Edit:oooops,double post with marcocet-very well explained btw!

Cheers,

Udo.
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: wthrelfall on April 07, 2012, 06:08:48 PM
Perfect description, appreciated.
thanks.


great, but it doesn't explain the fact there's only 3 wires but 4 pads...  what about the rear connections?

He did, but let me make it a little clearer.

Any condenser capsule has two major parts: The membrane and the backplate. When the membrane moves with changes in air pressure and the backplate stays still the difference between them creates an electrical signal that is analogous to the sound in the room. Many microphones have two membranes, one for the front and one for the back. This allows you to create varying polar patterns by blending the two signals.

The early U87 mics used a dual isolated backplate design. This means that each membrane has its own individual backplate. Hence the four pads on the pcb (front membrane, front backplate, rear membrane, rear backplate). The peluso capsules come with an easy solder tag along the rim to help you identify the front of the capsule. Connecting a wire to that tag will connect it to the front side backplate.

The fourth wire needs to be attached to the rear side backplate, which is electrically connected to the rear side of the rim of the microphone. If you'll notice, the capsule has three pairs of what looks like mounting holes around the outside of the rim. Two of them are spaced to hold the capsule to its mount, but the third ones are just there. You need to make an electrical connection between the one towards the rear of the capsule and the fourth pad on the PCB. I did it by putting a screw in to that hole and soldering a wire to it. It's as simple as that. A solder pad and shorter screw would have been more elegant, but the screws supplied with the capsule will work fine. Just keep in mind that the solder will not hold to the screw, so if you bang the mic around a lot it could eventually come loose.

If somebody else who has theirs handy could post some photos I'm sure they'd be appreciated.
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: wtmnmf on April 07, 2012, 10:02:41 PM
OK,  I've checked out my two Peluso capsules and they are the same, but different from the above description.

The side with the lead on the rim's face is connected to the brass rim of the other side.  The two brass rims are indeed isolated. Attaching the fourth lead as described above only duplicated the function of the existing lead.

So, does anyone know for sure if attaching to the other (opposite) rim connects to the other backplate?  And is the capsule really asymmetrical?  If so, which side is the front in light of the above?

I guess I'll try Peluso on monday if no one knows...   :P
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: HellfireStudios on April 08, 2012, 10:53:34 AM
OK,  I've checked out my two Peluso capsules and they are the same, but different from the above description.

The side with the lead on the rim's face is connected to the brass rim of the other side.  The two brass rims are indeed isolated. Attaching the fourth lead as described above only duplicated the function of the existing lead.

So, does anyone know for sure if attaching to the other (opposite) rim connects to the other backplate?  And is the capsule really asymmetrical?  If so, which side is the front in light of the above?

I guess I'll try Peluso on monday if no one knows...   :P

If you don't attach both backplates to the PCB you will only get a cardoid polar response. Both backplates are integral to the pattern selection.

The front capsule is the one with both leads attached already.

FWIW, when I got my Peluso K87i capsule, it came with a tiny brass screw-down terminal. It also came with three screws (two for the mount, one for the additional backplate).
Attach a wire to the terminal. Attach the terminal to the side of the capsule (look at the capsule that came with the mic), not on the rim like the front backplate. You can use any of the holes in the back backplate, after you've mounted the capsule. Just poke a hole in the tape and use the remaining screw for the terminal. I hope this is clear enough.
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: poctop on April 08, 2012, 12:57:23 PM
I had posted this in the thread on page 3

in this case with the peluso capsule as the original K87  the 2 backplate front and back are isolated electrically this is guaranteed,

The Answer is the front backplate tab already on the capsule is for the front capsule so this is how you recognize the front , there actually on opposite side because of that 
the (back) backplate will connect via a tab that you need to supply ( Peluso Wisher will be providede one) and attached to the mounting saddle connection so it will make contact will the back backplate only,

So the connection on the PCB are for FC = front capsule   (cap = capsule and bdy = backplate) and same for the back diaphragme  as the RC section on the PCB Cap= back capsule and bdy back backplate,
 
Hope this helps,
Dan,
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: wave on April 08, 2012, 01:41:21 PM
How much difference is there to the circuit if a 68Mohm is used in place of the 60Mohm?
Also, has anyone source the 10pf styrene from justradios? It's rated at 630V. Is it physically large? Could all the styrenes be that voltage rating (from a size perpective)?

Thanks
Dave
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: wtmnmf on April 08, 2012, 02:33:52 PM
I had posted this in the thread on page 3

OK, I see that now ;)

I have the picture labled with 2 as the front and 1 as the rear, but I don't think that there is any difference because the capsule does omni and figure eight, so the front and rear should be the same.  Right?

**************

Ignore spelling error below  :-[

Diaphragm not diaphram, diaphragm not diaphram   ::)
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: poctop on April 08, 2012, 03:35:40 PM
I had posted this in the thread on page 3

OK, I see that now ;)

I have the picture labled with 2 as the front and 1 as the rear, but I don't think that there is any difference because the capsule does omni and figure eight, so the front and rear should be the same.  Right?

In Theory they are the same but pratically it is always the one with better (if it is the case
) frequency response that is selected as the front because in the omni or 8 the back side is less sollicited, the capacitance is also optimize for best output with the front,  but without all the measuring apparatus we always reference the front with the one side that has the tab in place and that is on the other side of the capsule,  just an old rule i was always told.

By The Way thanks For The Picture i think it will help  others as well,
Dan,
 
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: saxmonster on April 08, 2012, 04:39:46 PM
Ok I am totally confused!!!! for the front I used the Side with both the membrane attach screw and a screw / tab that was attached to the front rim screw at the 6 o'clock position.  Do these two get attached the front section solder points on the pcb?  Or is the one that was already attached to the rim from the factory part of the rear section.  You would think John would have this on his site somewhere. Just frustrated now, sorry.  I thought I was done errrr.
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: wtmnmf on April 08, 2012, 06:37:00 PM
In Theory they are the same but pratically it is always the one with better (if it is the case
) frequency response that is selected as the front because in the omni or 8 the back side is less sollicited, the capacitance is also optimize for best output with the front,  but without all the measuring apparatus we always reference the front with the one side that has the tab in place and that is on the other side of the capsule,  just an old rule i was always told.

By The Way thanks For The Picture i think it will help  others as well,
Dan,
 

That's interesting.

A few tips for those using Aurycle bodies...  the saddle has two levels along the parting line, which doesn't matter if you are using screws on one side, but the way mine lined up I needed to drill one of the holes on the other side which resulted in the capsule leaning a little.  I wrapped a piece if sandpaper around a small bottle of the right diameter for the new capsule and sanded it both smooth and to the correct size.

My second body appears to have seen high enough G-forces to have ripped the saddle post 99% of the way off of the base!  The capsule was leaning over 45 deg. when I took the headbasket off.  I thought that cyanoacrylate would probably not work, but I gave it a try anyway, and it worked very well  :o   Maybe someone else will have a similar problem (what do you want for nearly free?).  I bought the assembled ones with shockmount and case.

The Peluso supplied screws are too long to attach the tab for the backplate connection, but they are fairly soft, and snapped off OK when I used the way-too-big screw cutter on my ring terminal pliers.  Loosing half of the length worked fine when fitted with a washer and the terminal.

Another issue that may be confusing, with regard to the capsules - if you're poking about with an ohm meter, is that some of the screws on the faces are insulated from the brass on that side (like the one for the front backplate), and some are threaded into the nearside.  I'm guessing that the construction is like a real U87 capsule where you can see three screws of a different type on each side that secure the two halves together without shorting them, except Peluso use the same screws type all around.  I saw a post on the Neumann site where someone tried to repair a broken off backplate tab by mounting it to the adjacent screw.  That was a non-functional solution.

BTW, the stock Aurycle capsules in my mic's had scrap in the holes under the diaphragm and sandwiched between the diaphragm and the brass (what is that part called?), as well as wrinkles in the diaphragm.  Those can't be good defects.
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: poctop on April 08, 2012, 09:22:11 PM
This is the Correct Way to make sure you have the front is the Front an the Back is the Back ;D

I have corrected your picture so everyone can take a peak at it  the connection for the front Backplate is actually on the other side the reason for that is that it uses insulated screws this are exactely like the vintage K87 capsule . the external tab mounted on the face of the diaphragme is always the Front Backplate connection i know this may be confusing but this is the way it is.

this is the correct connection to do and are labeled,

 Capsule connection side A
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: poctop on April 08, 2012, 09:22:37 PM
 Capsule Connection Side B,
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: saxmonster on April 08, 2012, 09:35:38 PM
Thanks Dan,

I am going to rewire it right now.  Do you think I will notice a difference in sound, hahahahah.  I can't believe I did it wrong.  Oh well thanks for correcting it.  Hopefully this will help others.  John should send directions with these, pictures are better then emails hahahaha.

Thanks again
-Scott

Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: poctop on April 08, 2012, 09:37:37 PM
Thanks Dan,

I am going to rewire it right now.  Do you think I will notice a difference in sound, hahahahah.  I can't believe I did it wrong.  Oh well thanks for correcting it.  Hopefully this will help others.  John should send directions with these, pictures are better then emails hahahaha.

Thanks again
-Scott

No Problem :

just adding to this that normally the Back Backplate connection is made trough the saddle if possible that make it easier to deal with.
A big tip is also to cover the capsule if you use a soldering iron do to anything nearby because you want to make sure that no flux end up in the diaphragme so be carfull and aware of this
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: wave on April 08, 2012, 09:59:57 PM
Could anyone comment on the possible audio differences between using tantalum or electros for the 22µF and the 4.7µF caps?

Thanks,
Dave
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: saxmonster on April 08, 2012, 11:05:54 PM
I don't have that much experience with different components as this was my first microphone build Wave, so I just put everything that the original had in it. 

I just did the rewire and the mic sounds even better with the voice check 123.  Will run some sax through it tomorrow.

-Scott

Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: kpearsall on April 09, 2012, 07:02:24 AM
ok guys, what are the considerations and process for building a "matched" pair. Do I just need to match the fets? how would I do this? Peluso doesn't seem to advertise matched capsules. At least, I didn't see it!
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: adeptusmajor on April 09, 2012, 07:52:29 AM
Thank you Scott and Dan for the pictures. Very helpful, I guess I was about to do it wrong.
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: adeptusmajor on April 09, 2012, 07:57:53 AM
Could anyone comment on the possible audio differences between using tantalum or electros for the 22µF and the 4.7µF caps?

Thanks,
Dave

If you check the first page of the white market thread, Dan built two mics with different components and gave a brief description of the differences in sound.
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: pavthefiddler on April 09, 2012, 09:01:30 AM
This is the Correct Way to make sure you have the front is the Front an the Back is the Back ;D

I have corrected your picture so everyone can take a peak at it  the connection for the front Backplate is actually on the other side the reason for that is that it uses insulated screws this are exactely like the vintage K87 capsule . the external tab mounted on the face of the diaphragme is always the Front Backplate connection i know this may be confusing but this is the way it is.

this is the correct connection to do and are labeled,

 Capsule connection side A

Thanks Dan for explaining this! I just wired my Peluso capsule and I would have done it wrong without it.

I'm almost done with the microphone, just waiting for a few more components from justradios.com and the cinemag tranny.

I'm using a B2 Pro body. I was lucky to have one without the engravings so I just painted it with green Hammerite (hammered finish), making sure I didn't paint over the both ends (to maintain the electrical contact with the rest of the mic).

I have 3 questions:

1. The boards don't quite fit the B2 Pro body (using the existing mount points). Has anyone come up with a tidy way to secure them and connect the PCB ground to the mic body?

2. B2 Pro body has the all 3 switches. They are mounted on a little board that keeps them in place. I just removed all the other components from the existing board, cut all the traces leading to the switches and I'm going to solder the leads directly to the switches and then to the 2nd PCB. Is that the correct way of doing it? Does anyone have any experience with B2 Pro body? Is it going to be beneficial to the sound/RF noise pickup/etc if I don't wire the switches and use just the jumpers on the PCB? I'll switching between the patterns quite regularly (that is if the mic works!).

3. How do I wire the pattern selection switch? I can't quite work out which pins on the PCB need to be connected to result in a particular pattern.

Thanks a lot!
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: pavthefiddler on April 09, 2012, 09:02:16 AM
Different angle
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: kante1603 on April 09, 2012, 09:24:49 AM
3. How do I wire the pattern selection switch? I can't quite work out which pins on the PCB need to be connected to result in a particular pattern.
Hi,see my reply #189 just one page back!

Udo. ;)
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: pavthefiddler on April 09, 2012, 09:28:45 AM
3. How do I wire the pattern selection switch? I can't quite work out which pins on the PCB need to be connected to result in a particular pattern.
Hi,see my reply #189 just one page back!

Udo. ;)

Thanks a lot! I never noticed the attachment.
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: pavthefiddler on April 09, 2012, 10:04:39 AM
How much difference is there to the circuit if a 68Mohm is used in place of the 60Mohm?
Also, has anyone source the 10pf styrene from justradios? It's rated at 630V. Is it physically large? Could all the styrenes be that voltage rating (from a size perpective)?

Thanks
Dave

I ordered all the optional capacitors from justradios.com a while back, they should arrive here any day now. I'll make sure I'll post some photos.
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: kante1603 on April 09, 2012, 10:24:01 AM
1. The boards don't quite fit the B2 Pro body (using the existing mount points). Has anyone come up with a tidy way to secure them and connect the PCB ground to the mic body?
Me again,
while waiting for capsules and trafos I worked a bit on this.
I widened up the mounting holes to 3mm (drill gently!).You´ll loose the ground connection at this point,but that´s no biggie:
You have several ground points on the pcb,just solder a wire to them and connect it to the mounting rail-done.
Oh-there´s an interesting thing about the rails:If your soldering iron gets hot enough you can directly solder that ground wire to the rails (worked fine on my build,I used a Weller WTCPS at 50 watts).
Or you can take a small eyelet and screw it to the rail using one of the existing screw holes.
Mounting the pcbs is easy then:Just use 2 screws (I took M2,5/16mm) and 2 nuts and washers.If you want you can secure the pcbs with a drop of 2k glue or so,but I don´t think it is needed at all after tightening the 2 screws well.

BTW:Mine is hammerite blue,hahaha.....
 
Cheers,

Udo.

See attached file please!
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: pavthefiddler on April 09, 2012, 10:47:38 AM
1. The boards don't quite fit the B2 Pro body (using the existing mount points). Has anyone come up with a tidy way to secure them and connect the PCB ground to the mic body?
Me again,
while waiting for capsules and trafos I worked a bit on this.
I widened up the mounting holes to 3mm (drill gently!).You´ll loose the ground connection at this point,but that´s no biggie:
You have several ground points on the pcb,just solder a wire to them and connect it to the mounting rail-done.
Oh-there´s an interesting thing about the rails:If your soldering iron gets hot enough you can directly solder that ground wire to the rails (worked fine on my build,I used a Weller WTCPS at 50 watts).
Or you can take a small eyelet and screw it to the rail using one of the existing screw holes.
Mounting the pcbs is easy then:Just use 2 screws (I took M2,5/16mm) and 2 nuts and washers.If you want you can secure the pcbs with a drop of 2k glue or so,but I don´t think it is needed at all after tightening the 2 screws well.

BTW:Mine is hammerite blue,hahaha.....
 
Cheers,

Udo.

See attached file please!

Hi Udo,

Thank you for the answer, it is the most helpful! I like how thorough you are documenting the whole project.

Your paintwork looks great. I only painted the tubular part of the body, but seeing your microphone I'm considering painting the whole thing. Especially now that I found out I have to change the polar pattern description anyway... Did you write it with marker and then sprayed with transparent lacquer coating? Also if that's not too much to ask, how did you make the badge?

Regards,

Pav
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: kante1603 on April 09, 2012, 11:04:03 AM
Hi Pav,

Hahaha...that was a fun thing I did since UT are my initials ;D
I tried to use water decal,but failed.Decided to use printable self adhesive foil then,transparent for inkjet plotters.Covered these with clear lacquer,about 3 layers or so.
The "badge":I used an old version of Appleworks (similar to MS Works I think).
Just create a square,fill it black,create a frame arround it and rotate the whole thing to 45 degrees.
Write something nice in and you are done-no joke.

Have fun,

Udo ;)
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: pavthefiddler on April 09, 2012, 11:39:57 AM
Hi Pav,

Hahaha...that was a fun thing I did since UT are my initials ;D
I tried to use water decal,but failed.Decided to use printable self adhesive foil then,transparent for inkjet plotters.Covered these with clear lacquer,about 3 layers or so.
The "badge":I used an old version of Appleworks (similar to MS Works I think).
Just create a square,fill it black,create a frame arround it and rotate the whole thing to 45 degrees.
Write something nice in and you are done-no joke.

Have fun,

Udo ;)

Thanks Udo, this is the most helpful.

Regards,

Pav
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: kante1603 on April 09, 2012, 03:29:13 PM
Last post for today,promised ;D???
Here´s a pic where you can see a possible ground connection.

Cheers,

Udo.
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: poctop on April 09, 2012, 03:53:50 PM
Hey Kante ,  please feel Free to post as much time you want in here as your post are very ressourcefull to Everyone,  ;)
your Mic is Awsome i also like the use of jumpers to get acces to capsule removal and try out so easy,
your an Artist,   8)
Dan,

Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: kante1603 on April 09, 2012, 04:12:58 PM
Hey Kante ,  please feel Free to post as much time you want in here as your post are very ressourcefull to Everyone,  ;)
your Mic is Awsome i also like the use of jumpers to get acces to capsule removal and try out so easy,
your an Artist,   8)
Dan,
Hi Dan,

thank you very much,nice that you like it.
Yes,I love these jumper pins-they keep everything nice and clean and are easy to service.Also you´ll have no trouble with solder flux
at the bottom side of the pcb (the high impedance parts).
Some minutes ago I made an initial voltage test as you recommended.I used an original Neumann phantom supply at 48,7vdc unloaded.
My readings are:

48,5 vdc at the 2,2k resistors
23,85 vdc at top of zener
41,7 at front Backplate connection
My reference 0v was taken from a mounting rail which I had soldered to a proper grounding point on the pcb before (therefore good working solution I think).

Doesn´t look too bad,does it :D

For now I can not do anything more because of the missing (usefull) parts like capsules and trafos,hahaha....

Cheers,

Udo.
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: poctop on April 09, 2012, 04:27:31 PM
Quote
48,5 vdc at the 2,2k resistors
23,85 vdc at top of zener
41,7 at front Backplate connection
My reference 0v was taken from a mounting rail which I had soldered to a proper grounding point on the pcb before (therefore good working solution I think).


This is right on !,  i am waiting for T13 from Tab to put it in,
thanks again for the great information you put there ,
Dan,
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: kante1603 on April 09, 2012, 04:36:52 PM
Thanks Dan,
I'm going the same way,T13 and Peluso.
Really looking forward to get it to our studios and do some tests!
Bedtime now I think,it is close to midnight here and I will have some work to do with my students tomorrow,

Best regards,

Udo (yes,my name is Udo,not kante ;)).
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: poctop on April 09, 2012, 04:53:28 PM
Got it Udo,  ;)
Keep me posted ,
D
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: tskguy on April 10, 2012, 10:17:29 PM
Hey all,
Just a little something I have been working on for my new U87 mic. Pretty much done with the machining, I still need to finish the outer rings and the center hole. Tuning is also pretty difficult from what I understand with this capsule so I still need to work that out. I have a rig to tune but I havent really tested it. I guess I will see. Enjoy...

(http://i280.photobucket.com/albums/kk187/tskguy/20120410_202609.jpg)
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: Matador on April 10, 2012, 10:28:18 PM
Now *that's* DIY!

Did you smelt the brass yourself too? ;)
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: adeptusmajor on April 10, 2012, 11:31:04 PM
Well I just finished a pair of mics earlier this evening: Peluso capsule, T13, styrene and tantalum caps, Aurycle body (painted HAMMERED silver 8)).

I did a simple voice test, everything is working as it should and sounding great. I don't have a real U87 to compare to, but I can tell there is definitely a nice color to these guys, "smooth and sweet" I think they call it. I'll get to do some more extensive playing once my cheapo chinese shock mounts that I just ordered on fleabay show up.

Thanks Dan for the awesome project.

Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: berkleystudios on April 10, 2012, 11:40:27 PM
props tskguy!!! you are definitely a brave man than I!
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: kante1603 on April 11, 2012, 01:39:24 AM
Hey all,
Just a little something I have been working on for my new U87 mic. Pretty much done with the machining, I still need to finish the outer rings and the center hole. Tuning is also pretty difficult from what I understand with this capsule so I still need to work that out. I have a rig to tune but I havent really tested it. I guess I will see. Enjoy...
Now that is awesome-I wished I had the competence to do things like that.Congratulations!

Best,

Udo.
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: kante1603 on April 11, 2012, 01:57:26 AM
Well I just finished a pair of mics earlier this evening: Peluso capsule, T13, styrene and tantalum caps, Aurycle body (painted HAMMERED silver 8)).
Congrats to your finished build.
Hammerite is cool (pics please?) :D
As I don't have the trafos yet,may I ask if the T13 has markings for primary and secondary or did you measure dc resistances,just curious.
Also I'd like to know which biasing method you prefered.
Seems that you have set up the mics exactly as I want to do mine,did you use the mica for the 10pf?

Best regards,

Udo.
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: adeptusmajor on April 11, 2012, 07:08:48 AM

Congrats to your finished build.
Hammerite is cool (pics please?) :D
As I don't have the trafos yet,may I ask if the T13 has markings for primary and secondary or did you measure dc resistances,just curious.
Also I'd like to know which biasing method you prefered.
Seems that you have set up the mics exactly as I want to do mine,did you use the mica for the 10pf?

Best regards,

Udo.

I need to figure out a way to brand the mic body, maybe I'll post some pics after that. A friend of mine has some wet transfer label sheets, I know someone said they were unsuccessful trying to use those, so if anyone has any better ideas I'm all ears.

The T13 has yellow as primary, black as secondary, I just followed the schematic and T13 data sheet when wiring. Looking at the side with the leads coming out I did left side yellow to pin 1, left side black to pin 4, right side yellow to pin 2, right side black to pin 3.

I used an oscilloscope to bias the fet, it was super easy and accurate.

I used the mica from the BOM, all the other caps are "vintage spec". Hopefully I don't lose any cool points over the mica.

The mics definitely sound like U87's to me, but I no longer have access to a real one to compare to. I'm more interested in having some great usable tools than creating a precise replica, so I would say mission accomplished. Now I am curious about the U89 circuit, and if it could be done on Dan's pcb. I would love to have a pair of those as well, maybe time for some more research.
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: poctop on April 11, 2012, 07:42:00 AM
Super Glad To hear a new Finished Build ;D ,  Congratulations Adeptusmajor ;D. thanks for the pointer on the T13 i am waiting for mine still  :P,



Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: kante1603 on April 11, 2012, 09:21:16 AM
Thank you for the fast reply!
I need to figure out a way to brand the mic body, maybe I'll post some pics after that. A friend of mine has some wet transfer label sheets, I know someone said they were unsuccessful trying to use those, so if anyone has any better ideas I'm all ears.
As said I failed,the ink came off,maybe an issue since this is all water based,even after coating the printed sheet.....
The T13 has yellow as primary, black as secondary, I just followed the schematic and T13 data sheet when wiring. Looking at the side with the leads coming out I did left side yellow to pin 1, left side black to pin 4, right side yellow to pin 2, right side black to pin 3.
That looks right to me.I have seen the pic as well as the drawing,just wanted someone to confirm if they both match physically,thanks for that.
I used an oscilloscope to bias the fet, it was super easy and accurate.
Cool!Did you monitor/measure with the transformer installed?I wonder if I should do the biasing with my scope connected to the trafo primary pins on the pcb.Will check over the weekend and report back.
I used the mica from the BOM, all the other caps are "vintage spec". Hopefully I don't lose any cool points over the mica.
O.K.,that´s exactly how I´m prepared.When the capsule and transformer are here I´ll check this in our studio,I have them still in my ears from ages ago.Bad thing is that I have only the U87Ai versions here (1986,different capsule) to compare-not fair,but maybe a new preference on vocal tracking,who knows?.
The mics definitely sound like U87's to me, but I no longer have access to a real one to compare to. I'm more interested in having some great usable tools than creating a precise replica, so I would say mission accomplished. Now I am curious about the U89 circuit, and if it could be done on Dan's pcb. I would love to have a pair of those as well, maybe time for some more research.
Same here,I like to have a good working (and sounding) microphone first,not having an exact copy.
Concerning the U89:I used them a lot in the late 80s to the early 90s,especially for classic recordings.Awesome microphones,but really completely different in sound.More direct sounding,more highs,absolutely different from an U87.It has a smaller capsule and different filtering as well as 5 polar patterns and 2 step hpf from what I remember so far.

Thanks again and best regards,

Udo.
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: geekmacdaddy on April 11, 2012, 09:37:22 AM
Greetings All! So excited to have ordered the boards, and to start the project, using the a460 just like Dany did. BTW Thank you for all the work you put in, Dany, and rest of the community. Aside from the biasing mysteries that lie ahead, I too was wondering if there was a pattern switch I could leave internally? If not, I have a busload of 47pf ceramic disc caps from pedal building in a drawer. Would that suffice for 51pf? Ultimately, I'll be using this as a vocal mic, so cardioid really is fine, I just want to explore the options.

Thanks!
Geek
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: adeptusmajor on April 11, 2012, 12:09:12 PM

Cool!Did you monitor/measure with the transformer installed?I wonder if I should do the biasing with my scope connected to the trafo primary pins on the pcb.Will check over the weekend and report back.

I did the bias procedure with no capsule or transformer installed. I followed Matador's instructions - xlr connected with 48V from preamp, test tone from DAW into C4, scope probe connected to fet drain, grounds connected to body. And the T13's unexpectedly showed up at my door just minutes after I finished biasing. ;D


Quote
Concerning the U89:I used them a lot in the late 80s to the early 90s,especially for classic recordings.Awesome microphones,but really completely different in sound.More direct sounding,more highs,absolutely different from an U87.It has a smaller capsule and different filtering as well as 5 polar patterns and 2 step hpf from what I remember so far.

I used to use them a lot, picked them over the U87s much of the time for instrument duties. But it's been over ten years since I've had my hands on one so I don't remember much of the details. Just looking at the model numbers and mic bodies suggest that a U87 and U89 would be similar beasts, but I guess it would be a different project altogether. Maybe one day.

Greetings All! So excited to have ordered the boards, and to start the project, using the a460 just like Dany did. BTW Thank you for all the work you put in, Dany, and rest of the community. Aside from the biasing mysteries that lie ahead, I too was wondering if there was a pattern switch I could leave internally?

FWIW, I find it easy enough to use the jumpers included in the mouser cart to switch patterns if you are leaving the switching internal. Seems like trying to find and fit a switch on the board would be more hassle than it's worth. Just keep the bag of jumpers in the case with the mic and you're good to go.

And to reiterate a point somebody else made- if you are using the Aurycle body with the Peluso capsule you will have to drill out the holes on the capsule mount to get it to fit. Be careful.
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: 0dbfs on April 11, 2012, 01:04:51 PM
I wonder if there is a suitable DIP style switch that may fit on the PCB. I don't mind keeping my greasy-grubby-paws off the PCB and using some needle-nose to place the jumpers but when it's out of my hands anything is possible, probably, and even likely.

Cheers,
jb
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: berkleystudios on April 11, 2012, 01:32:58 PM
just got my set of boards in! they look fantastic dan!
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: xqtion on April 11, 2012, 02:10:37 PM
Could anyone let me know how to wire the capsule for just cardiod pattern ? My capsule is a k67 type with just 3 wires (front, back, ground).

Thanks!!
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: poctop on April 11, 2012, 02:47:22 PM
Could anyone let me know how to wire the capsule for just cardiod pattern ? My capsule is a k67 type with just 3 wires (front, back, ground).

Thanks!!

in the FC section solder the front diaphragme to (cap) pad and the backplate to (bdy) pad, you can try both side if you want and take the one that sounds best to your ear  ;D just leave the extrawire unsoldered with a mini shrink wrap
Dan, 



 
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: xqtion on April 11, 2012, 03:10:49 PM
Ok understood~ thanks!! 
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: kante1603 on April 11, 2012, 04:52:27 PM
Quote from: adeptusmajor link=topic=48030.msg609849#msg609849 date

I did the bias procedure with no capsule or transformer installed. I followed Matador's instructions - xlr connected with 48V from preamp, test tone from DAW into C4, scope probe connected to fet drain, grounds connected to body. And the T13's unexpectedly showed up at my door just minutes after I finished biasing. ;
Great!Does that mean that if I start biasing immediately the T13s will show up tomorrow? ;D

Cheers,

Udo.
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: kante1603 on April 11, 2012, 05:02:33 PM
I wonder if there is a suitable DIP style switch that may fit on the PCB. I don't mind keeping my greasy-grubby-paws off the PCB and using some needle-nose to place the jumpers but when it's out of my hands anything is possible, probably, and even likely.

Cheers,
jb
Hi jb,

Hmmmmm....dip switches normally have either on or off position,they do not toggle.Also you want a center off position.I think if using a jumper with a small grip(?) on top of it could do the job:
It can be left in "park" position meaning just plugged to the middle pin for cardioid mode.This way it will not fall off the pin I bet.

Hope to have helped,

Udo.

Edit:I mean a jumper like this one:
http://www.reichelt.de/Stiftleisten/JUMPER-2-54GL-RT/index.html?;ACTION=3;LA=444;GROUP=C141;GROUPID=3220;ARTICLE=9018;START=0;SORT=user;OFFSET=16;SID=10T4NaaX8AAAIAAFA2Vmc8ea8dd0489375da635914b98337cee02
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: adeptusmajor on April 11, 2012, 05:37:25 PM
Quote from: adeptusmajor link=topic=48030.msg609849#msg609849 date

I did the bias procedure with no capsule or transformer installed. I followed Matador's instructions - xlr connected with 48V from preamp, test tone from DAW into C4, scope probe connected to fet drain, grounds connected to body. And the T13's unexpectedly showed up at my door just minutes after I finished biasing. ;
Great!Does that mean that if I start biasing immediately the T13s will show up tomorrow? ;D

Cheers,

Udo.


YES!!!
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: kante1603 on April 11, 2012, 05:49:12 PM
Quote
YES!!!
COOL!!! ;D ;D ;D
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: xqtion on April 12, 2012, 02:53:10 AM
Hi, now that I'm a lost done with the build, I'm going to do the FET biasing.
I have no scope so I'll just be doing the drain measure method to get it to about 10.5V or so.
So where exactly on the mic is the drain that everyone is talking about ? Do I measure it using my DMM ?

I went thru the whole thread but couldn't find this info.

Thanks!!
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: kante1603 on April 12, 2012, 03:36:25 AM
Hi, now that I'm a lost done with the build, I'm going to do the FET biasing.
I have no scope so I'll just be doing the drain measure method to get it to about 10.5V or so.
So where exactly on the mic is the drain that everyone is talking about ? Do I measure it using my DMM ?

I went thru the whole thread but couldn't find this info.

Thanks!!
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: xqtion on April 12, 2012, 03:41:30 AM
Thank you!!

Bare with me, so when I measure with my DMM, do I put both red and black test pins on pin 1 of the transistor ?
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: kante1603 on April 12, 2012, 03:48:08 AM
Thank you!!

Bare with me, so when I measure with my DMM, do I put both red and black test pins on pin 1 of the transistor ?
Please get familiar with some basics and look how to measure with your dmm.I bet it is all written in the manual.
For now do as follows:
Set your dmm to read vdc.
Connect the probes  to the corresponding jacks on your dmm.
The red probe connected to drain,the black one to 0v which is on several pcb points as well as on the mic case.

Udo.
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: xqtion on April 12, 2012, 04:32:41 AM
Got it thanks!!  :)
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: kante1603 on April 12, 2012, 04:56:47 AM
Got it thanks!!  :)
Cool!
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: xqtion on April 12, 2012, 08:10:43 AM
Ok another beginner question.

When biasing just using DMM, do I just connect the mic to a pre and then turn on 48V phantom power?
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: kante1603 on April 12, 2012, 08:34:20 AM
Ok another beginner question.

When biasing just using DMM, do I just connect the mic to a pre and then turn on 48V phantom power?
Yes,you need the phantom power.
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: xqtion on April 12, 2012, 08:36:08 AM
Ok thank you!! :)
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: xqtion on April 12, 2012, 09:53:29 AM
Hmm my DMM always shows in mV instead of just V. Anyways I set it so that it measures 10.5mV at the drain and then when I measure the potentiometer resistance, it comes out to 7.8k.

Does all this sound right ?

Also I plan to swap C7 tantalum with mundorf 1uf polypropylene cap later. Do I have to re-measure the bias when I do the C7 swap?

Thanks always!! :)
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: poctop on April 12, 2012, 10:04:16 AM
Quote
Hmm my DMM always shows in mV instead of just V. Anyways I set it so that it measures 10.5mV at the drain and then when I measure the potentiometer resistance, it comes out to 7.8k.


Do you mean 10500 mv  that would make more sense , 7.8K is in the ballpark ok, 
if you change the cap it would not hurt to Re-Bias in the final configuration for sure,
Hope this helps,

Dan,
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: xqtion on April 12, 2012, 10:16:17 AM
Hmm I've connected the capsule and I'm not getting any sound...

Is this Cinemag connection correct ?

RT = red from cinemag 2480 Transfo
SW = brown from cinemag 2480 TRansfo
WS = yellow from cinemag 2480 Transfo
BL =  orange fromcinemag 2480 Transfo,

Maybe the orange should goto WS ?

Any ideas ?

Also when I listen thru headphones, I hear this wind sound...???
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: poctop on April 12, 2012, 11:05:46 AM
Here is the cross reference for the CM2480 so the connection above are correct.
,  did you make sure you check all the initial voltage first ,  there are mentionned above in the thread,

do you have your drain voltage to 11V DC ,

is your mic body shielded and closed , ?

verify your capsule connection ?
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: xqtion on April 12, 2012, 11:16:29 AM
Drain voltage is still 10.5mV.
I'ma goto sleep for now and do more trouble shooting tomorrow. Maybe XLR pin 1 and 2 should be swapped ?
Thanks guys I'll let you guys know how it goes...
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: saxmonster on April 12, 2012, 11:21:44 AM
I made my drain volt 10.5 should i make it 11volts would i notice a difference?  What about 10 volts, maybe then i would have a resistor that would work instead of the 15.6kohms i need now which no one has.  or any combination of resistors.  errrr.. would still like to get rid of the pot.

Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: poctop on April 12, 2012, 11:33:16 AM
10.5-11V is the safe Zone, only a extensive Bias( room captulre THD or Matador Method )  you will give the optimum value,  that doesnt mean it might be very different  that much from that safe Zone anyway at the end the mic has to sound good to your hear ,  but still there is no counter indication to leave the pot inside if you can.

i will be building 2 extra mic very soon and i will try to setup a procedure with the Room capture software for evryone to see how it works,

Dan,

Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: poctop on April 12, 2012, 11:35:35 AM
Drain voltage is still 10.5mV.
I'ma goto sleep for now and do more trouble shooting tomorrow. Maybe XLR pin 1 and 2 should be swapped ?
Thanks guys I'll let you guys know how it goes...

Are you measuring  DC or AC 10.5mv is not gonna work you need approximatively 10.5-11V DC on the drain ,

Dan
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: Matador on April 12, 2012, 12:15:30 PM
I made my drain volt 10.5 should i make it 11volts would i notice a difference?  What about 10 volts, maybe then i would have a resistor that would work instead of the 15.6kohms i need now which no one has.  or any combination of resistors.  errrr.. would still like to get rid of the pot.

10-11V DC on the drain should be reasonable for most FETs that are around nominal values for IDSS.  The sound won't change much around this point, but headroom might be slightly less than optimum.

Where I noticed it most:  the signal to the FET gate must be pretty hot.  I tried close mike'ing a drum head, and set the bias so the signal clipped after about 100mV on the gate (drain sat at about 15V).  On quiet hits it sounded fine but on a hard hit there was an audible SPLAT and burst of distortion.

All in all I wouldn't worry about it:  this mike wasn't designed for that kind of duty in any case, but if you like to sweat the details then you can squeeze a bit more headroom on loud transient sources by hand selecting the FET and optimizing the bias point.
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: poctop on April 12, 2012, 12:30:45 PM
I guess we could add to that that there is actually 2 ideal Bias point where 1 is optimized for THD and the other one is optimzed on headroom so it is up for us to decide, 

Dan,


Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: saxmonster on April 12, 2012, 12:55:49 PM
I made my drain volt 10.5 should i make it 11volts would i notice a difference?  What about 10 volts, maybe then i would have a resistor that would work instead of the 15.6kohms i need now which no one has.  or any combination of resistors.  errrr.. would still like to get rid of the pot.

10-11V DC on the drain should be reasonable for most FETs that are around nominal values for IDSS.  The sound won't change much around this point, but headroom might be slightly less than optimum.

Where I noticed it most:  the signal to the FET gate must be pretty hot.  I tried close mike'ing a drum head, and set the bias so the signal clipped after about 100mV on the gate (drain sat at about 15V).  On quiet hits it sounded fine but on a hard hit there was an audible SPLAT and burst of distortion.

All in all I wouldn't worry about it:  this mike wasn't designed for that kind of duty in any case, but if you like to sweat the details then you can squeeze a bit more headroom on loud transient sources by hand selecting the FET and optimizing the bias point.



What is the "nominal values for IDSS"  I have two other fets hear to look at and or try.  Also The higher the voltage, say 11v compared to 10v would give you more headroom or is it the opposite?  in other words which gives you more head room 10v or 11v?  Louder or softer I guess right?  If I have a preamp with lots of gain I could go for the less headroom right?

-Scott
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: wave on April 12, 2012, 01:18:32 PM
What is the minimum power requirement for the biasing resistor?

Dave
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: saxmonster on April 12, 2012, 01:33:54 PM
I think when I was looking it was a 1/4 watt?  Don't quote me though it could be 1/2 watt anyone know for sure?
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: Matador on April 12, 2012, 02:37:44 PM
What is the minimum power requirement for the biasing resistor?

Dave

The source resistor has perhaps 1mA going through it and perhaps 2V dropped across it.  That's only 2mW....so essentially anything you can put in there will be adequate. ;)

What is the "nominal values for IDSS"  I have two other fets hear to look at and or try.  Also The higher the voltage, say 11v compared to 10v would give you more headroom or is it the opposite?  in other words which gives you more head room 10v or 11v?  Louder or softer I guess right?  If I have a preamp with lots of gain I could go for the less headroom right?

-Scott

The nominal value is that given in the datasheet:  somewhere around 10mA perhaps.  My statement was generic and does not apply to an individual FET in an individual board, etc.  "Optimum" may be 9V on one board, and 11V on another....this is why the biasing procedure must be done on each and every board/FET combination.  This is not unique to Dany's boards:  it's just a fact with this circuit topology.

Staying generic and speaking from 10,000 feet up:  running at higher currents should provide more gain, however everything else being equal it will take less input signal before the stage clips, which means headroom would be less.  In reality, VGSoff, IDSS, and gm all vary from transistor to transistor:  biasing by scope or by THD method optimizes the actual circuit around all of these (to the extent needed by this circuit).

So don't worry too much about the drain voltage unless it's WAY different from about half of the supply voltage (which in this circuit is about 21V at the top of the drain resistor).
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: wave on April 12, 2012, 03:56:36 PM
I asked that because saxmonster couldn't find a 15.6K resistor to replace the trimmer.
I found this one on mouser

http://www.mouser.com/ProductDetail/Vishay-Dale/RN55C1562BRE6/?qs=NVJATC80C4%2fyLVR6unXY27Zon6%2fPsp8TbniFs21qaqY%3d

it's 100mW
Could it be used?

Dave
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: poctop on April 12, 2012, 04:18:02 PM
I asked that because saxmonster couldn't find a 15.6K resistor to replace the trimmer.
I found this one on mouser

http://www.mouser.com/ProductDetail/Vishay-Dale/RN55C1562BRE6/?qs=NVJATC80C4%2fyLVR6unXY27Zon6%2fPsp8TbniFs21qaqY%3d

it's 100mW
Could it be used?

Dave

Absolutely, Nice Gesture Dave ,

Dan,
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: poctop on April 12, 2012, 04:40:36 PM
I have heard good things about this software based oscillscope so if someone is interested in trying it ,

here it is:
https://io.groupdiy.com/file/gdiy-2017/u/39511/58d0281993770 (https://io.groupdiy.com/file/gdiy-2017/u/39511/58d0281993770)

Cheers,
Dan,
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: kante1603 on April 12, 2012, 05:23:33 PM
Hi,

I did some first trials to bias mine without a capsule  or trafo connected and ended up as follows:
Using a scope and a variable sine generator gave me a nice feel,I was able trimming the pot pretty well where-while playing with the generator level forth and back-I easily was able to get a symmetric clipping.Nice so far I thought.
After that I measured the drain voltage at 11,9vdc and the pot at 12,56kohms (in-circuit,pardon me).
I used a fet at an idss of 8,7 which was the lowest one from a shootout from arround 20 pieces I had handy.
My feeling says that I'm right in trusting my scope readings.
Boosting the generator level gives me a really nice identical clipping at the same time and amount on both sides of the sinewave.
Condition was inserting the signal at c4,not at the recommended insert point between r9 and r10.
Will repeat this at the weekend on the measuring inputs,don't have the time now.

But in general:Am I right trusting the scope or am I too far off with drain voltage and/or resistor value?

Thank you all,

Udo.
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: poctop on April 12, 2012, 06:19:01 PM
Hi,

I did some first trials to bias mine without a capsule  or trafo connected and ended up as follows:
Using a scope and a variable sine generator gave me a nice feel,I was able trimming the pot pretty well where-while playing with the generator level forth and back-I easily was able to get a symmetric clipping.Nice so far I thought.
After that I measured the drain voltage at 11,9vdc and the pot at 12,56kohms (in-circuit,pardon me).
I used a fet at an idss of 8,7 which was the lowest one from a shootout from arround 20 pieces I had handy.
My feeling says that I'm right in trusting my scope readings.
Boosting the generator level gives me a really nice identical clipping at the same time and amount on both sides of the sinewave.
Condition was inserting the signal at c4,not at the recommended insert point between r9 and r10.
Will repeat this at the weekend on the measuring inputs,don't have the time now.

But in general:Am I right trusting the scope or am I too far off with drain voltage and/or resistor value?

Thank you all,

Udo.


Trust the Scope  ;D
what you see is what you get,

What then would be your Final Source Voltage and Iddle Current trough R11 Then? I am really curious how the THD method and Scope method will closely relate, i know i used both and they were very  similar results,  i am building 2 more so i will be able to add to this Topic, the Tricky Part is to Stop as in ( dont go to far for nothing bias Point where you loose SPL), I have found with the THD Method that at certain point arround 0.39% that the increase in Drain Voltage reflect in very poor decrase in THD there is where you stop.
impressively earing works well, can also try  is very fun and challenging i have done it many times as a 3rd method,
you inject the 1K and and right after passing the opening Fiz you will hear a nano-hiss  :o and just pass this point if you continue just a little bit and concentrate on the nano hiss you will hear it go faint on a very precise spot.
For now it makes all sense, you are in the Zone  8)
Dan,


 

 



Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: kante1603 on April 12, 2012, 06:35:19 PM
Quote from: poctop link=topic=48030.msg610082#msg610082 date
Trust the Scope  ;D
What then would be your Source Voltage and Iddle Current trough R11 Then? I am really curious how the THD method and Scope method will closely relate, i know i used both and they were very  similar results,  i am building 2 more so i will be able to add to this Topic,
For now it makes all sense, remember what you see is what you get,
Dan,
Thanks Dan,

it was just a quick shot I made,and having bought the scope pretty cheap on ebay (Old 2-ch. HAMEG HM204-2) it had to remember the how to use it stuff in a hurry.Haven't used one for about 25 years,but all is coming back now.
"what you see is what you get":that means I only get some green curves and no microphone? ;D

Will work on it a bit more,maybe I have some nice ideas for it,but must check them first....

Thx Dan,

good night,

Udo.
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: kante1603 on April 12, 2012, 06:40:13 PM
@adeptusmajor:

Fet is biased,but the T13s didn't show up!  >:(.... ???.... ::).... ;D ;D ;D

Udo.
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: geekmacdaddy on April 12, 2012, 06:51:09 PM
Thought I would throw this out there...as I was perusing the Aurycle site, I looked at the A570T as possible donor instead of the A460 kit for one reason, the polar pattern selector. Same price as the kit. http://www.aurycle.com/aurycle-a570t-large-diaphragm-multi-pattern-condenser-microphone.html (http://www.aurycle.com/aurycle-a570t-large-diaphragm-multi-pattern-condenser-microphone.html).

Geek
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: berkleystudios on April 12, 2012, 07:32:25 PM
no filter though. not a major issue but still doesnt have all three selectors on it
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: xqtion on April 12, 2012, 10:48:15 PM
Hmm... tried swapping XLR 1 and 2. No luck. I'm still getting 10.5mV instead of 10.5V.

By the way which pin is pin 1 on the potentiometer ? Is the pin closest to the screw pin 1 ?

Around what voltage should the drain measure without any resistor on R11 ?



Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: poctop on April 12, 2012, 11:51:58 PM
Hmm... tried swapping XLR 1 and 2. No luck. I'm still getting 10.5mV instead of 10.5V.

By the way which pin is pin 1 on the potentiometer ? Is the pin closest to the screw pin 1 ?

Yes,

Around what voltage should the drain measure without any resistor on R11 ?
Yes The pin 1 is the closest to Screw, 
What do you measure in between the  2.2K  resistor, and on top oF Zener diode, this are the basic Supply Voltage to start with.
Hope this Helps, 
Dan,
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: poctop on April 12, 2012, 11:53:54 PM
2 More Little friend looking to mate transformer and capsule  ;D
Still Waiting to try T13 and BV11  :P

All Original : C7, C8, C10 Tantalum - C6, C1, C3, C15, C4, Polystyrene,  I have been able to get some 10pf polyS from a Radio Guy just in town  ;D,

(https://io.groupdiy.com/file/gdiy-2017/u/39511/58d028199377f)



Dan,
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: xqtion on April 13, 2012, 12:25:07 AM
Yes The pin 1 is the closest to Screw, 
What do you measure in between the  2.2K  resistor, and on top oF Zener diode, this are the basic Supply Voltage to start with.
Hope this Helps, 
Dan,
[/quote]

Between R18 and Zener, I get 40.6V.
And between R19 and Zener, I get 41.5V.

Any ideas what might be wrong ? Thanks!!
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: kante1603 on April 13, 2012, 01:20:20 AM
no filter though. not a major issue but still doesnt have all three selectors on it
Exactly what I think,having all 3 is a must-have for me.

Udo("notoric experienced U87 user") :)
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: kante1603 on April 13, 2012, 01:24:42 AM
2 More Little friend looking to mate transformer and capsule  ;D
Still Waiting to try T13 and BV11  :P

All Original : C7, C8, C10 Tantalum - C6, C1, C3, C15, C4, Polystyrene,  I have been able to get some 10pf polyS from a Radio Guy just in town  ;D,


Dan,
Cool Dan,

So you will be able to compare between the 10pf mica and styrene soundwise...

Have fun,

Udo.
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: xqtion on April 13, 2012, 01:53:41 AM
I've found something weird.

When I measure R18 and R19, I get 1.1k when it should be 2.2k.

Can this have something to do with my symptoms ?


Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: Hank Dussen on April 13, 2012, 06:09:44 AM
Anyone knows where to buy these small toggle switches that they use for these mics?
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: poctop on April 13, 2012, 08:21:28 AM
I've found something weird.

When I measure R18 and R19, I get 1.1k when it should be 2.2k.

Can this have something to do with my symptoms ?

you are measuring the 2.2K in parralelle that is why you have 1.1K ,  you should get about 48V at pin 2 and pin 3 from the front end ,  and you should have around 24V or a bit less when you measure the Side of the Zener diode that is facing R16 150K, is your Zener diode oriented properly the black stripe must be facing R16 as well,  check you capacitor polarity. and double check for solder bridge or cold solder.
you really need to take the schematic for reference and go from there, most of the voltage are labeled on the originial schematic,

Hope this helps,

Dan,   

 
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: xqtion on April 13, 2012, 08:27:15 AM
I've found the problem.

The numbers on the PCB for XLR threw me off. I had literally connected 1 to 1, 2 to 2  and 3 to 3 of the XLR to the PCB.
But of course pin 1 of the XLR should of have connected to 3 ground and 2 to 1 hot and 3 to 2 cold. Duh...

Now I'm getting about 46.2V between zener and R18.

I'm running into one biasing problem though. The highest I can get the drain volt is 7.43V.
And potentiometer resistance is measuring about 26.5k.

Please help?
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: poctop on April 13, 2012, 08:45:06 AM
I've found the problem.

The numbers on the PCB for XLR threw me off. I had literally connected 1 to 1, 2 to 2  and 3 to 3 of the XLR to the PCB.
But of course pin 1 of the XLR should of have connected to 3 ground and 2 to 1 hot and 3 to 2 cold. Duh...

Now I'm getting about 46.2V between zener and R18.

I'm running into one biasing problem though. The highest I can get the drain volt is 7.43V.
And potentiometer resistance is measuring about 26.5k.

Please help?

Do you have your capsule disconnected ? did you use the middle pin of the pot and the one closest to the screw pin 1
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: xqtion on April 13, 2012, 08:48:44 AM
Yes pin 1 and the middle pin which is 2.

Also nothing connected to FC and RC.
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: poctop on April 13, 2012, 08:59:46 AM
Yes pin 1 and the middle pin which is 2.

Also nothing connected to FC and RC.

have you measured the top of Zener in regards to GND, to see if you have the 24V ish there ,
so red probe on black stripe and the other one on the other side,
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: xqtion on April 13, 2012, 09:03:31 AM
Yes I'm getting 23.22V on the zener.

Thanks for your help~ Any more ideas?
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: poctop on April 13, 2012, 10:34:13 AM
Yes I'm getting 23.22V on the zener.

Thanks for your help~ Any more ideas?

Note sure what happened with your connection as some point but if i remember well if R11 is out you shoulb be able to get the full load arround 20V on the right side of R11 , i would consider replacing the FET then try , it seems that your FET is loaded? ,
Hope this helps,

Dan,
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: kante1603 on April 13, 2012, 04:06:18 PM
Anyone knows where to buy these small toggle switches that they use for these mics?
Hi Hank,

Looking at my B2 switches under a magnifying glas I can't see the brand,only that they are specified at 1,5A.
Doing a search for (sub-)miniature toggle switches it seems to be Salecom types.
Remember the pattern switch is a 3 position SPDT with center off,the others are normal SPDT.
Found this one here:

http://www.banzaimusic.com/Salecom-SKS08LP-Subminiature.html

There are some more to look at on their site.Since you are from belgium that could be a way to go,but I bet these are standard toggles.

Hope to have helped,

Udo.

Edit:They are exactly the ones!The specs ("20mA/20V") stated at the site are bu*****t,must be a typo.When zooming in there it looks identical to the B2 switches.Dimensions meet them precisely!Great,now I`ve even found spare parts!Please see attached pic:
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: kante1603 on April 13, 2012, 06:48:18 PM
Here comes another one:

Height restriction problem for trim pot (R11) solved.Found this one here:

http://www.reichelt.de/Spindeltrimmer/962-20-20K/index.html?;ACTION=3;LA=444;GROUP=B23;GROUPID=3130;ARTICLE=3642;START=0;SORT=artnr;OFFSET=16;SID=13T1Hrb38AAAIAAA9EfA82e8ea4ec628ed638b45641452a29f413

Specs are 20KOhms,20 turns, just 6,4mm high.It´s longer than the one in the bom but does fit since there´s enough space to the front of pcb.
There´s a pdf on the site where more details can be found.

Please see attached file (sorry for the blurry pics,can´t do it better at the moment).

Cheers,

Udo.

Addendum:Dan gave me a hint that reversing the pot makes it way easier to reach the screw-DO IT!Works perfect!
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: poctop on April 13, 2012, 07:31:01 PM
This is Great Stuff Udo, just wandering if it would be even better to install it the other way arround , if you want to ultimately Bias with the pot in situ and leave the pot there you would have more room and angle to stick the screw driver in,  i have question myself if i could also do the same with the original pot but i had enough room to do it this way so i kept going in this direction,  the original pot is  a tight fit but if you use a pair of small snipper to cut the edge gently or file a bit, it will slide in no problem as in this picture here,  in my case the height was not the problem more like the contigueous width,  it is just barely too wide on the edge to fit perfectly without a bit of snipping, this is an example on the Mxl body wich is the same as the aurycle.

(https://io.groupdiy.com/file/gdiy-2017/u/39511/58d0281993789)

i am not sure if the B2 Pro body is even smaller in diameter for the pot to go in ,  also i use to indent the pot from underneath to make some room for the Leg to go underneath so it does not require as much filing adjustment,

i wish i could have a mouser PN for your pot so i could add it in in case people prefer it.

thanks Again Udo for your ressourcefullness on this matter this is great contribution to this project and very appreciated,
cheers,
Dan,




Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: kante1603 on April 13, 2012, 08:04:48 PM
Thanks for the nice words Dan,

In my case the height was more problematic than the width.I filed the edge and it went in the tube way better,but not good enough I thought,still too close the tubes inside.Since I had to order some stuff anyways I gave it a chance.I'm sorry I don't have parts numbers for you american guys,maybe one can try to get closer infos from the pdf on the site?
About the screw position:I will leave it this way.It comes closer to the front of the pcb,and if I remove the metall mounting plate which holds the capsules saddle it will be easy enough to reach I think.
The plate can be removed easily on a B2,it is held by 4 screws.
Will try this out over the weekend.

Best,

Udo.
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: Hank Dussen on April 13, 2012, 08:28:20 PM
Looking at my B2 switches under a magnifying glas I can't see the brand,only that they are specified at 1,5A.
Doing a search for (sub-)miniature toggle switches it seems to be Salecom types.
Remember the pattern switch is a 3 position SPDT with center off,the others are normal SPDT.
Found this one here:

http://www.banzaimusic.com/Salecom-SKS08LP-Subminiature.html

There are some more to look at on their site.Since you are from belgium that could be a way to go,but I bet these are standard toggles.

Hope to have helped,

Udo.

Thanks a lot!
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: Hank Dussen on April 13, 2012, 08:42:13 PM
Found this one here:

http://www.banzaimusic.com/Salecom-SKS08LP-Subminiature.html



Seems to be the same dimentions as this one: http://eu.mouser.com/ProductDetail/Mountain-Switch/108-2MS3T2B2M6QE-EVX/?qs=r%2frvCFLFL6efW6qOhf4KRUsJkF9R1dXjZkNH%252bHqY6Vk%3d (http://eu.mouser.com/ProductDetail/Mountain-Switch/108-2MS3T2B2M6QE-EVX/?qs=r%2frvCFLFL6efW6qOhf4KRUsJkF9R1dXjZkNH%252bHqY6Vk%3d)
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: kante1603 on April 14, 2012, 09:30:10 AM

Seems to be the same dimentions as this one: http://eu.mouser.com/ProductDetail/Mountain-Switch/108-2MS3T2B2M6QE-EVX/?qs=r%2frvCFLFL6efW6qOhf4KRUsJkF9R1dXjZkNH%252bHqY6Vk%3d (http://eu.mouser.com/ProductDetail/Mountain-Switch/108-2MS3T2B2M6QE-EVX/?qs=r%2frvCFLFL6efW6qOhf4KRUsJkF9R1dXjZkNH%252bHqY6Vk%3d)
Hi Hank,

Yes,seems to be the same,only the brand is different,cool.

Cheers,

Udo.
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: kante1603 on April 14, 2012, 08:10:53 PM
This is Great Stuff Udo, just wandering if it would be even better to install it the other way arround , if you want to ultimately Bias with the pot in situ and leave the pot there you would have more room and angle to stick the screw driver in,.............
Hi Dan,

you´re right with reversing the pot!Way easier to dial in,I must have been too tired yesterday to get it right-pardon me.
Made an addendum on my post #299,thanks for the hint Dan!
I modded my pcb,and it fits the B2 housing like a glove now-nothing touches the tube´s inside.Here´s the result:

(http://img403.imageshack.us/img403/5375/nupotassembled.jpg)

(http://img337.imageshack.us/img337/4003/nupottrimming.jpg)

I also made a swap at the 2,2k resistors to o,1% precision types since they´re not really expensive (19 Euro cents).This way I must not spend hours on matching them.
Readings on top of zener are 23,96 vdc now,front backplate is 41,83vdc-even better than before.
Then I biased again,this time I made pics for those who are interested in my little scope setup.
The upper dmm reads the drain voltage,the middle unit is a simple signal follower I built the drawing-by-numbers way ages ago.
I only used the generator part being a "Wien bridge" oscillator as it´s level is adjustable.Very easy to dial in!
The scope is a Hameg for arround 100 Euros from evil bay.Look:

Sinewave before clipping:

(http://img85.imageshack.us/img85/2513/priortoclipping.jpg)

Symmetric clipping after biasing:

(http://img11.imageshack.us/img11/3348/symclipping.jpg)

Best,

Udo.

Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: poctop on April 15, 2012, 10:42:56 AM
Hey Udo,  i guess nobody can tell you that you are not ready to receive your capsule and transfo,  if i could throw 1 to you on the other side of the ocean i would  :D,  i cant wait for your comment of your future mic,  great picture also ,



Best,

Dan,
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: kante1603 on April 15, 2012, 11:09:09 AM
Hey Udo,  i guess nobody can tell you that you are not ready to receive your capsule and transfo,  if i could throw 1 to you on the other side of the ocean i would  :D,  i cant wait for your comment of your future mic,  great picture also ,



Best,

Dan,
Then throw them,Im standing at the window with my hands open ;D
I'm close to dying of jealousy-have fun you T13 and PK87 owners (must calm down now.....).

Best,

Udo ;)
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: adeptusmajor on April 15, 2012, 02:30:44 PM

I'm close to dying of jealousy-have fun you T13 and PK87 owners (must calm down now.....).

Best,

Udo ;)


Oh, I am... ;D
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: kante1603 on April 15, 2012, 05:44:05 PM
For those who don´t have a scope but an iPad:
I tried this one in an Alesis io dock.Supersimple,2 channels,easy setup.Costs 11,99-Euros.
This will not replace a real oscilloscope,but could work in this case.
A nice toy to fool arround with,it has signal generators on-board,and if hooked up to an iPad compatible audio device (e.g. via USB)
you will have a signal source,line ins and outs,maybe mic in with phantom,a 2 channel scope, a way to monitor what happens via phones etc.I connected an external signal generator-worked from start,the auto button sets the trigger mode and levels for you to fit the displayed window.Calibration is super easy too.
If interested do a search for "Onyx" or "oscilloscope" in the app store.
Look at the attached pic.

Cheers,

Udo.
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: geekmacdaddy on April 16, 2012, 07:50:22 AM
Mac users; Will this scope do the trick for biasing? Thanks  :)

http://duncan.rutgers.edu/physicsfreewares.htm
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: geekmacdaddy on April 16, 2012, 08:40:37 AM
at the very least, it's a nice signal generator for this, which accepts external sound sources as well

http://download.cnet.com/WaveWindow/3000-2170_4-10532772.html

(shareware, 12.00 US)
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: kante1603 on April 16, 2012, 12:17:38 PM
Mac users; Will this scope do the trick for biasing? Thanks  :)

http://duncan.rutgers.edu/physicsfreewares.htm
Doesn´t install on none of my macs (incl.ppc and intels),what OS will this run on?

Cheers,

Udo.
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: kante1603 on April 16, 2012, 12:39:33 PM
at the very least, it's a nice signal generator for this, which accepts external sound sources as well

http://download.cnet.com/WaveWindow/3000-2170_4-10532772.html

(shareware, 12.00 US)
Hi,

sorry,but this is not really earth-shattering.Just 1 channel,not enough info,not really much to set in the preferences.
Was synching bad at low frequencies.No calibration possible.
My trial setup was rme fireface 800 as audio unit and Wandel & Goltermann as signal generator.
I believe there are better tools out there,so let´s do some further research.
At 1kHz it may work somehow,but I wouldn´t trust it.

Cheers,

Udo.
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: geekmacdaddy on April 16, 2012, 12:55:46 PM
10.7.2 Udo.
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: kante1603 on April 16, 2012, 01:06:25 PM
10.7.2 Udo.
O.K.,mine at home just go to 10.6.x,will give it a try at work.

Thanks for the info!

Udo.
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: kante1603 on April 16, 2012, 02:10:06 PM
Cuty pie?
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: saxmonster on April 16, 2012, 03:23:24 PM
so could i use my iphone as a scope and my daw which is an older mac to generate test tone is this all i would need?
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: kante1603 on April 16, 2012, 03:31:25 PM
so could i use my iphone as a scope and my daw which is an older mac to generate test tone is this all i would need?
Hi,

What are you refering to,the iphone in general or the onyx software?

Udo.

Edit :The pic above shows not a cell phone but a real scope!
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: poctop on April 16, 2012, 06:09:39 PM
Never tought one day i could bias The FET with my phone  8)

This is great stuff,  i am in,

Dan,
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: pavthefiddler on April 16, 2012, 06:49:11 PM
Almost finished building my mic. Peluso capsule, tantalum and styrene caps, cinemag trafo. I'm going to replace the cinemag with the tab-funkwerk in the nearest future. I'm using B2 Pro body, with all 3 switches wired to the board. The microphone sounds really good.

I ran into a small difficulty: when I initially assembled everything and did some test recording I noticed a very slight 50 Hz hum (visible on the spectrum analyser, but not really obvious in the recording). Also the high pass filter switch was acting as an antenna (really loud hum when touched or anything near it). I gathered it means that the switch body wasn't grounded properly. Indeed it turns out when I was cutting tracks on the original B2 switch PCB I cut the ground track leading to that switch. When I fixed that the hum is gone but the microphone is barely working - the signal is some 50dB lower than it should be.

I believe it has to be something very simple - a short circuit of some sort most likely. I'm going to try to fix it tomorrow and once it's done I'll post some pictures and sound samples.
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: wave on April 16, 2012, 10:45:30 PM
Almost finished building my mic. Peluso capsule, tantalum and styrene caps, cinemag trafo. I'm going to replace the cinemag with the tab-funkwerk in the nearest future. I'm using B2 Pro body, with all 3 switches wired to the board. The microphone sounds really good.

I ran into a small difficulty: when I initially assembled everything and did some test recording I noticed a very slight 50 Hz hum (visible on the spectrum analyser, but not really obvious in the recording). Also the high pass filter switch was acting as an antenna (really loud hum when touched or anything near it). I gathered it means that the switch body wasn't grounded properly. Indeed it turns out when I was cutting tracks on the original B2 switch PCB I cut the ground track leading to that switch. When I fixed that the hum is gone but the microphone is barely working - the signal is some 50dB lower than it should be.

I believe it has to be something very simple - a short circuit of some sort most likely. I'm going to try to fix it tomorrow and once it's done I'll post some pictures and sound samples.

Hi pavthefiddler,
If I may ask, what is the reason that you are going to change the transformer from the Cinemag to the Tab? I'm trying to decide which to get and I'm looking for as many opinions as I can get!
Hope you figure out your level issue.

Thanks,
Dave
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: saxmonster on April 16, 2012, 11:34:17 PM
just a quick question?

When i checked the drain to ground volts i had the capsule disconnected as stated but did i need to run a signal through the pads while i was adjusting the pot to get the correct voltage?

thanks
-Scott
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: kante1603 on April 17, 2012, 02:15:31 AM
Almost finished building my mic. Peluso capsule, tantalum and styrene caps, cinemag trafo. I'm going to replace the cinemag with the tab-funkwerk in the nearest future. I'm using B2 Pro body, with all 3 switches wired to the board. The microphone sounds really good.

I ran into a small difficulty: when I initially assembled everything and did some test recording I noticed a very slight 50 Hz hum (visible on the spectrum analyser, but not really obvious in the recording). Also the high pass filter switch was acting as an antenna (really loud hum when touched or anything near it). I gathered it means that the switch body wasn't grounded properly. Indeed it turns out when I was cutting tracks on the original B2 switch PCB I cut the ground track leading to that switch. When I fixed that the hum is gone but the microphone is barely working - the signal is some 50dB lower than it should be.

I believe it has to be something very simple - a short circuit of some sort most likely. I'm going to try to fix it tomorrow and once it's done I'll post some pictures and sound samples.
Congrats,you seem to be very close to finishing.
I would lift the switch connections on pcb first and try the functionality of them by shorting them dirctly there.This way you can shoot out the switch board.I can't tell you more about it since I can not test it (you all know why..... ::).Have only cut this one little trace I mentioned for not shorting the omni position to ground.Having all switches grounded can be essential.Did you twist the wires?-Just an idea....
I bet you have allready cecked continuity through the complete mic body and to the pcb.
This gain issue,does that mean you are 50 dB off or have to make up gain arround 50dB on your pre amp?
Maybe something weird with the trafo connections or swappped?(wasn't there at least one guy here having trouble with lowish level on output by using the cinemag)?
Must go to work now....please keep us informed,all will be good soon I bet,

Udo.
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: kante1603 on April 17, 2012, 03:52:05 AM
10.7.2 Udo.
Hi,

did a quick test on an OSX 10.7.x some minutes ago:Yes,it works!
Simple tool but very usefull,did not check in-depth but really loved the zoom functions,should be easy to dial the pot in for biasing.I used just what was connected to the computer,a digi 003 in this case,and fed a -50dB-ish sine from a neutrik minirator to mic in ch.1 to simulate a (dynamic) microphone-when using it check preferences for audio on your mac,after that everything is fine.

Thanks for sharing!

Udo ;)
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: wthrelfall on April 17, 2012, 07:25:07 AM
Dany, new board and new bom seem to have done the trick - it's working  :P  Happy!
One last thing, how do I set the pattern to figure eight?  put the jumper between "Hyper" and "8"? 
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: kante1603 on April 17, 2012, 08:37:01 AM
Dany, new board and new bom seem to have done the trick - it's working  :P  Happy!
One last thing, how do I set the pattern to figure eight?  put the jumper between "Hyper" and "8"?
Yes.

Udo.
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: wthrelfall on April 17, 2012, 08:44:15 AM
Dany, new board and new bom seem to have done the trick - it's working  :P  Happy!
One last thing, how do I set the pattern to figure eight?  put the jumper between "Hyper" and "8"?
Yes.

Udo.

thought so, but it doesn't work  :(
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: kante1603 on April 17, 2012, 08:50:37 AM
Does it work in omni mode?
If not then the voltage for the back capsule seems missing.
Check for shorts as well as back capsule wiring then.

Udo.
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: wthrelfall on April 17, 2012, 09:01:15 AM
Does it work in omni mode?

Yes, Omni and cardioid work ok.
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: kante1603 on April 17, 2012, 09:42:26 AM
Does it work in omni mode?

Yes, Omni and cardioid work ok.
Don't have the schemo handy,I'm at work now.
If the omni mode does really work it can't be too much,maybe just the figure eight connection has a cold solder blob.Trace this point back to the next parts for conntinuity.Compare to the schematics.
For testing omni vs cardioid:If talking to the front you will hear the signal a bit louder than in omni,it will have a level drop in omni mode.Also if talking to the side of the capsule the cardioid mode will get way quieter when moving arround the mic while in omni the sound should not or just very slightly change from front to side.Meaning the cardioid has it's maximum signal rejection at an 90 degree angle.

Udo.
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: pavthefiddler on April 17, 2012, 09:55:55 AM
Almost finished building my mic. Peluso capsule, tantalum and styrene caps, cinemag trafo. I'm going to replace the cinemag with the tab-funkwerk in the nearest future. I'm using B2 Pro body, with all 3 switches wired to the board. The microphone sounds really good.

I ran into a small difficulty: when I initially assembled everything and did some test recording I noticed a very slight 50 Hz hum (visible on the spectrum analyser, but not really obvious in the recording). Also the high pass filter switch was acting as an antenna (really loud hum when touched or anything near it). I gathered it means that the switch body wasn't grounded properly. Indeed it turns out when I was cutting tracks on the original B2 switch PCB I cut the ground track leading to that switch. When I fixed that the hum is gone but the microphone is barely working - the signal is some 50dB lower than it should be.

I believe it has to be something very simple - a short circuit of some sort most likely. I'm going to try to fix it tomorrow and once it's done I'll post some pictures and sound samples.

Hi pavthefiddler,
If I may ask, what is the reason that you are going to change the transformer from the Cinemag to the Tab? I'm trying to decide which to get and I'm looking for as many opinions as I can get!
Hope you figure out your level issue.

Thanks,
Dave

I've heard a mic with a Tab transformer before and I really liked the sound, hard to describe the difference but I really liked it. I did a classical recording a few years ago, a vocal + piano in a concert hall (2 mics in a M/S configuration) and the microphones with Tab transformers sounded more 'old style', like an old Deutsche Gramofon recording, that sort of sound. Obviously this is just my impression. But the guy who made the microphones was saying similar things, he really liked using them for classical music. Cinemag is cheaper so I just got one to check it out and I can always order Tab and use cinemag for the next project :-)

I'm just about to tackle the hum problem and hopefully I'll be able to post some sound samples later.
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: pavthefiddler on April 17, 2012, 09:59:12 AM
just a quick question?

When i checked the drain to ground volts i had the capsule disconnected as stated but did i need to run a signal through the pads while i was adjusting the pot to get the correct voltage?

thanks
-Scott

I believe the FET drain voltage is constant regardless of whether you inject the signal or not.
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: kante1603 on April 17, 2012, 11:12:28 AM
I'm just about to tackle the hum problem and hopefully I'll be able to post some sound samples later.
Hi,

So you've got your gain issue solved?

Best,

Udo.
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: pavthefiddler on April 17, 2012, 11:42:08 AM
I'm just about to tackle the hum problem and hopefully I'll be able to post some sound samples later.
Hi,

So you've got your gain issue solved?

Best,

Udo.

Yes and no. I disconnected all the wires going to the switches and the output signal level increased. But the whole switch board was still connected to the microphone body (3 screws) and anything near the switches would generate loud hum. I know it means there was a grounding problem. I decided to take the whole switch board out. That solved all the problems -  there is no 50 Hz hum, also the signal to noise ratio increased drastically. I cleaned the switch board with isopropyl alcohol, made sure all switches (their body) are grounded and that there is no short circuits (I cut all the other traces). I put it back in and the problems came back - hum and the RF noise.

So at this stage I decided to get rid of the switch board and switches, at least for the moment. I put the jumpers in and they work great. Would be great to have them, but they are not essential for me. I'm planning a transformer upgrade in a couple of months, I'll attempt to wire the switches again then.

I must say the microphone is quite quiet, it needs a good bit of gain. But the S/N ratio is great so it's not a big deal. It sounds really good. Tonight I'll record some violin samples and photos. Tomorrow I have a great singer coming over so I'll post some vocals too. Friend of mine has the U87Ai so I'm going to compare it to the clone - but I won't get a chance to do that for another couple of days.

Also I might consider removing a layer of the basket mesh, but I need to do some test with the singers first.

Anyway, thank you all, especially Dan and Udo! I learnt a lot and I'm already planning more DIY projects! But time to make some music first...
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: kante1603 on April 17, 2012, 12:34:52 PM

Yes and no. I disconnected all the wires going to the switches and the output signal level increased. But the whole switch board was still connected to the microphone body (3 screws) and anything near the switches would generate loud hum. I know it means there was a grounding problem. I decided to take the whole switch board out. That solved all the problems -  there is no 50 Hz hum, also the signal to noise ratio increased drastically. I cleaned the switch board with isopropyl alcohol, made sure all switches (their body) are grounded and that there is no short circuits (I cut all the other traces). I put it back in and the problems came back - hum and the RF noise.
Still don´t get it,have measured my switchboard today to make sure everythink is correct.As said I just have cut 1 small trace.
Readings where correct,none of the switches have contact to anything else including ground.The grounds connect properly to the switch shields amongst each other,and considering that the pcb will be mounted back to the 3 metall bolts having full contact to all the metall parts I can not imagine why this happens.
Except of one thing:Given that the switch-construction as acting as an antenna what will it pick up?Something from inside the microphone?I guess no....
So if this is comming from outside (where we have all those nice RF etc.) why isn´t it shielded enough,maybe the tubular part itself isn´t grounded?
All other parts are because they are screwed together so will have continuity from bottom to headbasket,but that does not include the tube.....hmmmmmm....must be put in somewhere....
Did any of the switch wires touch this high sensitive connection between the fet gate and the other board?....Just an idea.....
Holy sh.... -that I can not check it at the moment!
If the same happens to me I would maybe use foil shielded wires with the shield connected to the ground part and the other side left open,but as close as possible to the dedicated board pins to get rid if this.

So at this stage I decided to get rid of the switch board and switches, at least for the moment. I put the jumpers in and they work great. Would be great to have them, but they are not essential for me. I'm planning a transformer upgrade in a couple of months, I'll attempt to wire the switches again then.
I´m very curious now.... :o

I must say the microphone is quite quiet, it needs a good bit of gain. But the S/N ratio is great so it's not a big deal. It sounds really good. Tonight I'll record some violin samples and photos. Tomorrow I have a great singer coming over so I'll post some vocals too. Friend of mine has the U87Ai so I'm going to compare it to the clone - but I won't get a chance to do that for another couple of days.
As said some posts ago I´ll do the same,I have a couple of Ai´s at work which I know very good,exactly from 1986 when they where introduced.
Be aware that they have a different capsule (K67) and have more output;after the math it is a difference of 11dB (-40dBU vs -29dBU) due to changes in the voltage supply part (different filtering and a dc/dc converter added).

Also I might consider removing a layer of the basket mesh, but I need to do some test with the singers first.
?Why?

Anyway, thank you all, especially Dan and Udo! I learnt a lot and I'm already planning more DIY projects! But time to make some music first...
You´re welcome,but I have a bad feeling now....

BTW:What did you use for the 10pF,mica or styrene?

And::Could you post a close up pic of the switch board or have you "closed the file" ;D?

Have fun recording,hope to hear some results soon ;),

Udo.
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: saxmonster on April 17, 2012, 12:56:04 PM
Does this make sense?

I wanna try to bias it with a scope program on my mac.

So i take a signal generator out of my Daw say on channel one.  Using a 1.4 jack out of channel I cut the end of the wire and solder or clip it to the front capsule pads.  Now the signal will go into the mic.

How do I then get my scope program to see the signal?  Can I hook up a mic chord and plug it into channel two and set the scope program to analyze channel 2?  Then make adjustments to the resistor and output level of the signal?

Obviously I don't have a real scope or probe to use.

Let me know if this will work

-Scott


Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: kante1603 on April 17, 2012, 01:50:47 PM
Does this make sense?

I wanna try to bias it with a scope program on my mac.

So i take a signal generator out of my Daw say on channel one.  Using a 1.4 jack out of channel I cut the end of the wire and solder or clip it to the front capsule pads.  Now the signal will go into the mic.
No, use the measuring input points to inject the signal,the capsule disconnected of course.
Red("RT")=input,black("SW")=ground/0v.

How do I then get my scope program to see the signal?  Can I hook up a mic chord and plug it into channel two and set the scope program to analyze channel 2?
Don´t know neither the program you will use nor the computer you have.Normally the program will have a settings or preferences window where you can set these things.
Yes,you hook up the mics output to a microphone input,using a different channel is always a good idea since you avoid looping back the signal by accident.
After that you must apply phantom power to it,the mic needs it to work. 

Then make adjustments to the resistor and output level of the signal?

Obviously I don't have a real scope or probe to use.

Let me know if this will work

-Scott
Scott,if you are not so familiar in using a scope try to get this working first.Don´t hook the stuff up by now,do an initial trial first as follows:

*Set up your generator to sine wave,1kHz,at a low level of say -50dBU.This will emulate kind of a real expected level from a  microphone.Check if this signal is really comming from say channel 1 by temporarily plugging it to a real micpre (phantom not needed,therefore off).If all is good go to next step.

*Now plug it in to a mic input,say channel 2.You have a prooven kinda mic signal here now.

*Now learn how your scope program acts and behaves.Set it to get the input mic 2 for your measuring.If it has automatic functions for setting the x,y and trigger modes use them!You should see the sinewave now.Go ahead and try to change the x and y settings:The height as well as the width of the sinewave will change corresponding to them.If the wave doesn´t seem to be stable on the screen try toggling through the trigger settings until it works out good.

*If you have passed this little tutorial you can go on and try this with your microphone as described before.If not stop here,you will not risc to damage it,will you ;)

The biasing procedure is well described here in the thread-thanks to matador!!!

Post how it works and have fun,

Udo.

Disclaimer:I am not responsible for you doing something wrong,you must understand using things like a scope basically at least.
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: saxmonster on April 17, 2012, 03:57:15 PM
Ok kante, I actually understand everything u said.  Whooooooo!!!!!  Can I actually damage the mic?  What can happen. To damage it.  Will to hot of a signal do the damage.   Just don't want to fry anything but I do want to optimize this mic to its fullest.  Thanks for the info guys.
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: kante1603 on April 17, 2012, 04:34:54 PM
Ok kante, I actually understand everything u said.  Whooooooo!!!!!  Can I actually damage the mic?  What can happen. To damage it.  Will to hot of a signal do the damage.   Just don't want to fry anything but I do want to optimize this mic to its fullest.  Thanks for the info guys.
Hahaha.....,no,you won't damage it immediately,this was more meant to be very carefull and always being aware what you're doing(forgive me,I'm german and must still learn a lot,especially putting in the right words in english).
Concerning a too hot signal-no,you will use a 0dB sine at 1 kHz at a starting point to be injected at the measuring input.With the scope connected you will see a wave come up at a certain point.I measured the drain voltage in parallel on my dmm to get a rough idea where I'm at and not having to screw the full 25 windings on the pot.Moving the pot screw back and forth will change the symmetry of it.Try to get it in a good balance.
This is best seen at a lower generator signal first for just showing a sine wave.When boosting the generator the wave will start to flatten out,either at the top or bottom.The goal is to get both to flatten out the same way,this is the symmetric clipping.By increasing and decreasing the generator output you can play with it,zooming in on the scope will help to find this point more and more accurate.
It takes a while but is a fun thing to do.
Btw,if you monitor this procedure with your headphones you can clearly hear this spot since a sine wave doesn't have overtones (pay attention to the listening levels).I find this way pretty nice because you audition something while getting a visiual feedback.Not bad.

Happy biasing,

Udo.
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: saxmonster on April 17, 2012, 04:59:39 PM
Thanks Kante,
I will start this tomorrow night or some time this weekend.  Between regular work, showcases and wedding parties free time seems to exist no longer, errrrrrr.. But at least I am keeping busy, or else I would poor buying tons of other DIY projects, hahahaha.  Thanks again.

-Scott

ps what does a probe actually do on a scope?  Is there two probes or just one?  Would seem like you would need two?  one for like a ground and the other for "hot" stuff that you are measuring.
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: kante1603 on April 17, 2012, 05:23:41 PM
Thanks Kante,
I will start this tomorrow night or some time this weekend.  Between regular work, showcases and wedding parties free time seems to exist no longer, errrrrrr.. But at least I am keeping busy, or else I would poor buying tons of other DIY projects, hahahaha.  Thanks again.

-Scott

ps what does a probe actually do on a scope?  Is there two probes or just one?  Would seem like you would need two?  one for like a ground and the other for "hot" stuff that you are measuring.
Hi Scott,

my name is Udo,not "kante" ;).

I know this feeling very well since I had to work pretty hard the last few months,and ton s of my diy things are on hold now too.
A probe is  pencil-style thing with a tip for a scope to get a signal in it by either using a little clamp on front of it (when pulling the plastic front back you can see it) or pulling off the complete front part.You then have a small tip on it like the ones you know from your dmm.The cable has normally a bnc connector at the end and carries both the signal and the ground via the shield,somehow same as in a video- or antenna cable.Right on this "pencil" you can attach a short clamp ("U"-profile) to it having an alligator clamp on the other side.Since this is very short you can also derive the ground from a 4mm banana jack at the front of the scope.
In the englisch language this seems to be named "probe",whether on a dmm or scope.In german we have different words for that ("Mess-Spitze" and "Tastkopf").
The difference between "normal" probes and those for scopes is that there are a lot of varying impedance types available,each makes sense in a special measuring method.Also most of times a scope probe has a little slide switch on it.This is a voltage divider,normally working in dekades,e.g. 1:10 or 1:100.

Hope to have helped,

good night,

Udo.

Edit:Pics added.
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: poctop on April 18, 2012, 06:01:07 PM
Hi All,

i have a couples,  of Microphone transformer for sale , cinemag , peluso , AMI, for diefferent project  8)

PM me if your are interested i will send you a list of what i have,

Cheers,

Dan,
 
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: kante1603 on April 18, 2012, 06:17:53 PM
Thanks for the offer Dan,

if everything fails (what I´m not hoping,have ordered my t13s via the german supplier and paid) I will pm you.
Btw:Have you tried throwing one over the ocean? ;D

Udo.
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: kante1603 on April 18, 2012, 06:36:52 PM
Hi all,

Has anybody received the capsule from the group buy yet in germany or europe?

Udo :-[
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: poctop on April 18, 2012, 06:55:02 PM
Btw:Have you tried throwing one over the ocean? ;D

Udo.

I started an import export company a while ago and i kept trying throwing stuff in ocean but never worked i never made any money,
 :P
D
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: kante1603 on April 18, 2012, 07:10:02 PM

I started an import export company a while ago and i kept trying throwing stuff in ocean but never worked i never made any money,
 :P
D

Wrong ocean? ;D ;D ;D
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: saxmonster on April 18, 2012, 07:59:47 PM
Udo and others,

Here is what I have done so far.  I am using Tone Generator 1.0.2 to send a signal out of my 2408MKII.  I am sending this out channel one or the left side right into the mic PCB on the Rt and Sw points.  The capsule is unplug of course.  The Mic is plug into an xlr cable going to channel 2 of my mackie 1604 which is then sent to channel 2 of the MOTU 2408MKII through the insert on the mackie channel.  I then use Audio Explorer 1.3.1 for the oscilloscope.  I have to set to read channel 2 of the 2408mkII or the right side.  It is set to realtime and display is set to 5ms with a positive slope.  I have X & Y set to automatic. 

A few concerns.

How much gain do i have to use on the mackie channel where the mic is connected to.  I have it the normal position for mics. 

I can't really adjust the output of the tone generator volume wise.  How loud should the signal be going to the PCB?  I can measure it in volts too right?

If I tighten the pot all the way in it shuts the mic off but when I fully open it past the 11vdc mark I don't heard or see any distortion on the scope program.  Only when I turn the gain up on the mic channel do I hear some distortion but I don't think thats the right way to do it.

I am probably doing something wrong or its not set up right but I did do the test of using the tone program into the oscilloscope program.

I think i need to find a different program in which I can adjust the output of the tone generator.

What should is be set to volume wise or volts wise.?

My brain is fried, hahaha

-Scott
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: saxmonster on April 18, 2012, 09:20:03 PM
Ok I think i got it now.

I am taking the signal and sending it out of my computer into channel one on the mackie.  I then take the insert of that channel and hook it up to the pcb on the mic.  This give a gain adjustment to the signal going into the pcb. I then plug the mic into channel 2 of the mackie with no gain.  I send that back into the computer to feed the oscilloscope.  When I adjust the gain of the signal to the pcb I see the volts go up to 50v before I hear distortion in the headphones.
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: tskguy on April 18, 2012, 09:48:30 PM
Hey everyone,

Wanetd to post a bit of a success story. First of all I built this mic and had zero issues! Dan did a fantastic job creating this pcb as well as documenting everything. Thanks!! Second I just insatlled my first DIY capsule, and it sounds great!! so far I havent done much recording but I sent a sample to Dan and he said it was pretty spot on!! I am to say the least a bit pleased. I hope to have a decent recording that I can post on here. The one I sent to Dan is a bit embarrassing, I am a drummer not a guitarist and I recorded some really poor guitar playing mixed wih my 2 year old girl grabbing the mic and singing twinkle twinkle :) And yes that's a celebratory beer.
Anyway, Here are some pics.
(http://i280.photobucket.com/albums/kk187/tskguy/20120418_202319.jpg)
(http://i280.photobucket.com/albums/kk187/tskguy/20120418_202121.jpg)
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: saxmonster on April 18, 2012, 10:02:52 PM
NICE JOB TSKGUY!!!!!!!


Ok Success,
I was able to use the scope but did more by ear.  I set the out put of the signal to 4v as it said on the oscilloscope screen / chart.  I found my lowest  point when the distortion started to be 8.55 volts on the drain.  Then i found the highest point to be 13.00volts.  So when I take 13-8.55 I get 4.45 difference.  I then took 4.45 and divided in half to get 2.22 and then at that to 8.55 which equals 10.77.  So I take it this is the middle section between the distortion points and is probably the optimum point to have for this FET.  So I will then set drain voltage to 10.77volts.  Am I right in this thinking.  I had fun tonight figuring out this stuff.
Thanks guys

-Scott



Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: poctop on April 18, 2012, 10:11:46 PM
You got it  8)
Yep, This a lot of Fun,  ;D

D
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: kante1603 on April 19, 2012, 06:24:51 AM
@tskguy:

Congrats,building an own capsule is simply stunning;I´m not capable to do that,so therefore have my deepest respect-CHAPEAU BAS!!!

@Scott:

Sorry for replying late.
Seems you´ve got it now without really using the scope-Congrats!
It´s a great experience hearing the distortion on a sinewave,isn´t it?
You´ll remember this "sound" forever because it doesn´t compare to anything in the world (be aware that a sine is the purest wave we are able to hear and has absolutely no overtones;any other waveform has them and sounds completely different!).

If you still want to scope again:
I must first download your programs then,install them and then learn how to use them.I have a couple of 1604s at work to check back,this is no biggie.But it will take a couple of days to get this all managed due to a lot of "real work".Also be aware that I still don´t have a trafo,so must find a work-arround for that.

From what you described by listening to it sounds pretty good to me,you seem to be spot-on.

Just curious:
May I ask if you have measured the idss of your fet and what value it had?I had a higher drain-vdc at approx.12,xx volts,but the fet had an idss of 8,7mAs,so is right.It was the lowest of 40 fets or so.
If you don´t know leave it in place-seems you´re done my friend ;).

Now have fun recording with your new toy,

cheers,

Udo.
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: saxmonster on April 19, 2012, 06:48:29 AM
Udo,

I just remember that the fet was the highest one out of the three I had.  Don't know if that was a good or bad idea to use the highest one.  I really don't know if I measure it right too.  I think it was the two out side legs and got a 12 number or something.  I will measure the others and see what they say.    Don't worry about checking the programs I feel pretty confident that I got the mic optimized to its fullest specs.  Was a lot of fun too.  Thanks for everything.  I hope your transformer  comes today.

-Scott

Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: wthrelfall on April 19, 2012, 06:57:14 AM
I'm looking to get my next mic started soon, finally having finished my first successful mic (very nice!).
It would be great to source a decent capsule and transformer from Europe, to save on import duty and shipping - does anyone have some suggestions of suitable parts or manufacturers?
ps.  I spoke to Brian Sowter but they don't have a suitable transformer..
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: kante1603 on April 19, 2012, 07:01:51 AM
I hope your transformer  comes today.

-Scott
Transformers (plural) ;D ;D ;D
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: kante1603 on April 19, 2012, 07:20:45 AM
It would be great to source a decent capsule and transformer from Europe, to save on import duty and shipping - does anyone have some suggestions of suitable parts or manufacturers?
Hi,

I made an inquiry at AMI/TAB Funkenwerk a couple of weeks ago.Joe over there wrote that they wanted to push as much as possible through D.A.S.,a german company located in Hamburg.So I went this way,I´m waiting for them at the moment.
Here´s their site:

http://www.digitalaudioservice.de/

You can switch to english language at the top right of the page.

Hope to have helped,

Udo.
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: wthrelfall on April 19, 2012, 07:28:58 AM
It would be great to source a decent capsule and transformer from Europe, to save on import duty and shipping - does anyone have some suggestions of suitable parts or manufacturers?
Hi,

I made an inquiry at AMI/TAB Funkenwerk a couple of weeks ago.Joe over there wrote that they wanted to push as much as possible through D.A.S.,a german company located in Hamburg.So I went this way,I´m waiting for them at the moment.
Here´s their site:

http://www.digitalaudioservice.de/

You can switch to english language at the top right of the page.

Hope to have helped,

Udo.

Thanks Udo, I looked on the DAS site but I can't find the Tab Funkenwerk transformer - I presume you contacted them and placed a special order?
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: kante1603 on April 19, 2012, 07:35:51 AM
Thanks Udo, I looked on the DAS site but I can't find the Tab Funkenwerk transformer - I presume you contacted them and placed a special order?
Yes,I contacted them on the phone.I was led to a guy named Michael Bucur,he´s responsible for repairs an therefore for (spare) parts.Ask for him,he´s a very friendly guy.

Udo.
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: wthrelfall on April 19, 2012, 10:06:19 AM
thanks Udo.

Thanks Udo, I looked on the DAS site but I can't find the Tab Funkenwerk transformer - I presume you contacted them and placed a special order?
Yes,I contacted them on the phone.I was led to a guy named Michael Bucur,he´s responsible for repairs an therefore for (spare) parts.Ask for him,he´s a very friendly guy.

Udo.
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: kante1603 on April 19, 2012, 10:15:35 AM
thanks
You're welcome.
Wasn't it you with that figure eight problem?How did it work out,problem solved?
Please let us know,we all want to learn of it.

Thx,Udo.
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: wthrelfall on April 19, 2012, 10:46:16 AM
yes it was me.  Still not resolved, but I suspect that the connection I have from the rear backplate is to blame. I haven't had time to check properly, but will do soon..


thanks
You're welcome.
Wasn't it you with that figure eight problem?How did it work out,problem solved?
Please let us know,we all want to learn of it.

Thx,Udo.
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: kante1603 on April 19, 2012, 12:14:15 PM
yes it was me.  Still not resolved, but I suspect that the connection I have from the rear backplate is to blame. I haven't had time to check properly, but will do soon..
O.K.,if it is back capsule related the omni mode won´t work either.If it really does work (check sound on the 90 degrees angle and the slightly lower level in omni) I would recommend a deeper search in the area as shown in the pic.
Look for bad or cold solder joints,shorts and get rid of any flux there,this is a high impedance area,therefore very sensitive.

Udo.
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: tskguy on April 19, 2012, 07:49:40 PM

Link to an Acoustic recording with my new U87 and my diy capsule..... Crappy pre was used so its got that going for it :) No processing or eq.
http://dl.dropbox.com/u/55530129/u87DIYTest.wav

Let me know your honest opinions I would like to tweek the capsule if needed!!
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: geekmacdaddy on April 19, 2012, 08:29:29 PM
Just beautiful, tskguy. Congrats. Questionl; were you using your fingers or a pick?
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: saxmonster on April 19, 2012, 08:32:24 PM
TSKGUY,

Dude it sounds really good!!!!!  I would use in a track for sure!!!!!  Can you make another capsule type for a diy elam251 I am going to make out of an apex 460?  Keep up the great work!!!!!!!

-Scott


Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: kante1603 on April 19, 2012, 09:08:01 PM

Let me know your honest opinions I would like to tweek the capsule if needed!!
Very nice indeed,a bit too much low end though,but that is more about how close you´ve been (proximity effect) and the mic position.
That´s the cardioid,right?
Try with another pre,maybe one with a tuneable hpf (or a mixer channel) and you´ll get a pretty nice basic recording.
Very nice and smooth high end,not harsh.
As said:I´m really impressed you did the capsule by yourself,congrats again!
Tip:Build another one and do this in MS-technique,that would be a great sound for sure.....hahahaha......

Udo.
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: tskguy on April 19, 2012, 09:39:39 PM
Thanks everyone for the feedback,
You are all correct the Mic was pretty darn close to the hole, So proximity is for sure a factor. Yes this was recorded cardiod. The omni track I did but didnt post was much less proximity and a bit lower in gain. I do find myself really cranking the gain, I have read that thats pretty normal but Its tuff for me to judge if its the capsule or just the circuit. Anyway thanks again everyone.
Feels great to here the positive feedback so far!

Eric
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: sproto on April 20, 2012, 06:52:25 AM
OK, complete noob question here so, apologies up front.

I have build several compressors and mic pre's but only with some hand holding (at least slight instructions).  This is my first Mic build.  I have been lurking (admittedly have not read this ENTIRE thread).  Can anyone point me to a place with general build guides for this?  i.e. transformer, then capsule, look out for this etc. etc? 

There is a tone of information here but from what it I have read it mostly pertains to troubleshooting once the mic is assembled.

Any direction is greatly appreciated.

Thanks,
S
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: adeptusmajor on April 20, 2012, 06:54:23 AM
OK, complete noob question here so, apologies up front.

I have build several compressors and mic pre's but only with some hand holding (at least slight instructions).  This is my first Mic build.  I have been lurking (admittedly have not read this ENTIRE thread).  Can anyone point me to a place with general build guides for this?  i.e. transformer, then capsule, look out for this etc. etc? 

There is a tone of information here but from what it I have read it mostly pertains to troubleshooting once the mic is assembled.

Any direction is greatly appreciated.

Thanks,
S

Check page one of the white market thread.
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: poctop on April 22, 2012, 02:45:11 PM
I have 35 sets Left if anyone wants to have a try  at them
Regards,
Dan,
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: poctop on April 22, 2012, 03:01:08 PM
My Little Quatuor,  ;D


(https://io.groupdiy.com/file/gdiy-2017/u/39511/58d0281993797)
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: tskguy on April 22, 2012, 04:02:30 PM
Hi everyone,

Here is another quick sample with my u87 and a vocal track that I did this weekend.
I am to say the least pretty darn pleased!! I think it sounds great. No pop screen so there is one little plossive, and my la2a was over compressing a bit.
The track is cleen no proccessing or EQ. The chain was ssl9k to la2a then an old tango 24bit converter.
Let me know what you think, Eric
http://dl.dropbox.com/u/55530129/u87Vocal.wav
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: tskguy on April 22, 2012, 04:17:49 PM
And here is the same vocal in the mix, This is again pretty dry just some delay.

http://dl.dropbox.com/u/55530129/u87vocalMix.wav
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: wave on April 22, 2012, 04:18:32 PM
Eric,

Once again, i think your capsule sounds great! I love the sound of an LA2A on spank mode.
Whats in the guts of your U87? Tants + styrenes? Which trafo did you end up using?

Dave

p.s. I dig the little note drop at the end of the vocal
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: wave on April 22, 2012, 04:21:01 PM
And here is the same vocal in the mix, This is again pretty dry just some delay.

http://dl.dropbox.com/u/55530129/u87vocalMix.wav

What is the other instrument that comes with the lead guit at the end of the sample? Is it scratching or the vocal?
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: tskguy on April 22, 2012, 04:50:44 PM
Ha, that was the vocal at the end. The singer was just messing around.
As for caps I used pretty much all of the original ones unless mouser didn't have them in stock. The transformer is the 2480 Cinemag.
I did compare the u87 track to the original vocal that was recorded with a g7 and I think I like the u87 better.
Eric
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: kante1603 on April 23, 2012, 01:30:01 PM
Peluso capsules arrived in germany after 26 days-HURRAY!!! ;D
Only the trafos still aren´t here,must be patient again (but that´s soooooo hard......).

Cheers,

Udo.
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: poctop on April 23, 2012, 02:07:32 PM
you may want to start biasing again just in case something would show up to your door,  ;D

Keep me posted,

Dan,

Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: kante1603 on April 23, 2012, 02:40:00 PM
you may want to start biasing again just in case something would show up to your door,  ;D

Keep me posted,

Dan,
You mean biasing in advance?Well,if it works-why not,hahahaha.......

Udo :)
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: poctop on April 23, 2012, 07:20:59 PM
Well, 24 sets left,
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: geekmacdaddy on April 24, 2012, 06:21:28 AM
Does anyone have experience w/Thiersch? I need  to re-skin a K87 and Thiersch is reasonable, price-wise.

thanks
geek
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: geekmacdaddy on April 24, 2012, 10:05:24 AM
and..Hi Udo,
 Here's another possible scenario, while I save money for a capsule  ;) I have Logic, which has a plugin for tone generator. I have a free plugin for a simple scope'. Hmmm...send the tone out right channel of mbox into the board on the Mic (sans capsule), feed signal to mbox input, w/scope as insert? Does this sound plausible?

thanks
Geek
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: kante1603 on April 24, 2012, 12:09:31 PM
and..Hi Udo,
 Here's another possible scenario, while I save money for a capsule  ;) I have Logic, which has a plugin for tone generator. I have a free plugin for a simple scope'. Hmmm...send the tone out right channel of mbox into the board on the Mic (sans capsule), feed signal to mbox input, w/scope as insert? Does this sound plausible?

thanks
Geek
Hi Geek,

sounds plausible of course,although a scope as an "insert" device is a bit confusing as it doesn´t have an output.Anyways it will read the insert send then.
Don´t know the plug-ins you use guys,but from signal flow seen I would say yes-as soon you´ve got your scope working.
You could give it a try and record the generator to a track,then "insert" the scope and see what happens.If it shows a sine wave then you´re good to go I think.
Beware of feedbacks.
I can not proof all of this as long I don´t have my trafos.I did things without them using a real scope and a real generator.
Went into some oscillation trouble at the measuring input on the pcb at first,but after injecting signal at c4 everything was fine.
I guess with trafos in circuit the measuring inputs will be fine to use.
I would say give it a try.

Cheers,

Udo.
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: geekmacdaddy on April 24, 2012, 12:28:26 PM
Thanks Udo.
 I had the same thought of recording a tone....

Best
Geek
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: poctop on April 24, 2012, 02:43:01 PM
Quote
24 left? is this the last run? i sure hope not!

I was  not sure if it was worthed to have a third round of these board cause i tought that probably everyone enthousiast already has a set  by now  but i did receive plenty of PM regarding the availability after this round is finished and also just learned that Matt at advanced microphone parts as of next week will be producing a RK87 with 4 wire connection specially for this project and mounting saddle for only 109.00 US and he has very good feedback on his capsule,  So i guess i will go for a 3rd round of these to accomodate future interest in the project ,  i would like to thank all of you for this great sucess ,  after those are gone i will probably be out of these for about 2-3 weeks question of making some more, Again Thanks to all for your interest in this project , For Sure i will keep you posted as Matt RK-87 comes in .

Sincerly Dan,  ;D

Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: kante1603 on April 24, 2012, 02:54:26 PM
Thanks Udo.
 I had the same thought of recording a tone....

Best
Geek
You´re welcome.
Please keep us posted how it worked out.

Thanks in advance,

Udo ;)
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: mylesgm on April 24, 2012, 03:17:23 PM
That capsule sounds interesting, Where can advanced mic parts be found?
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: rmaier on April 24, 2012, 04:17:25 PM
Maybe something similar to this one?

http://microphone-parts.com/rk67-microphone-capsule/ (http://microphone-parts.com/rk67-microphone-capsule/)
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: poctop on April 24, 2012, 04:31:45 PM
Yep that is this same supplier so the RK-87 will be available on friday this week ,

over here ,

http://microphone-parts.com/ (http://microphone-parts.com/)

it is not advertised yet,
i will keep you posted as i go,

Dany,
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: poctop on April 24, 2012, 08:49:23 PM
Well , just a comment on Matador FET biasing method it works like a charm and to me it was found the easiest of all,

Thanks to Matador  8)

Adding To this a quick Tip for future build  that is ,  you can install R6 backward meaning that the body of the resistor is actually not on the resistor silk circle but the other way arround that does not change anything in the circuit but it will be super easy to tap in to inject your signal
you just clip on the R6 resistor Leg on top of the board . in this manner it inject direclty at C4 and the funs starts right away ,

(https://io.groupdiy.com/file/gdiy-2017/u/39511/58d02819937a5)
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: kante1603 on April 24, 2012, 09:13:15 PM
+1!

Udo ;)
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: berkleystudios on April 24, 2012, 11:51:21 PM
dang it dan you should have kept those a secret!! i had emailed matt earlier about them. these are going to be a really limited run, and unless they sell quickly it looks like it might be the only one :'(
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: wave on April 25, 2012, 01:01:05 AM
I talked to him last week about it too.

Matt told me today that Dan is gonna test one so maybe people will wait to hear his results.

The first batch will be a limited run but there will be another in 30 days

Dave
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: poctop on April 25, 2012, 08:54:56 AM
dang it dan you should have kept those a secret!! i had emailed matt earlier about them. these are going to be a really limited run, and unless they sell quickly it looks like it might be the only one :'(

Ho Ho,  Sorry about that , i hope then the run will somehow not too limited , as i have no idea of how much will be available  ,
 just hoping the capsule Goons will not show up at my door  :-X
D
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: berkleystudios on April 25, 2012, 07:47:28 PM
only 20 capsules will be sold, 1 goes to dan so that leaves 19. im getting 2 so that leaves 17 for yall haha
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: poctop on April 25, 2012, 08:10:30 PM
only 20 capsules will be sold, 1 goes to dan so that leaves 19. im getting 2 so that leaves 17 for yall haha

I am glad that you secured your order  8)   I was expecting i little more than that  :o

Cheers,
Dan,
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: wave on April 25, 2012, 10:21:25 PM
I'm def getting 1 so 16....

Dave
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: kante1603 on April 25, 2012, 11:00:05 PM
I'm really curious how they will compare to the Pk87 or the "real thing",looking at the price........

Udo.
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: kpearsall on April 26, 2012, 01:34:42 AM
I'm hoping to get 3 so 13 :P
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: poctop on April 26, 2012, 09:24:32 AM
Just tought i giving some figures regarding the bias of my new pair of U1621, suprisingly or not  ;D the Iddle current sit exactely at the same level for both mic after bias procedure ,   

Mic A  Drain Voltage 10.3V   source Voltage 2.77V    iddle current trough R11 12.2K =  0.226 ma

Mic B  Drain Voltage 10.1V   source voltage 1.86V    iddle current trough R11  8.2K   =   0.226ma ,

results from this JFET below


cheers,
Dan,


 

Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: Blue Jinn on April 26, 2012, 12:30:40 PM
Maybe this is obvious, but I've not seen this in the thread. For a single backplane dual diaphragm K67 style capsule (at some point I'll save up my pennies for a Peluso, or maybe look at the RK87 when it comes out, but I can only live so far outside my means...) is the backplane connected on the PCB to front body, rear body, or both? Both doesn't seem to make sense, and tracing the schematic it doesn't seem to matter, but I thought I'd ask anyway.

I'm tentatively planning on putting this in a MXL 2010 which has all the switches, and I have a two sided 34mm 67 style capsule on order.
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: poctop on April 26, 2012, 01:16:46 PM
Maybe this is obvious, but I've not seen this in the thread. For a single backplane dual diaphragm K67 style capsule (at some point I'll save up my pennies for a Peluso, or maybe look at the RK87 when it comes out, but I can only live so far outside my means...) is the backplane connected on the PCB to front body, rear body, or both? Both doesn't seem to make sense, and tracing the schematic it doesn't seem to matter, but I thought I'd ask anyway.

I'm tentatively planning on putting this in a MXL 2010 which has all the switches, and I have a two sided 34mm 67 style capsule on order.

Do you means using a K67 ,only on one side for cardiod pattern ?
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: poctop on April 26, 2012, 02:03:19 PM
Maybe this is obvious, but I've not seen this in the thread. For a single backplane dual diaphragm K67 style capsule (at some point I'll save up my pennies for a Peluso, or maybe look at the RK87 when it comes out, but I can only live so far outside my means...) is the backplane connected on the PCB to front body, rear body, or both? Both doesn't seem to make sense, and tracing the schematic it doesn't seem to matter, but I thought I'd ask anyway.

I'm tentatively planning on putting this in a MXL 2010 which has all the switches, and I have a two sided 34mm 67 style capsule on order.

Do you means using a K67 ,only on one side for cardiod pattern ?

if it is the case then connect the backplate to section FC pad (bdy)  and then pad (cap) to the diaphragme, you can leave the other diaphrgame wire unconnected,

hope this helps,
Dan,
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: Blue Jinn on April 26, 2012, 03:16:04 PM
Quote
Do you means using a K67 ,only on one side for cardiod pattern ?

No, I mean for a two sided capsule, (omni/card/8) but with a single backplane (three wires only, not four like the Peluso) I get the front/back connection, but which 'body' pad does the single backplane connect to front, back or both? or does it matter? Or do you *have* to use a dual backplane capsule?
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: poctop on April 26, 2012, 03:39:22 PM
Quote
Do you means using a K67 ,only on one side for cardiod pattern ?

No, I mean for a two sided capsule, (omni/card/8) but with a single backplane (three wires only, not four like the Peluso) I get the front/back connection, but which 'body' pad does the single backplane connect to front, back or both? or does it matter? Or do you *have* to use a dual backplane capsule?

you actually need a double-isolated backplate like the original circuit K87 Style  ,   the K67 will work fine in cardiod mode and you would connect it to the FC section,
D
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: kante1603 on April 27, 2012, 12:55:05 AM
@Blue Jinn
Hi,excuse me for chiming in.
Maybe you are swapping this build with the U87A,in which a capsule with a single backplate does work.
This is the circuit of the U87 which is the predecessor of the U87A.
Looking at the schemo you can see why it must be a dual backplate when looking arround the switch arrangement.
Neumann decided to go back to the single backplate design (like in the U67) in the mid 80s since the dual design wasn't a real improvement,both K67 and K87 are nearly identical soundwise.Also they changed the supply voltage filtering as well as implementing a dc converter giving a higher polarisation voltage;this way they achieved a slightly better s/n ratio and a higher output level at some plus 10 to 11 dBu (after the math).

So in this (vintage) circuit a dual backplate is a must-have.Only if one decided to just use the cardiod pattern the K67 capsule will work.The back diaphragm wire can be left isolated then.In case of the front diaphragm ever gets damaged you can use the left-over back diaphragm as a spare part-cool.

Hope to have helped,

Udo.
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: poctop on April 27, 2012, 10:00:56 AM
@abechap your inbox is full so cant response  :-X

D
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: Blue Jinn on April 27, 2012, 02:47:00 PM
Thanks Dany and Udo for explaining this. Mmmh. Looks like I'll need a Peluso at some point.

Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: kante1603 on April 27, 2012, 03:06:03 PM
Thanks Dany and Udo for explaining this. Mmmh. Looks like I'll need a Peluso at some point.
Well,don't have my T13s yet but I do have my Peluso capsules,hehehe..... ::)

Udo.
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: HellfireStudios on April 27, 2012, 07:06:56 PM
Did that situation, in which the switches were acting as antennae, ever resolve itself, or do I need to take some precaution against it? I believe sheilded wire between the PCB and switches was suggested. Could this help? Thanks.
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: berkleystudios on April 27, 2012, 09:32:09 PM
i cant bias without a transformer can i? boards are stuffed and waiting on the RK87 and CM2480 to come in. looking for some thing to do ha. i have the tranny from the a460. could i bias with this and then swap to the cm2480? or would i need to re bias?
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: poctop on April 27, 2012, 09:36:21 PM
Did that situation, in which the switches were acting as antennae, ever resolve itself, or do I need to take some precaution against it? I believe sheilded wire between the PCB and switches was suggested. Could this help? Thanks.


I have built 2 Aurycle body and i did wire the switch directly to the pads and it work fantastic, i did not even bother to twist the wire,  :)

So yes ,please Keep us posted on this issue, 

Dan,
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: poctop on April 27, 2012, 09:50:00 PM
i cant bias without a transformer can i? boards are stuffed and waiting on the RK87 and CM2480 to come in. looking for some thing to do ha. i have the tranny from the a460. could i bias with this and then swap to the cm2480? or would i need to re bias?

you sure can start to bias if you would like ,  but first thing that i would do is to measure my initial voltage the Zener reg and the 2K2, and backplate
in the other hand, i have good reason to believe that the stock transfomer is not compatible with this project. some says it is a 2:1 traffo but it has not been confirmed yet ,  it is more suited i think in the PNP follower topology circuit from the stock circuit.

but this does not prevent you from trying it and see what kind of output i has , still would be nice to evaluate the traffo dB loss to find out a bit more,

Hope this helps,
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: berkleystudios on April 27, 2012, 11:17:14 PM
my drain does not go above 7.3v? what am i doing wrong?
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: kante1603 on April 28, 2012, 01:03:10 AM
Did that situation, in which the switches were acting as antennae, ever resolve itself, or do I need to take some precaution against it? I believe sheilded wire between the PCB and switches was suggested. Could this help? Thanks.
Hi,
This happened to one guy and was related to a B2 mic.
He wrote that he'll take care later,meanwhile he's using the jumpers.
I allready posted possible solutions,please read the thead.

Udo.
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: kante1603 on April 28, 2012, 01:07:50 AM
my drain does not go above 7.3v? what am i doing wrong?
Hi,

This is not enough information.
Did you do Dan's initial voltage check?
Have you checked the IDSS of your fet?
Did you swap it?
Are you sure you measured right?

Etc.,etc,..........

More details please,

Udo.
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: poctop on April 28, 2012, 09:44:12 AM
my drain does not go above 7.3v? what am i doing wrong?

I know Xqtion had the same issue here ,
Quote
I'm running into one biasing problem though. The highest I can get the drain volt is 7.43V.
And potentiometer resistance is measuring about 26.5k.

Please help?

Does it feel the same way ,   Perhaps Xqtion can shed some light here ?
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: xqtion on April 28, 2012, 09:52:52 AM
Yeah I had the same issue but I couldn't figure out what the problem was.

I just ordered one more pcb to try to build a new one from scratch but didn't get to it yet.

Well if you ever solve the issue please let me know :) I thought I was going crazy trying to figure it out  :'(
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: poctop on April 28, 2012, 10:08:41 AM
 :) Attention to all completed project  ;D  your are very welcome to post in this thread to let us know how you are making out,  8)

Regards,

Dan,
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: kante1603 on April 28, 2012, 10:42:36 AM
:) Attention to all completed project  ;D  your are very welcome to post in this thread to let us know how you are making out,  8)

Regards,

Dan,
+1 on this,there seem to be a lot of of builds just half-working or so,I don't see the solutions.We all want a good working microphone,don't we?
And posting some statements about sound,maybe compared to a real U87(Ai) and telling us something about using different caps,trafos and capsules would really be nice of you.

Udo.
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: poctop on April 28, 2012, 12:09:08 PM
I Have those 4 Mics perfectly working but i guess that does not count does it ?  ;D

Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: kante1603 on April 28, 2012, 01:17:59 PM
I Have those 4 Mics perfectly working but i guess that does not count does it ?  ;D
No.

Sincerely yours,
"the-guy-who-dances-with-no-microphones-because-he-is-hungry-for-transformers" Udo. ;D
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: poctop on April 28, 2012, 06:06:17 PM
Here is a shot with my vintage U87 and  my beloved 2 clone,  with original Traffo and peluso capsule , i need to polish the capsule mount positioning tough because there is i believe some slight proximity effect difference i believe ,  fun game is to try finding the real one in those 3 regardless of the take slight difference and my horrible voice, now it is time for T13 and RK87 to show up and compete,.

have fun,  :)

there it is , :)

clone and neumann against sample,  8)
https://io.groupdiy.com/file/gdiy-2017/u/39511/58d02819937b3

Cheers,
Dan.,
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: wave on April 28, 2012, 09:03:55 PM
My guess is the real one is #1

Probably wrong tho. The similarity is intense. Do I hear some slight distortion on 2 and 3?

Dave
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: berkleystudios on April 28, 2012, 10:48:11 PM
okay when i introduce a 1k signal at -50db, i get a jump at the drain to about 15v, and then it fluctuates all over the place. it is not constant. could it be a grounding issue? will  put pics up later, just got off work so im to tired to do it now.

also i get no voltage at the gate, and the source typically is the same voltage as the drain.


this is the first time ive biased something so im sure im doing it wrong haha.

here is a rundown of what i am doing.
1) connect xlr cable an supply phantom power
2) check zener (shows 24 volts)
3) ground DMM on out side of mic XLR chassis(0.0V)
4) check voltage at drain (7.3v) (no signal applied), highest voltage achieved by adjusting trimmer
5) same voltage a source
6) apply signal to RT using a 1/8" TR adapter  on a 1/4" TR cable, 1khz at -50db
7) voltage fluctuates at drain and source but normalizes to 7. V eventually, adjusting trimmer does not increase.

what am i doing wrong? looks like 2.52k is max resistance
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: saxmonster on April 29, 2012, 01:48:05 AM
maybe the pot is trashed or they sent you a wrong one or a cold solder of the pot?
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: kante1603 on April 29, 2012, 01:48:35 AM
Hi,

O.k.,there's something wrong definetely.
Pics will help of course,best from both the parts and solder side.
I guess you had the capsule disconnected?
At first check for even smallest solder blobs and shorts.
The 2,52k,did that refer to your pot fully dialed in to one side or did I misunderstand something?If this is the "end value" and arround 0ohms on the other side then you might have put in a wrong pot.
It can be the fet is broken or has a connection between source and drain,same voltage on both is wrong I think.
The 24vdc on top of zeners is right,even perfect.
Also you started with -50dB on the measuring input,but that's a different thing.Let's get the mic up and running first.

Best regards ,

Udo.

Edited,let´s check the pot first.
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: kante1603 on April 29, 2012, 02:21:36 AM
Hi Dan,

the last sample is distorted,sorry....

Udo.

Edit:If you can record a short sentence containing all (the german word is "Vokale") vowels(?,meaning A-E-I-O-U) it might help.An "A" e.g. has the highest energy,a "U" tells something about low mids etc.."Check,check...." is too little to judge a sound.
Anyway,all mics sound good on a first listen,and they don´t have the sharpness all this china stuff has,nice!
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: kante1603 on April 29, 2012, 02:25:17 AM
My guess is the real one is #1

Do I hear some slight distortion on 2 and 3?

Eeeehhhmmmmm....."slight" distortion on #3?
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: kante1603 on April 29, 2012, 06:41:37 AM
Just tought i giving some figures regarding the bias of my new pair of U1621, suprisingly or not  ;D the Iddle current sit exactely at the same level for both mic after bias procedure ,   

Mic A  Drain Voltage 10.3V   source Voltage 2.77V    iddle current trough R11 12.2K =  0.226 ma

Mic B  Drain Voltage 10.1V   source voltage 1.86V    iddle current trough R11  8.2K   =   0.226ma ,

results from this JFET below


cheers,
Dan,
Hi Dan,

It's boring to wait for parts,so I did a comparison to your results.
I have 2,568vdc as source voltage and 12,56 k for R11.Idle current therefore is 0,205mAs.
As said idss from my fet was lower,arround 8,7 mAs.
Still in the ballpark I think.
Just for info.

Cheers,

Udo.
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: poctop on April 29, 2012, 11:50:34 AM
My guess is the real one is #1

Do I hear some slight distortion on 2 and 3?

Eeeehhhmmmmm....."slight" distortion on #3?

Yep there is definately  a little something going on with number 3 , i have been identifying mike with a color scheme bevcause they are exactely the samething,  i am now suspecting the 10pf styrene i obtained from a garbage can, i realy need to polish my capsule placement as well i am not totally happy the way it is mounted inside the mic ,  also the mic will make some room for the RK87 from matt to test out,
still workin on it for sure,   
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: kante1603 on April 29, 2012, 12:32:25 PM

Dan,does that mean the others have micas for the 10pf and the "normal" styrenes stated as original in the bom?
Just curious,

Udo.
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: wave on April 29, 2012, 02:21:35 PM
My guess is the real one is #1

Do I hear some slight distortion on 2 and 3?

Eeeehhhmmmmm....."slight" distortion on #3?

Haha! Makes me laugh every time I read it. I like the throat clearing sound in text form.

Dan- Maybe the garbage can cap has something to do with it? Funny as well!
+1 for Udo's question about whether the others are mica

Dave
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: kante1603 on April 29, 2012, 02:41:03 PM
Yes,I have read this eeeeehhhmmmmmmm in one of Igor's replies,made me laugh too ;D

Cheers,

Udo.
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: poctop on April 29, 2012, 03:11:58 PM
okay when i introduce a 1k signal at -50db, i get a jump at the drain to about 15v, and then it fluctuates all over the place. it is not constant. could it be a grounding issue? will  put pics up later, just got off work so im to tired to do it now.

also i get no voltage at the gate, and the source typically is the same voltage as the drain.


this is the first time ive biased something so im sure im doing it wrong haha.

here is a rundown of what i am doing.
1) connect xlr cable an supply phantom power
2) check zener (shows 24 volts)
3) ground DMM on out side of mic XLR chassis(0.0V)
4) check voltage at drain (7.3v) (no signal applied), highest voltage achieved by adjusting trimmer
5) same voltage a source
6) apply signal to RT using a 1/8" TR adapter  on a 1/4" TR cable, 1khz at -50db
7) voltage fluctuates at drain and source but normalizes to 7. V eventually, adjusting trimmer does not increase.

what am i doing wrong? looks like 2.52k is max resistance

I have updated a lot of info for the project i would like you to verify you initial voltage check in the Read this First and also make sure your gate is actually connected to the other board circuitry and make sure you measure the FET Drain Voltage not the Source Voltage,  you may want to Not solder the potentiometer on the board for now mount it externally so you wont start damaging the pads meanwhile troubleshooting.
make sure also the XLR pinout is respected as a start refer to silk screen.

here is some info that you can find on the First page,  just added them.  hope this will helps finding why you have this problem.


(https://io.groupdiy.com/file/gdiy-2017/u/39511/58d1402a02266)
(https://io.groupdiy.com/file/gdiy-2017/u/39511/58d1402a02275)
(https://io.groupdiy.com/file/gdiy-2017/u/39511/58d1402a02284)
(https://io.groupdiy.com/file/gdiy-2017/u/39511/58d1402a02290)
(https://io.groupdiy.com/file/gdiy-2017/u/39511/58d02819937c1)
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: poctop on April 29, 2012, 03:14:47 PM
And Surely this,

Read This First : Assembly Instruction , Excel BOM and Tips For Assembly and  Imporant Considerations Here: https://io.groupdiy.com/file/gdiy-2017/u/39511/58d02819937d0 (https://io.groupdiy.com/file/gdiy-2017/u/39511/58d02819937d0)
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: poctop on April 29, 2012, 03:23:23 PM

Dan,does that mean the others have micas for the 10pf and the "normal" styrenes stated as original in the bom?
Just curious,

Udo.

Yep they were all poly,  i am suspecting this old cap for sure but also the FET cause when i initially looked at it with the THD meter behavior it seemed to had a less nice THD profile just after the Bias point ,  I Will try another one for now with lower IDss and see. :P.

Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: kante1603 on April 29, 2012, 03:46:21 PM
Thanks for the great guide Dan,this will help a lot,especially the guys who are not-so-experienced.
Running the 4 connection wires on the bottom sides is a great idea,this will keep the top side cleaner.
May I suggest to add something to your considerations list?
That is to tell people to never touch the capsule or parts of it directly with the fingers.This is the very high impedance part and is absolutely non-forgiving.Wearing thin gloves does the trick.

Best,

Udo.
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: poctop on April 29, 2012, 03:47:25 PM
okay when i introduce a 1k signal at -50db, i get a jump at the drain to about 15v, and then it fluctuates all over the place. it is not constant. could it be a grounding issue? will  put pics up later, just got off work so im to tired to do it now.

also i get no voltage at the gate, and the source typically is the same voltage as the drain.


this is the first time ive biased something so im sure im doing it wrong haha.

here is a rundown of what i am doing.
1) connect xlr cable an supply phantom power
2) check zener (shows 24 volts)
3) ground DMM on out side of mic XLR chassis(0.0V)
4) check voltage at drain (7.3v) (no signal applied), highest voltage achieved by adjusting trimmer
5) same voltage a source
6) apply signal to RT using a 1/8" TR adapter  on a 1/4" TR cable, 1khz at -50db
7) voltage fluctuates at drain and source but normalizes to 7. V eventually, adjusting trimmer does not increase.

what am i doing wrong? looks like 2.52k is max resistance

Make sure you inject at C4-R6 point your 1K tone also , make sure your gate is connected and also the capsule is disconnected, make sure you have used pin 1 and pin 2 of the potentimeter and cut pin 3,
Do not use the RT Pad for this method  check here , Put your Probe or Measure the Voltage on the Drain Pin of the FET

Precious Info on how to use a scope to Bias a Fet (Thanks To Matador) http://www.groupdiy.com/index.php?topic=46109.40
also here a reference :
https://io.groupdiy.com/file/gdiy-2017/u/39511/58d02819937e2 (https://io.groupdiy.com/file/gdiy-2017/u/39511/58d02819937e2) By ZapnSpark
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: poctop on April 29, 2012, 03:57:06 PM
Thanks for the great guide Dan,this will help a lot,especially the guys who are not-so-experienced.
Running the 4 connection wires on the bottom sides is a great idea,this will keep the top side cleaner.
May I suggest to add something to your considerations list?
That is to tell people to never touch the capsule or parts of it directly with the fingers.This is the very high impedance part and is absolutely non-forgiving.Wearing thin gloves does the trick.

Best,

Udo.

thanks Udo for the kind word just added your suggestions  :)

D
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: Blue Jinn on April 29, 2012, 07:01:33 PM
BTW, FYI, Marik has a 10:1 transformer, there is a white market listing for his transformers.
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: poctop on April 29, 2012, 10:50:17 PM
My guess is the real one is #1

Do I hear some slight distortion on 2 and 3?

Eeeehhhmmmmm....."slight" distortion on #3?

I will have to find out if an ExtraPush in drain will give me some better result tHd wise ,  i was under the impression that when i'd used the tHD indicator i had a bit higher final Drain voltage i will report my findings and more result  :P  i should maybe consider testing with a pop filter too
 :D
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: kante1603 on April 30, 2012, 01:29:39 AM
My guess is the real one is #1

Do I hear some slight distortion on 2 and 3?

Eeeehhhmmmmm....."slight" distortion on #3?

I will have to find out if an ExtraPush in drain will give me some better result tHd wise ,  i was under the impression that when i'd used the tHD indicator i had a bit higher final Drain voltage i will report my findings and more result  :P  i should maybe consider testing with a pop filter too
 :D
You're using a large diaphragm mic and being close while talking to it without pop filter?
That's "brave" ( and a capsule killer:moisture is the enemy #1,followed by dust).

Udo.
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: Ayman59 on April 30, 2012, 11:30:01 AM
Guys,
Long life to this forum!!!
I have a question for U???

About my B2 Pro mic that does not have the
metal tube casing at the bottom of it. The one that separates
the circuitry from the xfmr.

Is the xfmr supposed to have a metal shield over it?
or anybody put the xfmr into it without this protection?

Thank u for u're advices!!!
Jérôme
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: kante1603 on April 30, 2012, 12:02:29 PM
Guys,
Long life to this forum!!!
I have a question for U???

About my B2 Pro mic that does not have the
metal tube casing at the bottom of it. The one that separates
the circuitry from the xfmr.

Is the xfmr supposed to have a metal shield over it?
or anybody put the xfmr into it without this protection?

Thank u for u're advices!!!
Jérôme
Hi and welcome,

funny I worked on that exactly today for my B2pro builds-no joke!
For non-b2 builders:this mic is transformerless but has a little space for it at the bottom.
I decided to cut some metall tube from an old damaged chair off,say arround 35mm,approx. 25mm diameter.I will glue it to the bottom and leave it open on top to run the wires.The T13 trafo should fit in there and will be held by rubber foam.That's what I'm going to do.
Having metall as shield won't hurt I think since the trafo has no can,but I think it is not necessary.
Anyway,be carefull that you don't short out the xlr connectors,I used shrink tube at this point.

Hope to have helped,

Udo.
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: saxmonster on April 30, 2012, 12:05:30 PM
Why are we using r6 now?  Does this mean that I have to re-bias?

thanks
-Scott
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: poctop on April 30, 2012, 12:12:47 PM
Why are we using r6 now?  Does this mean that I have to re-bias?

thanks
-Scott

Did you bias with the scope ?  the R6-C4 point is the injection point for the signal to calibrate as the Matador method ,  there is other way using the RT and SW pad but i dont want to create confusion , so we will stick to Matador Method Now.
Sorry for the confusion.
Dan,
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: saxmonster on April 30, 2012, 12:59:48 PM
Yea i use the rt and sw pads with a scope on my computer and picked the clear middle point between when the distortion points starts at both ends of the screwing in the pot and unscrewing it.

-Scott
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: kante1603 on April 30, 2012, 01:08:09 PM
Scott,

That's o.k.,c4 is just another injection point,it's the point matador suggested for the scope method.
Since somebody else here and me ran into oscillation trouble during measuring via rt using a real scope I gave it a try and it worked out fine for us.
Anyway,I think you're done.

Best,

Udo.
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: poctop on April 30, 2012, 01:36:18 PM
I just Added in the BOM  Udo Suggestion ( thanks Udo)  using molex header for the Traffo connection pad LC, capsule connection and all pad connection it make it easier just have to cut the pin a bit , it makes it cleaner also and more tolerant for resoldering if any  ;D
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: wave on April 30, 2012, 02:09:31 PM
RK-87 arrived today

(http://farm8.staticflickr.com/7178/7128983929_0083dae952.jpg) (http://www.flickr.com/photos/wavedealer/7128983929/)

Now I need my donor mics!

Dave
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: poctop on April 30, 2012, 02:20:40 PM
 :)Wow that Was Quick so it seems you are officialy the First Beta Tester , wich traffo will compliment this one ?




Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: wave on April 30, 2012, 02:35:17 PM
:)Wow that Was Quick so it seems you are officialy the First Beta Tester , wich traffo will compliment this one ?

Dan,
I am going to test this capsule in 2 flavors.

1. All styrenes and the AMI T-13
2. Mica, Films and electros and the Cinemag 2480

You actually might get to the testing first as I'm still waiting for the donor mics.

Dave
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: marshman on April 30, 2012, 02:39:03 PM
Quick question regarding the idss...

when measuring this, is there an optimum value to look for? Highest? Lowest?

Thanks,

mm
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: berkleystudios on April 30, 2012, 03:22:13 PM
Just got my capsule today!!!

i will be doing mine with the cm2480 flavor. once cinemag ships it of course....
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: poctop on April 30, 2012, 03:32:04 PM
Quick question regarding the idss...

when measuring this, is there an optimum value to look for? Highest? Lowest?

Thanks,

mm

Lower is Better, if you can find between 8-12 you will be in the nominal range and you will be fine, 
Dan,
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: kante1603 on April 30, 2012, 07:24:24 PM
:)Wow that Was Quick so it seems you are officialy the First Beta Tester , wich traffo will compliment this one ?

Dan,
I am going to test this capsule in 2 flavors.

1. All styrenes and the AMI T-13
2. Mica, Films and electros and the Cinemag 2480

You actually might get to the testing first as I'm still waiting for the donor mics.

Dave
Wow Dave,that´s cool.
I´m really interested in how the old or vintage version compares to the budget but modern style flavor wise.
Will you build 2 microphones at the same time or one after the other-having both at the same time is better to compare since one can test record from the same source.

Cheers,

Udo.
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: kante1603 on April 30, 2012, 07:35:29 PM
Quick question regarding the idss...

when measuring this, is there an optimum value to look for? Highest? Lowest?

Thanks,

mm
Hi,

look for lowest.
The Fairchild spec sheet says the lowest IDSS is 2mAs,the max. is at 20mAs.
Have tested a couple of them,arround 40 pieces.
Most where in the range of 10 to 12mAs,none exceeded 14mAs.
I have one with 8,7mAs in my build,and the best I found is at 5,9mAs.
So I think it´s worth to shoot out a bunch of them.They´re cheap and easy to source.Here in germany they are at 15 Euro cents for a single,price will decrease a bit when bought in hundrets or so.
For this I have made a small veroboard for easily testing them.
The pics:

(http://img402.imageshack.us/img402/8742/idsschecker.jpg)

(http://img37.imageshack.us/img37/3460/idsscheckerclose.jpg)

A nice little helper that cost nearly nothing and takes just 5 minutes to solder.

Best,

Udo.
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: adeptusmajor on May 01, 2012, 01:24:24 AM
a couple of pictures:

(http://www.groupdiy.com/gallery/0/38684-010512010454.jpeg)

(http://www.groupdiy.com/gallery/0/38684-010512010554.jpeg)


and a link to a thread I made just for the gearslutz, with a few more explicit pictures  ;D

http://www.gearslutz.com/board/so-much-gear-so-little-time/724466-check-out-pair-u87s-i-built.html (http://www.gearslutz.com/board/so-much-gear-so-little-time/724466-check-out-pair-u87s-i-built.html)
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: marshman on May 01, 2012, 07:40:58 AM
Thanks Dan and Udo!

Udo, I built a test rig almost identical to what you have. Worked great. I tested both ways (resistor/voltage drop and current) just for the experience and got pretty much identical numbers.

The two lowest I had were 10.20, so I am using those.

Thanks!

mm
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: kante1603 on May 01, 2012, 07:57:47 AM
Thanks Dan and Udo!

Udo, I built a test rig almost identical to what you have. Worked great. I tested both ways (resistor/voltage drop and current) just for the experience and got pretty much identical numbers.

The two lowest I had were 10.20, so I am using those.

Thanks!

mm
Hi marshman,

Yep,that's nearly the middle of 2 and 20 mAs,you're ready to go! ;)

Udo.
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: poctop on May 01, 2012, 10:12:53 AM
Hi All,  Matt from Microphone Parts is looking for 1-2  Beta tester excluding myself  ;D,  to have a try to the capsule rK87  the only thing is that the capsule will be sent to the person who's having the whole mic built and ready to go ,wihout capsule, because he'd like to have feedback as quickly as possible question of planning for the future ,

http://microphone-parts.com/rk87-microphone-capsule/

those Beta Tester who are interested please PM as soon as you can there is only 2 opening,  :o 

Dan,  :)

Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: poctop on May 01, 2012, 11:20:15 AM
Quote
and a link to a thread I made just for the gearslutz, with a few more explicit pictures 

http://www.gearslutz.com/board/so-much-gear-so-little-time/724466-check-out-pair-u87s-i-built.html


I really would like to see the Kissing picture here out too, Love it or Love em  :-*
congrats
Dan,
 
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: rmaier on May 01, 2012, 02:05:12 PM
Congratulations on your builds, Adept - very nice, the finish looks great. Judging by the photos, it seems safe to assume you're happy with the twins!
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: kante1603 on May 01, 2012, 02:17:04 PM
Yes,congrats from germany too,well done!

Have fun fecording,

Udo.
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: HellfireStudios on May 01, 2012, 03:20:17 PM
I ordered a Peluso BV11P just before I found out about the T13. So I was wondering about a few things. Will the BV11P work with the U-87i circuit? (I've heard that the ratio is 5:1) Also, can someone confirm that this is the correct ratio for the BV11P? I know more output would result, but would biasing become problematic? Thanks.

-James
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: adeptusmajor on May 01, 2012, 07:27:20 PM
Thanks for the comments everyone.

Dan - to answer some of your questions from your PM - I used the Peluso capsules from the group buy and the AMI transformers, polystyrene and tantalum caps, and the mica. I had the mics working perfectly with the trimmers in there, didn't really get to put them through their paces because I didn't have a shockmount that I trusted enough at the time, but they were sounding great on the few tests I did. I replaced the trimmers with resistors after finding the bias value, and after about 80-100 resistors I guess I still didn't get a pair that were close enough to the trimmer values. I now have some hissing and distortion in both mics, so I am putting the lower profile side adjust trimmers in both mics and calling it a day. I just wasn't comfortable with the amount of stress that the mic body was putting on the original trimmers, they had to come out. Anyway, I PM'ed you regarding my interest in Matt's beta test, I would be glad to help if you'd like me to.
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: adeptusmajor on May 01, 2012, 07:34:14 PM
Quote
and a link to a thread I made just for the gearslutz, with a few more explicit pictures 

http://www.gearslutz.com/board/so-much-gear-so-little-time/724466-check-out-pair-u87s-i-built.html


I really would like to see the Kissing picture here out too, Love it or Love em  :-*
congrats
Dan,


Well, I try to keep the "low brow" trolling efforts over at gearslutz, seems the only thing that place is good for anyway, but since you asked nicely:


(http://www.groupdiy.com/gallery/0/38684-010512193017.jpeg)
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: poctop on May 01, 2012, 07:41:23 PM
Thanks for the comments everyone.

Dan - to answer some of your questions from your PM - I used the Peluso capsules from the group buy and the AMI transformers, polystyrene and tantalum caps, and the mica. I had the mics working perfectly with the trimmers in there, didn't really get to put them through their paces because I didn't have a shockmount that I trusted enough at the time, but they were sounding great on the few tests I did. I replaced the trimmers with resistors after finding the bias value, and after about 80-100 resistors I guess I still didn't get a pair that were close enough to the trimmer values. I now have some hissing and distortion in both mics, so I am putting the lower profile side adjust trimmers in both mics and calling it a day. I just wasn't comfortable with the amount of stress that the mic body was putting on the original trimmers, they had to come out. Anyway, I PM'ed you regarding my interest in Matt's beta test, I would be glad to help if you'd like me to.

Do you mean the mic was not hissing or distorting before  you replaced R11? we have some upper little margin there, better put it a bit higher so you go past the point where the FET opens and surely not be arround this point just digging into spl a bit , have you scope biased .  ?
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: poctop on May 01, 2012, 07:55:10 PM
I ordered a Peluso BV11P just before I found out about the T13. So I was wondering about a few things. Will the BV11P work with the U-87i circuit? (I've heard that the ratio is 5:1) Also, can someone confirm that this is the correct ratio for the BV11P? I know more output would result, but would biasing become problematic? Thanks.

-James

I must have misheard from John the BV11 is 5:1  :o it will not belong here then , i will try confirming that with him as the impedance ratio as well, if it is not the Case then i will remove that erroneous information , my appologies.
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: adeptusmajor on May 01, 2012, 09:13:01 PM


Do you mean the mic was not hissing or distorting before  you replaced R11? we have some upper little margin there, better put it a bit higher so you go past the point where the FET opens and surely not be arround this point just digging into spl a bit , have you scope biased .  ?

I returned your pm regarding this. I did bias with a scope, and the hissing was after I put a fixed resistor in. What you are saying makes sense because the values of the resistors were slightly low. I don't think I had but a few from the batch I got that were higher values, or nearly as close to what I needed. I will look again. If not I will probably put the old trimmers back in place while I wait for a lower profile ones. I was able to get the old ones to fit in the body, it was just tighter than I would like it to be, especially if I am removing the body every time I want to change the pattern.

I know somebody had a picture on here with a shorter side adjust trimmer, anyone have the mouser part number? Searching anyway...
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: poctop on May 01, 2012, 10:43:51 PM
Here is a new pot that i added in the Bom,

it is 3mm lower than the original and only 4mm wide so it should be fitting even better in any body, it is 12 turns.http://www.mouser.com/ProductDetail/Murata/PV37X253C01B00/?qs=sGAEpiMZZMukHu%252bjC5l7YWQ4frFPcQ6jyZnR59GhPbA%3D (http://www.mouser.com/ProductDetail/Murata/PV37X253C01B00/?qs=sGAEpiMZZMukHu%252bjC5l7YWQ4frFPcQ6jyZnR59GhPbA%3D)

Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: HellfireStudios on May 01, 2012, 11:04:50 PM
I must have misheard from John the BV11 is 5:1  :o it will not belong here then , i will try confirming that with him as the impedance ratio as well, if it is not the Case then i will remove that erroneous information , my appologies.

If the BV11P is supposed to be similar to the BV11, the ratio should be around 10:1 based on the AMI info on their BV11 replacement. Others have stated the BV11P as 11.5:1. I'm still without a definitive answer, and Mr. Peluso hasn't answered my email yet. Is there any way to test the transformer before sticking it in the mic?
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: poctop on May 01, 2012, 11:20:21 PM
I must have misheard from John the BV11 is 5:1  :o it will not belong here then , i will try confirming that with him as the impedance ratio as well, if it is not the Case then i will remove that erroneous information , my appologies.

If the BV11P is supposed to be similar to the BV11, the ratio should be around 10:1 based on the AMI info on their BV11 replacement. Others have stated the BV11P as 11.5:1. I'm still without a definitive answer, and Mr. Peluso hasn't answered my email yet. Is there any way to test the transformer before sticking it in the mic?

If you do find out let me know as i can correct the infomation in the thread  :P,
Dan,
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: wave on May 01, 2012, 11:35:29 PM
Don't you hate when a better part for the job is discovered after you've already ordered all the parts for your build?
I sure do (sigh). It's a good thing I'm working on like 4 different projects right now and I'm sure another Mouser order is right around the corner.

So I've got this idea for some mic body finishing (if using the standard brass Aurycle body) totally in the spirit of DIY including a custom mic badge that hopefully will be easy to form to the radius of the mic body. I've got some sample aluminum stock on the way. If everything works out, I will post a guide on doing everything.
Stay tuned...

Dave
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: poctop on May 02, 2012, 12:09:06 AM
Quote
Don't you hate when a better part for the job is discovered after you've already ordered all the parts for your build?
I sure do (sigh). It's a good thing I'm working on like 4 different projects right now and I'm sure another Mouser order is right around the corner.


Using the Aurycle body wich is pretty tight ,all i had to do is to file a bit the edge corner of the pot and it slides right in, Maybe the other pot will make it even easier no filing at all,  i prefer it out (solder with wire) to bias and forget about the pot.
Dan, 
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: kante1603 on May 02, 2012, 09:14:48 AM
So I've got this idea for some mic body finishing (if using the standard brass Aurycle body) totally in the spirit of DIY including a custom mic badge that hopefully will be easy to form to the radius of the mic body. I've got some sample aluminum stock on the way. If everything works out, I will post a guide on doing everything.
Stay tuned...

Dave
Hi Dave,

funny I did the same yesterday.Took the cover of an old hard disc drive and put a transparent inkjet foil on it.Looks very nice.
I experimented with a lot of kitchen tools to get them bent.There are some nice working solutions.
Have put clear laquer on it,it´s drying at the moment.
Will report back when I´m done,

cheers,

Udo.
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: kante1603 on May 02, 2012, 09:21:16 AM
I know somebody had a picture on here with a shorter side adjust trimmer, anyone have the mouser part number? Searching anyway...
Hi,

that was me.Bad news is I don´t have mouser parts numbers since I´ve sourced it here in germany,sorry :-\
See my replies #299 and #305.

Cheers,

Udo.
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: wave on May 02, 2012, 11:03:07 AM
Udo,
That is a great idea. God knows I have enough old hard drives around here. Time to re-purpose them!

Dave
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: kante1603 on May 02, 2012, 01:28:22 PM
Udo,
That is a great idea. God knows I have enough old hard drives around here. Time to re-purpose them!

Dave
Yes Dave,

this is true diy!
Here´s a little "proof" of my prototyped badges,I was just fooling around with colours and materials-because I´m still bored of waiting....
This is the "How To Create Badges" from hard discs,should we open a thread for it ;D
(BTW:I still don´t know how to bias a cheesecake).
Will do more experiments,I might have a sheet of chromium metall somewhere,who knows.....

Have fun!

Udo ;)
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: wave on May 02, 2012, 02:26:18 PM
I dig it! I actually ordered an aluminum sample pack from an online metal place.
It's 6 - 4"x4" sheetes in various thicknesses (pretty thin tho) Should be easy to bend. I've been talking to Chae at Prodigy engraving about laser engraving them as he did a great job with my first batch

(http://farm8.staticflickr.com/7119/7136302513_e4bbaa1f20.jpg) (http://www.flickr.com/photos/wavedealer/7136302513/)

These are 2mm anodized aluminum and were pretty hard to bend. I ended up using a ratchet strap with the badge on a piece of steel pipe first. A little hammering also helped  :)

Dave
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: kante1603 on May 02, 2012, 02:36:18 PM
Wow!Looking great!

Udo.
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: poctop on May 02, 2012, 02:41:49 PM
This is amazing stuff hooray for recycling and having fun doing it , you guys are impressive,

Can't wait to see those working mic under those badges  ;)

Dan,
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: kante1603 on May 02, 2012, 03:17:13 PM
Yes,that's a lot of fun!
The more I'm waiting for my trafos the more ideas come to my mind.
Next step is modelling a mic body from potato salad with a head basket from crocheted parsley ;D

Udo.
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: HellfireStudios on May 02, 2012, 04:11:11 PM
Just some info I was able to obtain about the BV11P transformer.
I tested the step-down voltage of the BV11P against the CM-2480. The 2480 takes 10.6VAC to about 1VAC off the secondary. This indicates the 10:1 ratio is accurate. The BV11P takes the same voltage down to only 2.2VAC. I can only assume this means it is in fact a 5:1. Please tell me I am wrong.

The 2480 I have is for a Royer mod I'm in the middle of. I'd hate to stall that project while waiting to afford the 4-5 Cinemags I'm going to need next.
I should find out if the BV11P would work in that circuit... I just hope I didn't waste my time/money.
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: poctop on May 02, 2012, 06:26:41 PM
Just some info I was able to obtain about the BV11P transformer.
I tested the step-down voltage of the BV11P against the CM-2480. The 2480 takes 10.6VAC to about 1VAC off the secondary. This indicates the 10:1 ratio is accurate. The BV11P takes the same voltage down to only 2.2VAC. I can only assume this means it is in fact a 5:1. Please tell me I am wrong.

The 2480 I have is for a Royer mod I'm in the middle of. I'd hate to stall that project while waiting to afford the 4-5 Cinemags I'm going to need next.
I should find out if the BV11P would work in that circuit... I just hope I didn't waste my time/money.

i am sorry to hear this and i will take all the blaim for it , i was totally induced in error from my conversation with John, so i removed all reference to this transfomer since it is 5:1 ratio like as you determined ,  that does not mean that the traffo will not work tough you will proably end up with more gain and a slighty different impedance ratio but i think it would still worth a try you could be surprise by the result in a good manner i hope. 
Sincerly
Dan,
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: wave on May 02, 2012, 07:16:16 PM
Hey Udo,
I forgot to ask, what did you end up cutting your aluminum with? I'm diggin the way you're doing it – super DIY!

Dave
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: Blue Jinn on May 02, 2012, 07:36:35 PM
Quote
Just some info I was able to obtain about the BV11P transformer.
I tested the step-down voltage of the BV11P against the CM-2480. The 2480 takes 10.6VAC to about 1VAC off the secondary. This indicates the 10:1 ratio is accurate. The BV11P takes the same voltage down to only 2.2VAC. I can only assume this means it is in fact a 5:1. Please tell me I am wrong.

FWIW/FYI, I'm getting a pair of "BV11" transformers from AAMicrophones for the HST-11a mod. His specs are 5:1 also.
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: kante1603 on May 03, 2012, 01:33:34 AM
Hey Udo,
I forgot to ask, what did you end up cutting your aluminum with? I'm diggin the way you're doing it – super DIY!

Dave
Hi Dave,

In german it is called "Blechschere",I guess it's "metal shear",a small one.

Udo.
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: HellfireStudios on May 03, 2012, 09:39:01 AM

FWIW/FYI, I'm getting a pair of "BV11" transformers from AAMicrophones for the HST-11a mod. His specs are 5:1 also.

That's what I was afraid of...
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: saxmonster on May 03, 2012, 09:56:24 AM
what size wire is used on the transformers.  I am looking for heat shrink tubing for that size wire and some for 1/4w resistors and components.  What size tubing should i get?
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: HellfireStudios on May 03, 2012, 10:44:27 AM
what size wire is used on the transformers.  I am looking for heat shrink tubing for that size wire and some for 1/4w resistors and components.  What size tubing should i get?

If left in the original transformer casing, electrical tape would be a fine alternative to heat shrink tubing (no one would see the ugliness that accompanies electrical tape either). If not, the smallest size at Radioshack (usually in multi-size packs) will work. The transformer wires tend to pretty thin.
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: Matador on May 03, 2012, 12:21:06 PM

FWIW/FYI, I'm getting a pair of "BV11" transformers from AAMicrophones for the HST-11a mod. His specs are 5:1 also.

That's what I was afraid of...

All may not be lost....what will you be plugging this mike in to?  What kind of preamp?
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: poctop on May 03, 2012, 03:29:50 PM
 :o :o I tought i was driving nuts but i finally decided to call John Peluso myself and asked him again about the BV11P and said that the BV11P is really 10:1   ;D ;D  i said his first batch long time ago had a tap for 5:1 and 10:1 operation and this is the source of the confusion,

I am really pleased to annonce that your BV11P will be just fine afterall,  Sometime information maybe misleading but the Conversation on the phone with the creator is for sure the right thing, Enjoy!

Cheers,

Dan, 
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: Blue Jinn on May 03, 2012, 04:25:18 PM
I'm still confused (although that isn't hard to do)

Dave Thomas's BV11's are published at  5:1 (I don't have one yet)

This thread says the orig BV11 was 5:1: http://www.groupdiy.com/index.php?topic=34417.0 and hellfirestudios voltage test for the BV11P vs the C-2480 were different. (see post from 2 May)

However, AMI says their T49 is the same as the BV11 and states a 10:1 ratio....

Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: poctop on May 03, 2012, 05:18:06 PM
I'm still confused (although that isn't hard to do)

Dave Thomas's BV11's are published at  5:1 (I don't have one yet)

This thread says the orig BV11 was 5:1: http://www.groupdiy.com/index.php?topic=34417.0 and hellfirestudios voltage test for the BV11P vs the C-2480 were different. (see post from 2 May)

However, AMI says their T49 is the same as the BV11 and states a 10:1 ratio....

I did mentionn those data to John and he did not seems to worried about that he said that the actuall ratio of the cinemag maybe just be higher than it spec,  the only thing i can confirm for sure is that if you ask John personnally yourself he will tell you that it is a 10:1  wich is why i did originally included the BV11P as potential traffo , i did removed it tough since this confusion, and intersting thing i mentionned also was that his c12 style t14 are actually 14:1
Hope this helps.
Dan,
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: saxmonster on May 03, 2012, 10:15:41 PM
Hey Guys,
Ok I was doing a little testing and fooling around with the microphone and recording and this is a new first or i never really noticed it before.  As I was recording and listening to dead air I heard some little popping in the mic.  Its not the preamp or anything else except for that little ground hum I need to fix.  I crank the gain up on my 1073 clone.  I hook up my akg c414 and did not hear any little pops.  But once I plug the 87 back in I can hear them.  Now granite they are very low and you probably wound not hear them in a mix but I gotta figure out what is causing the little pops.

here is an mp3 to listen to, hope fully you can hear them i did juice the mic up for it.

http://www.ehornstudios.com/media/little%20pops.mp3

-Scott
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: poctop on May 03, 2012, 11:50:26 PM
Hey Guys,
Ok I was doing a little testing and fooling around with the microphone and recording and this is a new first or i never really noticed it before.  As I was recording and listening to dead air I heard some little popping in the mic.  Its not the preamp or anything else except for that little ground hum I need to fix.  I crank the gain up on my 1073 clone.  I hook up my akg c414 and did not hear any little pops.  But once I plug the 87 back in I can hear them.  Now granite they are very low and you probably wound not hear them in a mix but I gotta figure out what is causing the little pops.

here is an mp3 to listen to, hope fully you can hear them i did juice the mic up for it.

http://www.ehornstudios.com/media/little%20pops.mp3

-Scott
Well, for sure i will not hear this with my laptop speaker  ;D
You do have abnormal crackle artefact at -60 db you should consider checking for [RC] [FC] section and also the [G] Pad for flux contamination or grease, clean with alcool  or fluxsolv between the pads, That should take care of the problem.
hope that helped.
Dan,
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: saxmonster on May 04, 2012, 06:53:15 AM
Thanks Dan,
I did clean the area in between the pads of Fc and Rc.  I scraped these areas with a tool I have and I also used isopropyl alcohol to clean it.  Its still there but it might be a tad softer, hard to tell though.

can I remove the capsule wires to see if its there without the wire connected?

The only thing I did was bias with a scope on the rt and sw section.  I have a little solder left on those rings from when  I soldered a wire on to each area.  Could this be causing it.

Could a component be bad, maybe a cap or resistor?

What is the best way to put new ends on the capsule wires,  they are very thin.  Too thin for strippers.

Thanks
-Scott


Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: poctop on May 04, 2012, 08:58:23 AM
did you clean arround the (G pad) on the board where is the capsule connection, check you gate solder point,  chack the cleaniliness of the board underneath also,have you been using the telfon standoff for the FET connection the gate pin is lifted.
Dan,
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: HellfireStudios on May 04, 2012, 08:59:32 AM

What is the best way to put new ends on the capsule wires,  they are very thin.  Too thin for strippers.

Thanks
-Scott

Some have suggested using the tip of their soldering iron to burn it off does the trick. I think it might be messy at best, and detrimental to the iron at worst. I suggest, with the capsule protected, using a lighter or other small flame source to heat the wire sleeve to a just-barely-melted state, and quickly pull off the desired amount with your fingerrnails. A small set of scissors or needle nosed pliers have done stand-in work for my fingernails on occasions when the sleeving was too hot to touch. Hope this helps.

-James-
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: saxmonster on May 04, 2012, 09:37:00 AM
Capsule pads are clean so is the G area.  Don't know what it could be, could I have damaged it by inserting to loud of a signal during biasing.  Cause it took me a while to figure out how to do it properly.  maybe a component is going bad.  Can I test anything with me dmm?
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: poctop on May 04, 2012, 09:58:02 AM
Capsule pads are clean so is the G area.  Don't know what it could be, could I have damaged it by inserting to loud of a signal during biasing.  Cause it took me a while to figure out how to do it properly.  maybe a component is going bad.  Can I test anything with me dmm?

I Guess what you could do is try a new FET in and Rebias,   FET transistor are very fragile entity so it is possible you may have damaged it
Been there done that with FET and Zener also,

Dan,
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: poctop on May 04, 2012, 10:03:38 AM
Here is a pointer on Really good solder any ongoing future project  ;)  it is no clean solder type with virtually no flux 0.81mm it is smooth as butter and leave virtually no residue , this is the best stuff i had a chance to try and i have been using it for years now,

Dan,

Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: saxmonster on May 04, 2012, 10:56:20 AM
I put a new fet in and its doing the same thing, so I put the old one back in, hahahaha.  I just don't remember hearing the sound before so I don't think it was always there.  And this was the first I used the mic since i baised it two weeks ago.  What supplys the phantom power to the mic.  Becasue of the non consistent noise maybe its releated to that?

I hope this can be fix, getting nervous, I am sure it can be
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: kante1603 on May 04, 2012, 02:39:58 PM
I put a new fet in and its doing the same thing, so I put the old one back in, hahahaha.  I just don't remember hearing the sound before so I don't think it was always there.  And this was the first I used the mic since i baised it two weeks ago.  What supplys the phantom power to the mic.  Becasue of the non consistent noise maybe its releated to that?

I hope this can be fix, getting nervous, I am sure it can be
Hi,
Please let us know a bit more of the surrounding conditions.
As this seems to be non-consistant the causes can be the outside of the mic as well as the inside.
Easy check is to shoot out the outside.Just plug the mic to another channel,swap the xlr cable.
After this you'll know a lot more.
When it is the mic itself we must know a little bit more to help you.
What's the gain on your preamp or channel input set to and how exactly do you monitor this?
We need as much as possible info!Sometimes it's not the issue you're looking at (the mic ) but something completely different-maybe just a broken headphone amp or a section on the monitor controller etc.So let's shoot these possibilities out first.Maybe you have never noticed it because any signal will cover these plops.
O.K.,up to here.
Next step is investigating the mic.The plops don't sound like a loose wire,more like a part is charging and discharging randomly.Can be a faulty cap.
A very important question is then in which mode this happens?
If it is in cardioid check the plops again,listen to them and switch the mics hpf in and out.If the sound of the plops change then I bet it's the capsule itself.If not it must be after it in the circuit,I would still think then it is in the high impedance part.

So first make clear all surrounding stuff and the listening situation.

Let us know,good luck,

Udo.
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: saxmonster on May 04, 2012, 06:29:13 PM
This is what I did so far.

I know it's not the preamp or headphones or cable.  I plugged in a different mic that needed phantom power and it's not there.  I reattached the capsule pads and transformer pads and cleaned along them before and after I reattached.  With alcohol. I replaced the fet and swapped c6 with a wima cap.  I also replaced the pot with resistors that added up to it.  Still snapping crackeling and popping granite  It is soft.  Just shouldn't be there.  Could it be a cap or what. How About the capsule wire over heating from attaching on and off many time,  errr I just want it to be fix, hahhahahah.
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: HellfireStudios on May 04, 2012, 08:05:26 PM
My Peluso BV11P test results are in. After mutiple rounds of testing. I finallly came up with a way to get the results I know I heard. This is the signal path:

I ran the output of a cable tester's signal generator to the secondary of both the Cinemag and the Peluso transformers (I'm using them in reverse for step-up operation). Their primary sides were sent to two sides of a very handy A/B box. The box's output was then routed to a small Marshall Guitar amp. A KRK reference omni was pointed directly at the center of the speaker (like it matters in omni). An iPad2 and Alesis I/O Dock were set up to provide preamp, phantom power, and register SPL through the SignalScopePro app (not cheap) from the KRK mic. Canare quad core cable with Neutrik XLR's were used for the mic signal.

My, hopefully scientific enough, results are:

The Cinemag CM-2480 was measured at 91dB. With no changes to mic placement or wiring, the Peluso BV11P was switched in place of the Cinemag via the aforementioned A/B box. It measured 87.9dB. That's a tad over 3dB. If memory serves, when a signal is doubled (like when duplicating a track in your DAW) it's output increases by 3dB. This alone indicates to me that the Peluso is only stepping up the voltage by 1/2 the amount the Cinemag is. In this reversed-from-normal operation, their outputs should have been similar. If the Peluso is over spec'd, as John claimed it might be, It's output should have been slightly higher not 3dB lower. As far as I'm concerned the information at hand proves what the voltage tests told me days ago. This Peluso BV11P is a 5:1.

If anyone, with more knowledge than I, could find fault in my testing method or outcome. Please speak up. I don't want to be right, but I'm afraid I might be.

-James-
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: poctop on May 04, 2012, 10:20:29 PM
My Peluso BV11P test results are in. After mutiple rounds of testing. I finallly came up with a way to get the results I know I heard. This is the signal path:

I ran the output of a cable tester's signal generator to the secondary of both the Cinemag and the Peluso transformers (I'm using them in reverse for step-up operation). Their primary sides were sent to two sides of a very handy A/B box. The box's output was then routed to a small Marshall Guitar amp. A KRK reference omni was pointed directly at the center of the speaker (like it matters in omni). An iPad2 and Alesis I/O Dock were set up to provide preamp, phantom power, and register SPL through the SignalScopePro app (not cheap) from the KRK mic. Canare quad core cable with Neutrik XLR's were used for the mic signal.

My, hopefully scientific enough, results are:

The Cinemag CM-2480 was measured at 91dB. With no changes to mic placement or wiring, the Peluso BV11P was switched in place of the Cinemag via the aforementioned A/B box. It measured 87.9dB. That's a tad over 3dB. If memory serves, when a signal is doubled (like when duplicating a track in your DAW) it's output increases by 3dB. This alone indicates to me that the Peluso is only stepping up the voltage by 1/2 the amount the Cinemag is. In this reversed-from-normal operation, their outputs should have been similar. If the Peluso is over spec'd, as John claimed it might be, It's output should have been slightly higher not 3dB lower. As far as I'm concerned the information at hand proves what the voltage tests told me days ago. This Peluso BV11P is a 5:1.

If anyone, with more knowledge than I, could find fault in my testing method or outcome. Please speak up. I don't want to be right, but I'm afraid I might be.

-James-
  since i dont own any more bv11p i would strongly suggest that you give a call to John yourslef and explain your findings to him,
i think that would be important to this stage . he always answer the phone when he is in is workshop, he is quitly available and ressourfull when you talk to him.
Hope this will help figuring out this ordeal of Bv11,
Dan,
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: kante1603 on May 04, 2012, 11:15:25 PM
This is what I did so far.

I know it's not the preamp or headphones or cable.  I plugged in a different mic that needed phantom power and it's not there.  I reattached the capsule pads and transformer pads and cleaned along them before and after I reattached.  With alcohol. I replaced the fet and swapped c6 with a wima cap.  I also replaced the pot with resistors that added up to it.  Still snapping crackeling and popping granite  It is soft.  Just shouldn't be there.  Could it be a cap or what. How About the capsule wire over heating from attaching on and off many time,  errr I just want it to be fix, hahhahahah.
O.K.,
seems to be the mic.
But for the further checks:You have only repeated what you have already written in your previous posts but did not answer my questions.Again,this is really important.If we don't have enough information we can not help you.Especially the hpf check as mentioned would be interesting now.

Udo.

P.S.:In what invironment did you record the sound sample,was that kind of a dead room?What was the gain setting on the pre?

Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: kante1603 on May 05, 2012, 12:28:38 AM
@James

Hi,
duplicating a track in a daw will result in +6 dB,not 3.Don't swap dB calcs ( that's a different story).
Actually there's a nice discussion about how to identify tech. specs of transformers here:

http://www.groupdiy.com/index.php?topic=48544.0

Maybe you can get better info on yours with one of the described methods there....

Hope to have helped,

Udo.
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: HellfireStudios on May 05, 2012, 01:17:38 AM
Even a three decibel output difference is far too much. Especially for transformers said to have the same ratio. Voltages don't lie (most of the time). The difference in output was corresponding with what my ears heard and what the SPL meter read.
In proper orientation for this circuit, I would likely see a 3dB increase in volume. While that sounds good in theory, wouldn't Neumann have put a cheaper-to-manufacture and louder-output-to-boot transformer in their mics in the first place? Unless, of course, the impedance would be off, and the tonal shift from preamp to preamp would be unlike the original we are trying so hard to copy.
I'll be giving John a call very soon. He was pleasant the last time I spoke with him. I wouldn't think he would knowingly sell a 5:1 as a 10:1. I'll see if I can get this resolved quickly, and get back with some answers probably only I need...
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: wave on May 05, 2012, 01:56:39 AM
Just got home from a gig. Somebody was nice enough to drop a little box with donor mics in it  :)

Tomorrow we shall have some audio samples of the RK-87.

First up vintage flavor...

Dave
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: kante1603 on May 05, 2012, 02:06:40 AM
Just got home from a gig. Somebody was nice enough to drop a little box with donor mics in it  :)

Tomorrow we shall have some audio samples of the RK-87.

First up vintage flavor...

Dave
Very nice Dave,
I'm really curious how this works out.

Have fun,

Udo.
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: kante1603 on May 05, 2012, 03:02:18 AM
Even a three decibel output difference is far too much. Especially for transformers said to have the same ratio.
Agreed.
Voltages don't lie (most of the time).
Wrong,it depends on the measuring method (e.g. the loads) and-if done with a dmm-if it is capable to really read a voltage at say 1kHz etc.
I'll be giving John a call very soon. He was pleasant the last time I spoke with him. I wouldn't think he would knowingly sell a 5:1 as a 10:1. I'll see if I can get this resolved quickly, and get back with some answers probably only I need...
I can´t imagine that either.Please keep us posted even if it´s just "only" your problem,it might help others in the future.

Btw:Matador was kind enough to write something for a possible work-around in your case.Have you replied?Just curious,I guess I know what he´s refering to.

Good luck,

Udo ;)
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: DUDE GUY on May 05, 2012, 04:04:48 AM
Hello all,
 
I hope your builds are going well. Mine seems to have hit a wall. First, some
perspective:
 
Source V: 48.0V
L1 & L2: 46.6V
Zener: 22.88V
R18: 46.6V
R19: 46.1V
Top of R17: 22.89V
FET Drain: 10.53V
FET Source: 2.62V
R12: 10.54V
R13: 43.4V
R14: 20.73V
R8: 39.7V
 
Issues:
 
1. The mic will not output the 1k sine tone. I see it on the scope, but cannot
see any signal coming back into my daw (I've checked my signal chain going to my
daw and all is good). Thoughts?
 
2. I attempted the bias procedure, but the only symmetrical distortion I can
achieve looks like the attached picture and I assume this is bad. My scope is
pretty old, maybe it's the problem?
 
Your help is very much appreciated, thanks everyone.
 
- DUDE GUY
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: DUDE GUY on May 05, 2012, 04:08:02 AM
Here's another shot of my scope with the 1k sine tone at a higher output.
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: MagnetoSound on May 05, 2012, 05:16:17 AM
Hey there, Dude ...

1. The mic will not output the 1k sine tone. I see it on the scope, but cannot
see any signal coming back into my daw (I've checked my signal chain going to my
daw and all is good). Thoughts?
 
2. I attempted the bias procedure, but the only symmetrical distortion I can
achieve looks like the attached picture and I assume this is bad. My scope is
pretty old, maybe it's the problem?


Where are you scoping that signal? At the drain or coupling cap? If so, that distortion, and the fact that there is no output from the mic, suggest a short at the secondary.

The scope is not the problem.

Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: HellfireStudios on May 05, 2012, 10:56:56 AM
Voltages don't lie (most of the time).
Wrong,it depends on the measuring method (e.g. the loads) and-if done with a dmm-if it is capable to really read a voltage at say 1kHz etc..

Btw:Matador was kind enough to write something for a possible work-around in your case.Have you replied?Just curious,I guess I know what he´s refering to.

[/quote]

I apologize about the misunderstanding. In my other thread about possible uses for a 5:1, I mentioned doing a voltage test with a 10.6VAC supply and read the stepped down voltages at the ends of both transformers. This test indicates the same thing as the listening/SPL test did. Check out the "There's no UNDO button" post for and my findings.
 
Udo, where is the Matador write up on a work around?
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: saxmonster on May 05, 2012, 11:02:30 AM
Udo,

The surrounding conditions are in my project studio /  office where I do most of my recording.  I have used the mic in here before and have done many things in here with other mics and never had a problem.  I have not changed anything in the room either.  I have also run an xlr into the next bedroom with is a dead space and still the popping continued. 

I have tried the mic in different preamps and still get the sound.  I even tried the preamp on a mackie at the school where i teach and it still had the problems.  I have used different wires and cable too, different channels.

The gain is set between 2/3's to 3/4 on the mackie 1604.  Doesn't matter if I give more or less gain the sound still stays consistent in ratio with the s/n ratio of the mic as it gets louder or softer.  I have the headphones plug directly into the mackie and the vol is about halfway up. 

When I switch the hpf the sound is still there too just a little less bass, hahhahahah.  And the -10db switch helps but I can still faintly hear it in there.

Its seem that when the mic is cold it doesn't do it until it warms up.  I will have to check that later though. once its cold again.

Thanks for all your help.
-Scott



I put a new fet in and its doing the same thing, so I put the old one back in, hahahaha.  I just don't remember hearing the sound before so I don't think it was always there.  And this was the first I used the mic since i baised it two weeks ago.  What supplys the phantom power to the mic.  Becasue of the non consistent noise maybe its releated to that?

I hope this can be fix, getting nervous, I am sure it can be
Hi,
Please let us know a bit more of the surrounding conditions.
As this seems to be non-consistant the causes can be the outside of the mic as well as the inside.
Easy check is to shoot out the outside.Just plug the mic to another channel,swap the xlr cable.
After this you'll know a lot more.
When it is the mic itself we must know a little bit more to help you.
What's the gain on your preamp or channel input set to and how exactly do you monitor this?
We need as much as possible info!Sometimes it's not the issue you're looking at (the mic ) but something completely different-maybe just a broken headphone amp or a section on the monitor controller etc.So let's shoot these possibilities out first.Maybe you have never noticed it because any signal will cover these plops.
O.K.,up to here.
Next step is investigating the mic.The plops don't sound like a loose wire,more like a part is charging and discharging randomly.Can be a faulty cap.
A very important question is then in which mode this happens?
If it is in cardioid check the plops again,listen to them and switch the mics hpf in and out.If the sound of the plops change then I bet it's the capsule itself.If not it must be after it in the circuit,I would still think then it is in the high impedance part.

So first make clear all surrounding stuff and the listening situation.

Let us know,good luck,

Udo.
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: kante1603 on May 05, 2012, 12:24:26 PM
@Hellfire

Hi,

haven't seen the other thread,sorry for that.
I didn't write he has a workaround but a possible one. He's asking you to tell him what preamp you are using,I bet he wants to know the load impedance of it.Might work,give it a try.

Cheers and sorry for overseeing,

Udo.
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: kante1603 on May 05, 2012, 12:55:59 PM


When I switch the hpf the sound is still there too just a little less bass, hahhahahah.  And the -10db switch helps but I can still faintly hear it in there.

Its seem that when the mic is cold it doesn't do it until it warms up.  I will have to check that later though. once its cold again.

Thanks for all your help.
-Scott

O.K. Scott,we're getting closer!
Yes,it is the mic that is faulty,not the listening condition,hahahahaha....... :D
Since the hpf affects the sound we can clearly say that it is coming from the source before(!) the filter,right?And that's the capsule.Please look at the schemo,there are not many parts around it.
Best to check first if this issue is really temperature sensitive.
And you can do another check to get closer to it:
Given that this happens in cardioid mode (you haven't answered that) you can exclude a possible capsule fault from the surrounding parts.Lift the front capsule wires temporarily and swap them to the back capsule.Stay in cardioid mode while testing.Remember you have two nearly identical capsules working there which are even completely isolated from each other.
See if the plops change or even go away,you must check sounds from the back side then.
Have you touched the capsule while mounting,unpacking or screwing to the saddle?

Best,

Udo.

Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: saxmonster on May 05, 2012, 02:00:33 PM
Udo,
Yes the mic is in cardioid.  Its the only pattern on this mic as it is the Aurycle 460 and i don't have switches for it right now.  Now i just started it up again today and this noise wasn't there but as it warmed up and I did some testing 123 through it it came back.  It almost sounds like when you sit in a leather sofa you get that rubbing / popping sound but it is really faint and below the actually headroom of the mic if that makes sense.   I will try the capsule reverse thing later tonight or tomorrow as I have to go to a gig soon.  If both capsules show the noise then it has to be a competent inside on the pcb right?  I was very careful not to touch the capsule at all when installing it.  I just touched the sides where the screws go into to attach it to the mic.

Thanks again
 I will post my results when I flip the capsule sides by flipping the wires.

Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: DUDE GUY on May 05, 2012, 02:34:04 PM
I'm scoping at the drain and I neglected to mention that I have no transformer connected. From what I've read in this thread, I don't need the transformer to bias the FET. Am I mistaken?

Also, I'm injecting the 1k tone at R6 (installed backwards, as suggested by poctop). Correct?

Thanks Magneto.

Hey there, Dude ...

1. The mic will not output the 1k sine tone. I see it on the scope, but cannot
see any signal coming back into my daw (I've checked my signal chain going to my
daw and all is good). Thoughts?
 
2. I attempted the bias procedure, but the only symmetrical distortion I can
achieve looks like the attached picture and I assume this is bad. My scope is
pretty old, maybe it's the problem?


Where are you scoping that signal? At the drain or coupling cap? If so, that distortion, and the fact that there is no output from the mic, suggest a short at the secondary.

The scope is not the problem.
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: kante1603 on May 05, 2012, 03:20:28 PM
Udo,
Yes the mic is in cardioid.  Its the only pattern on this mic as it is the Aurycle 460 and i don't have switches for it right now.  Now i just started it up again today and this noise wasn't there but as it warmed up and I did some testing 123 through it it came back.  It almost sounds like when you sit in a leather sofa you get that rubbing / popping sound but it is really faint and below the actually headroom of the mic if that makes sense.   I will try the capsule reverse thing later tonight or tomorrow as I have to go to a gig soon.  If both capsules show the noise then it has to be a competent inside on the pcb right?  I was very careful not to touch the capsule at all when installing it.  I just touched the sides where the screws go into to attach it to the mic.

Thanks again
 I will post my results when I flip the capsule sides by flipping the wires.
Cool to hear,yes,you're right:If the same plops are audible with the back capsule attached to the front capsule pcb connection then it is just a component,I would guess a cap then.
Thank you for the reply,have a nice gig,

Udo.
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: saxmonster on May 05, 2012, 04:53:59 PM
Would the mic work if I had the capsule totally disconnected this way if I still hear the noise I would know its inside.
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: wave on May 05, 2012, 07:12:13 PM
It should right?
I think you have to put in the 51pF caps in place of the capsule diaphragms tho.

Dany, Udo, anyone else feel free to correct me!

Dave
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: kante1603 on May 05, 2012, 07:48:24 PM
Hi,

looking at the original schemo Neumann specifies both capsule sides having a capacitance of 50pF,so I think yes it should work.
But I'm still interested if it is the same when the front and back capsule flipped  ::)

Cheers,

Udo.

Edit:just in case the plops stay as they did before,do you have styrenes in your mic?I know that styrenes definetely don't like too much heat,only short soldering.Maybe something like that......
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: HellfireStudios on May 06, 2012, 12:55:51 AM

FWIW/FYI, I'm getting a pair of "BV11" transformers from AAMicrophones for the HST-11a mod. His specs are 5:1 also.

That's what I was afraid of...

All may not be lost....what will you be plugging this mike in to?  What kind of preamp?

Sorry, I must have completely missed this post on the first read. The preamp will most likely be a modded GAP Pre73 (1.2k ohm and 300 ohm selectable input impedance/Transformer coupled).  A Trident A-Range Clone may be down the line as well. I apologize again that it took this long to answer.

-James-
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: kante1603 on May 06, 2012, 02:27:38 AM
@Scott,

Did some search on the aurycle site and hopefully I do now get this right when saying you use the stock capsule?Is that the reason why your mic works in cardioid only?
That would make sense then you asking for dropping in a cap instead.
Little confused now(have built DOAs the whole night long and am tired at the moment),

Udo.
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: wave on May 06, 2012, 11:21:12 AM
So I have a few transistors and I don't have a rig like Udo's for testing nor do I have the parts to make one. My question is,
what kind of test can I do with my DMM (true RMS Fluke) to pick the best transistor? The meter does not have a transistor socket

Thanks,
Dave
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: poctop on May 06, 2012, 01:17:40 PM
So I have a few transistors and I don't have a rig like Udo's for testing nor do I have the parts to make one. My question is,
what kind of test can I do with my DMM (true RMS Fluke) to pick the best transistor? The meter does not have a transistor socket

Thanks,
Dave

Lowest Idss you can find ,

here is the method
How To measure FET Idss By Matador :https://io.groupdiy.com/file/gdiy-2017/u/39511/58d02819937f0 (https://io.groupdiy.com/file/gdiy-2017/u/39511/58d02819937f0)
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: wave on May 06, 2012, 01:18:42 PM
Another question:
Does the low cut engage when the pin connections are shorted? The Aurycle comes wired with the switch being closed in the low cut off position. So if the low cut engages on the mic when the pins are shorted the wire on the Aurycle switch needs to be rewired.

Dave
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: kante1603 on May 06, 2012, 01:52:28 PM
Another question:
Does the low cut engage when the pin connections are shorted? The Aurycle comes wired with the switch being closed in the low cut off position. So if the low cut engages on the mic when the pins are shorted the wire on the Aurycle switch needs to be rewired.

Dave
Hi Dave,

Yes,you're right.Somebody else here had the same issue.Please see my reply #153.

Cheers,

Udo.
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: wave on May 06, 2012, 01:57:07 PM
Thanks Udo!
I know I should have gone back and re read the thread but I'm at the point where I just want to be finished with this one.

Here's another which has probably been answered.
Can I solder the 2 50pF caps right to the FC and RC headers the proceed to biasing and testing before I put the actual capsule in?

I know I'm being lazy please feel free to flame me at your leisure :)

Dave
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: kante1603 on May 06, 2012, 02:16:39 PM
Thanks Udo!
I know I should have gone back and re read the thread but I'm at the point where I just want to be finished with this one.

Here's another which has probably been answered.
Can I solder the 2 50pF caps right to the FC and RC headers the proceed to biasing and testing before I put the actual capsule in?

I know I'm being lazy please feel free to flame me at your leisure :)

Dave
Had to look for what your last sentence meant,still learning english,hahaha....
For biasing:No,you leave the capsule pads open,don't solder the caps in.These are meant for replacing the capsule(s) when you are tracking errors and do not want to damage them.
Biasing is done without capsule.

Best,

Udo. ;)
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: wave on May 06, 2012, 02:29:17 PM
Thanks Udo!
I'm trying to assemble some clear concise instructions for the 1K tone listening bias method.

Dave
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: DUDE GUY on May 06, 2012, 02:55:42 PM
Hello All,

I'm having some issues here. I'm not able to see the 1k tone coming out of the mic into my DAW. I can see the 1k at the FET drain and I've checked my signal chain coming out of the mic into my DAW and all is in order. Additionally, my FET bias resulted in symmetrical distortion, but there is clearly something wrong (see attached pic).

Info:

-My scope is connected at the FET drain.
-I have no transformer connected (waiting for a T13)
-I'm injecting the 1k tone at R6 (installed backwards)
-I have no capsule connected and I do not have anything in place of the capsule (i.e. 51 pF caps)

Source V: 48.0V
L1 & L2: 46.6V
Zener: 22.88V
R18: 46.6V
R19: 46.1V
Top of R17: 22.89V
FET Drain: 10.53V
FET Source: 2.62V
R12: 10.54V
R13: 43.4V
R14: 20.73V
R8: 39.7V

According to MagnetoSound, I may have a problem with my secondary. As a total noob, I'm not exactly sure what the secondary is (a second gain stage?) nor do have any idea where to start troubleshooting.

Any help with this would be much appreciated. Thanks very much everyone!!!

-DUDE GUY
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: wave on May 06, 2012, 03:00:54 PM
Can anyone tell me which wires are which on the AMI T-13?

Dave

EDIT: Found it in one of Adeptusmajor's posts
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: poctop on May 06, 2012, 03:01:38 PM
Hello All,

I'm having some issues here. I'm not able to see the 1k tone coming out of the mic into my DAW. I can see the 1k at the FET drain and I've checked my signal chain coming out of the mic into my DAW and all is in order. Additionally, my FET bias resulted in symmetrical distortion, but there is clearly something wrong (see attached pic).

Info:

-My scope is connected at the FET drain.
-I have no transformer connected (waiting for a T13)
-I'm injecting the 1k tone at R6 (installed backwards)
-I have no capsule connected and I do not have anything in place of the capsule (i.e. 51 pF caps)

Source V: 48.0V
L1 & L2: 46.6V
Zener: 22.88V
R18: 46.6V
R19: 46.1V
Top of R17: 22.89V
FET Drain: 10.53V
FET Source: 2.62V
R12: 10.54V
R13: 43.4V
R14: 20.73V
R8: 39.7V

According to MagnetoSound, I may have a problem with my secondary. As a total noob, I'm not exactly sure what the secondary is (a second gain stage?) nor do have any idea where to start troubleshooting.

Any help with this would be much appreciated. Thanks very much everyone!!!

-DUDE GUY

Si if you have been able to have symetrical clipping adjusting the Pot and measure the signal at the drain then this is good,
probalby the reason why you dont see anything in your daw from the mic it is because you have no output trnsformer you need that in order for the mic to generate is output , let me know if that make sense,

hope this helps,

Dany,
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: kante1603 on May 06, 2012, 04:05:31 PM
Hello Dude guy,

Secondary means the second or output winding of your transformer.
There must be two wires going to pins 2 & 3 on the xlr connector.
Measure them for a short,this is what  member magneto meant.

Good luck,

Udo.
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: DUDE GUY on May 06, 2012, 04:21:10 PM
Thanks very much Dany and Udo. So with no transformer installed, I have no output to my DAW. I get that. But why does my scope show that strange distortion? Is this also due to the fact that I have no transformer installed? Thanks for your help.

-DUDE GUY
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: wave on May 06, 2012, 04:24:08 PM
So what about the little black wire that connects to both switches in the stock Aurycle donor mic? Does it need to be connected anywhere?

Also when I inject a 1K sine into the RT and SW pads I use the "+" and "-" from a balanced line with a floating ground on that side?

Dave
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: kante1603 on May 06, 2012, 04:32:38 PM
Thanks very much Dany and Udo. So with no transformer installed, I have no output to my DAW. I get that. But why does my scope show that strange distortion? Is this also due to the fact that I have no transformer installed? Thanks for your help.

-DUDE GUY
No trafo=no output,correct.
Have you checked the original output of your signal generator directly connected to your scope?
This way you can proof a) your generator puts out a sine wave and b) if your scope is working properly.

Cheers,

Udo.
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: kante1603 on May 06, 2012, 04:39:37 PM
So what about the little black wire that connects to both switches in the stock Aurycle donor mic?
Hi Dave,

Don't know the aurycle mic,but if the switches are connected this could(!) be a ground connection.
Measure for continuity to the mic housing or pin 1 on the xlr.
I'm building a B2 so I'm not 100% sure,maybe Dan can chime in?

Udo.
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: poctop on May 06, 2012, 05:15:38 PM
So what about the little black wire that connects to both switches in the stock Aurycle donor mic?
Hi Dave,

Don't know the aurycle mic,but if the switches are connected this could(!) be a ground connection.
Measure for continuity to the mic housing or pin 1 on the xlr.
I'm building a B2 so I'm not 100% sure,maybe Dan can chime in?

Udo.

The black wire is an extension of the ground for both switch body to the basket and mic body ,
i did solder mine to the (gndlink pad) so everyone is happy,
Dan,
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: poctop on May 06, 2012, 05:18:35 PM
Thanks very much Dany and Udo. So with no transformer installed, I have no output to my DAW. I get that. But why does my scope show that strange distortion? Is this also due to the fact that I have no transformer installed? Thanks for your help.

-DUDE GUY

can you make sure that is signal from your tone generator is not just way too hot.. can you actually reduce the level and see a proper sine wave to the Drain pin with the scope also make sure you use a probe with a 10X divider in it ,
Hope this helps,
DAn,
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: DUDE GUY on May 06, 2012, 05:59:37 PM


can you make sure that is signal from your tone generator is not just way too hot.. can you actually reduce the level and see a proper sine wave to the Drain pin with the scope also make sure you use a probe with a 10X divider in it ,
Hope this helps,
DAn,

Hey Dan, I am able to see a clean sine wave with my scope with my signal generator at a low level. And yes, I do have a 10x probe. I can see symmetrical distortion that's similar to what I've seen in other people's posts, except the flattening of my 1k sine occurs at an angle (see pic on post #516). Then if I increase the 1k tone level, I see really strange distortion (see pic on post #517). Thoughts? Thanks.

-DUDE GUY
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: poctop on May 06, 2012, 06:08:13 PM


can you make sure that is signal from your tone generator is not just way too hot.. can you actually reduce the level and see a proper sine wave to the Drain pin with the scope also make sure you use a probe with a 10X divider in it ,
Hope this helps,
DAn,

Hey Dan, I am able to see a clean sine wave with my scope with my signal generator at a low level. And yes, I do have a 10x probe. I can see symmetrical distortion that's similar to what I've seen in other people's posts, except the flattening of my 1k sine occurs at an angle (see pic on post #516). Then if I increase the 1k tone level, I see really strange distortion (see pic on post #517). Thoughts? Thanks.

-DUDE GUY

So if i understand well you obtain symetry at
FET Drain: 10.53V
FET Source: 2.62V
This looks pretty good , the pad and nor the Lcut is not jumpered ,  have your signal probe ground connected to the mic body ,

since you are pretty much in the right condition, i would not be too much worried about the shape of your distorsion at the point that they behave symetrically and this is what is the most important , is your scope set to AC coupling or dC coupling , just a tought.
Keep on the good work, you almost there ,
Dan,

 
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: wave on May 06, 2012, 06:16:08 PM
SO.......
I dont have a scope. I did the listen method. To me I thought it sounded kinda distorted the whole time. I could hear the tone come up in volume then some of the "fizz" go away and come back.

Fine. I put the RK-87 in. Lots of hum until I put the body on. Now there's some capacitor noise (like low thunder) and the signal will drop quieter every now and then but come back.

Besides that the mic sounds pretty good. I have all styrenes in the positions that could use them (10, 220, 470, 560 pF)
Could the noise be coming from one of those? Both the cap noise and the volume drops are intermittent.

Bias pot is still in as I'm not sure I got that right yet.

Dave
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: poctop on May 06, 2012, 06:51:09 PM
SO.......
I dont have a scope. I did the listen method. To me I thought it sounded kinda distorted the whole time. I could hear the tone come up in volume then some of the "fizz" go away and come back.

Fine. I put the RK-87 in. Lots of hum until I put the body on. Now there's some capacitor noise (like low thunder) and the signal will drop quieter every now and then but come back.

Besides that the mic sounds pretty good. I have all styrenes in the positions that could use them (10, 220, 470, 560 pF)
Could the noise be coming from one of those? Both the cap noise and the volume drops are intermittent.

Bias pot is still in as I'm not sure I got that right yet.

Dave

Quote
I put the RK-87 in. Lots of hum until I put the body on
this  perfectly normal as there is no shield for the mic,

Quote
Now there's some capacitor noise (like low thunder) and the signal will drop quieter every now and then but come back.

what is your final Drain voltage ?

could you be more precise on the thunder sounds and capcitor noise i am not sure of those meanings,

can you try setting the pot such as you have arround 11.5V at the drain and try it again to see what happens.

hope this will help,

Dan,


Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: wave on May 06, 2012, 07:17:06 PM
Hi Dan
interestingly enough when I was doing the fet bias my final drain voltage was around 12.2
i manually dialed it back to 10.5 then put the capsule in and listened. dont ask me why I did that.
Could this be the reason that the mic is a bit on the quiet side too?
I will adjust the drain voltage and report back.
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: saxmonster on May 06, 2012, 07:54:21 PM
Ok so I flipped the front with the back capsule and I still have the noise.  I am going to switch some of the caps with the others that came with the the BOM as optional.  Is there an order I should start it or just take a guess and maybe get lucky.  I will keep track of what I do though.

Dave,
This thunder sound that you have, is it very low on the mic.  Like you need to turn the gain up and headphone vol up to really hear it.  This is sorta what my mic is doing too.  Almost sounds like bad electricity or like a capacitor is expanding or when you first sit on a leather sofa.  But in the background or the sound of the mic.

-Scott
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: saxmonster on May 06, 2012, 08:35:30 PM
Ok Guess who has a clean mic sound now!!!!!!!!!!!


OH YEA ITS ME HAHAHAHAHAHAH!!!!!!!!

C1 was the culprit!!!!!!!!!!!!!!!!  Something must have happen to it.  So I will order a new styrene for it but the wima is working very quiet now, hahahaha.

Only 4 components had to be swapped before I found, not to bad.  It could have been a lot worse. HHAHAHAHAH

Thanks again Udo and Dan and everyone else, this is a great mic build.  I must have fried the styrene at some point.

-Scott

Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: wave on May 06, 2012, 08:53:07 PM
Sax,
What kind of noise did you have? My "thunder" noise is very quiet.

Dany,
I changed the drain voltage to 11.5V as you suggested and the mic seems to be better. I haven't heard any of the weird volume drops since and overall I think it's nice and as my friend said - "vintagey"

Here is a link to a clip of me doing an extremely rough vocal for a song I'm working on

http://soundcloud.com/waveaudio/u87-clone-11-5-drain/s-jdZvb (http://soundcloud.com/waveaudio/u87-clone-11-5-drain/s-jdZvb)

Let me know what you think.

Dave
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: Matador on May 06, 2012, 09:00:02 PM


can you make sure that is signal from your tone generator is not just way too hot.. can you actually reduce the level and see a proper sine wave to the Drain pin with the scope also make sure you use a probe with a 10X divider in it ,
Hope this helps,
DAn,

Hey Dan, I am able to see a clean sine wave with my scope with my signal generator at a low level. And yes, I do have a 10x probe. I can see symmetrical distortion that's similar to what I've seen in other people's posts, except the flattening of my 1k sine occurs at an angle (see pic on post #516). Then if I increase the 1k tone level, I see really strange distortion (see pic on post #517). Thoughts? Thanks.

-DUDE GUY

Can we see what the peak-to-peak amplitude is of your input signal (or just show us a scope picture and tell us what the volts/division is set to)?
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: saxmonster on May 06, 2012, 09:23:56 PM
Dave,

I hear is a sound file of the issue.  You might have to crank it a bit and use headphones. It turn out to be C1 a bad styrene cap

http://www.ehornstudios.com/media/little%20pops.mp3

I hope this helps.
-Scott
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: DUDE GUY on May 06, 2012, 11:54:18 PM


can you make sure that is signal from your tone generator is not just way too hot.. can you actually reduce the level and see a proper sine wave to the Drain pin with the scope also make sure you use a probe with a 10X divider in it ,
Hope this helps,
DAn,

Hey Dan, I am able to see a clean sine wave with my scope with my signal generator at a low level. And yes, I do have a 10x probe. I can see symmetrical distortion that's similar to what I've seen in other people's posts, except the flattening of my 1k sine occurs at an angle (see pic on post #516). Then if I increase the 1k tone level, I see really strange distortion (see pic on post #517). Thoughts? Thanks.

-DUDE GUY

Can we see what the peak-to-peak amplitude is of your input signal (or just show us a scope picture and tell us what the volts/division is set to)?

In the pic attached to this post, I'm sending -22.6 dB (Peak-to-Peak) and my volts/division is set to .5. Thanks for your help.

-DUDE GUY
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: kante1603 on May 07, 2012, 02:17:28 AM
Congrats Scott,well done.
Styrenes don't like too much heat,just very short solder times.Maybe that's what it was.
Just for future refence,do you have c1 still laying around,can you measure it for dead short?
Would be nice because we can trace errors better then.

Thank you,

Udo.
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: saxmonster on May 07, 2012, 02:27:06 AM
Udo, I still have it. Can I use a DMM to measure it?
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: nashkato on May 07, 2012, 05:27:29 AM
Quote
  Just for future refence,do you have c1 still laying around,can you measure it for dead short?
Quote
Udo, I still have it. Can I use a DMM to measure it?

you can measure continuity for a short.
can you measure  capacitance with your DMM ?
(there are ways to measure the capacitance with a coil and frequency generator in a resonant circuit as well)



Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: letterbeacon on May 07, 2012, 05:49:52 AM
Out of the Aurcycle, the B2 and the MXL 2010, which one has a head basket the most similar to a U87?
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: HellfireStudios on May 07, 2012, 11:31:15 AM
Out of the Aurcycle, the B2 and the MXL 2010, which one has a head basket the most similar to a U87?

The Aurycle, but none are perfect. Check out the U87 "How It's Made" video on YouTube. There's a lot of good footage of the headbasket being made. Find the one closest in size/shape you can.
Chances are, even if there was a Chinese-made exact copy, it would have different wire mesh or some other seemingly innocuous change. So unless someone machines their own U87 clone bodies (which would be expensive), none of the current "clones" will match.
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: letterbeacon on May 07, 2012, 11:36:35 AM
The Aurycle, but none are perfect. Check out the U87 "How It's Made" video on YouTube. There's a lot of good footage of the headbasket being made. Find the one closest in size/shape you can.
Chances are, even if there was a Chinese-made exact copy, it would have different wire mesh or some other seemingly innocuous change. So unless someone machines their own U87 clone bodies (which would be expensive), none of the current "clones" will match.

Interesting, thanks for the reply.  I suppose the downside to the Aurcycle is the lack of a pattern switch.  I haven't seen it mentioned in this thread, so how are people tackling it?  Adding their own switch?
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: nashkato on May 07, 2012, 02:13:54 PM
hi
has anyone ordered from cinemag lately ?

they were really fast in responding about prices and shippig information for a CM2480 transformer for this project ,
but didn´t respond to my 2 mails ordering one .
it´s been over 2 weeks now.

any experiences ?

thx
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: kante1603 on May 07, 2012, 02:26:24 PM
Hi all,

I received a message from the Hamburg company who are selling the T13s to me.
Seems that a big order (not just mine) from AMI/TAB Funkenwerk is either held back for some reason or is even lost.
Therefore I can´t go on building my mics.I wanted them to be ready as soon as possible to make more tests with trafos attached to circuit (more ways for biasing,more detailed description on the B2pro build,sound checks etc.).
Sorry that I can´t :'(
Just for info.

Udo.
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: rmaier on May 07, 2012, 02:57:12 PM
hi
has anyone ordered from cinemag lately ?

they were really fast in responding about prices and shippig information for a CM2480 transformer for this project ,
but didn´t respond to my 2 mails ordering one .
it´s been over 2 weeks now.

any experiences ?

thx

Similar experience here - no response to a couple of emails, so I just phoned them. After that, my order shipped on the same day and my 2480s were here in about a week.
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: Blue Jinn on May 07, 2012, 03:38:41 PM
Ok Guess who has a clean mic sound now!!!!!!!!!!!


OH YEA ITS ME HAHAHAHAHAHAH!!!!!!!!

C1 was the culprit!!!!!!!!!!!!!!!!  Something must have happen to it.  So I will order a new styrene for it but the wima is working very quiet now, hahahaha.

 point.

-Scott

Another FYI, I stumbled across a thread at tapeop about alcohol damaging polyester caps when cleaning up flux, etc.
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: kante1603 on May 07, 2012, 03:55:49 PM
Another FYI, I stumbled across a thread at tapeop about alcohol damaging polyester caps when cleaning up flux, etc.
Yes!

Udo.
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: wave on May 07, 2012, 03:57:51 PM
I used acetone for cleaning the flux off of my board. You think that could damage styrenes in the same way?

Dave
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: kante1603 on May 07, 2012, 04:10:32 PM
I used acetone for cleaning the flux off of my board. You think that could damage styrenes in the same way?

Dave
Hi Dave,
May be yes,maybe no,I don't use it anymore since the day a colleague "cleaned" the display of our very expensive level meter (Wandel&Goltermann).It went blind.I use isopropanol for that.Anyways it is well known that pure alcohol and styrenes don't go together.
Hopefully it did not happen in your case.

Good luck,

Udo.
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: poctop on May 07, 2012, 06:28:17 PM
Quote
May be yes,maybe no,I don't use it anymore since the day a colleague "cleaned" the display of our very expensive level meter (Wandel&Goltermann).It went blind.I use isopropanol for that.Anyways it is well known that pure alcohol and styrenes don't go together.
Hopefully it did not happen in your case.

Good luck,

Udo.

 >:( ......:-\ .....:-[.... :o..... :'(...... For Sure Acetone is a very strong Solvent and will attack about everything to plastic to poly,
but Still says that  :  I See, Said the Blind Men ,
Sorry for your loss Udo,
Dan,

 
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: wave on May 07, 2012, 07:50:15 PM
I was the nail polish remover kind. Not nearly as strong as hardware store acetone! I mostly soldered on the back of the boards and was careful not to get the acetone on to the components. I dip a toothbrush in it and clean away. Hoefully I didn't damage anything.

I think my mic sounds pretty good. It definitely has a "vintagey" vibe to it. It's very warm and silky on the top IMHO.

It's all subjective right?

Dave
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: poctop on May 07, 2012, 07:58:30 PM
I was the nail polish remover kind. Not nearly as strong as hardware store acetone! I mostly soldered on the back of the boards and was careful not to get the acetone on to the components. I dip a toothbrush in it and clean away. Hoefully I didn't damage anything.

I think my mic sounds pretty good. It definitely has a "vintagey" vibe to it. It's very warm and silky on the top IMHO.

It's all subjective right?

Dave

So the one you got is the  RK87-T13 or PK87i and 2480.
Just curious  :-\

I am really Glad you like it ,  :D
I like the Vintagey Term  8)

Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: wave on May 07, 2012, 11:33:04 PM
The first one I have made is the RK-87 and the T-13 with styrenes in the 10, 220, 470, 560 positions

Dave
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: kante1603 on May 08, 2012, 01:46:15 AM
The first one I have made is the RK-87 and the T-13 with styrenes in the 10, 220, 470, 560 positions

Dave
Congrats Dave!
And if the cleaning is done with a tooth brush properly just at the bottom side everything is o.k.,I do it the same way when there's too much flux.You won't touch the components.
Since your mic is working you didn't damage anything.

Udo.
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: DUDE GUY on May 08, 2012, 08:51:41 PM
Hello All,

I received my T13 today!! Woohoo!! And it came with an AMI sticker! Bonus! haha

Question for those with T13's: does yours actually say "T13 AMI Made in USA" as shown in the T13 spec sheet? Mine does not...just a black wrap (not yellow) with the number 106 (see pic). I just want to make sure I actually have a T13.

Can't wait to install it and hear some glorious 1k come out of my mic! (no capsule yet, saving up for a peluso)

Thanks everyone.

-DUDE GUY
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: poctop on May 08, 2012, 09:35:51 PM
Hello All,

I received my T13 today!! Woohoo!! And it came with an AMI sticker! Bonus! haha

Question for those with T13's: does yours actually say "T13 AMI Made in USA" as shown in the T13 spec sheet? Mine does not...just a black wrap (not yellow) with the number 106 (see pic). I just want to make sure I actually have a T13.

Can't wait to install it and hear some glorious 1k come out of my mic! (no capsule yet, saving up for a peluso)

Thanks everyone.

-DUDE GUY

If you got the AMI sticker your On, 
Maybe you got one of the Prototype  8)

D
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: wave on May 08, 2012, 11:39:17 PM
Hello All,

I received my T13 today!! Woohoo!! And it came with an AMI sticker! Bonus! haha

Question for those with T13's: does yours actually say "T13 AMI Made in USA" as shown in the T13 spec sheet? Mine does not...just a black wrap (not yellow) with the number 106 (see pic). I just want to make sure I actually have a T13.

Can't wait to install it and hear some glorious 1k come out of my mic! (no capsule yet, saving up for a peluso)

Thanks everyone.

-DUDE GUY

Mine looks just like the pic on the website. Maybe Dany is right about yours being a proto?

Dave
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: saxmonster on May 08, 2012, 11:39:32 PM
How does the pattern selection work on the PCB.  If I short pins 1 and 2 I get what? 2 and 3?  then is it 1 and 3?  I will just have to open the mic and do it by hand with the shuter/jumper clip thingy.

-Scott
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: poctop on May 09, 2012, 12:18:24 AM
How does the pattern selection work on the PCB.  If I short pins 1 and 2 I get what? 2 and 3?  then is it 1 and 3?  I will just have to open the mic and do it by hand with the shuter/jumper clip thingy.

-Scott

Indeed,
No Jumper = Cardiod
Jumper (pin1-pin-2) = figure 8
Jumper (pin 2- pin-3)  = Omni,

Cheers,
Dan,
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: adeptusmajor on May 09, 2012, 12:56:27 AM

Mine looks just like the pic on the website.

Same here.
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: kante1603 on May 09, 2012, 03:05:46 AM

Mine looks just like the pic on the website.
Don't know..... :'(
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: sr1200 on May 09, 2012, 11:14:52 AM
Has anyone used a OSP body for this mic? 
OSP stm-1300C (http://www.ospworldwide.com/sound/mics/studio.html)
Its a pretty low price point, and has all 3 switches.  Only downfall is that the existing circuit board has the transformer MOUNTED to the board, so theres no cool little "cap" to cover the replacement trafo.  (the board thats in that mic is WEIRD lookin too...)

I should be getting my transformer any day now, but still waiting on that one cap that ONLY newark seems to stock.  The switches on that OSP are all mounted on a separate little board.  Ill post a pic tonight when i get to the shop.  just wondering what the wiring is going to be like for this thing...
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: poctop on May 09, 2012, 12:02:59 PM
Has anyone used a OSP body for this mic? 
OSP stm-1300C (http://www.ospworldwide.com/sound/mics/studio.html)
Its a pretty low price point, and has all 3 switches.  Only downfall is that the existing circuit board has the transformer MOUNTED to the board, so theres no cool little "cap" to cover the replacement trafo.  (the board thats in that mic is WEIRD lookin too...)

I should be getting my transformer any day now, but still waiting on that one cap that ONLY newark seems to stock.  The switches on that OSP are all mounted on a separate little board.  Ill post a pic tonight when i get to the shop.  just wondering what the wiring is going to be like for this thing...

Check this thread they talk about that for that generic mic body wihout the cap there discussion about lenght and other dimension , i never had a body like this in my hand but from reading this thread  it seems it will work ,

http://www.groupdiy.com/index.php?topic=48552.0 and Here : http://www.groupdiy.com/index.php?topic=48061.0

Cheers,
Dan,

Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: sr1200 on May 09, 2012, 12:40:15 PM
After trolling the hardware store, i found a plumbing cap that will fit perfectly for about $2. :) :)
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: DUDE GUY on May 09, 2012, 02:32:01 PM
After trolling the hardware store, i found a plumbing cap that will fit perfectly for about $2. :) :)

Oh nice! I need one of those covers too. Which hardware store did you find it at? Or is it a pretty generic product that I could find at most hardware stores? Might you post a picture?

Thanks,

-DUDE GUY
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: DUDE GUY on May 09, 2012, 02:40:24 PM
To those waiting on a T13:

I received my T13, but it doesn't look like the pic in the spec sheet. I emailed AMI to see if my transformer is actually a T13. It turns out it is a normal T13 (not a prototype). AMI said that one of their new employees tested and sent out some T13's before wrapping them with the yellow wrap that says, "T13 AMI Made in USA." So if you get one that doesn't look like the pic in the spec sheet, do not fear, you still have a T13.

-DUDE GUY
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: sr1200 on May 09, 2012, 03:04:01 PM
Home depot in the plubming aisle lol, its a copper cap.  they are in little baggies where the connectors would be.
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: DUDE GUY on May 09, 2012, 08:37:39 PM
Hello all,

HELP!!!

Having issues with my T13. I installed it and then all my voltages changed drastically and I couldn't even see the 1k with my scope. I checked and double checked the wiring and I think it's good. I removed the T13 and voltages went back to normal.

Wiring (oriented the same as T13 spec sheet pic):

Yellow Left: 1 (RT)
Black Left: 4 (WS)
Yellow Right: 2 (SW)
Black Right: 3 (BL)

Should I see continuity between the two yellow leads of the T13? When I installed the T13, both of the yellow leads showed a continuity to ground. Then when I uninstalled the T13, my dmm showed continuity between the two yellow leads. Is this normal or do I have a bad T13?

Thanks,

- DUDE GUY

EDIT: After thinking more about it, continuity between both pairs of wires would make sense-yellow leads=primary, black leads=secondary. Anyone?
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: wave on May 09, 2012, 09:27:44 PM
Dudeguy,
Your wiring looks like it was correct. I don't know about the continuity issue as mine is soldered in and I put shrink tube over the pins.

Dave
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: DUDE GUY on May 10, 2012, 06:01:28 AM
More T13 trouble.

With the T13 installed, I get 1.5V at L1 and L2, .15V at FET drain, and .8V across the Zener...

I'm guessing I have a bad T13?

Voltages measured normal without the transformer.

Thoughts?

-DUDE GUY
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: MagnetoSound on May 10, 2012, 06:47:21 AM
More T13 trouble.

With the T13 installed, I get 1.5V at L1 and L2, .15V at FET drain, and .8V across the Zener...

I'm guessing I have a bad T13?

Voltages measured normal without the transformer.

Thoughts?

Did you forget the coupling cap?

Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: DUDE GUY on May 10, 2012, 01:36:21 PM
More T13 trouble.

With the T13 installed, I get 1.5V at L1 and L2, .15V at FET drain, and .8V across the Zener...

I'm guessing I have a bad T13?

Voltages measured normal without the transformer.

Thoughts?

Did you forget the coupling cap?

I don't think so...I populated the entire board with BOM. Which cap is the coupling cap? Am I missing something? Thanks.
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: poctop on May 10, 2012, 02:07:37 PM
More T13 trouble.

With the T13 installed, I get 1.5V at L1 and L2, .15V at FET drain, and .8V across the Zener...

I'm guessing I have a bad T13?

Voltages measured normal without the transformer.



Thoughts?

Did you forget the coupling cap?

I don't think so...I populated the entire board with BOM. Which cap is the coupling cap? Am I missing something? Thanks.

Could you remove the traffo and retake the Volatge reading again might somthing happen to the zener diode , this is very fragile component as you can have all the roght voltage dont not put the T13 yet,  before we are straight the traffo,
Dan,
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: MagnetoSound on May 10, 2012, 02:11:24 PM
Which cap is the coupling cap? Am I missing something? Thanks.

The 1u cap between the drain and the primary winding.

This cap blocks the DC from the drain circuit from reaching the transformer, if you connect the primary winding directly to the drain it will load down the drain voltage.

As long as the coupling cap is in place it should not affect the drain voltage when you connect the transformer.

You should try connecting the primary wires first and see what happens - the cap could be leaky - if the voltages stay OK, connect the secondary wires and observe the difference.

You may also just have made a solder bridge somewhere that is causing a short. Sharp eyes needed.  ;)

Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: DUDE GUY on May 10, 2012, 04:32:46 PM

You should try connecting the primary wires first and see what happens - the cap could be leaky - if the voltages stay OK, connect the secondary wires and observe the difference.

I disconnected the secondary leads and my voltages went back to normal. Then I reconnected the secondary and my voltages went bad. What does this mean? Thanks.

-DUDE GUY
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: poctop on May 10, 2012, 05:52:44 PM
Can you verify that you xlr pin out is good ,
number 1 on pcb=  is hot  pin 2 xlr
number 2 on pcb= is cold pin 3 xlr
number 3 on pcb = gnd

verify on the silk screen if this is correct, it is labeled there ,

Dany,


Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: poctop on May 10, 2012, 05:56:31 PM
the Boards are Back in Stock  :D
Dan,
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: DUDE GUY on May 10, 2012, 07:05:24 PM
Can you verify that you xlr pin out is good ,
number 1 on pcb=  is hot  pin 2 xlr
number 2 on pcb= is cold pin 3 xlr
number 3 on pcb = gnd

verify on the silk screen if this is correct, it is labeled there ,

Dany,

Everything looks good, 1=pin 2, 2=pin 3, 3=ground

Correct me if I'm wrong, but if my voltages are good without the T13 and then my voltages go bad with it installed, doesn't that imply that there's an issue with my T13?

Thanks,

-DUDE GUY
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: poctop on May 10, 2012, 07:19:40 PM
where do you connect the traffo,  wich pad on the PCB you connect it  ,   could you measure the DC resistance of the coil and compare with a collegue here ,  if someone has a T13 available for measuring that would be extra so we could compare them , for T13 user

what is the configuration of the color code for it ? i just dont have on at the moment,

thanks for you precious input.,

Dan,
 
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: Matador on May 10, 2012, 07:42:42 PM
According to the spec sheet, the T13 primary is the two yellow wires, and the secondary is black.

With the transformer removed, you should show continuity between the two yellow wires.  You should also have continuity between the two blacks.  However there should not be continuity between any yellow and any black (with the transformer removed).  It almost sounds like there is a primary to secondary short, and since the primary is ground referenced, that would cause a short on the secondary side through the 2K2 resistors (and collapse the phantom voltage as well).
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: DUDE GUY on May 10, 2012, 08:06:57 PM
According to the spec sheet, the T13 primary is the two yellow wires, and the secondary is black.

With the transformer removed, you should show continuity between the two yellow wires.  You should also have continuity between the two blacks.  However there should not be continuity between any yellow and any black (with the transformer removed).  It almost sounds like there is a primary to secondary short, and since the primary is ground referenced, that would cause a short on the secondary side through the 2K2 resistors (and collapse the phantom voltage as well).

Hit the nail on the head, Matador! I have a short between my primary and secondary. That'll ruin your day! I'm going to contact AMI for a replacement ASAP. At least now I'll have two AMI stickers, double bonus! Ha.

Thanks for your help everyone, specifically matador, poctop, magnetosound, and wave. This is really an efficient and productive forum. I'll post my progress once I get a new T13.

-DUDE GUY
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: wave on May 10, 2012, 11:53:23 PM
Dudeguy,
For reference when you get your new AMI T-13

(http://farm8.staticflickr.com/7241/7174554600_240a084539.jpg) (http://www.flickr.com/photos/wavedealer/7174554600/)



Dave
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: DUDE GUY on May 11, 2012, 12:33:32 AM
Awesome! Well done, thanks Dave.
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: poctop on May 11, 2012, 10:01:26 AM
Thanks For the Pointer Dave ,
Dan.,
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: poctop on May 11, 2012, 02:23:32 PM
I finally had a chance to put my RK-87 in the U1621 and compare it to my real Vintage Neumann , i have to say that i was lucky enough to be able to use the original traffo that a bought on ebay a while ago and the final results are that the RK-87 is pretty close to the original K-87 subtile differene in the top end wich the RK-87 has a bit higher top end and the transient were a bit sharper,  in the low end it would react pretty much the same, i did like the openess of the RK-87 as well,  Overall i would say that for the money the RK-87 is a very good investement , I had also the chance to compare the Modern flavor with film and electro instead of tantalum and polystyrene and i have to say that it did behave better with the tantalum and polystyrene flavor ,it was much closer to the real thing than the other combination ,  i really hope for those using the T13 with their build will be able to achieve comparable results with pairing the RK-87 to this project. 

Sincerly ,  ;D
Dan,
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: berkleystudios on May 11, 2012, 04:36:20 PM
i have been waiting for weeks for my CM2480 ??? how long does it take cinemag to make these things? im surprised i haven't heard anything yet. normally i would pay any mind but im trying to finish my testing of the RK87 for Matt and post results for everyone.
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: sr1200 on May 11, 2012, 05:01:40 PM
NEVER send email to cinemag. Call them, you'll have it in less than a week.
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: poctop on May 11, 2012, 05:15:41 PM
I usually call and asked for invoice straight out  ;D that works great too.
D
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: rmaier on May 11, 2012, 09:58:28 PM
Yes. terrible email service, awesome phone service.
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: Matador on May 11, 2012, 10:55:00 PM
I finally had a chance to put my RK-87 in the U1621 and compare it to my real Vintage Neumann....

I wonder how much of the difference is due to the 3 micron Mylar (RK-87) vs. 6 micron (I believe the original)?

Here's a quick experiment:  increase the value of C6 (220pF) up to the 270pF to 330pF range and try the RK-87 again.  It will shave a few db off the high end in the 7k-10k range and not effect the gain too much.
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: berkleystudios on May 11, 2012, 11:39:46 PM
i already paid my invoice. is it possible they forgot? ill give them a call tomorrow.
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: mparts on May 12, 2012, 02:23:30 AM
I wonder how much of the difference is due to the 3 micron Mylar (RK-87) vs. 6 micron (I believe the original)?

The thinner film affects the high-frequency response, as you suggest, but it will have faster transient response, too, which is not something (IMO) Dan's vocal test would have revealed.

Historical note - Large-diaphragm capsules with thin film diaphragms (thinner than 6 micron) were pioneered by the late Stephen Paul. His eponymous firm lives on, and still provides capsule rebuilding and tuning with ultra-thin films, down to 0.9 micron (!).
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: tskguy on May 12, 2012, 12:35:04 PM
The thinner films also stretch out over time, Thats what I was told by some pretty well known capsule experts. I honestly havent been able to A B the difference  so I have no opinion on what sounds better. I think the Lawson microphone capsules use 3 micron skins as well. 

Eric
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: wave on May 12, 2012, 10:34:21 PM
EXTREMELY HUGE NEWS!!!!

I went to Guitar Center to get a shockmount for my mic. Whenever I have to buy anything from GC I buy from the GC Pro sales person at my local store as he can give me much better discounts than the regular staff.

So I called him up to see if they had a mount I could use and they did. I asked if he wanted me to bring the mic in to have a listen. He did.
I showed him the mic and I could tell, since it's still the bare brass and no logo yet, that he was a little unimpressed.
He showed it to a couple other sales people there and they decided that not only did they want to listen but they wanted to A/B my mic with a brand new Neumann U87 AI.
So we all go into the studio room where they have their computer recording gear set up and they plugged in the Neumann to a Focusrite Saffire.
We did some checks and some singing into the mic. Sounds like a U87 because it is.
Then we plugged in my mic.
Their faces showed astonishment. All 3 GC guys liked my mic way better. They commented on how warm and silky it sounded. "It sounds like a tube mic" was the phrase associated with my mic.
Now they want me to do a limited production of them and sell them in the store. I said I had to think about that.
They all want me to build them one!
I am sold on the RK-87. I think the capsule is intrinsic to the sound I'm getting. That and the combo of the styrenes and T-13 has yielded one very sweet mic and now I have the experience of putting it up side by side with a real U-87.

Great project Dany. You have given us the ability to make a great sounding unique microphone!

Also, I explained to them how I could use different components (capsule, trafo, caps..etc) to shape the sound of the mic differently and they all agreed that I should change nothing.



Dave
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: saxmonster on May 12, 2012, 10:59:13 PM
So did you get the shockmounth that is the important part here right?  HAHAHAHA Excellent news!!!!!!!!!!! 
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: wave on May 12, 2012, 11:12:54 PM
HAHA! I did get the shock mount. I also got some acoustic guitar strings so I can do some tests with my guitar (which was the other reason for going)

Dave
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: saxmonster on May 12, 2012, 11:24:41 PM
How does the pattern selection work on the PCB.  If I short pins 1 and 2 I get what? 2 and 3?  then is it 1 and 3?  I will just have to open the mic and do it by hand with the shuter/jumper clip thingy.

-Scott

Indeed,
No Jumper = Cardiod
Jumper (pin1-pin-2) = figure 8
Jumper (pin 2- pin-3)  = Omni,

Cheers,
Dan,

So without the jumper its Hyper Cardioid?  Not just cardioid right?

Also does anyone know what size screw are used for the transformer housing area.  There are 6 of them down there and one keeps coming loose and I think it might be the screw that is stripped not the hole.
Title: Re: Neumann U87 Vintage Circuit Build Thread
Post by: kante1603 on May 13, 2012, 02:41:47 AM

So without the jumper its Hyper Cardioid?  Not just cardioid?
Scott,

No U87 in the world has a hyper cardioid mode.I think it is just a typo.So when no jumper plugged in it is cardioid.

Udo.
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: saxmonster on May 13, 2012, 10:28:48 PM
Ok so I am still waiting for my C1 styrene replacement to arrive but I do have the mica in there so I was itching to record tonight.  So as I was working on some sax reeds I decided to record another draft of the melody to the Mr. Magic demo.  I really can't get over how great this mic sounds.  Even with crappy reeds It's fantastic.  I am getting better and better at using it and working it into a mix.  I love how the sound is so fat and punchy yet clear and clean.  It gives me everything that is coming out of the sax.   No hype upper end and no boxy type sound.  When I go to record the horn-section I might use this u87 on the trombone or as a room mic, I will have to experiment a bit with it on a horn section.

Here is the signal chain.

U87 --->  EZ1073 ----> DBX266 (barley on) --->  into DP MOTU 2408mkII  --->  Waves true-verb.

still a work in progress.

http://www.ehornstudios.com/media/MRMEDIT.mp3

-Scott
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: tskguy on May 14, 2012, 10:25:58 AM
Sounds great!!! Very smooth. 8)
Is that the Peluso capsule?

Eric
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: pasarski on May 14, 2012, 10:42:07 AM
Ok so I am still waiting for my C1 styrene replacement to arrive but I do have the mica in there so I was itching to record tonight...

Please let us know which one you prefer after you've changed it!
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: sr1200 on May 14, 2012, 11:01:24 AM
Yeah, im still waiting for mine from Newark (did you get the May 17th shipping date too?)  I just got my T-13 on friday... I gotta see if the mount i have on my host mic will fit the peluso capsule though.  Im gonna try and use that OSA mic that has the 3 switches which i gotta figure out the wiring for as well.
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: saxmonster on May 14, 2012, 11:57:06 AM
Yes this is using the Peluso capsule K87i with all original u87 guts from the bom.  Its sounds so good.  I am actually getting my styrene from justradios.com  I will keep you posted if I do hear a difference with styrene vs mica in the C1.

Thanks
-Scott
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: wave on May 14, 2012, 12:40:49 PM
Scott,
Are you sure it's a mica? C1 is a 470pF cap and the replacement if not using the styrene is a pulse film. The only mica in the BOM is the 10pF cap.

Dave
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: saxmonster on May 14, 2012, 01:03:45 PM
Yes it is pluse film sorry
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: wave on May 14, 2012, 03:31:10 PM
Here is a take with my Epiphone 12-string.

http://soundcloud.com/waveaudio/12-string-take/s-LBxSG

Signal path is:
U87 --> 9098 (pre only)--> LA2A (p2p, sowter transformers, 6dB gain reduction)--> MOTU 2408 MKII--> Protools 9

I'm a bit heavy handed and my luthier set up this 12 string with lights. Gotta learn to not bang on it so much

Dave

EDIT: Soundcloud's encoding leaves a bad taste in my mouth. I can A/B with my PT session and the soundcloud version is a bit harsh.
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: Edward on May 16, 2012, 11:00:40 AM
Hi all!

I would need some help with the calibration process, I apologize in advance if this is a dumb question or if it has discussed before and I missed it.

Boards are fully stuffed, AMI T13 transformer, no capsule yet. My problem is that I can't hear the 1KHz sinus tone through the microphone in my DAW. I am feeding the tone to RT + ,SW -, but all that comes out at the XLR is a big buzz. When I turn R11 all the way to one side the buzz goes away. If i turn it the other way nothing changes.

I made some measurments:

47.52V Phantom in. At the zener i measured 23.6V. R18 47.69V, R19 47.24V. At C10 I got 20.85V and when measuring at FC I have 40.78V.


What am I missing, are the measurments good enough? Any help would be highly appreciated! 
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: sr1200 on May 16, 2012, 11:29:40 AM
OK now i have a dumb question.. I got the Peluso K87i capsule, and there are 3 wires connected to it.  I have the parts for the 4th wire, but the screws they supply dont fit, they seem to bottom out like 1/8" in. I dont want to force it, is this right?
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: wave on May 16, 2012, 12:16:56 PM
OK now i have a dumb question.. I got the Peluso K87i capsule, and there are 3 wires connected to it.  I have the parts for the 4th wire, but the screws they supply dont fit, they seem to bottom out like 1/8" in. I dont want to force it, is this right?

Chop it off. Def don't force it. The backplate wire screws in the RK-87 are like 2mm.

Dave
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: MagnetoSound on May 16, 2012, 12:35:01 PM
OK now i have a dumb question.. I got the Peluso K87i capsule, and there are 3 wires connected to it.  I have the parts for the 4th wire, but the screws they supply dont fit, they seem to bottom out like 1/8" in. I dont want to force it, is this right?

Is it meant to screw in through the mount?

Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: poctop on May 16, 2012, 02:24:33 PM
Hi all!

I would need some help with the calibration process, I apologize in advance if this is a dumb question or if it has discussed before and I missed it.

Boards are fully stuffed, AMI T13 transformer, no capsule yet. My problem is that I can't hear the 1KHz sinus tone through the microphone in my DAW. I am feeding the tone to RT + ,SW -, but all that comes out at the XLR is a big buzz. When I turn R11 all the way to one side the buzz goes away. If i turn it the other way nothing changes.

I made some measurments:

47.52V Phantom in. At the zener i measured 23.6V. R18 47.69V, R19 47.24V. At C10 I got 20.85V and when measuring at FC I have 40.78V.




What am I missing, are the measurments good enough? Any help would be highly appreciated!

Do you have a scope to bias ? your voltage looks goods, the behavior of the FET seems to be proper execpt for the buzz,  could you try setting your drain voltage at 11.5V and then connect the capsule and try the mic with the body installed and everything. that will tell us if there is an underlying problem with your buzz ,  make sure the pcb is properly grounded to the mic body so in this manner you take a step forward to come back with more answer.  please visit the first page of the white market thread as there is a ton of info for troublshooting and hint on capsule connection as well.
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: poctop on May 16, 2012, 02:27:14 PM
OK now i have a dumb question.. I got the Peluso K87i capsule, and there are 3 wires connected to it.  I have the parts for the 4th wire, but the screws they supply dont fit, they seem to bottom out like 1/8" in. I dont want to force it, is this right?

Is it meant to screw in through the mount?

Yes one of them is suppose to screw trough the mount indeed ,  please refer to picture on the first page of the white market all the connection point to the peluso are illustrated
Hope this helps,
Dan,
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: sr1200 on May 16, 2012, 02:31:02 PM
yeah the screws i got with the mic are like 5+ mm (same screws as the mounting screws for the capsule, too long to screw in all the way on the body of the capsule)  so as long as its making electrical contact with that brass lookin part im good, yes?  (i have old screws laying around that would work for this)  Hopefully I'll be getting my cap from Newark tomorrow and can start getting things going.
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: poctop on May 16, 2012, 02:41:59 PM
OK now i have a dumb question.. I got the Peluso K87i capsule, and there are 3 wires connected to it.  I have the parts for the 4th wire, but the screws they supply dont fit, they seem to bottom out like 1/8" in. I dont want to force it, is this right?

The 4th wire connection will actually go trough the mount and in the backplate you should not have to cut the screws for the peluso capsule, please refer the the white market first page there is guidance picture there,
hope this helps,
Dany,
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: sr1200 on May 16, 2012, 03:33:15 PM
The pic on the first page of the white market thread shows an arrow pointing to the side screw hole and an X over the existing one, theres nothing there saying anything about the screws or lengths, but either way, i know WHERE its supposed to go,  I think that peluso sent me a wrong screw and just wanted to see if anyone else had the same issue.
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: wave on May 16, 2012, 03:46:59 PM
Did you try screwing it through the mount?

Dave
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: sr1200 on May 16, 2012, 04:00:08 PM
I guess i could, but i think the way my mount is the capsul would be backwards from the way I want to orient it with the switches.  I guessi could reverse the mount entirely too... ugh lol.
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: Edward on May 16, 2012, 04:15:51 PM
Hi all!

I would need some help with the calibration process, I apologize in advance if this is a dumb question or if it has discussed before and I missed it.

Boards are fully stuffed, AMI T13 transformer, no capsule yet. My problem is that I can't hear the 1KHz sinus tone through the microphone in my DAW. I am feeding the tone to RT + ,SW -, but all that comes out at the XLR is a big buzz. When I turn R11 all the way to one side the buzz goes away. If i turn it the other way nothing changes.

I made some measurments:

47.52V Phantom in. At the zener i measured 23.6V. R18 47.69V, R19 47.24V. At C10 I got 20.85V and when measuring at FC I have 40.78V.




What am I missing, are the measurments good enough? Any help would be highly appreciated!

Do you have a scope to bias ? your voltage looks goods, the behavior of the FET seems to be proper execpt for the buzz,  could you try setting your drain voltage at 11.5V and then connect the capsule and try the mic with the body installed and everything. that will tell us if there is an underlying problem with your buzz ,  make sure the pcb is properly grounded to the mic body so in this manner you take a step forward to come back with more answer.  please visit the first page of the white market thread as there is a ton of info for troublshooting and hint on capsule connection as well.

Thank you for your answer!

Unfortunately I do not have access to a scope, I was planning to do a THD / Tone calibration. I'm gonna make the ground connection better to the microphone body because I made it poorly just so I could start testing. I don't have a capsule yet but will order one soon, or actually I have the one I pulled out from my donor microphone... would that work for testing? It is a single sided capsule, the micophone was a TSL U87.

Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: kante1603 on May 16, 2012, 04:21:53 PM
I guess i could, but i think the way my mount is the capsul would be backwards from the way I want to orient it with the switches.  I guessi could reverse the mount entirely too... ugh lol.
Yes!
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: Matador on May 16, 2012, 04:28:00 PM
Thank you for your answer!

Unfortunately I do not have access to a scope, I was planning to do a THD / Tone calibration. I'm gonna make the ground connection better to the microphone body because I made it poorly just so I could start testing. I don't have a capsule yet but will order one soon, or actually I have the one I pulled out from my donor microphone... would that work for testing? It is a single sided capsule, the micophone was a TSL U87.

If you don't inject a signal, do you hear anything?  With no signal, the gate should be grounded through R7 and the mike should be (relatively) silent.

How about if you place your finger on the teflon standoff connected to the JFET gate connection?  Your body will act as a nice antenna for 60Hz radiation, so you should hear a nice 60Hz hum coming through the speakers (of course replace 60Hz with 50Hz if you live in Europe) ;).

You can also try working backwards:  disconnect the primary transformer lead that comes from the coupling cap (leaving the other side connected to circuit ground), and directly inject your unbalanced test signal there.  If you can hear the tone then you need to work 'backwards' through the circuit until you can find the problem.
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: DUDE GUY on May 16, 2012, 04:29:38 PM
Ah ya, back in business!!!

Got my replacement T13 (and another AMI sticker!!!) ha. This one looks like the pic in the spec sheet, which is nice. I'm going to install tonight and I'll post the results.

Happy building to everyone.

-DUDE GUY
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: kante1603 on May 16, 2012, 04:55:06 PM

How about if you place your finger on the teflon standoff connected to the JFET gate connection?  Your body will act as a nice antenna for 60Hz radiation, so you should hear a nice 60Hz hum coming through the speakers (of course replace 60Hz with 50Hz if you live in Europe) ;).

I have 10 fingers-which one should I use? ;D ;D ;D

(Sorry,couldn´t resist....)
Udo ;)
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: Matador on May 16, 2012, 05:22:34 PM

How about if you place your finger on the teflon standoff connected to the JFET gate connection?  Your body will act as a nice antenna for 60Hz radiation, so you should hear a nice 60Hz hum coming through the speakers (of course replace 60Hz with 50Hz if you live in Europe) ;).

I have 10 fingers-which one should I use? ;D ;D ;D

(Sorry,couldn´t resist....)
Udo ;)

After all my years of soldering, I only have one finger left....so it's redundant to me. ;)
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: poctop on May 16, 2012, 08:37:10 PM
Quote
I have the one I pulled out from my donor microphone... would that work for testing? It is a single sided capsule, the micophone was a TSL U87.


you can sure use the only side you have just connect it to FC section,
Cheers,
Dan,
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: DUDE GUY on May 16, 2012, 10:16:22 PM
GREAT SUCCESS!!!  8)
 
New T13 installed and all is well. I heard some glorious 1k going through the mic, music to my ears.

Thanks again Wave for the T13 reference pic, very handy.

-DUDE GUY
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: poctop on May 16, 2012, 10:32:31 PM
GREAT SUCCESS!!!  8)
 
New T13 installed and all is well. I heard some glorious 1k going through the mic, music to my ears.

Thanks again Wave for the T13 reference pic, very handy.

-DUDE GUY

Where will you put the AMI sticker Then  8)
Excellent
D
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: Edward on May 17, 2012, 02:04:24 PM
Thank you Matador an Dan for your excellent help!

I noticed the buzz went away as soon as I put the PCBs inside the microphone body, so that problem is solved. This just proves what a complete noob I am. Placing a finger on the teflon standoff made the exact same type of 50Hz buzz. By the way I used my right hand little finger for this task Udo :)

I also set the drain voltage to 11.5V and connected the capsule that was in my donor microphone, and man I have to say the microphone sounded really good already. I was truly amazed by that.

So back to trying the THD / Tone calibration method then...


I also need to make a decision on either the Peluso P-K87i or the Microphone Parts RK-87 capsule... which one do you recommend?
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: kante1603 on May 17, 2012, 02:10:56 PM
By the way I used my right hand little finger for this task Udo :)

O.K.,I´m going to try it with my nose (imagine that funny picture) ;D

Have fun with your build,seems you are very very close to get a cool microphone (while I´m still stuck...... >:().

Cheers,

Udo ;)
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: wave on May 17, 2012, 07:13:38 PM
Thank you Matador an Dan for your excellent help!

I noticed the buzz went away as soon as I put the PCBs inside the microphone body, so that problem is solved. This just proves what a complete noob I am. Placing a finger on the teflon standoff made the exact same type of 50Hz buzz. By the way I used my right hand little finger for this task Udo :)

I also set the drain voltage to 11.5V and connected the capsule that was in my donor microphone, and man I have to say the microphone sounded really good already. I was truly amazed by that.

So back to trying the THD / Tone calibration method then...


I also need to make a decision on either the Peluso P-K87i or the Microphone Parts RK-87 capsule... which one do you recommend?

I can answer this one with a question...

What kind of capacitors did you use in the 10, 220, 470, and 560pF positions?

Dave
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: saxmonster on May 17, 2012, 11:31:05 PM
I took my grill off tonight  to look at my capsule because I wanted to double check the wiring on it for another project I am starting but I noticed that the front capsule has a few pieces of something on it.  Maybe loose particles from the head basket / grill.  I don't think its dust or dirt.  So how do you clean this off?

Can I use a very small soft tip artistic paint brush to gentle wipe or pick this off?  The pieces are on the gold plating too.


Errr, always something.  The mic sounds fantastic so maybe I will just leave it alone.

-Scott

edward

here is my sax through the Peluso P-K87i

http://www.ehornstudios.com/media/MRMEDIT.mp3

HTHS
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: MagnetoSound on May 18, 2012, 02:18:43 AM
The mic sounds fantastic so maybe I will just leave it alone.

Good call.  ;)

Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: kante1603 on May 18, 2012, 04:18:02 AM
I took my grill off tonight  to look at my capsule because I wanted to double check the wiring on it for another project I am starting but I noticed that the front capsule has a few pieces of something on it.  Maybe loose particles from the head basket / grill.  I don't think its dust or dirt.  So how do you clean this off?

Can I use a very small soft tip artistic paint brush to gentle wipe or pick this off?  The pieces are on the gold plating too.

@Scott (and anybody who´s interested):

I have found a guide to clean a capsule,written by Neumann originally in april 1988.It´s in german language of course,so I tried to translate the last chapter about

cleaning the membrane:

"Each membrane should be cleaned with destilled water,applied using a very soft brush drenched with it.
The water containing now the loose dirt should be  picked up with a piece of soft and good absorbent blotting paper.
Repeat this step until final cleaninig.
Membranes that can not be cleaned this way must be exchanged.

It is not allowed to use solvent for this procedure.
Solvent has a low viscosity and is too volatile:There is no time to do a gentle cleaning,it will cause cords ("Schlieren") on the membrane:Solvents go under the membrane ring and take the dirt with them.
Solvents cool down the membrane-they will generate humidity under it which can badly evaporate then.
Additionally there is the danger to remvove the tension of the membrane."


And I can not repeat it often enough:
Never ever touch the membrane or the contact- and isolation elements with your fingers!No high impedance part likes it!
Even the smallest dirt or fat parts from your skin can definetely decrease the isolation and then cause interfering voltages!!!

Wear gloves!

Hope to have helped,

best regards from germany,

Udo.
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: MagnetoSound on May 18, 2012, 05:52:14 AM

Gotta say, capsule cleaning is a very risky procedure and should only be carried out in cases of serious contamination.

If there is no audible problem - that is, if the sound is not disappearing under the breath test, there is no problem.


... I noticed that the front capsule has a few pieces of something on it.

This is in no way a problem. Best to leave it alone.
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: kante1603 on May 18, 2012, 06:14:20 AM

Gotta say, capsule cleaning is a very risky procedure and should only be carried out in cases of serious contamination.

If there is no audible problem - that is, if the sound is not disappearing under the breath test, there is no problem.


... I noticed that the front capsule has a few pieces of something on it.

This is in no way a problem. Best to leave it alone.
I absolutely agree with you Dan!
I just wanted to make people get aware of what this is about,I think it helps a bit to understand how sensitive this is,therefore taking special care on handling capsules.Have translated this from the original NEUMANN-INFORMATION "88 042".Thought it might help.
But you´re right:
Never change a running system!

Have a good day,

Udo. ;)
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: saxmonster on May 18, 2012, 07:08:33 AM
Thanks guys it will stay in there and not be touched!!!!!!!!!!!
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: Edward on May 18, 2012, 07:35:20 AM
Thank you Matador an Dan for your excellent help!

I noticed the buzz went away as soon as I put the PCBs inside the microphone body, so that problem is solved. This just proves what a complete noob I am. Placing a finger on the teflon standoff made the exact same type of 50Hz buzz. By the way I used my right hand little finger for this task Udo :)

I also set the drain voltage to 11.5V and connected the capsule that was in my donor microphone, and man I have to say the microphone sounded really good already. I was truly amazed by that.

So back to trying the THD / Tone calibration method then...


I also need to make a decision on either the Peluso P-K87i or the Microphone Parts RK-87 capsule... which one do you recommend?

I can answer this one with a question...

What kind of capacitors did you use in the 10, 220, 470, and 560pF positions?

Dave


220, 470 and 560pF are Polystyrenes. The 10pF is a Mica, but I just found a 10pF Polystyrene at Farnell that maby would fit so I'm thinking about getting that.
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: adeptusmajor on May 18, 2012, 08:41:43 AM
I'm curious if anyone at this point has swapped the mica for a styrene and noticed any significant difference.

I have the micas as per the BOM in my mics, can't say there is anything I don't like about them. But better is always better...

Just wondering if it is worth the effort to hunt down and replace one cap.
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: tskguy on May 18, 2012, 09:23:59 AM
Hello fellow Mic geeks,

So our good friend Wave and I have spent some time together to A/B our new Microphones. First I want to say what a very cool guy Dave aka Wave is, we had a great time! So some details regarding these clips. I used my SSL 9k pre my LA2A and then in to a crappy ada8000 converter at 24bit 44.1 khz.
Dave's mic had the la2a in but only compressing about 3 db max. After my la2a warmed up we noticed a bad tube so we bypassed it for my mic. Wave is singing and gives a nice intro detailing the caps. His mic is using a microphone parts rk87 and my mic is using my second and more accurate hand made k87 capsule.
Wink wink ;) ;).  Please let us know what you think! One major difference is my mic has a cinemag and Wave's is using the t13.

http://dl.dropbox.com/u/55530129/test87_ericmic3.wav
http://dl.dropbox.com/u/55530129/test87_Davemic.wav

Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: DUDE GUY on May 18, 2012, 03:57:50 PM
Wave & tskguy:

Both mics sound fantastic, well done. The only real difference I hear is in the upper high end, maybe 8-10k. Tskguy, your mic sounds a bit more true to a vintage 87 sound, veeeery smooth, very controlled sibilance, whereas Wave's mic has a bit more air and detail in the high end. The sibilance was slightly more pronounced in Wave's, but nowhere near undesirable. I would guess this difference is due to the capsules, but there are multiple variables in this case (I do not have the technical knowledge to make connections between differing sounds and differing components).

Conclusion: I would reach for tskguy's U87 if I were recording a vocalist with overpronounced sibilance or if If I wanted a bit of a darker sound on an instrument or room mic. I would reach for Wave's if I wanted some sheen or airy detail in a vocal, cymbals, acoustic guitar, etc.

Lastly, Wave, nice singing. Your voice is not only nice, but very well suited for such a mic test. Full bodied, well balanced.

Great job, guys!

-DUDE GUY

 
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: Edward on May 18, 2012, 06:53:49 PM
Both sound really good, interesting to hear a a/b test like this so thanks for that. Amazed how good the hand made k87 capsule turned out.

Is the LA2A adding any of the sibilance we hear on Waves microphone?

Listened to Saxmonsters saxophone sound clip as well with the Peluso P-K87i capsule and I liked the "vintage" sound it had, warm and round.
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: saxmonster on May 18, 2012, 07:22:16 PM
Hello fellow Mic geeks,

So our good friend Wave and I have spent some time together to A/B our new Microphones. First I want to say what a very cool guy Dave aka Wave is, we had a great time! So some details regarding these clips. I used my SSL 9k pre my LA2A and then in to a crappy ada8000 converter at 24bit 44.1 khz.
Dave's mic had the la2a in but only compressing about 3 db max. After my la2a warmed up we noticed a bad tube so we bypassed it for my mic. Wave is singing and gives a nice intro detailing the caps. His mic is using a microphone parts rk87 and my mic is using my second and more accurate hand made k87 capsule.
Wink wink ;) ;).  Please let us know what you think! One major difference is my mic has a cinemag and Wave's is using the t13.

http://dl.dropbox.com/u/55530129/test87_ericmic3.wav
http://dl.dropbox.com/u/55530129/test87_Davemic.wav

Both mics do sound great.  But I agree with Dude Guy with the second one being a bit brighter it the extreme high end.  But its not bad, I just wouldn't use it on a bright sound source.  Very nice job guys.

-Scott
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: tskguy on May 18, 2012, 08:33:01 PM
Thanks for the great feedback guys. I dont think the La2a was adding the brighter sound on Daves mic, Im saying that just because i know my la2a and it normally doesnt do that. Dave and I wonder how much the tx has to do with the sound as well as the capsule.
I did let Dave borrow my first capsule it will be interesting to see how it sounds in his mic. Im really glad you guys like the sound of my capsule. I may make a few more of these things so let me know if anyone would be interested.

Eric
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: HellfireStudios on May 19, 2012, 03:04:04 AM
Thanks for the great feedback guys. I dont think the La2a was adding the brighter sound on Daves mic, Im saying that just because i know my la2a and it normally doesnt do that. Dave and I wonder how much the tx has to do with the sound as well as the capsule.
I did let Dave borrow my first capsule it will be interesting to see how it sounds in his mic. Im really glad you guys like the sound of my capsule. I may make a few more of these things so let me know if anyone would be interested.

Eric

As usual, it depends on the price... let us know.
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: tskguy on May 19, 2012, 08:33:38 AM
Thats hard part isnt it..... Let me hold off on saying how much for now, I want to make sure that everything works out getting some things made in terms of components.
So far the last and most difficult part is getting the mylar coated, I have a source but Im doing a bit of shopping around. I will say that the price will be competetive. And it willl be 100% machined and and tuned by me. 100% made in the USA. 

Eric
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: saxmonster on May 19, 2012, 10:56:08 AM
Anyone know what size screws are on the transformer housing area? 6 of them right?   i have a loose one and would like to have a couple on hand for the apex 460 project i am doing.  I wonder if all chinese mics are the same size screws..
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: HellfireStudios on May 19, 2012, 04:39:24 PM
Anyone know what size screws are on the transformer housing area? 6 of them right?   i have a loose one and would like to have a couple on hand for the apex 460 project i am doing.  I wonder if all chinese mics are the same size screws..

In my experience, they tend to use the same size screws in the same places.
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: sr1200 on May 20, 2012, 11:22:03 AM
Finished my build.  Very nice sounding circuit and capsule.  Used an OSP body, the peluso caps and all the "original" components listed on the BOM.

Gear Porn Here (http://www.facebook.com/media/set/?set=a.4001203791599.171283.1326207212&type=1)
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: saxmonster on May 20, 2012, 02:09:35 PM
So is there a screw chart online to compare these screws and to tell what the thread count is?
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: kante1603 on May 20, 2012, 02:54:47 PM
Finished my build.  Very nice sounding circuit and capsule.  Used an OSP body, the peluso caps and all the "original" components listed on the BOM.

Gear Porn Here (http://www.facebook.com/media/set/?set=a.4001203791599.171283.1326207212&type=1)
Could you please show the pics so everybody can see them,not only on facebook?
Personally I don't want to sign in there.

Cheers,

Udo.
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: sr1200 on May 20, 2012, 11:07:05 PM
You shouldn't have to sign in there, its a public album.

edit: but it would help if i put up the public link to the pics... duhhhhhh

Try this link, should be no login needed sorry bout that (http://www.facebook.com/media/set/?set=a.4001203791599.171283.1326207212&type=1&l=7b043c8b58)

Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: HellfireStudios on May 21, 2012, 02:57:39 PM
Good news from Peluso. I called today to get an update on my BV11P return. He told me, after I checked the dimensions of my donor mic, that he would send a BV8P-S in its place (the metal cover is going to need to be removed for it to fit). It has two taps on the primary for 5.5:1 or 11:1 and two secondary taps at 50 and 200 ohms. The larger size should translate to a fuller bass (this might explain the "tighter/faster" sound of Poctop's Peluso/Cinemag version). It's the transformer John Peluso said he would use. It should be shipped tommorrow. I can't wait.
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: poctop on May 21, 2012, 03:45:46 PM
Good news from Peluso. I called today to get an update on my BV11P return. He told me, after I checked the dimensions of my donor mic, that he would send a BV8PS in its place (the metal cover is going to need to be removed for it to fit). It has two taps on the primary for 5.5:1 or 11:1 and two secondary taps at 50 and 200 ohms. The larger size should translate to a fuller bass (this might explain the "tighter/faster" sound of Poctop's Peluso/Cinemag version). It's the transformer John Peluso said he would use. It should be shipped tommorrow. I can't wait.

Let me know if you like it , got an extra one for sale here , if That might interest anyone ,
This looks promising as you could make it selectable for even  more fun  ;D
Cheers
D

Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: DUDE GUY on May 21, 2012, 06:18:38 PM
Hello builders,

I stumbled my way into mic building by first modding cheap chinese FET condensers. With these cheap mics, many people suggested dampning both the mic body and headbasket with some sort of absorptive material. Theoretically, as I'm sure many of you know already, this is supposed to greatly diminish standing waves and thus improve frequency response. Are any of you adding this kind of dampning to your U87 builds? Is this type of thing necessary or is resonance caused by standing waves addressed in the circuit design? Just curious. If anyone has tried this, was it beneficial? Pointless? Thanks everyone.

-DUDE GUY
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: adeptusmajor on May 21, 2012, 06:35:33 PM
Hello builders,

I stumbled my way into mic building by first modding cheap chinese FET condensers. With these cheap mics, many people suggested dampning both the mic body and headbasket with some sort of absorptive material. Theoretically, as I'm sure many of you know already, this is supposed to greatly diminish standing waves and thus improve frequency response. Are any of you adding this kind of dampning to your U87 builds? Is this type of thing necessary or is resonance caused by standing waves addressed in the circuit design? Just curious. If anyone has tried this, was it beneficial? Pointless? Thanks everyone.

-DUDE GUY

I hadn't even considered modding the headbasket (using Aurycle bodies). I think the mics sound pretty great as they are. Honestly, I haven't had enough battle time with them yet to get really familiar with them, but I'm not seeing headbasket resonance being a problem at this point. Time will tell.

But Fletcher over at gearslutz does seem to think that my mics must be complete garbage because the headbasket is not a perfect replica of the Neumann. Or maybe it's because he doesn't sell the PCBs... ::)
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: poctop on May 21, 2012, 07:18:06 PM
Quote
But Fletcher over at gearslutz does seem to think that my mics must be complete garbage because the headbasket is not a perfect replica of the Neumann. Or maybe it's because he doesn't sell the PCBs...


Just by Curiousity ,  Who is Flectcher ?  ???
Dan,
 :-\
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: wave on May 21, 2012, 08:34:59 PM

I hadn't even considered modding the headbasket (using Aurycle bodies). I think the mics sound pretty great as they are. Honestly, I haven't had enough battle time with them yet to get really familiar with them, but I'm not seeing headbasket resonance being a problem at this point. Time will tell.

But Fletcher over at gearslutz does seem to think that my mics must be complete garbage because the headbasket is not a perfect replica of the Neumann. Or maybe it's because he doesn't sell the PCBs... ::)

Funny because I A/B'ed mine with a real Neumann U87AI and all of us thought my mic sounded better hands down so Fletcher can relax about all that.

Dave
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: DUDE GUY on May 21, 2012, 09:37:35 PM



Just by Curiousity ,  Who is Flectcher ?  ???
Dan,
 :-\

Someone correct me if I'm wrong, but I believe Fletcher is the owner of Mercenary Audio and a common voice in the gearslutz forum.

-DUDE GUY
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: kpearsall on May 22, 2012, 03:29:15 AM
yea well, Fletcher is Fletcher. Maybe some of Joe Meek's "crazy" rubbed off on him.
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: adeptusmajor on May 22, 2012, 07:08:40 AM
yup, not trying to pick a fight or anything. I actually like Fletcher. I just thought it was an amusing anecdote.
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: kpearsall on May 22, 2012, 07:56:17 AM
Yea I like Fletcher too. He's just VERY opinionated, and not always right. Personally though, Ive been thinking of a way to make the head basket a little less cheap sounding. It may be subtle, but I know it's affecting the sound. It's not a huge deal though, and I'm not gonna get uptight about the proper shape.
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: HellfireStudios on May 22, 2012, 08:50:33 AM
If it is a chinese U87 style body, you could always hammer the headbasket grill into a flatter, more Neumannesque shape. That should reduce standing waves in the headbasket. RTV silicon in the mic body should fix any resonances there.
I say put the mic together and tap all over it, if any resonances are even there, then deaden the resonances with the aforementioned RTV silicon (the electronics safe kind).
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: tskguy on May 22, 2012, 09:36:50 AM
It’s interesting topic, There are a bunch of self-proclaimed pros that say the head basket shape changes the sound considerably. They may be 100% correct but I have no real way of testing the theory. I would love to have an original basket to compare different shapes to. I guess an anechoic chamber would be needed as well to really see the difference. I highly doubt any ears would be able to subjectively tell the difference.  I only assume that Neumann spent tons of money on R&D to best design the current u87 head basket!  ;D
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: kante1603 on May 22, 2012, 12:20:37 PM
Info on pattern modes:
On the homepage for the RK87 capsule it says the original U87 ("non-A-Version") had only omni and figure-eight patterns.
http://microphone-parts.com/rk87-microphone-capsule/
This is wrong,even in 1972 it had a cardioid pattern,easy to see at the original schematics.
We owned some of them in our company,ours definetely had a cardioid mode.Later we exchanged them to "A" types in 1986.


Udo.

Edited,all good now.....
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: MagnetoSound on May 22, 2012, 05:39:27 PM
Info on pattern modes:
On the homepage for the RK87 capsule it says the original U87 ("non-A-Version") had only omni and figure-eight patterns.

I think you misunderstood. It actually says ...

Quote
"The U87 (non-A revision) ... could only create the Omni and Figure-8 polar patterns with a 4-wire capsule. If you are recreating the original U87, you need a 4-wire capsule for multipattern operation."

... which means something completely different, and happens to be true.  :)

Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: mparts on May 22, 2012, 10:17:45 PM
I think you misunderstood...

Dan, thank you for replying to Udo's comment. The text to which Udo refers was somewhat poorly written, and has since been revised to be (we hope) more clear.

Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: kante1603 on May 23, 2012, 12:55:19 AM
@Dan(magnetosound):Yes,if one pronounces different it gets a different meaning.
@(mparts):Excuse the confusion.Have read your new text,it is way more clear to read now.

Udo ;)

P.S.:Will change my original post.
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: HellfireStudios on May 25, 2012, 01:44:30 PM
I recieved the Peluso BV8P-S yesterday. It looks to be about double the size of the Cinemag 2480. It does have taps for both 5.5:1 and 11:1 operation. I'll try to post acoustic guitar clips when I find time to build this thing. I have a djembe I could mic up, as well, to get a feel for the low end. I'll keep all of you posted.

-James-
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: tskguy on May 25, 2012, 08:49:10 PM
Little sneak peak  ;)
 (http://i280.photobucket.com/albums/kk187/tskguy/20120525_193333.jpg)
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: berkleystudios on May 25, 2012, 10:14:57 PM
Finally got my cinemag in. installed and shot it out against my bluebird. much lower output than my blue bird but it remained quite. with low self noise. was surprised as how bright it was  on my acoustic guitar. the bluebird was far warmer. but the u1621 had a very fast and punchy. very happy. forgot my external HHD or i would have posted my results. ill try do do that soon.

using the rk87/cm2480/micas
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: HellfireStudios on May 26, 2012, 12:11:26 AM
tskguy, any prices yet?
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: tskguy on May 26, 2012, 08:34:27 AM
Hi all,

 I decided on $225, I am still a 2 or 3 weeks away from being able to finish them. The company I found locally to do the mylar coating has a bit of a lead time before its completed.  I will update this thread as I get closer. My first run is pretty limited, I have enough backplates for 20 capsules and some are already spoken for.  If it goes well I will for sure make more!! 100% made in the USA!

Eric
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: wave on May 26, 2012, 08:49:04 AM
Eric,
The backplates look great! I wish I was there to see them.  :(

Dave
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: tskguy on May 26, 2012, 09:03:17 AM
Thanks!
So far things are looking very good. Let me know when your around and you can see them in person:)

Eric
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: sr1200 on May 26, 2012, 01:34:06 PM
TSK, if its not too much trouble, can you start a thread showing the process of making them (not tryin to rip you off, cause i would NEVER have the patience to do something that intricate, but i am really interested in how that all works!)
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: tskguy on May 26, 2012, 03:48:01 PM
I am thinking of starting my own thread but not until I start to put them together. There are a few other parts that Im waiting on. As soon as I have all the parts I will take some pics and start a for sale thread.

Eric
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: saxmonster on May 26, 2012, 06:29:42 PM
I love how its made videos!!!!!!!!
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: Studio Mollan on May 28, 2012, 06:16:52 PM
Hi all!
I just completed my three microphones and I'm VERY pleased with the sound! One concern though is the output level. In comparison to my u89 the output is way lower. Singing softly into it needs full gain from my API 2488 preamps for a proper input to ProTools. The files from the clones are a bit noisier than the files from the u89 but only because of the preamp from what I can hear. The mike itself seems to be quiet. I know its been a topic here but i just wanted to confirm that. Anybody having any real trouble with noise in actual recording situations? 
Seems to e a lot smoother compared to the u89 sound wise. As stated earlier in this thread, very vintage sounding. Great! in other words. I'll put them to test in my next sessions.

There's also an annoying pop when i change between omni, card, 8 and also when I engage the hipass and pad. Also a slight tendency for resonance in the body. When holding the u89 the handling noise is very low frequency. The clones are more midrangey, perhaps caused by the different housing. Any ideas?
Im using peluso capsules and ami transformers.
The body is perhaps not historically correct but I thought the looked cool!
Thanks for all your help!!!
Let's all get together for a beer some time!  :)
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: poctop on May 28, 2012, 07:39:41 PM
Hi all!
I just completed my three microphones and I'm VERY pleased with the sound! One concern though is the output level. In comparison to my u89 the output is way lower. Singing softly into it needs full gain from my API 2488 preamps for a proper input to ProTools. The files from the clones are a bit noisier than the files from the u89 but only because of the preamp from what I can hear. The mike itself seems to be quiet. I know its been a topic here but i just wanted to confirm that. Anybody having any real trouble with noise in actual recording situations? 
Seems to e a lot smoother compared to the u89 sound wise. As stated earlier in this thread, very vintage sounding. Great! in other words. I'll put them to test in my next sessions.

There's also an annoying pop when i change between omni, card, 8 and also when I engage the hipass and pad. Also a slight tendency for resonance in the body. When holding the u89 the handling noise is very low frequency. The clones are more midrangey, perhaps caused by the different housing. Any ideas?
Im using peluso capsules and ami transformers.
The body is perhaps not historically correct but I thought the looked cool!
Thanks for all your help!!!
Let's all get together for a beer some time!  :)

congrats, your mic body are simply awesome,  great Job looks even more  vintage imho  8),  don't worry about the poping when switching ,  my real vintage does exactely the same thing no exception , as for the output, the vintage u87 put out the same output , i did some compare with my build with the original trafffo and it is virtually the same output level at same gain ,  it will be indeed about 10db lower output than the modern version.

Thanks for your post,

Best
Dan,
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: mylesgm on May 28, 2012, 11:22:35 PM
which Mic bodies are those?
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: kante1603 on May 29, 2012, 12:55:14 AM
Hi,

congrats to your builds.
Switching patterns causing a pop is normal,remember you switch the second part of your capsule in and out.Even modern U87A types do so.
Soundwise you can not compare them to a U89 since this is a totaly different microphone.
The level drop compared to U87A version is -11dB from the math.

Udo.
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: Studio Mollan on May 29, 2012, 06:06:08 AM
Hi,

congrats to your builds.
Switching patterns causing a pop is normal,remember you switch the second part of your capsule in and out.Even modern U87A types do so.
Soundwise you can not compare them to a U89 since this is a totaly different microphone.
The level drop compared to U87A version is -11dB from the math.

Udo.

Thanks for your reply! And for your earlier posts that have been very helpful!

-11db seems to be in the ballpark of what I'm experiencing here. Great sounding microphone. I must say I did to expect them to be this good.
Actually I hade a hard time hearing any difference between my u89 and a new u87 in a session last summer. Male vocals. The 87 was a bit brighter, cleaner and better shape capsule?, but otherwise pretty close. The guy singing couldn't tell the difference at all! That's why I used the 89 for reference. A friend of mine has got a vintage 87 that's will compare my clones with. I'll post the results here ASAP.
/
Emil
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: Studio Mollan on May 29, 2012, 06:08:22 AM
which Mic bodies are those?

They are from a thomann retro tube II. Pretty cheap mike still including a pretty descent shock mount.
/
Emil
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: kante1603 on May 29, 2012, 09:06:50 AM
Hi Emil,

Cool,a comparison to a vintage type is most useful for us!
Concerning comparison between an actual U87a and an U89:Something must have gone completely wrong,they absolutely don't sound equal or close to each other.Maybe the 89 is in a worse condition than the 87A?I have worked with both of them for ages and I swear they are very different in comparison,an U89 normally has a faster resonse,different mid range like more linear,different highs etc.Also it's capsule is smaller.

Just for info,have fun with your new toys,

Udo ;)
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: sr1200 on May 29, 2012, 09:38:32 AM
If someone wanted to bring the mic level up say 6db or more, what would have to change in the circuit/transformer?
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: tskguy on May 29, 2012, 03:03:19 PM
My first How its made video :)
;D


(http://i280.photobucket.com/albums/kk187/tskguy/th_20120528_160504.jpg) (http://s280.photobucket.com/albums/kk187/tskguy/?action=view&current=20120528_160504.mp4)
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: adeptusmajor on May 29, 2012, 05:18:36 PM
My first How its made video :)
;D


sweet!!!
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: kante1603 on May 29, 2012, 08:06:22 PM

Thanks for all your help!!!
Let's all get together for a beer some time!  :)
Where are you located Emil? ;D
Cheers,
Udo.
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: HellfireStudios on May 30, 2012, 09:32:00 AM
Nice CNC. The kind of stuff you can do with that makes me jealous. The Sony C800G capsule is where I would start. The mic is far too expensive for most, and I would befirst to in line to pick up a clone capsule. *hint, hint*
Cool stuff. How do you test a capsule to make sure it falls within spec? The only reason I ask is that Neumann supposedly rejects about 70% of their capsules, and the Telefunken R-F-T line supposedly rejects about 30%. I assume, in Neumann's case, they go back for re-skinning if defective. Just curious. Thanks.

-James-
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: burglar on May 30, 2012, 11:38:46 AM
Hi Poctop

It's going to be a couple months before i can get to work on the PCB's I've ordered but I was wondering if you have any plans to do a more comprehensive build guide and or wiring diagram for the 2 transformers & capsules you recommend, + a calibration guide would be very useful.  I'm confident I can populate the boards painting by numbers and I plan to use the AMI tranny but I'm a total beginner and a wiring guide would be a huge help. 

If anyone else has some literature that might make this a bit easier it would be much appreciated.  This is my first project away from all inclusive kits.  Sorry for the newbism.   
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: tskguy on May 30, 2012, 01:30:21 PM
Hellfire,

I have some steps that I take to make sure things are consistent. In terms of tuning there are ways to verify the resonant frequency as well as the capacitance after it is skinned. Those are the most important things you can measure after skinning. The other factors are accuracy and repeatability during the machining process, this is key for consistency over multiple capsules.
My CNC is accurate to .001 mm and holds that very well. The back plates I am making are absolutely identical to the original k87 back plate I have access to, the only difference with my capsule will be the outer rings and the screws holding it down. I chose to use stainless 0-80 thread screws instead of the less common 1.1mm size screws Neumann uses. To be honest it will have no effect on the sound as well as being much easier to machine! Every other part is the dimensionally the same.  I have also had the pleasure of gaining a wealth of knowledge from a long time capsule repairman, he has provided me with a large number of tips and tricks to help be as consistent as possible.  It is for sure a black art! ;)

Eric
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: poctop on May 30, 2012, 04:21:02 PM
Hi Poctop

It's going to be a couple months before i can get to work on the PCB's I've ordered but I was wondering if you have any plans to do a more comprehensive build guide and or wiring diagram for the 2 transformers & capsules you recommend, + a calibration guide would be very useful.  I'm confident I can populate the boards painting by numbers and I plan to use the AMI tranny but I'm a total beginner and a wiring guide would be a huge help. 

If anyone else has some literature that might make this a bit easier it would be much appreciated.  This is my first project away from all inclusive kits.  Sorry for the newbism.   

Make Sure you read all the build thread and white market thread as we have spread some info there as well  and download all the file from the white market page there is instruction on how to proceed but this is not that hard to make ,  basically you populate the boards and follow the pointer given in the excel file then you tune the FET and install the linked boards in the mic boady and then connect the capsule and enjoy the mic , again there is a lot of info on the construction in this thread and also in the white market thread ,

Keep me posted if you need any other hints ,

cheers,
Dan,
 
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: burglar on May 30, 2012, 04:36:47 PM

Ok, thanks Dan.  I'll let you know how I get on.  That was a nice re-assuring post.  Smiley face.
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: HellfireStudios on May 30, 2012, 05:16:27 PM
Hellfire,

I have some steps that I take to make sure things are consistent. In terms of tuning there are ways to verify the resonant frequency as well as the capacitance after it is skinned. Those are the most important things you can measure after skinning. The other factors are accuracy and repeatability during the machining process, this is key for consistency over multiple capsules.
My CNC is accurate to .001 mm and holds that very well. The back plates I am making are absolutely identical to the original k87 back plate I have access to, the only difference with my capsule will be the outer rings and the screws holding it down. I chose to use stainless 0-80 thread screws instead of the less common 1.1mm size screws Neumann uses. To be honest it will have no effect on the sound as well as being much easier to machine! Every other part is the dimensionally the same.  I have also had the pleasure of gaining a wealth of knowledge from a long time capsule repairman, he has provided me with a large number of tips and tricks to help be as consistent as possible.  It is for sure a black art! ;)

Eric

I appreciate the info. Sounds like you know what you're talking about. I'm sure it puts anyone considering your capsule at ease to know they're not just slapped together. Thanks.

-James-
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: tskguy on May 30, 2012, 08:36:59 PM
Thanks Hellfire, So how many do you want??? ;D ;D ;D ;D
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: Matador on May 31, 2012, 04:16:52 PM
Just a note on the tone of the U87 vs. other mikes:  I've A/B'd this Aurycle mike with the K67-type capsule in this circuit against others like the C12 tube design and various other Schoeps-like designs. 

What I find is that if you go head-to-head against mikes that do not de-emphasize the upper frequencies (like everything above 6kHz), the U87 tends to sound "dull" in comparison.  However in a mix (especially mixes that are denser than just singer/songwriter and acoustic guitar), I find that the U87 just "drops right in" with very little tweaking.  In fact, I've found that the U87 in cardioid just puts the vocal in the exact right spot for a modern rock mix, where the meat of the midrange is where the vocal sits, but the air is removed to not interfere with the cymbals and other high-transient material.  For an every more laser-focused midrange sound (like heavy rock with 4 doubled guitar parts), the SM7 works even better, but the U87 is very close.

Every time I've tried to use my C12 in this situation I've always had to low pass filter it to get it to sit just right, whereas I know with the U87 is probably will "just work" with minimal tweaking during the mix.  The high end is there, it's just not pronounced enough to get in the way of anything else.

Of course the magic of recording is capturing the essence of each part that will work well when mixed together, given the restrictions of the frequency content that each part is occupying.  This is why I pull out the C12 when I need to capture the air, and the U87 when I don't.  It's one less plugin and one less hassle for me later. ;)  However when set up head to head on a single source I've almost always preferred the C12 because it seems to be the best "DC to microwaves" kind of sound (to steal Ethan Winer's line) that works on every single isolated source you can possibly find. 

It just doesn't always work best in the mix....

If someone wanted to bring the mic level up say 6db or more, what would have to change in the circuit/transformer?

I've been thinking about this too.  The three main areas are:

1) Increase gain in the JFET front end:  if you pull more current through the JFET, we can theoretically swing more output signal for a given delta input signal (e.g. the slope of the load line increases).  However the only way to pull more current through the JFET is to pull that current from the phantom supply, which drops the polarization voltage available to the capsule (because the increased current drops more voltage across the 2K21 resistors).  Less polarization means less sensitivity which means less apparent gain, so it's ultimately self defeating.

The only way to combat this is to use a charge-pump-like circuit to increase the polarization voltage (which decouples the polarization voltage from the current being used in the rest of the circuit), which requires a whole new circuit.  This is exactly what Neumann did with the U87AI.

2) A far easier way to is add a PNP follower after the JFET.  This reduces the output impedance of the JFET stage from 40k-ish down to several hundred ohms.  This means you can use a transformer with a much smaller ratio, which means less voltage loss.  Even moving down to a 5:1 BV11P-type would give you back the 6dB of signal you are looking for.  Ideally you could use a 2:1 transformer which would give you back 14dB.

This is how the stock Aurycle circuit works (although they use an NPN follower and cap couple it for some reason), but it sounds slightly different.  The highs are more present, and the mike responds much more to sharp transients like pick attacks on acoustic guitar:  the mike sounds less U87-like, if that makes any sense.  I think part of the mellow U87 sound comes from the high output impedance driving the high-ratio transformer.  It's subtle, but it's definitely different.

3) Reduce negative feedback:  as I hinted at earlier in the thread, you can decrease the value of C6 (or remove it entirely) and it will give you back 3dB to 6dB, however the sound also changes as well.  If you like the "EQ-ed" sound, lowering C6 will take that away, however the mike will be hotter.  If you like/want the "air" it's a very simple mod to do and doesn't require any expensive or complicated circuit changes.  The sound change is FAR more drastic than #2 above (removing C6 can make it sound like a completely different mike).
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: sr1200 on May 31, 2012, 04:47:28 PM
Matador, awesome read man.  So for #3 youre saying just clip out c6... do you replace with a jumper or just leave it out entirely (im at work now, and done have the schemo infront of me atm).  This would seem the only viable options being i dumped a nice chunk of change into the TAB transformer. 

Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: Matador on May 31, 2012, 07:43:27 PM
Matador, awesome read man.  So for #3 youre saying just clip out c6... do you replace with a jumper or just leave it out entirely (im at work now, and done have the schemo infront of me atm).  This would seem the only viable options being i dumped a nice chunk of change into the TAB transformer.

Just remove it, don't jumper across it.  You can probably reheat the solder to get it out should you decide you don't like it and want to put it back.

Or if you are careful, you can snip one side, then move the cap over a little bit and place a piece of electrical tape over the part left in the board.  That would make it easier to solder back.
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: HellfireStudios on June 01, 2012, 09:54:35 AM
Thanks Hellfire, So how many do you want??? ;D ;D ;D ;D

Ha. Unfortunately, I'm about five mics and more than a few electronic endeavors away from new capsules. If you keep making them, I'll pick at least one up when my bank account and project list get to more acceptable levels.

And to Matador, the best way to give the U-87 more gain is to make similar circuit changes that are present in the U-87a (10-11dB). If it's good enough for Neumann... It also sounded very similar in the shootout loudville did on youtube. I'm not sure of all the changes made between models, but I'm sure that information is obtainable.
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: tskguy on June 06, 2012, 03:47:52 PM
No problem Hellfire, I know how it goes. I am doing a pretty small first run and depending on how it goes I will do more.  We will see,
And let me know if you change your mind.
Eric
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: rmaier on June 07, 2012, 01:47:36 PM
Just finished a pair of these, using Peluso capsules, Cinemag transformers, and Apex 530s as donors. The sound on spoken voice is smooth and "finished," at least to my ears. Will be trying them out on a solo classical guitar session tomorrow. Thanks to Dan and everyone for a nice project with plenty of helpful tips - managed to get these working without too much trouble (not counting a mistake I made wiring up the capsules the first time).
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: rmaier on June 07, 2012, 01:52:18 PM
Shot of the inside. I followed the BOM for the vintage version on both mics where possible, with the exception of the few parts that mouser didn't carry. I'll see if I can post a sound clip later.

Ralph
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: kante1603 on June 07, 2012, 01:54:41 PM
Hello guys!

Believe it or not-I´m done with my first mic!
Seems I´m the last one here to get this managed.Thinking of how many posts I wrote without being able to finish anything...... ;D
Finally the T13s came in,there are two big parts orders from ami/Tab funkenwerk missing from my supplier in Hamburg,Germany.They had to order the complete stuff again.All this took 55 days....which gave me a lot of time to think about this project........
Meanwhile I did 2 preamps,a dual 51x psu,2 51x racks,2 compressors,2 eqs and that before mentioned cheesecake (Hi Dave!).
But this had a good side:Seems I´m still the first to build one in a B2 housing with all switches working right from the start!
No issues like rf noise or hum!
I have tried to make some pics during these last steps to finishing,especially for the minority of us,the B2 builders.
So if anybody of you "B2" guys is interested,I have some nice hints and solutions for you to get this baby fully working like the real thing.Things like how to mount the trafo,grounding improvement and so on.Tell me and I´ll post it.

My setup is all-styrene caps except of c3,Peluso capsule and T13 transformer.

And now:
Dan,my friend:You´ve done an awesome job on this!Thank you for all the support,always being friendly and the unbelievable patience with us-I definetely owe you one!!!
Also a big thank you matador,dave  and all of you who contributed so much here,it made the build doable with excellent results!

Cheers to everybody and a big kick in the asses of all you guys at the customs who make our life in the diy world so hard!

Udo
;)


P.S.:Will take the mic to our studios these days and do some comparisons with our real U87As.

Edit:Deleted pics for bigger ones in my next post,these have been too small.
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: sr1200 on June 07, 2012, 02:32:20 PM
Congrats!!! Its about time, welcome to the club!
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: wave on June 07, 2012, 02:42:34 PM
Nice work Udo!
The DIY badge is the icing on that cake. +1 on your customs comment. I can't believe you had to wait almost 2 months.

I need sound samples!

Dave
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: rmaier on June 07, 2012, 02:49:49 PM
Agreed. I'd really like to hear some comparisons.

Udo, your finish looks great.

Cheers,

Ralph
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: geekmacdaddy on June 07, 2012, 02:58:39 PM
Looks fantastic, Udo. Congrats on your build, and patience. Wish the photo's could blow up to a bigger size..
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: kante1603 on June 07, 2012, 03:35:51 PM
Thank you all for your nice comments!

@geekmacdaddy:

Sorry,I´m no good photographer,here´s the trial for some bigger ones:

Outside pics:
(http://img35.imageshack.us/img35/1970/viewright.th.jpg) (http://imageshack.us/photo/my-images/35/viewright.jpg/)
(http://img443.imageshack.us/img443/1259/viewleft.th.jpg) (http://imageshack.us/photo/my-images/443/viewleft.jpg/)
(http://img403.imageshack.us/img403/5223/viewfront.th.jpg) (http://imageshack.us/photo/my-images/403/viewfront.jpg/)
(http://img685.imageshack.us/img685/825/viewback.th.jpg) (http://imageshack.us/photo/my-images/685/viewback.jpg/)

The outside tube,this pic gives a better view of the real colour,it´s Hammerite blue:
(http://img546.imageshack.us/img546/4271/tubee.th.jpg) (http://imageshack.us/photo/my-images/546/tubee.jpg/)

Inside with my very special trafo mount assembly-it is from an old broken kitchen chair ;D
(http://img27.imageshack.us/img27/7509/creatingthebottomtube3.th.jpg) (http://imageshack.us/photo/my-images/27/creatingthebottomtube3.jpg/)

Empty housing,I didn´t change it....
(http://img690.imageshack.us/img690/3914/completehousing.th.jpg) (http://imageshack.us/photo/my-images/690/completehousing.jpg/)

Inside view with all switches soldered:
(http://img545.imageshack.us/img545/5770/allswitchesdone3.th.jpg) (http://imageshack.us/photo/my-images/545/allswitchesdone3.jpg/)

Have fun,

Udo.


Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: tskguy on June 07, 2012, 03:43:35 PM
Thats nice!!!

Sound samples please ;). Good to some more getting finished. I am actually doing my first session with my mic this weekend. I will make sure and shre my results!! Again great job!
Eric
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: geekmacdaddy on June 07, 2012, 03:49:48 PM
Thank you Udo.  :)  I am one step closer to my U87a clone, as I just purchased a beautiful home-made capsule made by Mr. tskguy, which as you know is the tough financial part of this build. That with my populated boards brings me ever closer to the completion of this exciting project. Woohoo.
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: kante1603 on June 07, 2012, 04:06:29 PM
Thank you Eric,

where do you guys load up your samples?Haven´t done that so far because I absolutely hate mp3 stuff and will not do it,what you hear is a lie!Looking for the ability to share some seconds,but at least in 16 or better 24 bit format.

@geekmacdaddy:
Yes,this diy stuff can be a bit expensive,but nobody can pay the amount of money of what this means for your soul!
I have set up 2 "channelstrips" I always dreamed of and that was a lot of money,but I couldn´t have afforded all this stuff by buying them.Look here (scroll to the jpeg at the bottom of the page):
http://www.groupdiy.com/index.php?topic=48610.20
Now I´m really proud of what I have achieved- signal chains completely built by myself,sounding 1o times more expensive than they really are!
Believe me,you will not regret this experience.

All the best and good luck (and lots of money too),

Udo ;)
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: geekmacdaddy on June 07, 2012, 04:09:38 PM
Preaching to the choir, brother Udo! I play guitar through a rig that I built completely. Amp, my 14+ pedal setup, guitar...there is NOTHING more gratifying! BTW, your channel strips rock!
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: kante1603 on June 07, 2012, 04:16:26 PM
Preaching to the choir, brother Udo! I play guitar through a rig that I built completely. Amp, my 14+ pedal setup, guitar...there is NOTHING more gratifying! BTW, your channel strips rock!
Thanks and hallelujah! ;D ;D ;D
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: saxmonster on June 07, 2012, 07:45:22 PM
Congrats Udo, thanks for all your help along the way.  I am very jealous of your channel strips right now.  Who makes the LA500?

Thanks
-Scott

I might get a used lunch box and start some 500 stuff.
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: kante1603 on June 07, 2012, 09:41:47 PM
Hi Scott,

Thank you for the nice words.
Pm sent!

Cheers,

Udo.
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: wave on June 07, 2012, 11:24:28 PM
Sick strips Udo. I was just talking to Eric yesterday about building some VP28s (drool).

Geek - you're gonna love Eric's capsule. What tranny are you teaming it up with?

Dave
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: kante1603 on June 07, 2012, 11:49:08 PM

Geek - you're gonna love Eric's capsule. What tranny are you teaming it up with?

Hi Dave,

You mean which transformer?Come on,that's why I'm so late with finishing my build-it is my "beloved" T13s!Just wait for them about 55 days and you have them immediately :)
Udo.
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: LTJazz on June 08, 2012, 12:59:30 AM
Does anyone build and sell these (as I have no DIY skill for electronics...) I'd buy one from someone.

Also, if you're trying to keep the cost down, someone can PM me as I've been in touch with the factory that produces the Peluso Capsules / Microphone Parts Capsules. They also make bodies/head-baskets. You could probably get an unbranded body/basket and the capsule together for less than the donor mic body....

If anyone wants to try doing a group buy for Capsules/Parts, we could try to arrange it.
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: kante1603 on June 08, 2012, 01:39:43 AM
Does anyone build and sell these (as I have no DIY skill for electronics...) I'd buy one from someone.
this is a diy forum....we all had to learn and practice and have put a lot of work in here....
So sorry but from my point of view no.
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: wave on June 08, 2012, 01:49:09 AM
Does anyone build and sell these (as I have no DIY skill for electronics...) I'd buy one from someone.

Also, if you're trying to keep the cost down, someone can PM me as I've been in touch with the factory that produces the Peluso Capsules / Microphone Parts Capsules. They also make bodies/head-baskets. You could probably get an unbranded body/basket and the capsule together for less than the donor mic body....

If anyone wants to try doing a group buy for Capsules/Parts, we could try to arrange it.

LTJazz  Welcome to the forum!

I will build you one if you want.
I have my recommendations as far as components go (you can read the whole thread and see that)
You should strongly consider purchasing on of Eric's (tskguy) capsules. They are great. The Rk-87 is a great capsule for the money but you def need to go with the T-13 and all vintage caps with that capsule. I used that combo in my first mic and there are some samples I posted of it earlier in the thread.

I have been asked by a few other people to build mics for them and I'm pushing Eric's capsules to them as well.
Nothing against Peluso's, I just haven't heard one in my setup and I can get Eric's work for no shipping.

Think about it and PM me if you want.

Dave
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: wowi on June 08, 2012, 05:08:48 AM
Hi Udo, great work.
And you are not the last one who get ist started.  ;)
Cause of some other projects i just started yesterday to build it based on the B2pro.
So if you have some hints for the B2Pro, that are not on the thread already, you are allways welcome  :D

Best
Wolfgang

Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: geekmacdaddy on June 08, 2012, 05:52:35 AM

Geek - you're gonna love Eric's capsule. What tranny are you teaming it up with?


Hi Wave,
 I was going to use the Tab, but after hearing the shootout clips, I can see no reason why not to save 50.00 and go with the cinemag. It sounded great, and I think tskguy's capsule will take me where I need to go.

Jeff
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: kante1603 on June 08, 2012, 10:44:32 AM
So I made my very first comparison to a U87Ai today.
Just my voice running through 2 identical SPL Gainstations (no tube section active tec,just hpf at 50Hz).
I must say that I really liked what I heard,both are pretty close to each other on a first listen.On a second one there´s slightly more highs on the clone,really marginally,and it seemed a very slight bit more boomy when getting pretty close to it due to the proximity effect.All in all very very nice!
But:
What I didn´t like was that I needed tons of gain to get a useful signal from it,not some 10 to 12 but more like 16 and more dBs difference.
I wondered what this could be,the only thing I remember was that I used a fet with the lowest idss (around 8,xx mAs).
Since most of the fets I have here have  more like 10mAs I´m thinking to swap it to one of these.I´m not 100% sure if it is the right way to handle it,but as far as I can remember a higher idss gives less dynamic but more gain,no?

Must think about it....sh*t,this break caused by waiting for the T13s was way too long........

Any suggestions?

Udo.
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: LTJazz on June 08, 2012, 03:03:14 PM
Thank's for the offer. You may find a message in your inbox shortly!

In response to the criticism, I do understand this is a DIY forum, and I'm reading and trying to learn but to be honest it's going to take some time to build up my skills. However, you also have a market section here. So until I am competent enough to work with electronic components, I have the option of buying a kit and botching it, wasting my money, buying an overpriced mic from a standard company, or possibly commissioning work from an established DIYer that has a passion for building quality mics.

I think I'll choose the latter. If that brings me criticism, so be it.  ;D

Does anyone build and sell these (as I have no DIY skill for electronics...) I'd buy one from someone.

Also, if you're trying to keep the cost down, someone can PM me as I've been in touch with the factory that produces the Peluso Capsules / Microphone Parts Capsules. They also make bodies/head-baskets. You could probably get an unbranded body/basket and the capsule together for less than the donor mic body....

If anyone wants to try doing a group buy for Capsules/Parts, we could try to arrange it.

LTJazz  Welcome to the forum!

I will build you one if you want.
I have my recommendations as far as components go (you can read the whole thread and see that)
You should strongly consider purchasing on of Eric's (tskguy) capsules. They are great. The Rk-87 is a great capsule for the money but you def need to go with the T-13 and all vintage caps with that capsule. I used that combo in my first mic and there are some samples I posted of it earlier in the thread.

I have been asked by a few other people to build mics for them and I'm pushing Eric's capsules to them as well.
Nothing against Peluso's, I just haven't heard one in my setup and I can get Eric's work for no shipping.

Think about it and PM me if you want.

Dave
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: wave on June 08, 2012, 03:10:33 PM
Udo,
When I did my A/B against a U87AI I had a big difference in gain between the 2 as well.

LTJazz - Let me know whenever

Dave
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: kante1603 on June 08, 2012, 04:23:00 PM

Udo,
When I did my A/B against a U87AI I had a big difference in gain between the 2 as well.
Thanks for the reply Dave,

As said before this is a really really nice microphone soundwise.

But what does "a big difference"mean in numbers approximately?
Given an expected difference of 11dB (taken from the Neumann specs,have posted about this part earlier) I thought I was too far off.Thinking say 6dB more gain equals twice(!) the level.
I can't remember we ever had problems concerning gain structure when we used the originals back in the early 80's.
Which kind of pres did you use?
At the moment I think that using it with my new vp28s might not fit.These have about 60dB of gain from the imput stages (another 12dB handy from the output fader gain stage of course....) and I wonder if I'll run into (preamp-) noise with it.Can check this during the next week,today it was a bit too much busines in our studios,and I did the before mentioned very first soundcheck pretty quick.

Anybody else here who can give us some "numbers"?

Thanks,

Udo.
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: wave on June 08, 2012, 05:04:21 PM
Hi Udo,
Well I didn't have a way to gauge the gain difference numerically when I did my A/B test.
Here in my studio I have been doing my tests with my Amek 9098 mic pres.
They have about 72 db of gain. There is about 11-12 db of gain difference between my U1621 and my 414 TLII (the 414 being hotter)
That said, on the 9098s I'm not coming close to maxing out the gain knob with the U1621 (I'm getting up to 42 on the gain knob markings).

When we did the A/B at GC they plugged the mics into a Focusrite interface and it was almost maxed on input to get the same volume as the U87AI.
It would be nice to be able to get some extra gain from these mics internally. I can confidently say that they need to be used with pres that have some good headroom.

Dave
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: kante1603 on June 08, 2012, 05:29:01 PM
Cool Dave!

That´s where I approximately ended up on my SPL Gainstations.
Gain knob marking was at around 39dB with the output set to +6dB,that seems to be in the ballpark.
On the U87Ai I had a setting of 29dB with no additional gain on output.

At least they´ll work on my ssl pres,the have tons of gain.And concerning the vp28s I´ll test them when I find the time,no biggie now.

Thanks for sharing!

Udo ;)
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: kante1603 on June 08, 2012, 06:11:56 PM
Here´s my next little thing for you B2Pro builders:

How to create a nice housing/bottom for the transformer

The B2Pro is a transformerless microphone.So it has nothing but a gap on it´s bottom end.
I thought a bit about how to securely mount my T13 in my build.
I have read people tried to do that with unbelievable techniques like cable straps or even let them wiggle around inside.This can cause shorts on the xlr connections and therefore is an absolute "NO-GO"(...I wanted to avoid the word "B**LS**T"....).
After some investigation of my cellar storage I found some old and broken kitchen chairs like this:

(http://img191.imageshack.us/img191/2763/freischwinger.th.jpg) (http://imageshack.us/photo/my-images/191/freischwinger.jpg/)

The construction is from chromium plated steel at a diameter of 28mm.Cool!
So I cut off a piece of 35mm length and inserted it to the bottom part where the xlr is seated.
Like this:

(http://img266.imageshack.us/img266/37/creatingthebottomtube1.th.jpg) (http://imageshack.us/photo/my-images/266/creatingthebottomtube1.jpg/)

I put on some shrink tube over the blank solder joints prior to that.
For putting it in I used a 2 component glue-this construction withstands even a tank attack.
Next step was to cut some stripes of rubber foam and carefully insert the transformer.
Like this:

(http://img838.imageshack.us/img838/6764/creatingthebottomtube2.th.jpg) (http://imageshack.us/photo/my-images/838/creatingthebottomtube2.jpg/)

Once fully seated slide back the pcb assembly so it sits flush to the bottom tube.Tighten the screws.Now you have no more moving parts-prominsed!And here´s the spot where you can apply your AMI sticker ;D
After all wires soldered it should look kinda this:

(http://img265.imageshack.us/img265/7509/creatingthebottomtube3.th.jpg) (http://imageshack.us/photo/my-images/265/creatingthebottomtube3.jpg/)

Done!

Have fun,

Udo.

P.S.:I calulated that I can build around 700+ bottom tubes from my leftover broken chairs,not bad.....
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: geekmacdaddy on June 08, 2012, 06:30:40 PM
DIY brilliance.
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: kante1603 on June 08, 2012, 06:57:11 PM
DIY brilliance.
No,just having fun ;D

Udo.
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: kante1603 on June 08, 2012, 07:52:58 PM
And another cheap but helpful hint:

Improving the continuity between the bottom part and the metal tube

A good ground connection between all metall parts is essential in this build,otherwise you´ll run into trouble with rf noise and hum.
Here´s a cheap way to make the contact way better.
Just take a piece of solid core wire,I used a silver plated type,known as bus wire.
Form a ring of it and insert it to the bottom part.
This increases the pressure from the bottom part to the tube and guarantees a very good conductive connection,at least it does on a B2Pro.
Look:

(http://img196.imageshack.us/img196/4507/goodgrounding2.th.jpg) (http://imageshack.us/photo/my-images/196/goodgrounding2.jpg/)

(http://img809.imageshack.us/img809/5195/goodgrounding1.th.jpg) (http://imageshack.us/photo/my-images/809/goodgrounding1.jpg/)

Some sanding/grinding is useful too because some metal parts tend to corrode pretty fast.

Cheers,

Udo.
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: kante1603 on June 08, 2012, 08:10:42 PM
And finally

The peluso capsule mounting and wiring

I know,wiring has been covered a thousand times,but still sometimes confusing.
Thought some additional pictures might help.
For B2Pro builders:I purchased the capsule mount from Peluso too.
Found out that the upper part (the saddle/the white plastic piece) fits perfectly on the lower orignal rubber mount.
Just swap it.
Exchanging the rubber mount could only be done by drilling 2 extra holes in the metal mounting plate because the original part has a centered screw while the peluso uses 2 screws.
Here the pics:

(http://img221.imageshack.us/img221/7623/pelusopk87wiring3.jpg)

(http://img403.imageshack.us/img403/5064/pelusopk87wiring2.jpg)

Here you can see the wire (red/blue in my case) you have to put on by yourself.Solder before attaching!Use the flat washers that are supplied with the capsule.

(http://img85.imageshack.us/img85/2097/pelusopk87wiring1.jpg)

Remember not to touch anything with your fingers in the high impedance area,wear gloves (colour doesn´t matter ;D)

Bye,

Udo.


Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: wowi on June 09, 2012, 02:38:00 AM
Hi Udo,

thanks for your tips. Your transformer mount is really DIY  :)
I will now go in my cellar and will see what i find.

Wolfgang
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: kante1603 on June 09, 2012, 03:01:03 AM
Hi Udo,

thanks for your tips. Your transformer mount is really DIY  :)
I will now go in my cellar and will see what i find.

Wolfgang
Hi Wolfgang,

Sanitärbereich hat auch viel Zeug,z.B. Haltegriffe oder Handtuchhalter,heheheheh....

Tschüsskes,

Udo. ;)
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: Matador on June 09, 2012, 05:42:22 PM
We all might think about trying a higher gm JFET like a 2SK170BL....
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: HellfireStudios on June 09, 2012, 06:43:17 PM
We all might think about trying a higher gm JFET like a 2SK170BL....

There has got to be a better FET than the one put in the chinese mic in the first place. Any suggestions?
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: Matador on June 09, 2012, 10:03:49 PM
We all might think about trying a higher gm JFET like a 2SK170BL....

There has got to be a better FET than the one put in the chinese mic in the first place. Any suggestions?

What exactly is wrong with it?
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: wave on June 09, 2012, 10:27:16 PM
Matador,
I looked at a datasheet for a Toshiba 2SK170BL on Mouser and I couldn't tell if the orientation of the FET would be the same looking at the diagram on the sheet. What do you think?

Dave
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: Matador on June 10, 2012, 12:33:31 AM
The SK170 has the same pinout as the 2N3819 that's stock in the circuit: it's a drop in replacement (other than the rebias of course).
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: kante1603 on June 10, 2012, 04:26:14 AM
The SK170 has the same pinout as the 2N3819 that's stock in the circuit: it's a drop in replacement (other than the rebias of course).
Why not give it a try?Matador,do you think we must tweak anything around the fet then or simply swap and re-bias it?

Thanks,

Udo.

Edit:I tried to get some more infos from the both schemos:The 1972 version says it was a "S2436".Tried to google it but only found out that it is either a zip code or an indian flight number etc. so far.....hmmmmmmpfffffff......
In the 1980s version only this number can be found:8280800006.6 which seems to be an internal parts number at the neumann company.On the neumann homepage there´s a button for spare parts but there´s only a blank field showing up.

Edit#2:Found them here in germany and ordered some of them,let´s wait and check it out.
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: geekmacdaddy on June 10, 2012, 12:42:35 PM
Go Udo! I have 1 spare 2SK170BL here, wondering if i should pull the 2N3819 and put it in....
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: poctop on June 10, 2012, 03:04:40 PM
Hi All,  i am currently working on a u67 pcb but i am starting to wonder if i should have made a version of the u87ai as well question of having the DC-DC converter for the capsule as it will put out the same gain as the aI,  just a tought  :-\ ,

Cheers ,

Dan,
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: kante1603 on June 10, 2012, 03:16:46 PM
Go Udo! I have 1 spare 2SK170BL here, wondering if i should pull the 2N3819 and put it in....
I would say do it.What's the situation with your capsule,have you received it?
I bet some guys here will give it a try because they're not lucky with the gain situation.
In my case it will take a while,my "real live/life work" gets me back from tomorrow on,some shows here in germany and then in vienna austria.I'm thinking about swapping it in my build or even build another one to have a comparison.Not sure yet.And I will also try a styrene in the c3(10pF) position and see- pardon-hear what happens.As said mine sounds really like a neumann in the complete mid range,so I'm pretty close to get what I want.
Thinking the 2sk170bl will give me some more output and c3 softens the highs just a very small bit
would end up in a nearly perfect clone soundwise and will make me really happy!

Cheers "brother geek",

Udo :D

Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: kante1603 on June 10, 2012, 03:31:10 PM
Hi All,  i am currently working on a u67 pcb but i am starting to wonder if i should have made a version of the u87ai as well question of having the DC-DC converter for the capsule as it will put out the same gain as the aI,  just a tought  :-\ ,

Cheers ,

Dan,
Hi Dan,

Any solution in getting more gain from the mic would be wonderful at the moment because it offers the use of way more "old"preamps with lower available gain therefore more "colours" soundwise.
If so you should call it something like "u1621v2" or so,the u87Ai is still in production.

Just a thought,

Udo.
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: geekmacdaddy on June 10, 2012, 03:34:08 PM
Udo,
 My capsule won't be shipped until monday, but that still leaves the host aurycle, and the cinemag. And my rat-trap car that is late for inspection (they fine you here) which needs a muffler. So I'm 2-3 weeks away. Excited, but patient.

Tell it from the mountain, brother Udo!
Geek
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: poctop on June 10, 2012, 03:59:07 PM
Quote
Any solution in getting more gain from the mic would be wonderful at the moment because it offers the use of way more "old"preamps with lower available gain therefore more "colours" soundwise.

Thanks Udo, great wisdom as usual.

i will give it a tought as well ,   question ? can i be in the brothers Club too,  8)

Best ,
Dan,
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: saxtim on June 10, 2012, 04:10:10 PM
I've been thinking about building one of these U87's for quite a while, but I'd be more interested in the u87ai.  I tried to DIY one some years ago. There will be a couple of threads on it somewhere, probably around 2004. I got the DC-DC converter going - it does have an autotransformer on it but I managed to scramble wind one that did the job fine and got around +/- 50V. These voltages were loaded down by my meter, I didn't have a scope but I'd be guessing they were closer to +/-60V without the meter loading them down.

I never got the actual head amp going properly though - I was using a cinemag 2480 transformer and a 2N3819 FET. I think the FET may have been the problem - I couldn't get it biased right (I probably needed to buy 100 or so of them and hand pick one that would bias well, but at the time I gave up). It may have been something else though, I never finished it and pulled the circuit apart and built something more simple.

The other advantage of the U87ai is that you don't need isolated backplates for the capsule to get the polar patterns.

But anyway - a definite vote for the U87ai here!

Tim

Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: kante1603 on June 10, 2012, 04:13:14 PM

Welcome brother Dan! ;D

@Brother geek:Won't a new muffler bring it down soundwise?Is that what you want? ;D

Hallelujah,praise the board!

Udo.
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: Matador on June 10, 2012, 04:15:50 PM
The 2SK170 has about 4-8 times the gm as the 2N3819, but much higher input capacitance.  This will also be multiplied by the Miller effect.  I'll have to run some sims to measure the effect, but since the mike is low pass filtered anyway it might not be so bad.

But higher gain means less headroom for loud sources...no free lunch here!

I would say if there's a V2 of the PCB, one might want to add a provision for a PNP follower for those that struggle with the gain and want to use a lower ratio transformer.
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: geekmacdaddy on June 10, 2012, 04:21:54 PM
can i be in the brothers Club too,  8)

We are all brothers of the solder fume. You are the FATHER figure...(at least in this thread) as well as a brother.  ;D
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: kante1603 on June 10, 2012, 04:58:56 PM
But higher gain means less headroom for loud sources...no free lunch here!

Hi Matador,

Thanks a lot for the infos!
Thinking the mic wasn't designed to pick loud sources it might be a way to go.
As you are our "transitor guru" we all would be grateful if you can run the simulations and then tell us the results.
It would be great if this works out good because most of us have spent certain amounts of money for the transformers,buying new ones again would make this project a bit expensive......

Thanks for all your efforts,keep up your good work please!

Udo :)
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: Matador on June 10, 2012, 05:53:38 PM
You bet:  I finally got my Teflon standoffs so I can build two more mikes
...I'll try both FETs and see how much gain I can squeeze from each one.
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: kante1603 on June 10, 2012, 06:03:06 PM
You bet:  I finally got my Teflon standoffs so I can build two more mikes
...I'll try both FETs and see how much gain I can squeeze from each one.
GREAT!
Teflon standoffs?That means a different project,no?

Thank you in advance,

Udo :)
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: kpearsall on June 10, 2012, 09:49:37 PM
Dan I almost had a heart attack when you said u67 PCB. I had to concentrate on fixing my car before hand, which I've just finished thankfully, but I know a guy who has two 67's I was going to work on cloning. Seriously my favorite mic ever and it's been a dream of mine for years to own one. Please make that board!!!! :) :) :) :) I was just going to try to perf board it but... Definately count me in for at least TWO whenever that's read. And I'll cross my fingers that it's ready soon  ;D
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: tskguy on June 10, 2012, 10:21:47 PM
Hi all,

Good stuff, especially the u67 board!! I may have a capsule that will just be fine for that.... Anyway, I just finished a good old fashined 3 day recording session using my u87. I am pretty pleased to say the least.  Here is a link to a Very ruff mix, try not to be to critical :) all of the vocals as well as a few other tracks were recorded with my u87 and my capsule. Listen to the end it rocks ;D
http://dl.dropbox.com/u/55530129/who%20you%20want%20me%20to%20be_Mix.wav

The chain is U87, access 312, LA2A, RME fireface.
Eric 

Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: spase on June 10, 2012, 10:38:06 PM
i will take 2 - u67 boards depend on the price :)
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: poctop on June 11, 2012, 12:25:09 AM

Work in progress Sneek Peek ,  :P

D
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: wave on June 11, 2012, 12:31:35 AM
Dany,
AWESOME!. Eric and I were just talking about you doing this project and him offering a capsule for it. Are your ears burning? Haha!

Keep up the great work brother Dany!

p.s. I love the fact that I have 3 more mics to do right now as well as a couple rack units in the queue and I'm already mentally committing to this project before it's even off the drawing board.
In other words, put me down for 4 of the initial run.

Dave
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: kpearsall on June 11, 2012, 01:56:47 AM
FANTASTIC!!! I'm in the same position. 8 channels of API, 20 S800 EQ, barry porter EQ, 1084's, refurb 4 Ampex 351's, fix an SWR bass amp, and tons more but you know what? I've been waiting so damn long for the 67, EVERYTHING will get pushed back when it's ready. I remember falling in love with it before I even got to use one when I found out most of my fave vocals were recorded with it. T. Rex, Bowie, Nilsson, and I believe even Rufus Wainwright. After using one there was just nothing else I'd use instead if I had the choice :) Thank you Dan. You just became my hero.
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: geekmacdaddy on June 11, 2012, 04:34:07 AM
all of the vocals as well as a few other tracks were recorded with my u87 and my capsule.

Vocals sound great. Real nice drum sounds too, btw.
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: kante1603 on June 11, 2012, 07:07:18 AM
Hi Matador,

I've seen at the bottom of the specs page1 that there are 3 types of the 2sk170 existing.

Note: IDSS classification
GR: 2.6~6.5 mA, BL: 6.0~12 mA, V: 10~20 mA


Any preferences?

Cheers,

Udo.
Title: Re: Neumann U87 vintage circuit build thread
Post by: dandeurloo on June 11, 2012, 11:29:02 AM
Put your DMM in current measuring mode.  Take a Jfet, short gate and source together, and connect to negative terminal of a 9V battery.  Connect one DMM probe to the drain, the other to the positive 9V battery terminal.  You should be able to read the IDSS on the meter.

Matador or anyone else.  I did this method to all 3 of my Jfets.  They all came out at 6.65v.  Does that seem correct?  I had my meter set to read DCV.  I am assuming that is correct.

Thanks guys.  I am close now that I have all my parts.  NOS transformers and capsules!
Title: Re: Neumann U87 vintage circuit build thread
Post by: kante1603 on June 11, 2012, 11:37:32 AM
Put your DMM in current measuring mode.  Take a Jfet, short gate and source together, and connect to negative terminal of a 9V battery.  Connect one DMM probe to the drain, the other to the positive 9V battery terminal.  You should be able to read the IDSS on the meter.

Matador or anyone else.  I did this method to all 3 of my Jfets.  They all came out at 6.65v.  Does that seem correct?  I had my meter set to read DCV.  I am assuming that is correct.

Thanks guys.  I am close now that I have all my parts.  NOS transformers and capsules!
Hi Dan,

No,seems you've measured dc voltage.We want dc current to get the idss.So you have to set the dmm to measure "mAs or As"and plug the probe(s) to the corresponding jacks for current.
Black probe-normally called "Com" goes to drain,red one to the positive terminal of the battery.

Hope to have helped,

Udo.
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: dandeurloo on June 11, 2012, 12:26:00 PM
Ok, that is what I was wondering/thinking.  My DMM must not do that.  Any other way to do it or else I can try and get over to a friends place who has much better test equipment.

Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: spase on June 11, 2012, 01:20:53 PM
we are waiting for that :)))
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: Matador on June 11, 2012, 01:46:45 PM
Hi Matador,

I've seen at the bottom of the specs page1 that there are 3 types of the 2sk170 existing.

Note: IDSS classification
GR: 2.6~6.5 mA, BL: 6.0~12 mA, V: 10~20 mA


Any preferences?

Cheers,

Udo.

GR's tend to be difficult to find.  The BL's are common and work fine.  Remember that the 2N3819's are spec'd from 2mA to 20mA which covers the same range. ;)

Since this circuit hand-selects source resistances, and runs such a low quiescent current, it really doesn't matter which IDSS value you select in practice.  If the circuit was running higher current, a higher IDSS JFET would give you a bit more signal swing before the device hit's saturation but it's academic in this circuit.

Ok, that is what I was wondering/thinking.  My DMM must not do that.  Any other way to do it or else I can try and get over to a friends place who has much better test equipment.

Place a small resistor between the drain and the positive supply (like 10ohms).  You can then measure the voltage drop across it and calculate the current.
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: kante1603 on June 11, 2012, 02:39:26 PM
GR's tend to be difficult to find.  The BL's are common and work fine.  Remember that the 2N3819's are spec'd from 2mA to 20mA which covers the same range. ;)

Since this circuit hand-selects source resistances, and runs such a low quiescent current, it really doesn't matter which IDSS value you select in practice.  If the circuit was running higher current, a higher IDSS JFET would give you a bit more signal swing before the device hit's saturation but it's academic in this circuit.
Thank you!
That's what I was thinking.
Just stumbled over GR's on evil bay from a guy who sold them as matched quads.
O.K.,waiting for BL types now.

See you,

Udo.
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: HellfireStudios on June 11, 2012, 03:25:06 PM
Just a thought... If Nuemann could increase the gain significantly by replacing a single FET, don't you think they might have already done so? It seems strange they went to all the trouble to increase capsule voltage in the U87a without trying easier/cheaper methods of increasing gain. I'm definitely not against experimentation. There could be a FET that could better the performance of one that's design is decades old, though. If it works out, let us know.
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: kante1603 on June 11, 2012, 04:18:06 PM
Just a thought... If Nuemann could increase the gain significantly by replacing a single FET, don't you think they might have already done so? It seems strange they went to all the trouble to increase capsule voltage in the U87a without trying easier/cheaper methods of increasing gain. I'm definitely not against experimentation. There could be a FET that could better the performance of one that's design is decades old, though. If it works out, let us know.
I see this different.
It's not a question of why Neumann didn't change the fet.We're talking about a part that is not available anymore,and we look for a part that might fit better because we're definetely off the specs
Neumann wrote in the 70's.Seen from my results I'm about 6dB off from what was to be expected.
That's twice the level.
Now thinking we're transporting an old piece of gear to this digital age lowish levels can be a big issue since one might not be able to drive the a/d converters hot enough without getting to noise trouble.
So every dB helps.
And please remember all designs in the pre digital aera where made for totally different reference levels,e.g. German Broadcast was +6dBm etc.Nowadays were talking about a 0dBFs point that equals something 14 to18 dB prior to hard digital clipping at a refence level of normally +4dBu.
So we are looking at least for a solution that will give us the spec'd level back,right now we're off from that.
As said the mic sounds beautiful,it has just a too low output level.

Udo.
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: mrcase on June 11, 2012, 05:05:07 PM

So if anybody of you "B2" guys is interested,I have some nice hints and solutions for you to get this baby fully working like the real thing.Things like how to mount the trafo,grounding improvement and so on.Tell me and I´ll post it.

My setup is all-styrene caps except of c3,Peluso capsule and T13 transformer.

And now:
Dan,my friend:You´ve done an awesome job on this!Thank you for all the support,always being friendly and the unbelievable patience with us-I definetely owe you one!!!
Also a big thank you matador,dave  and all of you who contributed so much here,it made the build doable with excellent results!

Cheers to everybody and a big kick in the asses of all you guys at the customs who make our life in the diy world so hard!

Udo
;)

I would be very interested in that kind of information. I will be building this mic in a b2 body as soon as I have more time! :)


P.S.:Will take the mic to our studios these days and do some comparisons with our real U87As.

Edit:Deleted pics for bigger ones in my next post,these have been too small.
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: kante1603 on June 11, 2012, 05:42:14 PM
Hi mrcase,

is that you Martin?
What´s the question?
Maybe you´ve overseen it,I already have posted my hints & tricks for the B2Po,please see the replies #s 750/753/754.

Cheers,

Udo. ;)
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: mrcase on June 11, 2012, 05:48:42 PM
hehe, yes - too impatient again! have found the info! THX

cheers!
martin
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: poctop on June 11, 2012, 06:29:39 PM
Just a thought... If Nuemann could increase the gain significantly by replacing a single FET, don't you think they might have already done so? It seems strange they went to all the trouble to increase capsule voltage in the U87a without trying easier/cheaper methods of increasing gain. I'm definitely not against experimentation. There could be a FET that could better the performance of one that's design is decades old, though. If it works out, let us know.
I see this different.
It's not a question of why Neumann didn't change the fet.We're talking about a part that is not available anymore,and we look for a part that might fit better because we're definetely off the specs
Neumann wrote in the 70's.Seen from my results I'm about 6dB off from what was to be expected.
That's twice the level.
Now thinking we're transporting an old piece of gear to this digital age lowish levels can be a big issue since one might not be able to drive the a/d converters hot enough without getting to noise trouble.
So every dB helps.
And please remember all designs in the pre digital aera where made for totally different reference levels,e.g. German Broadcast was +6dBm etc.Nowadays were talking about a 0dBFs point that equals something 14 to18 dB prior to hard digital clipping at a refence level of normally +4dBu.
So we are looking at least for a solution that will give us the spec'd level back,right now we're off from that.
As said the mic sounds beautiful,it has just a too low output level.

Udo.


Hi Udo, here is some information regarding the different FET used in the vintage and Modern Version
http://repforums.prosoundweb.com/index.php/topic,11630.0.html
 (http://repforums.prosoundweb.com/index.php/topic,11630.0.html) ,  this is where  i decided to go with the 2N3819,  however the sk170 is the one in my orginal and the gain is very comparable i really hope you find the source of your problem

Best
DAn,
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: Corusco on June 11, 2012, 07:36:51 PM
You should strongly consider purchasing on of Eric's (tskguy) capsules. They are great. The Rk-87 is a great capsule for the money but you def need to go with the T-13 and all vintage caps with that capsule. I used that combo in my first mic and there are some samples I posted of it earlier in the thread.

I have been asked by a few other people to build mics for them and I'm pushing Eric's capsules to them as well.

Dave

Hi Dave,

Based on your story at GC and my personal preference for Funkenwork iron, I had planned on using the RK-87 capsule with styrene caps.  Is your recommendation for tskguy's capsules based on (aside from their apparent high quality) their capability with the Cinemags and modern components?  Do you plan on trying Eric's capsule in the T-13/styrene circuit to see how the capsules sound comparatively?

Thanks!
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: Marc Duchesne on June 11, 2012, 08:55:51 PM
Just finished my built, works great and sounds very vintage like. RK-87 capsule with styrene caps, AMI transformer. Excellent combination. I still have some leftovers styrene caps (470pf and 10pf) that I could ship, it will make you save some dollars plus they are hard to get by...
Just let me know,
-marc
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: 0dbfs on June 11, 2012, 09:29:39 PM
Ok, that is what I was wondering/thinking.  My DMM must not do that.  Any other way to do it or else I can try and get over to a friends place who has much better test equipment.

Dan,
You could insert a 1k resistor between drain and + on the battery and measure voltage drop across the R then solve for current through the resistor (I=E/R). Check also with a 10k and/or a 100 ohm resistor to confirm that the 1k resistor is not limiting the current.

Cheers,
jb
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: Matador on June 11, 2012, 09:43:48 PM
Just a thought... If Nuemann could increase the gain significantly by replacing a single FET, don't you think they might have already done so? It seems strange they went to all the trouble to increase capsule voltage in the U87a without trying easier/cheaper methods of increasing gain. I'm definitely not against experimentation. There could be a FET that could better the performance of one that's design is decades old, though. If it works out, let us know.

It all depends on what you want to optimize for:  for example, gain and headroom are often at the expense of one another.  If you record loud transient sources up close you might not need much gain.  Distance mike'ing of quiet sources has different requirements.

I think the design is a good balance of the two, probably tipped in favor of headroom.  Keep in mind, once the circuit clips you are toast on one loud transient:  compression later won't help you.  However most preamps can give you 6-10dB more gain without problem so it seems like a reasoned circuit design decision.

I toyed with the idea of making the source resistor a constant current sink using a regular NPN BJT and few diodes.  Gain increases from 9dB up to 30dB, and the circuit becomes less susceptible to FET variation.  But input headroom falls by an order of magnitude, which means feedback is likely necessary and the circuit won't sound the same.

But this is the beautiful thing about DIY:  you can tailor the design to your needs!
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: wave on June 11, 2012, 10:34:43 PM
So I messaged Matador and he said we should debug this in the thread.

I'm having an issue where my mic (the first one) powers up and sounds great but I have random complete volume dropouts.
The volume will totally drop and then kind of ramp back up to full. Then it will randomly happen again.
Do you guys think this is an issue with one of my caps (I'm using styrenes and they are a bit touch sometimes :) )?

Dave
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: saxmonster on June 11, 2012, 10:41:25 PM
I had an issue with C3 being noisy and static pops. I used the other option and it went away so I had to order a new styrene.  Could it be the phantom power dropping out or something?
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: wave on June 11, 2012, 10:49:36 PM
You should strongly consider purchasing on of Eric's (tskguy) capsules. They are great. The Rk-87 is a great capsule for the money but you def need to go with the T-13 and all vintage caps with that capsule. I used that combo in my first mic and there are some samples I posted of it earlier in the thread.

I have been asked by a few other people to build mics for them and I'm pushing Eric's capsules to them as well.

Dave


Hi Dave,

Based on your story at GC and my personal preference for Funkenwork iron, I had planned on using the RK-87 capsule with styrene caps.  Is your recommendation for tskguy's capsules based on (aside from their apparent high quality) their capability with the Cinemags and modern components?  Do you plan on trying Eric's capsule in the T-13/styrene circuit to see how the capsules sound comparatively?

Thanks!

Hi Corusco,
I know that if you go with the RK-87, T-13, and styrenes you will have a great sounding mic. If you put one of Erics capsules in with those same components you will have a great sounding mic with creamy mids and super silky top end.
If you can afford it, do it for sure.

I have a 2480 here already but I think my long term plans are to use Eric's capsules with either iron.
I do plan on dropping one in my AMI/styrene mic soon.

Welcome to the forum by the way!

Dave
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: sr1200 on June 11, 2012, 10:54:39 PM
Yeah i have an issue where the mic cuts out but if you switch the pad on/off it comes back for a sec or 2 then just fizzles out.
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: wave on June 11, 2012, 11:51:57 PM
SR1200,
Are you using styrenes in your build too?

Dave
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: poctop on June 12, 2012, 01:26:46 AM
So I messaged Matador and he said we should debug this in the thread.

I'm having an issue where my mic (the first one) powers up and sounds great but I have random complete volume dropouts.
The volume will totally drop and then kind of ramp back up to full. Then it will randomly happen again.
Do you guys think this is an issue with one of my caps (I'm using styrenes and they are a bit touch sometimes :) )?

Dave

sounds to me as a bad contact anything arround the Fet or supply to it or R11,

have a double check just to make sure ,

Hope this helps,

D
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: DUDE GUY on June 12, 2012, 05:29:08 AM

Work in progress Sneek Peek ,  :P

D

YESSSSS, I'LL BUY 2!!!!
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: kante1603 on June 12, 2012, 05:53:29 AM
Hi brother Dan,

Maybe it's a good idea to open a new thread before topics get messed up here?
Just a thought....... ;)

Udo.
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: sr1200 on June 12, 2012, 10:09:49 AM
The one thats working fine is styrenes, the non working one no styrenes.  It looks to me i might have some bad caps at the top, i gotta replace them and see if that does it. they may have cooked too long with the iron.
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: Matador on June 12, 2012, 12:01:06 PM
For those using styrenes:  those are notoriously hard to solder.  You really have to hit the joint with the iron and get it soldered within a few seconds.  One tip that helps is to add a thermal mass to the joint:  such as an alligator clip that has no wires.  You can clip it to the lead coming out of the board on the component side, then solder on the underside of the board.  The idea is that the lead will absorb some heat before it gets to the cap to minimize the change of damage.

Caps that go to ground with a ground plane are especially hard as you have to heat the plane as well which takes even more time and is prone to cold solder joints.
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: poctop on June 12, 2012, 12:30:27 PM
Hi brother Dan,

Maybe it's a good idea to open a new thread before topics get messed up here?
Just a thought....... ;)

Udo.

you are correct Sorry for the confusion ,  i am not at the thread stage yet tough  :-X
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: poctop on June 12, 2012, 12:31:51 PM
For those using styrenes:  those are notoriously hard to solder.  You really have to hit the joint with the iron and get it soldered within a few seconds.  One tip that helps is to add a thermal mass to the joint:  such as an alligator clip that has no wires.  You can clip it to the lead coming out of the board on the component side, then solder on the underside of the board.  The idea is that the lead will absorb some heat before it gets to the cap to minimize the change of damage.

Caps that go to ground with a ground plane are especially hard as you have to heat the plane as well which takes even more time and is prone to cold solder joints.

This is a great wisdom and experience comment from Matador. have a look to the Capacitor that are in the ground plane connection,

Dany,
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: kante1603 on June 12, 2012, 12:33:23 PM
+1 on this matador,thanks for pointing us to it!
Styrenes are easy to kill,sometimes it helps to solder multiple parts on just one leg each and then move to the next part.I do this any time when soldering switches built in weak plastic housings or multipin parts like transistors,ICs etc.When soldering alternating the previous soldered parts have more time for cooling down.
The alligator clip is really "cool" ;)
Udo.
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: kante1603 on June 12, 2012, 12:36:00 PM
you are correct Sorry for the confusion ,  i am not at the thread stage yet tough  :-X
No confusion yet,it was meant as a preventive post...

Cheers,

Udo.
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: HellfireStudios on June 12, 2012, 02:23:15 PM
Don't know why this crossed my mind, but I remember someone earlier in this thread mentioning using a small value cap (1.5-2.2pF) across the FET to bring it to proper THD and frequency response spec.
Here is the post I saved for future reference.

"Hi Dan,
Did you measured amp specs via test input? There is Neumann U87i specification at page 8:
 http://www.neumann.com/download.php?download=copi0042.PDF
I had a problem to meet frequency response specs, as well as THD specs. 
After some research I found simple way to tune the circuit to original specs by adding 1.5-2.2pF capacitor between Gate and Drain of FET. Why so? I think that modern 2N3819 FETs have much lower reverse capacitance than original ones from 70s.
Hope it can help in U87 black magic."

The reason I posted this? Is it possible that the gain of the 2N3819 could be adversly by this lack of reverse capacitance. I honestly don't have enough electrical knowledge to even guess, but it doesn't hurt to ask. I hope we can resolve the lower-than-it-should-be gain problem soon. I'm itching to build.
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: poctop on June 12, 2012, 04:46:48 PM
Don't know why this crossed my mind, but I remember someone earlier in this thread mentioning using a small value cap (1.5-2.2pF) across the FET to bring it to proper THD and frequency response spec.
Here is the post I saved for future reference.

"Hi Dan,
Did you measured amp specs via test input? There is Neumann U87i specification at page 8:
 http://www.neumann.com/download.php?download=copi0042.PDF
I had a problem to meet frequency response specs, as well as THD specs.
After some research I found simple way to tune the circuit to original specs by adding 1.5-2.2pF capacitor between Gate and Drain of FET. Why so? I think that modern 2N3819 FETs have much lower reverse capacitance than original ones from 70s.
Hope it can help in U87 black magic."

The reason I posted this? Is it possible that the gain of the 2N3819 could be adversly by this lack of reverse capacitance. I honestly don't have enough electrical knowledge to even guess, but it doesn't hurt to ask. I hope we can resolve the lower-than-it-should-be gain problem soon. I'm itching to build.

The gain will be lower that the AI version this is a fact of the circuit,  i did order a replcement FET for my vintage neumann a while ago strating the project and the 2N3819 was the FET i received straight from berlin with the matching R11 at 8.26K so there is no doubt it is doing the Job

i did compare the U87 vintage to the u1621  here and the gain is virtually the same,  using the T13 will be at 9.5:1 and cinemag at 10:1.  Hence i have no problem with the gain as i record with both with great sucess,  just my 2 cents,

Dan,

Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: Matador on June 12, 2012, 04:56:34 PM
Don't know why this crossed my mind, but I remember someone earlier in this thread mentioning using a small value cap (1.5-2.2pF) across the FET to bring it to proper THD and frequency response spec.
Here is the post I saved for future reference.

"Hi Dan,
Did you measured amp specs via test input? There is Neumann U87i specification at page 8:
 http://www.neumann.com/download.php?download=copi0042.PDF
I had a problem to meet frequency response specs, as well as THD specs.
After some research I found simple way to tune the circuit to original specs by adding 1.5-2.2pF capacitor between Gate and Drain of FET. Why so? I think that modern 2N3819 FETs have much lower reverse capacitance than original ones from 70s.
Hope it can help in U87 black magic."

The reason I posted this? Is it possible that the gain of the 2N3819 could be adversly by this lack of reverse capacitance. I honestly don't have enough electrical knowledge to even guess, but it doesn't hurt to ask. I hope we can resolve the lower-than-it-should-be gain problem soon. I'm itching to build.

This is a way to add a touch of local negative feedback which reduces gain at high frequencies. ;)  It's possible the new FET has higher bandwidth and this is a way to tame that bandwidth down.
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: HellfireStudios on June 12, 2012, 05:56:49 PM

The gain will be lower that the AI version this is a fact of the circuit,  i did order a replcement FET for my vintage neumann a while ago strating the project and the 2N3819 was the FET i received straight from berlin with the matching R11 at 8.26K so there is no doubt it is doing the Job

i did compare the U87 vintage to the u1621  here and the gain is virtually the same,  using the T13 will be at 9.5:1 and cinemag at 10:1.  Hence i have no problem with the gain as i record with both with great sucess,  just my 2 cents,

Dan,

Good to know that it seems to be the same gain as the vintage it clones, but I believe Udo feels his is about 6dB quieter than it should be. I believe he feels it is about 16dB quieter than the U-87Ai he has for comparison. It should be 10-11dB, right? This is why I asked.

Thanks for the explanation, Matador. It might help, if anything seems harsher than I feel it should be.

-James-
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: kante1603 on June 12, 2012, 07:09:41 PM
Good to know that it seems to be the same gain as the vintage it clones, but I believe Udo feels his is about 6dB quieter than it should be. I believe he feels it is about 16dB quieter than the U-87Ai he has for comparison. It should be 10-11dB, right? This is why I asked.

-James-
Hi James (and all you brothers of the solder fume of course),
I did some further searches.Dave (member "wave") was so kind to share his results comparing his clone to an AKG C414 B-TL II.
He wrote they´re about 11 to 12 dB off from another.O.K.,so far so good.
But when you look at the specs there must be something wrong,too far off at least:

Again:
A U87 vintage version seems to not have changed in  output level between 1972 and 1980,the specs say 0,8mV/microbar.This is the same as 8mV/Pa.This equals -41,9xxx dB (dB re 1V).
Next we have the U87Ai (btw,the "i" only means "international type and refers to the xlr connector,just for info....).This is specified at 28mV/Pa which equals -31,05xxxx dB (dB re 1V).
O.K.,we all know that this is much hotter.

Funny thing:An AKG C414B-TL II is (or was,it´s discontinued...) specified at 12,5mV/Pa which means -38dB (dB re 1V)-and that is-compared to our clones-around 3dB off (C414 hotter of course),but not 11 to 12 dB!

Maybe I don´t get this right?Or is it only my clone thinking of that it seems I had the lowest idss of all?But why is Dave´s clone off too?Questions,questions,questions............. ::)

For your thoughts,good night,

Udo.

ADDENDUM:I looked at the original schematics some minutes ago-the voltages at the capsule pads should be 47vdc-I remember most of us had around 40 or 41vdc at the pad-is that a hint,have we overseen something at this point?
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: poctop on June 12, 2012, 07:38:35 PM
Quote
ADDENDUM:I looked at the original schematics some minutes ago-the voltages at the capsule pads should be 47vdc-I remember most of us had around 40 or 41vdc at the pad-is that a hint,have we overseen something at this point?

I did measure on my vintage with my fluke here and it does read the same as the clone 40V,  however if somemone would be able to confirm that back with another vintage then that would be extra ,  the HZ bias measurement on the meter is the same for both tough , so i might be 47V but they read the same hopfully,  are you  Brther Dave and  Udo  running on the same capsule ?, for sure the cinemag should affect the output a tiny bit more than the T13 but still be very comparable.

that would be very interesting on establishing sort of a reference at somepoint, 

anybody with a vintage that could corroborate these data ,


Dan,
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: kante1603 on June 12, 2012, 07:50:03 PM
My combination is peluso pk87 and T13 for trafo.

Udo.
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: poctop on June 12, 2012, 07:57:14 PM
My combination is peluso pk87 and T13 for trafo.

Udo.

I really hope your capsule is not responsible for that and also i would really hope we get in the bottom of this ,

Best,
Dan,
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: kante1603 on June 12, 2012, 08:24:31 PM

I really hope your capsule is not responsible for that and also i would really hope we get in the bottom of this ,

Best,
Dan,
Oh.......  :o?.......you mean the pk87 in general or especially the one in my build?
As said it is really great soundwise,very close to a U87Ai.
That would be very bad financially,I have two from the group buy.....
And I measured the capacitance of it prior to mounting,it was close to 50pF,so spot on to the specs....
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: poctop on June 12, 2012, 08:47:27 PM

I really hope your capsule is not responsible for that and also i would really hope we get in the bottom of this ,

Best,
Dan,
Oh.......  :o?.......you mean the pk87 in general or especially the one in my build?
As said it is really great soundwise,very close to a U87Ai.
That would be very bad financially,I have two from the group buy.....
And I measured the capacitance of it prior to mounting,it was close to 50pF,so spot on to the specs....
Udo,
no to scrare you Sorry  ,this was just a tought i had bad capsule from the best provider ,  but we still can't exclude it from the deal ,
measuring capacitance at rest in something but once polarized if the capsule has lost his tension equilibrium or too loose and get suck to the back plate when polarized then there will be a output loss,  but most proably covered with a rumbly mic , is your pair of mic behaving the same?

I really hope you can solve  the issue and enjoy the mic  after all,
if anyone would like to comments on the output level of their mic are very welcome as do So as an evolving point of view.
Anyone Suffering from very low output ?



Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: wave on June 12, 2012, 09:40:12 PM
Well I guess I'm stupid.
I removed the body and did some visual inspection and I noticed I had the leads reversed on the front of the capsule.
I switched them and I'm not getting any issues so far. Plus it still sounds awesome.

Dave
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: sr1200 on June 12, 2012, 10:30:34 PM
Mine is about on par with my SM7B which is ridiculously LOW output. 
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: 0dbfs on June 12, 2012, 11:28:15 PM
Arrggh! I've just placed my mouser and justradios order for parts to finish four of these buttery morsels.
Already have PCB's, Aurycle bodies, T13 trafo's, and peluso capsules. He he he...
Looking forward to putting these babies together, playing with a hot iron, and slinging some solder so watch out!...
Been very busy with sessions and some studio commissioning so haven't had time to get my DIY on... But I figure no time like the present.

And hey, I personally think most mic's have way too much output anyway. Looking forward to a handful of lower output mic's so I can crank up the gain on my pre's and have less NFB and more FUN!

Ciao!
-jb
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: kante1603 on June 13, 2012, 02:12:10 AM
Udo,
no to scrare you Sorry  ,this was just a tought i had bad capsule from the best provider ,  but we still can't exclude it from the deal ,
measuring capacitance at rest in something but once polarized if the capsule has lost his tension equilibrium or too loose and get suck to the back plate when polarized then there will be a output loss,  but most proably covered with a rumbly mic , is your pair of mic behaving the same?
Hi Dan,

No,I don't have a pair of clones yet.But I have two capsules,so there are at least two ways to shoot things out:
Building a second microphone and compare to my first build.Will take some time.
Or exchanging parts on my existing mic which as faster to do,especially changing the fet and re- bias.
I don't believe in a capsule issue at the moment,the sound it excellent.If say tension was low it would have resulted in a bad sound I think.This one is nearly identical compared to our U87Ais.

Udo.
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: kante1603 on June 13, 2012, 02:22:21 AM
Mine is about on par with my SM7B which is ridiculously LOW output.
Yes,the sm7b is spec'd for -59,0 dBV/Pa / 1,12 mV/Pa,it is a dynamic mic.Seems to be too low too.

Udo.
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: sr1200 on June 13, 2012, 10:26:48 AM
Dumb question, but does the calibration process effect the output at all?  I left the pot IN my mic and I "THINK" i calibrated it correctly.
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: Joekkel on June 13, 2012, 10:27:55 AM
i just finished my u1621 :D first impressions are great, listen to them here (http://soundcloud.com/jbudweiser/u1621-u87diy).

pics here (http://www.facebook.com/media/set/?set=a.4238812415379.180676.1437576141&type=3&l=7da61ccd75).

it is certainly not the most beautiful build ever. the behringer b2-body has it's faults and i'm not really talented in metal-works neither do i have any instruments. i just left one of the straight metal-connections between the headbasket and bottom away, so i had enough space for the boards.

the trafo is just iso-taped to the bottom, will build a metal-shield some time soon, but for now, this is entirely sufficient. don't forget, this is my first diy-build ever (beside some trial/error-circuit-bending some years ago...). i am proud of me and all of you who have built this mic :D

thanks a lot dan!! feels like christmas
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: Joekkel on June 13, 2012, 12:37:41 PM
hi there, so...my previous post was a little too enthusiastic. the mic sounds great, but output ist low, so i measured voltage from ground to aa: 28.5v and ground to cc: 17.8v (same as front-backplate) c6 is sharing these voltages. how to find the mistake?

fet-voltage-drain is 10.3v
zener 23.6v
top of r14 21.2v
c13 40.4v
c11 35.8v
top of r13 28.6v
top of r12 11.6v

compared to this measurements:

Dany

I removed the transformer connections, and the connections to the capsule, and also removed the fet and R11.  original bom components elsewhere.  Here are my voltages:

Phantom power is 48.6v

top of L1 - 48.6v
top of L2 - 45.9v
top of R18 - 48.6v
top of R19 - 45v
bottom of R17 - 45v
top of R17 - 23.18v
Zener 23.17v
FET drain pad 23.15v
FET source pad 0.089v
top of R12 23.15v
top of R13 42.4v
top of R14 23.14v
top of R8 41.8v


What is R9 & R10 doing?  I got 0v there..

i think the fault is either on r13, r12 or c9, as the measurments begin there, to drift apart. what do you think?

thanks, joachim
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: Joekkel on June 13, 2012, 03:14:10 PM
forget everything i just wrote!! don't know about the measurments...they stink. i just compared my u1621 to a lineaudio cm3 which specs as -44dB sensitivity. i positioned both mics close to each other, amplified both with exactly the same amount and played a sinewave. guess what? the u1621 is about 2 dB hotter, which means about -42dB sensitivity!

merry x-mas again!
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: Matador on June 13, 2012, 03:41:18 PM
Polarization voltages cannot be measured with a regular DMM at the capsule as the impedance is too high by several orders of magnitude.  About the only place is the last decoupling cap before the 60M resistors.

Here are some sims of the circuit with some various changes:

(http://www.musicalsparks.com/images/aurycle/transformer_loading.jpg)

The green line is the stock circuit with a 10:1 transformer.  Gain is roughly 27dB in the passband of 40Hz to about 9kHz (or an overall voltage gain of roughly 22 times, so a 1mV signal looks like a 22mV signal to the preamp's inputs).  The red line is what happens if you try to use a 5:1 transformer with no other circuit changes.  The transformer loads down the front end below 500Hz, and the bass response basically disappears.  This effect will become more pronounced the lower the primary L of the transformer (or the smaller the coupling cap).

The yellow line is the response after adding two resistors and another active device:  a PNP follower.  Here is the circuit:

(http://www.musicalsparks.com/images/aurycle/u87-test1.jpg)

The follower reduces the output impedance of the front end from 47kohms to about 270ohms.  This means that the lower ratio doesn't effect the pass band:  you can see the yellow line is identical to the green line, just 6dB higher everywhere.  In fact, this circuit can happily drive a 2:1 transformer which will give back 13dB over the stock circuit.

This new circuit pulls an additional 0.5mA from the phantom supply which will drop the polarization voltage slightly.  One needs to adjust the values of the 56K and 10K drain supply resistors as well to keep the Zener regulating.

Dany:  you might consider adding a provision to a future version of the circuit board for those who need more gain:  the extra components can be easily left off and jumpered across for those that want to stick with the original topology.
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: HellfireStudios on June 13, 2012, 04:53:24 PM
A U-87a PCB might make the people who need more gain happy. I would be in for one. If the pnp follower works, and sounds correct, let us know. Maybe a cheap (but great-sounding) fixed-gain inline preamp might fix the problem. It could also be used for other lower output mics as well. Just a thought.
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: Gus on June 14, 2012, 07:07:48 AM
Matador did you see this thread?
http://www.groupdiy.com/index.php?topic=47569.0
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: HellfireStudios on June 14, 2012, 09:02:08 AM
My earlier post suggested an inline preamp might help the gain situation. While reading other unrelated material, I stumbled upon Naiant mics, and they now have an inline preamp.

http://www.naiant.com/naiant/inlinedevices.html

It's the ITP. At $89, it is hard to tell whether it is a good value or crap product. Any experience with the brand?
Is the Cloudlifter a viable product (w/ standalone P48 box placed prior to Cloudlifter) to rectify the situation?
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: tskguy on June 14, 2012, 10:47:07 AM
So how many of you guys used a scope to bias your fet? I did the headphone method first and the output of the mic seemed a bit low. After scope biasing my mic it had more gain, I didnt really measure the difference but it for sure had more gain. When Dave and I did our shootout it was clear baising with the scope had a impact,   Im also a bit blown away by everyones need to try and get more gain, I just did a session with my u87 and had zero problems getting a nice level.

E
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: sr1200 on June 14, 2012, 11:27:51 AM
E, If your mic has any more gain than mine does it's no wonder you didnt have a problem.  When you have to crank a 70 db pre up to 9 or 10 to get a decent input level, its an issue.  The mic sounds awesome, theres no argument there, just could use a little LESS head room lol.
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: tskguy on June 14, 2012, 11:44:25 AM
How did you bias the fet???
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: sr1200 on June 14, 2012, 11:59:33 AM
This relates to my earlier post about biasing... so, if what you're saying is correct then im going to need to find a new scope... I had to do the bias by ear since my scope died a few months back and i haven't yet replaced it. Hell even 3 or 4 dB would be a vast improvement.  Although I do like the prospects of an additional 6 as stated above...
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: kante1603 on June 14, 2012, 12:06:21 PM
So how many of you guys used a scope to bias your fet?
I did-as well as some others here....
Im also a bit blown away by everyones need to try and get more gain, I just did a session with my u87 and had zero problems getting a nice level.
It´s not everyone´s need,it´s mainly mine (and some others who  wrote about a "lowish" level without defining anything).
If you had my mic you wouldn´t have had any problems too-but only when recording in the middle of a punk band!
It is getting on my nerves now that I always must repeat that my mic has not the correct out level and doesn´t meet the Neumann specs >:(
I am working on it,but for getting the level up,not for creating an "A" version of it....
I know both of them,I work with the "A" nearly daily and I worked with the vintage version from the early/mid 80´s on.
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: kante1603 on June 14, 2012, 12:07:14 PM
E, If your mic has any more gain than mine does it's no wonder you didnt have a problem.  When you have to crank a 70 db pre up to 9 or 10 to get a decent input level, its an issue.  The mic sounds awesome, theres no argument there, just could use a little LESS head room lol.
Exactly!
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: tskguy on June 14, 2012, 02:13:22 PM
Didn’t mean to add salt to the wound,  :-\  I was just sharing the fact that Wave and I noticed my mic had noticeably more gain than his. We both thought it could have been the biasing method.
I wish you luck in troubleshooting your issue. 
Eric
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: wave on June 14, 2012, 02:38:23 PM
So i should probably chime in.
Eric is correct we did need more gain out of hi 9K preamp when doing our A/B comparison. Also, I did the listen method and he did the scope method.
That being said, when I initially did the listen method, my drain voltage was at 12.1 V.
Since I had the problems I stated earlier with the volume drops I changed the drain voltage to 11.5V on the advice of Dany.
Since the mic worked and sounded good I haven't gone back to re-bias yet as my philosophy is "If the car isn't broken, don't fix it".
No I'm def more of a musician than a technician so I don't know if having the .6V difference (between when I "biased the FET to 12.1V and when I changedit to 11.5V) would equate to the actual gain being that much different.

I have noticed that now that the front side of my capsule is wired up correctly (I still feel like an idiot for that one) the mic is experiencing no volume drops or pops or thunder sounds. In fact, it is sounding awesome.
We will have some more techinical opinions after tonight as I think Eric will be by and we can set our mics up side by side into matching 9098 mic pres.

More to come

Dave
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: sr1200 on June 14, 2012, 03:27:18 PM
I cant wait to hear the results of the side by side.  IS there a way to calibrate just using a DMM?
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: kante1603 on June 14, 2012, 06:32:25 PM
Didn’t mean to add salt to the wound,  :-\  I was just sharing the fact that Wave and I noticed my mic had noticeably more gain than his. We both thought it could have been the biasing method.
I wish you luck in troubleshooting your issue. 
Eric
You can see my Reply #305,the last two pics,this shows how it looked like when I biased mine.

Udo.
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: kante1603 on June 14, 2012, 06:47:52 PM
I cant wait to hear the results of the side by side.  IS there a way to calibrate just using a DMM?
Hi,

Sadly I don't think it will work.We are looking for clipping points meaning the points when the waveform changes from a perfect sine to more rectangular,exactly when it starts to flatten out both on the positive and the negative side of it.
A normal dmm can not "see" this.
Maybe  you should try to get a scope as a plug in for your computer or an iPad or so?This is a cheap way to visualize the procedure.I did some general scopings with my iPad set into an i/o dock.Seemed to work pretty good.Didn't do this on my build so far because I have a real scope.I think I will check it too when I get back to my mic,I bet it works.

Hope to have helped,

Udo.
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: geekmacdaddy on June 15, 2012, 08:45:19 AM
"how the U87 is made" Though some of this rudimentary, still very cool...  http://www.youtube.com/watch?v=cvtjHhtxmpI&feature=related (http://www.youtube.com/watch?v=cvtjHhtxmpI&feature=related)
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: HellfireStudios on June 15, 2012, 12:25:15 PM
If anyone is building a U87 clone and wants a capsule, I have two spares of what I'm pretty sure are the RK87 capsule. They're brand new and come in a little plastic container.

Pretty sure? How do you not know the origin of the capsules?
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: poctop on June 15, 2012, 12:46:10 PM
if it is a rk87 the 2 backplate will show open circuit noit a short .

Dan,
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: HellfireStudios on June 15, 2012, 10:21:58 PM
Enchilada, I meant no offense. The wording just put up a red flag (modern marketing made me this way). I just want to make sure no one here gets screwed over by symantics.

Unfortunately, that is the k67-style capsule, and they won't work with this project. On the other hand, the U-67 PCB that may be in the works would definitely work with those capsules. The U-87A is also a canidate. Not to mention almost any mic that uses the K67 style capsule (and there are a lot). I hope you can unload your unwanted capsules.

-James-
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: kante1603 on June 16, 2012, 01:02:30 AM
My understanding is that not all U87 mics had isolated backplates. Also, the U67's has 6 micron diaphragm. These capsules are 3 micron.
That's right,only the vintage versions had them until 1986.By introducing the U87A(i) Neumann went back to the k67 capsule,they found that the isolated version doesn't give a real improvement.They're the same acoustically,Neumann stated this at least.

Udo.
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: geekmacdaddy on June 16, 2012, 10:29:19 AM
Here's what I have so far. I am officially tskguy's first customer of his K87 clone. Arrived yesterday, and as you know, the biggest hurdle in the financial part of this deal. I have the missing components for the board. To my ears, this is the best sounding capsule replacement, and the clips posted were with the cinemag. My brain tells me that pairing this capsule with the Tab Funkenwerks would be a few degrees closer yet still, but, I have this chinese C12 clone here that is begging for the upgrades as well....2 cinemags for the price of 1 tab.....grrrr.....sucks being poor. Anyway, in the words of Grand Funk Railroad, "I'm getting closer to microphooooone".

(http://i52.photobucket.com/albums/g9/geekmacdaddy/U87a%20Clone/IMG_2847.jpg)

(http://i52.photobucket.com/albums/g9/geekmacdaddy/U87a%20Clone/IMG_2845.jpg)

(http://i52.photobucket.com/albums/g9/geekmacdaddy/U87a%20Clone/IMG_2805.jpg)

(http://i52.photobucket.com/albums/g9/geekmacdaddy/U87a%20Clone/IMG_2793.jpg)
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: kante1603 on June 16, 2012, 10:45:35 AM
Cool brother Geek!
Yes,this money thingy hurts at the moment,but wait until it´s done because you´ll have a  2 to 3 thousand dollar mic soundwise.Not bad at all ;)
May I suggest you to run the 4 interconnecting wires ("A to AA" etc.) at the bottom sides of the pcbs and solder from top;this way the build will be even "cleaner" I bet,and you´ve got a lot of room to run the capsule wires without touching anything then.
I will do so on my next one.
Nice headers btw...... ;D

Udo (BOTSF).
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: geekmacdaddy on June 16, 2012, 11:04:18 AM

May I suggest you to run the 4 interconnecting wires ("A to AA" etc.) at the bottom sides of the pcbs and solder from top;this way the build will be even "cleaner" I bet,and you´ve got a lot of room to run the capsule wires without touching anything then.
I will do so on my next one.


Indeed you may, BOTSF Udo. And thank you! I shall do exactly that. Am I correct in understanding that if the screws ground the boards properly, I don't need to mess with pads CGND and GNDLINK?

BOTSF Jeff
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: kante1603 on June 16, 2012, 11:26:16 AM
Indeed you may, BOTSF Udo. And thank you! I shall do exactly that. Am I correct in understanding that if the screws ground the boards properly, I don't need to mess with pads CGND and GNDLINK?

BOTSF Jeff
Exactly,you can see this easily when measuring continuity among all grnd points including the mounting holes.
In my case I had to widen up them with a drill - which opens the continuity to ground-because the pcbs didn't fit the B2Pro and ran a (thick) wire for grounding to the rail.
As long as you can attach/screw them to the metal rails everything is fine.

Cheers,

Udo.
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: poctop on June 17, 2012, 12:06:20 AM
I am working on these and almost ready to try this  ;D,  I have the BV12 From Max pined In but no tranformer yet ,  but also would like to include AMIT67 Package  :P
This is crazy packed up but maybe i would be able to free some room between component and ajust size for braketing, thinking about a standard size available mic body ?
Just wandered if anyone would  recommend an standard fit into available body for the next step,  I hope there is room for expansion  :D

I hope to have mange enough room for Big PIO at tube Height  :)

Oh By the way..... I really hope it works !


D67 transfo,   D67 socket ,   Du67,    really need to go sleep now :P
Power:
(https://io.groupdiy.com/file/gdiy-2017/u/39511/58d1402a02325)

Transfo PCB:
(http://db.tt/pdxaOoKD)

Socket PCB
(https://io.groupdiy.com/file/gdiy-2017/u/39511/58d02819937fe)

Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: berkleystudios on June 17, 2012, 01:07:48 AM
Dan my mouth is watering for that u67. will have to pic up a few boards later.
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: mrcase on June 17, 2012, 04:44:17 AM
awesome! :o
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: kante1603 on June 17, 2012, 04:57:40 AM
Removed post,replied in the "D67"thread.
Brother Dan,you've posted twice!Must have been late last night....
Great work!

Udo.
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: kante1603 on June 17, 2012, 10:58:56 AM
B2Pro builders:

There was a discussion about different versions of this mic.
It´s true!
Here are my results,took just a quick look at them.

Positive is the identical outside,same length and diameter,and the headbasket is the same (same mesh,size and position)-cool.
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: kante1603 on June 17, 2012, 11:09:48 AM
Negative is the deep engravings,but this can be worked around by sanding and filling them,I did this with 2 component glue on my MK47 build,easy one.
But:The head is not screwed to the rails as on the new version,it is plugged in like the Neumann style,the rest is held by latching rails.
The plastic part (with that barcode on it) takes away around 1cm of useful inner length,I must get rid of it.
The latches don´t feel strong enough.
The pcbs go down to to bottom end,in the new one there´s a gap where I mounted my transformer.
All in all it seems to get weak mechanically when I do further disassembly,must think about it first.The new version feels way better constructed,and certainly has a better ground connection between the head and the rest.
Will post more pics when I´m at it again,for now I can´t go further (I have a real job too... ;)).

CU,

Udo.
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: poctop on June 17, 2012, 11:15:39 AM
Removed post,replied in the "D67"thread.
Brother Dan,you've posted twice!Must have been late last night....
Great work!

Udo.

oupss,Thanks Udo,   Not Just LAst night ..... :P

Dan,
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: kante1603 on June 17, 2012, 11:19:15 AM
Good morning...... ;D
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: Lowfreq on June 19, 2012, 06:22:50 PM
Hey guys,

Just a quick question for those of you who have used the arcycle A460 fet bodies for this project.
Are the markings engraved or just painted on? The pad, hpf and the cardioid logo.

I was thinking that since this project is fairly low output, I could ditch the pad and use that switch for the polar patterns. Granted it would only give me two out of the three, but most of the time I only use cardiod and figure 8.

But if it is engraved, then I wouldn't be so happy with the markings conflicting with what the switch actually does.
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: poctop on June 19, 2012, 08:38:23 PM
bought mine from aurycle the brass version (kit) no marking i like the brass thing tough,
see at aurycle.com
D
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: Lowfreq on June 19, 2012, 08:57:42 PM
Interesting, so yours came with no markings on the hpf and pad switch? I understand the body is plain brass.

It's hard to tell from the pics I've seen on the website,
(http://www.aurycle.com/A460DIY-004.jpg)
and even this pic from earlier in the thread.
(http://strangeweathercustom.files.wordpress.com/2012/03/photo-e1332469395496.jpg?w=480&h=642)

They look slightly engraved with a black infill from the pics. But it's just balck paint, then that'd be great, coz it's easy to get off.
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: poctop on June 19, 2012, 10:14:52 PM
Sorry i tought you were concerned about the logo beeing engraved in the metal shell but your right ,

Cheers,
Dany,
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: Marcocet on June 19, 2012, 11:02:35 PM
Yep, it's engraved in the head basket. However Aurycle makes another mic (the 570t) that looks as if it's probably exactly the same inside but has a pattern select switch. I just wonder if it has a transformer shell or not since the mic is transformerless.

I'm planning to use them for my next three mics, so I'll let you know.
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: Lowfreq on June 19, 2012, 11:24:46 PM
Yeah, I looked at the 570t. Might be a good option. I'd change the pad to a hpf.
(http://www.aurycle.com/images/a570t-main-2.gif)

I doubt it would have a transformer cover, but I don't know how necessary that would be. Most of my tube mics don't have any cover for the transformer and I have no problems with those. The shield of the mic seems to be enough.
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: HellfireStudios on June 19, 2012, 11:44:31 PM
If the transformer cover were made of mu-metal, it would be effective against the magnetic fields the transformer produces. As far as I know, the brass or stainless steel most mics are made of isn't mu-metal. The U-87 doesn't use a cover. Most old tube mics don't either. I wouldn't worry about it.
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: micaddict on June 20, 2012, 05:06:10 AM
Udo (et al), I've posted my Behringer B-2 Pro pics in the 67-thread:
http://www.groupdiy.com/index.php?topic=49002.0 (http://www.groupdiy.com/index.php?topic=49002.0)

Oh, about the Aurycle. I'm sure the measurements have been posted before, but could someone repeat them for me, please?


Henk
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: kante1603 on June 20, 2012, 05:13:27 AM
Udo (et al), I've posted my Behringer B-2 Pro pics in the 67-thread:
http://www.groupdiy.com/index.php?topic=49002.]


Henk
 (http://www.groupdiy.com/index.php?topic=49002.0)
Have seen it,great!
Thx Henk,

Udo.
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: geekmacdaddy on June 20, 2012, 06:23:01 PM
Got my donor. A Pacific Pro Audio 99.00 job. Just need the transformer now....close......

(http://i52.photobucket.com/albums/g9/geekmacdaddy/U87a%20Clone/IMG_2848.jpg)

(http://i52.photobucket.com/albums/g9/geekmacdaddy/U87a%20Clone/IMG_2851.jpg)

(http://i52.photobucket.com/albums/g9/geekmacdaddy/U87a%20Clone/IMG_2852.jpg)
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: sr1200 on June 20, 2012, 11:12:52 PM
So an update on my mic... (low output issue) i dunno what happened, but the mic decided to just wake up today.  I just did a session with it and now instead of needing like 60-65 db of gain i was gettin a nice signal at 45-50.... dunno what happened or why, but this thing just rocked the hell out of my client! 
to quote... "What the hell is that thing?  I ain't never heard my vocals sound like that!"  So he looked at the mic (which still says OSP... my donor body... never re-painted it) and said... "OSP huh? never heard of it.." I said that wasn't really what the mic was... that it was a clone of a vintage style Neumann U87.  He asked how much a real one was....  my answer was the end of the conversation.
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: kante1603 on June 21, 2012, 02:47:50 AM
So an update on my mic... (low output issue) i dunno what happened, but the mic decided to just wake up today.  I just did a session with it and now instead of needing like 60-65 db of gain i was gettin a nice signal at 45-50.... dunno what happened
Hi,

Nice the singer liked it,but a mic "waking up"????????
Can you investigate that?
Thinking of a kinda self-healing microphone:A wonder?Magic?No-for me it's nothing but HORROR!
Are you sure you can shoot out the preamp and/or the signal chain?

I'm really curious now about what has happened!
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: berkleystudios on June 21, 2012, 11:21:14 AM
Got my donor. A Pacific Pro Audio 99.00 job. Just need the transformer now....close......

(http://i52.photobucket.com/albums/g9/geekmacdaddy/U87a%20Clone/IMG_2848.jpg)

(http://i52.photobucket.com/albums/g9/geekmacdaddy/U87a%20Clone/IMG_2851.jpg)

(http://i52.photobucket.com/albums/g9/geekmacdaddy/U87a%20Clone/IMG_2852.jpg)

interesting, the PPA PCB is identical to the arycule a460...
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: sr1200 on June 21, 2012, 11:35:22 AM
which is almost identical to the MXL 2001...

If i had to put a guess on what was going on with the mic... im going to blame it on the cable, since i put the mic through the same pre that I initially tested it with...  Used it for the better part of 3 hours without a hitch.  Anything other than that... i have NO idea...  The other mic thats been dropping level after a few sec... i have dismantled and am going to start from scratch on that one.
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: wave on June 21, 2012, 12:34:00 PM
Yo SR1200,
What is the setup of the mic that you have dismantled?
Are you using styrenes? Which capsule are you using?

Dave
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: sr1200 on June 21, 2012, 02:13:20 PM
The dismantled one i was working on wasn't the u87 board... I got an Aurycle mic to use as the donor... then found the OPC body which had all 3 switches on it... so i built the Aurycle and that board just wouldn't work...

 the one that IS working however, has styrenes, TAB trafo and peluso capsule.
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: geekmacdaddy on June 21, 2012, 04:41:44 PM
Ordered the Cinemag CM2480 from Dave...he has to wind some next week so it will be 2 weeks before I see it....gaaah! Can't wait to bring this to fruition.
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: kante1603 on June 22, 2012, 01:15:35 AM
Yes,I know how it feels to wait for transformers for ages ;D

Heads up my brother,we're with you!

Udo ;)
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: geekmacdaddy on June 22, 2012, 04:40:27 AM
 ;D
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: geekmacdaddy on June 22, 2012, 05:11:31 PM
Of interest;

Emailed Matt from Microphone Parts, and he says that the new batch of RK-87's will be ready to ship in about 10 days.
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: geekmacdaddy on June 24, 2012, 11:43:19 AM
What to do while waiting on transformers to arrive in the mail (Brother Udo will certainly appreciate the sentiment);

Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: kante1603 on June 24, 2012, 11:48:26 AM
YES ;D
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: tskguy on June 25, 2012, 03:35:47 PM
Hi all,

As many of you know I have been building capsules for a while, I haven’t really officially started production mainly because I  had a very limited number of gold coated targets. Until now!!! Check out these pics! So I now am officially selling these capsules in 2 styles, the HK87 and the HK67 both have identical back plates but have different back plate connections. Price is 250 plus shipping of your choice.   Anyway here some pics of the coating process..

Enjoy, Eric

(http://i280.photobucket.com/albums/kk187/tskguy/20120625_090214.jpg)
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: 0dbfs on June 25, 2012, 04:09:24 PM
What, Is that a spray bottle full of liquid gold in there?

Just kidding.... That looks like some awesome DIY!

Cheers,
jb
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: wave on June 25, 2012, 09:08:05 PM
Hello fellow cloners!
So if I wanted to drop a 2SK170 in place of the 2N3819, would the 25K trimmer still be the right range for biasing the different FET?

Dave
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: poctop on June 25, 2012, 09:28:57 PM
Hello fellow cloners!
So if I wanted to drop a 2SK170 in place of the 2N3819, would the 25K trimmer still be the right range for biasing the different FET?

Dave

Yep you should be all fine ,  my guess is it will bias around 5-6K,  Let me know
Dan,

Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: HellfireStudios on June 27, 2012, 12:40:52 PM
I just got done testing my twenty five 2N3819's IDss last night. I had a reading of 3.8 mA on nineteen of them, 3.79 mA on five, and it fluctuated between the aforementioned values on just one of them. Does this sound right? I thought they were supposed to be all over the place in IDss values.

To test IDss, I set my DMM for mA. Then, I shorted Gate and Source of the FET, and attached the negative side of a 9V battery. The positive 9V side of the battery was hooked to one of my DMM probes. The other probe was hooked to Drain. Let me know if you see any problems with my testing method or results. Thanks.
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: Hank Dussen on June 27, 2012, 01:31:04 PM
I guess that's within the specs of the datasheet but it does seem low to me.
Mine were all around 10mA...
But maybe they're from from a low IDss batch?

Title: Re: Neumann U87 vintage circuit build thread
Post by: Hank Dussen on June 27, 2012, 01:39:29 PM
with nothing connected to the  Front Capsule nor Rear Capsule ( important )For the sine Tone Method and THD Method : use the big RT and SW Pad on the board,  RT + ,SW -
feed it 0db (0.775VAC) at 1Khz and tweak the pot , if using your Daw as sine tone ,you should be able to hear what come from the mike with headphone or something you need to be able to ear separtely what come from the mike,  tweak the pot fully in 1 way and then fully the other way you should ear the sounds come louder and then get to almost dissapear, what you need to do is to tweak just after it becomes louder and there is no more Fizz in the sounds, you will clearly ear fizzing when the FET opens, just a bit past this point is the good approximative Bias, if you go too Far the Signal will becomes fizzy again but more subtile past this point.( easier to see on a scope) At this point the method is the same for using the Room capture demo software with the THD Meter you only use the THD Meter as an indicator , when the FET opens the Meter goes up at near 25-30% THD so you can clearly see what happening the more you tweak past the opening point the Less THD on the Meter until your reach about 0.4% thd that is fine. if you go too far the THD will slowly rise backup as the fizz in the sounds as the sine symmetry seen in a scope meter, doing it a couple of times is good pratice and you can actually verify your method with the ending drain Voltage if the ending voltage makes sense.

Hope this helps,
Dany,

I want to make some samples with different capacitors in the microphone to compare them.
Is it an idea to inject audio straight into the circuit as described above, and thus being able to objectively compare the sound of the caps, or is a stupid idea?

Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: Hank Dussen on June 28, 2012, 10:00:52 AM
When I trim the transistor I hear the least distortion at about 3V at the drain.
When I set it to 10,5V it's a bit louder but also a bit more distorted.

When I push the input signal only the top of the sine wave clips. However I set trimmer I can't get any symmetrical clipping...

The IDss of that fet was about 11mA.

Any suggestions?
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: Matador on June 28, 2012, 11:30:14 AM
I just got done testing my twenty five 2N3819's IDss last night. I had a reading of 3.8 mA on nineteen of them, 3.79 mA on five, and it fluctuated between the aforementioned values on just one of them. Does this sound right? I thought they were supposed to be all over the place in IDss values.

To test IDss, I set my DMM for mA. Then, I shorted Gate and Source of the FET, and attached the negative side of a 9V battery. The positive 9V side of the battery was hooked to one of my DMM probes. The other probe was hooked to Drain. Let me know if you see any problems with my testing method or results. Thanks.

Transistors from similar lots will be close.  If you ordered them simultaneously from the same place it's likely that they broke up a tape and reel which would explain the similarities.

The datasheet is the the manufacturers "get out of jail card" so they tend to be overly conservative.

Your testing method was spot on.
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: Matador on June 28, 2012, 11:31:27 AM
When I trim the transistor I hear the least distortion at about 3V at the drain.
When I set it to 10,5V it's a bit louder but also a bit more distorted.

When I push the input signal only the top of the sine wave clips. However I set trimmer I can't get any symmetrical clipping...

The IDss of that fet was about 11mA.

Any suggestions?

What is the voltage at the top of the Zener diode and the top of the drain resistor?
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: Hank Dussen on June 28, 2012, 04:34:59 PM
Been doing some more measurements.

I've tried two fets, IDss of 11mA and 12ma.

When I set the fet drain to 10,5V I get these voltages:
fet source: around 3V
zener: 23,4V
top R14: around 21V

These voltages seem to be right according to the schematic but there's no symmetrical clipping, only the top, however I set the trimmer and it sound too distorted as well...

BTW: I've got the scope on the output of the mic.
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: poctop on June 29, 2012, 12:04:09 PM
Been doing some more measurements.

I've tried two fets, IDss of 11mA and 12ma.

When I set the fet drain to 10,5V I get these voltages:
fet source: around 3V
zener: 23,4V
top R14: around 21V

These voltages seem to be right according to the schematic but there's no symmetrical clipping, only the top, however I set the trimmer and it sound too distorted as well...

BTW: I've got the scope on the output of the mic.

you have to put the scope on the Drain Leg of the Fet ,  to do the adjustment ,  these voltage looks perfect to me ,  Have you actually set the capsule and try the mic ,  is your transormer connected properly ? maybe the signal is fizzing from the starting point ?
Hope this help,

Dany,
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: wave on June 29, 2012, 05:01:19 PM
Some more T-13s showed up today!

(http://farm8.staticflickr.com/7266/7468363914_e9bed1cbd3.jpg) (http://www.flickr.com/photos/wavedealer/7468363914/)

Also, for your listening pleasure I have an A/B test of my RK-87 and Eric's K-87.
The tracks are acoustic guitar and they were done by recording with one mic. First the RK-87 was used then I swapped out the capsule for Eric's
Check out the tonal difference.

https://www.dropbox.com/sh/04bghkvc9m22b9i/bYHNf_5RiF

Dave

Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: Lowfreq on June 29, 2012, 05:42:55 PM
Interesting comparison. I thought the RK-87 sounded fuller than the other capsule, but without being there to hear what the guitar sounded like in real life, it's hard to say what capsule was closer to the source.

The RK-87 could sound tubby on some things compared to the Eric capsule. They sure sound different.

Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: wave on June 29, 2012, 08:00:31 PM
Interesting comparison. I thought the RK-87 sounded fuller than the other capsule, but without being there to hear what the guitar sounded like in real life, it's hard to say what capsule was closer to the source.

The RK-87 could sound tubby on some things compared to the Eric capsule. They sure sound different.

Thanks for the comment. I have added a couple scratch vocals including one done with my AKG 414 TLII.

https://www.dropbox.com/sh/04bghkvc9m22b9i/bYHNf_5RiF

EDIT: I noticed a little distortion on the word Why leading the third phrase on the Vox Eric's K-87.wav track . This was a peak on input to the recorder. Sorry guys.

Dave
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: gevermil on June 29, 2012, 09:14:53 PM
Thats a dramatic difference  ???
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: kante1603 on June 30, 2012, 02:08:42 AM
Hi Dave,

Have both mics been in the same position?
How far away have they been?
What transformer did you use?
Is there a hpf set too high on eric's capsule?
From what I hear and not knowing the original sound of the guitar both capsules don't match in any case.Both are completely different microphones soundwise.

On the RK87 there is way too much bass (proximity effect?),on some low notes there are resonances (!!!) and even distortion (slightly but well noticable).This sound is faaaaaaarrrrrrrrr off from anything a Neumann does,it sounds "chinese"in a way-I definetely don't like it.
Eric's capsule is way closer to the "goal",but is lacking of sub frequencies.I like the mid/high section and definition.
Can you explain a bit more in detail how the setup was (position/transformer/micpre and hpf)?

Thanks,

Udo.

P.S.:I would never take a 87 for recording acoustic guitars,but that's a different story........
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: kpearsall on June 30, 2012, 02:43:11 AM
isn't the RK-87 a thinner material too? I would expect it to be more detailed than I'm hearing in those files.
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: wave on June 30, 2012, 11:48:39 AM
Udo,
I guess I should have said that this was as about as controlled of a recording test that I could muster.
The mic was setup about 8 inches off of the 12th fret of my guitar.

I used the same mic for each recording and swapped the capsule. It's not 2 mics.
I used the same mic pre for both recordings, an Amek 9098
The HPF is set to 60Hz.

Dave
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: kante1603 on June 30, 2012, 01:07:45 PM
Udo,
I guess I should have said that this was as about as controlled of a recording test that I could muster.
The mic was setup about 8 inches off of the 12th fret of my guitar.

I used the same mic for each recording and swapped the capsule. It's not 2 mics.
I used the same mic pre for both recordings, an Amek 9098
The HPF is set to 60Hz.

Dave
Thanks Dave,

I think I got that right with swapping the capsules.
What I mean saying "...Both are completely different microphones soundwise...." is that they form completely different sounding microphones.It was some kind of an translation error,sorry for that.
Anyway,at least I know which capsule not to buy ever.....at 8 inches proximity begins maybe very slightly,but not like this-compared to the real thing of course.Where would the RK87 end up when doing close-miking....an earthquake :o?
Can you tell us again which transformer it was and the caps setup (all styrenes or not) please?
Thanks for sharing,

Udo ;)
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: wave on June 30, 2012, 01:14:59 PM
Udo,
All styrenes and T-13 trafo. I'm gonna swap the RK back in and do another test. Maybe when I was playing I moved some or got into it too much.
I just cut another track with Eric's K87 in place and made sure I played very static.
Sometimes I have a heavy pick hand too. it comes from being a rocker and banging on my Gibson on stage.
The last track I cut I was easy on the strum and I backed off the mic pre 6db to make sure there were no peaks on input

Dave
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: kante1603 on June 30, 2012, 02:08:51 PM
Udo,
All styrenes and T-13 trafo. I'm gonna swap the RK back in and do another test. Maybe when I was playing I moved some or got into it too much.
I just cut another track with Eric's K87 in place and made sure I played very static.
Sometimes I have a heavy pick hand too. it comes from being a rocker and banging on my Gibson on stage.
The last track I cut I was easy on the strum and I backed off the mic pre 6db to make sure there were no peaks on input

Dave
Thanks Dave,
Moving while playing is o.k. as long it's not too much,I hope you monitor yourself during recording ;D
Setup is nearly the same as mine electronically except of the mica.As said this combination with the peluso capsule brought me pretty close to an U87Ai soundwise.
Will work on my gain issue in a couple of weeks or so when I have holiday time.The more I think of it the more I believe it's just the fet,not more.Meanwhile I have around 60 pieces here,all idss checked.
A comparison between Eric's and John's capsule would be very interesting in this cap/trafo combination.
But there is an air-line distance of 7.274,107km between us,maybe we can meet in the middle (don't forget your bathing suit,I'll bring the field recorder). ;D

Cheees,

Udo.
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: burglar on June 30, 2012, 02:20:16 PM
Good comparison,

IMO the K-87 is the winner and clearly the closest to the original.  It has the present mid range and very little sibilance.  I'm willing to bet that it would take eq better. 
Both sound good, but by & large, I tend to lean toward darker condensers for male vocals because in my experience, they are far easier to deal with come mixdown. 

Also, didn't like the transient/body ratio of the RK on acoustic guitar compared to the K-87 
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: BarneyBrougham on July 01, 2012, 04:50:37 AM
Hey Everyone.

I have finished 2 U87s now....they both work.
Im using the Peluso capsule and the CM transformer.

Just a question....when testing them next to a cheap AKG c3000b the difference in level is quite a lot.

i have the level on my API with the AKG on 0 and the level is totally enough, actually i need to use a pad if the sound source is loud.

with with both neumann clone i have to turn the API up half way....theyre both set at 10.5v.

is this normal? is this the normal character of the microphone....low gain....it also sound quite dark.

cheers,
Damian


Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: kante1603 on July 01, 2012, 06:16:46 AM
Hey Everyone.

I have finished 2 U87s now....they both work.
Im using the Peluso capsule and the CM transformer.

Just a question....when testing them next to a cheap AKG c3000b the difference in level is quite a lot.

i have the level on my API with the AKG on 0 and the level is totally enough, actually i need to use a pad if the sound source is loud.

with with both neumann clone i have to turn the API up half way....theyre both set at 10.5v.

is this normal? is this the normal character of the microphone....low gain....it also sound quite dark.

cheers,
Damian
Hello Damian and welcome,

The low level is absolutely normal.Look at the Neumann specs for U87 (not U87A!,this is the next generation introduced in 1986 with a way higher output level).
It is at 8mV/Pa while your C3000B is at 25mV/Pa.This difference is extremely huge!

About sound:

Yes,a U87 is darker compared to most cheap condenser mics,especially when comparing them directly to another.This way the Neumann will be too dark to your ears at the moment,but this impression is wrong.Do it the other way round (U87 first,then AKG)'then you'll feel the AKG sounding very harsh,but after some short time you'll maybe even like it.This is the same effect as when using these horrible exciters in the early days they came up,your ears will accustom to the sound pretty fast,followed by wanting even more!Definetely one of the major errors in doing a mix wrong.
Give your ears a good break!
Record say vocals and then try to place them in the mix-you'll know what I mean then.
A Neumann nearly always sits right in it while cheap mics won't,even with heaviest use of equalizers.
They secret is "burried" in their mid/high mid range which make them sound like a Neumann!
Today most of the younger people have seriously damaged their ears by using mp3 players etc. at full level.This is irreversible!!!I always tell my students not do that.Also because of this they are not used to what a good sound or well balanced mix is,and their ears are not in training.

Of course this all is a matter of taste partwise,but we can't talk about things like sound when not knowing anything about basics.So always listen,listen,listen,get experienced.Your brain is able to store millions and billions of so-called Sound or Acoustic Patterns,but you can only use them when you train your ears all the time and learn as much as you can.
Listen to all sound sources with an open mind,even to music or noise in your environment you don't like,it's the best recommendation I can give to young people.

And take care of your ears,they are the most valuabe instruments you have when you really love the wonderfull world of sound.The rest is pure experience.

Hope to have helped,

Udo ;)
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: tskguy on July 01, 2012, 08:50:51 AM
Nicely put Udo ;D I agre with you completly, I have recorded vocals with a number of microphones but I havent ever had a vocal track sit as well as my new u87 clone. I of coarse think my capsule has something to do with that as well.  :P

Eric
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: kante1603 on July 01, 2012, 10:01:57 AM
Nicely put Udo ;D I agre with you completly, I have recorded vocals with a number of microphones but I havent ever had a vocal track sit as well as my new u87 clone. I of coarse think my capsule has something to do with that as well.  :P

Eric
You can bet on it.It's the 40th anniversary of the real thing now,and it still gets awards,not bad!
So there is a reason why.... :)
If all summed up the right capsule and transformer together with the original schematics and the"original parts" e.g. styrenes will do their job.

Cheers,

Udo.
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: BarneyBrougham on July 03, 2012, 06:27:07 PM
Hey there.

Can i hurt my U87 clones by having them in front of a loud guitar speaker cabinet?

i just finished 2....had 1 in the front of my cab all day, and today when i turned the 48v on, the mic started making a weird sound...kind of like there is wind blowing. sounds like wind through my monitors.

any ideas?

thanks
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: wave on July 03, 2012, 07:22:09 PM
Did you use styrenes in your build? Double check your capsule connections too. I had mine accidentally reversed and I had the same noises. Could be one of the caps if you used styrenes as well.

Dave
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: HellfireStudios on July 03, 2012, 07:56:01 PM
Are the styrenes from the BOM polarized? I don't see any markings that indicate polarity. The tantalums/electrolytics are, but I haven't heard of polarized styrenes. If so, wouldn't the silkscreen indicate the positive or negative side for proper installation?
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: mukole on July 03, 2012, 09:06:42 PM
This is my first post here,

I'd like to thank poctop for making this project possible, and all the others who have contributed their valuable information.
I've built 5 of these sets using styrenes/tantalums and using the t13 transformer. I'm in Australia so the best i could seem to find
for a donor body with all 3 switches locally was the isk bm600 which i managed to get at a discount locally for 5. The pcb's fit the mic body comfortably
and the pcbs including the switches are easily modified to work in this project. The bm600 doesn't include a can for the transformer however as the original circuit has the transformer mounted on the pcb, but this seems to make little difference.

I'm now just trying to decide which capsules to use, i originally intended on the rk87, but after listening to Daves sample's am inclined toward Erics k87 capsules. My first real test will be on drum overheads and as room mics so if anyone has any feedback to offer on the different capsules it would be appreciated.

One thing i wanted to share is that i had a lot of trouble biasing the fet at the start.
I followed the instructions using the scope method, but every time i connected the oscilliscope to the drain of the fet and increased the signal level the sine would lean over into a sawtooth. I tried various methods for generating the tone, a couple of different sources for phantom power, as well as pc based oscilliscope using the output of the mic into an mbox2 which just showed clipping on the positive side of the wave regardless of the bias setting.

Also I noticed that with the scope there appeared to be much more level at the gate than the drain of the fet.
So after rechecking all my voltages, checking my transformer wiring, and looking at the schematic i tried again with the primary of the t13 disconnected.

Voila!!! The biasing worked as it was intended.

I referred to the instructions several times during my attempts at biasing, and didn't notice any notes about the transformer needing to be dissconnected, but please excuse my ingorance if its already stated.
I'm not sure if this is a problem with the cinemag but it definetely made scope biasing impossible with the t13.

Apart from that, i've tried one mic in cardoid mode with the stock capsule connected and it sounds very promising.
I can't wait to hear my final build.


Are the styrenes from the BOM polarized? I don't see any markings that indicate polarity. The tantalums/electrolytics are, but I haven't heard of polarized styrenes. If so, wouldn't the silkscreen indicate the positive or negative side for proper installation?

No styrenes aren't polarised, I believe only electrolytics including tantalums are.


Cheers

Mick
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: HellfireStudios on July 03, 2012, 09:47:04 PM
Much like mukole, I've been running into problems with biasing the FET with a scope. I'm using a Carvin CM-87S with stryrenes/films/tantalums and a Peluso BV8P-S wired 11:1. Peluso capsule, as well, but that doesn't matter at this point.

The scope is Signalscope Pro for the iPad. All ins and outs are handled by an Alesis I/O Dock. When the signal is sent directly to/from the iPad, a perfectly good sine wave appears on screen. When sent through the mic (with phantom power being supplied by a standalone phantom supply), the signal resembles what was described as oscillation earlier in the thread (I believe wthrelfall was having this problem). When I get the chance, I'll try and post some screenshots of my scope.

I'm using a 2N3819 with an IDss of 3.8mA. Below are my measurements. As I can't get the scope/mic combo to respond properly, the pot (25k) is in an arbitrary position a few turns from fully counter-clockwise.

top of L1 - 47.2v
top of L2 - 47.2v
top of R18 - 47.2v
top of R19 - 46.6v
bottom of R17 - 23.4v
top of R17 - 23.4v
Zener 23.4v
FET drain pad 6.7v
FET source pad 2.8v
top of R12 6.7v
top of R13 21.3v
top of R14 20.2v
top of R8 11.5v

Some of my readings don't seem to be right. Any suggestions as to what could be causing these unsettling problems?
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: tskguy on July 03, 2012, 10:00:43 PM
I am pretty sure Wave was refering to the actual microphone capsule wires being reversed.  Not the styrene caps. You also may have a bad capsule. Does the capsule do this worse when you breath on the capsule? It could be getting sucked to the backplate. Its really hard to say without hearing the sound as well. Anyway I hope you get it figured out. And Mukole please let me know, I would love to have some of my capsules down under!!

Eric
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: HellfireStudios on July 03, 2012, 10:12:37 PM
Here is a the direct Sine wave into the iPad.
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: HellfireStudios on July 03, 2012, 10:14:34 PM
Here is the Sine wave sent thru the mic into the iPad at minimum volume on the I/O Dock.
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: HellfireStudios on July 03, 2012, 10:17:56 PM
Here it starts to oscillate as the volume increases a little.
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: HellfireStudios on July 03, 2012, 10:20:17 PM
Finally, here is the full on oscillation at any healthy volume level. BTW, the signal doesn't seem to clip. It just gets louder.
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: mukole on July 03, 2012, 10:42:39 PM
I think that looks like 50 or 60 hz interference, i had the same thing when i put the high impedance side of the mic face down on the table,
it would lessen if i picked it up, and dissappeared when i put the mic body on





Finally, here is the full on oscillation at any healthy volume level. BTW, the signal doesn't seem to clip. It just gets louder.
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: mukole on July 03, 2012, 10:52:06 PM
Hi Hellfire,
Your voltages on r8 and r13 are much lower than mine,
what are your voltages on r15 and r16?

Have you double checked the 2 electrolytics  c11 and c13 are installed the right way around?

Also I'm guessing you may need to rotate your pot anticlockwise to increase the voltage depending which pins you
used on the pot.

cheers







top of L1 - 47.2v
top of L2 - 47.2v
top of R18 - 47.2v
top of R19 - 46.6v
bottom of R17 - 23.4v
top of R17 - 23.4v
Zener 23.4v
FET drain pad 6.7v
FET source pad 2.8v
top of R12 6.7v
top of R13 21.3v
top of R14 20.2v
top of R8 11.5v

Some of my readings don't seem to be right. Any suggestions as to what could be causing these unsettling problems?
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: poctop on July 04, 2012, 09:59:37 AM
Hi Hellfire,
Your voltages on r8 and r13 are much lower than mine,
what are your voltages on r15 and r16?

Have you double checked the 2 electrolytics  c11 and c13 are installed the right way around?

Also I'm guessing you may need to rotate your pot anticlockwise to increase the voltage depending which pins you
used on the pot.

cheers







top of L1 - 47.2v
top of L2 - 47.2v
top of R18 - 47.2v
top of R19 - 46.6v
bottom of R17 - 23.4v
top of R17 - 23.4v
Zener 23.4v
FET drain pad 6.7v
FET source pad 2.8v
top of R12 6.7v
top of R13 21.3v
top of R14 20.2v
top of R8 11.5v

Some of my readings don't seem to be right. Any suggestions as to what could be causing these unsettling problems?


FET drain pad 6.7v
 this seems to be a bit on the low side for sure i would expect it to be arround 11-13V after the bias,

DAny ,
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: sr1200 on July 04, 2012, 10:24:03 AM
Hey i finally found out what happened to my mic!  It wasn't a miracle from the gods afterall... seems i had the pad switch wired backwards... when i recorded with it last, i must have inadvertently switched it by accident.   :-[ :-[ :-[ :-[
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: kante1603 on July 04, 2012, 10:53:37 AM
Hey i finally found out what happened to my mic!  It wasn't a miracle from the gods afterall... seems i had the pad switch wired backwards... when i recorded with it last, i must have inadvertently switched it by accident.   :-[ :-[ :-[ :-[
Aaaaaaaaaahaaaaaaaaaahhhhh,
Cool you keep us posted!
Yes,it's easy to reverse switch connections on toggles,glad you got it sorted,

Rock on,

Udo :)
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: HellfireStudios on July 04, 2012, 11:34:47 AM



FET drain pad 6.7v
 this seems to be a bit on the low side for sure i would expect it to be arround 11-13V after the bias,

DAny ,
[/quote]

There was no biasing that could be done on the scope. As I said earlier, no matter how much signal I pumped into the mic, it would not clip. It would just start to look wobbly until the wobbles started to create their own wobbles (the last screenshot). So I'm nowhere near biased at this point.

Mukole, I checked all my electrolytics and tantalums. They are all oriented correctly. I even went as far as to recheck all my resistor/capacitor values to make sure I didn't make a stupid mistake. Cold solders are a thing of the past for me (I use silver-bearing solder to make my life a lot easier). None of my switches are hooked up. Just the transformer. Could my very low IDss FET be the culprit (3.8mA)? Thanks for your help so far.
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: kante1603 on July 04, 2012, 01:10:41 PM
Hi Hellfire,

Even if you have other problems the biasing must be done accurate first.
Some questions to your procedure:
Is the capsule disconnected?
Where do you insert your test signal (sine)?
Is the transformer connected?
From which point do you pick up the signal to the scope?

Cheers,

Udo.
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: mukole on July 04, 2012, 04:47:58 PM
As i couldn't get anything useful on the scope i set the voltage on the drain to 10.5v as dany suggested to do all my testing. This was pretty close to the final bias settings anyway. It wasn't until i disconnected the primary connections to the transformer that the scope started showing me anything useful.
Have you tried scoping without the transformer connected?




None of my switches are hooked up. Just the transformer. Could my very low IDss FET be the culprit (3.8mA)? Thanks for your help so far.
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: HellfireStudios on July 04, 2012, 05:35:08 PM
Hi Hellfire,

Even if you have other problems the biasing must be done accurate first.
Some questions to your procedure:
Is the capsule disconnected?
Where do you insert your test signal (sine)?
Is the transformer connected?
From which point do you pick up the signal to the scope?

Cheers,

Udo.

The capsule is disconnected. I insert the positive of the sine wave at the top of R9 (which is in direct contact with RT). The negative goes to ground via the negative leg of C11. The transformer IS connected, and I use an XLR cable to hook it to my I/O Dock's mic input straight from the mic's XLR.

As i couldn't get anything useful on the scope i set the voltage on the drain to 10.5v as dany suggested to do all my testing. This was pretty close to the final bias settings anyway. It wasn't until i disconnected the primary connections to the transformer that the scope started showing me anything useful.
Have you tried scoping without the transformer connected?




None of my switches are hooked up. Just the transformer. Could my very low IDss FET be the culprit (3.8mA)? Thanks for your help so far.

I may do the biasing-by-voltage technique first to get the circuit close to where it should be. Then, retest my voltages.
When I do go back to the scope, where would I tap the signal from without the transformer connected? Also, if my scope is showing possible 60HZ hum, how can I tweak the pot with the mic's body in place?
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: mukole on July 04, 2012, 06:30:22 PM
You need to scope at the drain of the fet, once I disconnected the transformer I could see a much greater signal at the drain of the fet and the interference was no longer noticable on the scope.
I Hope this helps
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: HellfireStudios on July 04, 2012, 07:33:41 PM
You need to scope at the drain of the fet, once I disconnected the transformer I could see a much greater signal at the drain of the fet and the interference was no longer noticable on the scope.
I Hope this helps

I appreciate the tip. I'll try it tonight, and let you guys know if that does the trick. I don't know where I got the idea to hook the mic's output to the scope... Thanks again.

-James-
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: kante1603 on July 05, 2012, 03:00:37 AM
James,

best to do this is the matador method.
What you have on your scope is a heavy oscillation,I ran in the same thing when I did it the first time-with a real scope!
We want to bias the fet,therefore it is best not to have too many surrounding parts here influencing the measuring.
Capsule and transformer should be disconnected first.
Next step is to insert the sine signal at the right point.For us it is not "rt" and "sw",it´s the junction between R6 and C4,the cap that is leading to the fet´s gate.
For picking up the signal for the scope you attach your probe to the fet´s drain connection.
Follow matador´s instructions (you find it in the other thread,first page).
It´s easy to understand and also alot of fun.
This should work now.

Hope to have helped,

cheers,

Udo ;)
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: Matador on July 05, 2012, 05:53:34 PM
I cannot claim credit, I got the method from Zapnspark on micbuilders. ;)

You should be able to bias the FET with the transformer connected.  But try to load the secondary with an appropriate resistance if you leave it in circuit.  A 1k resistor across pins 2 & 3 is ok to represent the inputs to a mike pre.

However you STILL always measure the drain AC coupled in order to do the biasing:  don't measure on the secondary side of the transformer.
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: HellfireStudios on July 05, 2012, 07:30:50 PM
Alright, I disconnected the primary side of the transformer, hooked a 1/4" guitar plug to two gator clips (+ hooked to "flipped" R6, Gnd hooked to ground), and ran a sine sine wave at 1000Hz through said cables. Then, I hooked another plug to my mic/guitar input (+ goes to drain of FET, Gnd goes to ground). This cable goes to the oscilliscope. I now get something resembling a sine wave, but I'm still unable to get any clipping from the mic no matter the level (when line outs are at maximum, the positve wave stays the same, while the negative side widens considerably). I can get the mic pre on the I/O Dock to clip, but that's it. Rotating the pot clockwise raises the amplitude, and counter-clockwise the opposite. No clipping regardless of the pot's setting, as well.

I may have inadvertently shorted some FET leads while phantom power was applied. Could this cause a fault?
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: tskguy on July 05, 2012, 10:29:03 PM
You are feeding it 48volts correct?? :D
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: wave on July 05, 2012, 10:32:13 PM
Hellfire,
Can you set the drain to 11.5V and take another screenshot and post it?

Dave
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: HellfireStudios on July 06, 2012, 01:08:28 AM
You are feeding it 48volts correct?? :D

I am using a standalone phantom power supply at 47 to 48 VDC.
Hellfire,
Can you set the drain to 11.5V and take another screenshot and post it?

Dave

I set the drain voltage to 11.5VDC by setting the positive probe of my DMM on the drain lead and the negative probe to ground. The screenshot is of a healthy signal before it starts to act funny (when more gain is added).
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: HellfireStudios on July 06, 2012, 01:20:15 AM
With these next screenshots, I took 8 successive shots while the signal went haywire.
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: HellfireStudios on July 06, 2012, 01:27:37 AM
It basically cycles between positive and negative clipping ina chaotic manner. Here is some negative clipping.
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: kante1603 on July 06, 2012, 02:38:18 AM
It basically cycles between positive and negative clipping ina chaotic manner. Here is some negative clipping.
This cycling behavoiur could be something with your program you´re running on the iPad I think,maybe a sync issue.
Anyway,the waveforms the pics are showing are exactly what we´re looking for,meaning the sine flattens out.
Try adjusting the pot and see if the displayed waveform follows the pot movement.
You must work with the input level from the generator too,there´s an interaction between level,the resistance from the pot and on which side the sine flattens out.The goal is to get the flattening out on both sides at the same time and the same amount.
If you´re absolutely unsure about your fet I would replace it (just a few cents),this way you can shoot out if the cycling behaviour is related to the fet or the ipad/Scope program.
Some posts ago you wrote that you weren´t able to get a distorted on your scope-now you are!So there´s a little success in debugging your build,no? ;)
You´re close to it!


Cheers,

Udo.
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: HellfireStudios on July 06, 2012, 03:21:45 AM
Well, not quite. The way it seems to be working is:

- I'll adjust levels until a stable sine wave appears.
- Then, I zoom in on the waveform to get a closer look.
- Following this success, I turn up the master output on the I/O Dock.
- The once-stable sine wave starts to fluctuate, and then clip wildy and erratically, until the volume is brought down, and a stable sine wave appears again.

Due to this erratic nature (the clipping seems to be at constantly changing points), I can't decypher when it is clipping, which side of the swing is clipping, or to what degree it clips. I wish I could show you guys video of this stuff.

As far as the iPad scope program goes, I was able to get a clean sine wave when plugging direct from the signal generator to the oscilliscope. The signal stayed clean until the I/O Dock's input clipped. Could my scope still be the problem?

Just to put my mind at ease, did I test the drain voltage correctly ( DMM + to drain, DMM - to ground)? Thanks again. One of these days, I'll get an amazing mic.

-James-
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: mukole on July 06, 2012, 09:01:04 AM
Hi James,

I totally undersand how impossible it is to perform this procedure when you can't see what your supposed to be seeing.

I think your definitely on the right track, I was looking over your first lot of pictures again and in the first pic (Direct Sine Wave) you can clearly see a 1 khz sinewave, the following picture (Sine thru u87 (low level)) is in fact showing a 50-60hz sinewave if you check the timescale along the bottom.
The 2 pictures after that show the 50-60hz sine mixed with your 1khz tone which seems unusally low in level but is what appears as "oscillation".

Comparing these to your second lot of pictures you are getting far more level now (97-100pa vs 4.4pa), I don't understand how the pa reading relates to mV as i use a stand alone oscilliscope which measures mV. But one thing i did notice is that the "pa" scale on the left varies over your last few pics. Are you manually zooming in and out or does the software also automatically zoom?

I think udo may have a point about you having a possible sync setting.
Do you have any option in your software to manually set the "trigger" or "trigger lock"?
If you do, then adjust this setting with your 1khz tone running into your scope input until you can clearly view the sinewave, then try rebiasing.

I 'm not familiar with your software at all and this is just a guess but maybe its possible that the trigger is losing its sync as you increase the signal, when i was biasing if i turned the signal down too far i would lose sync and see my waves scrolling past on the screen.

Another thing i would check is that your cable connections are good and solid, they can cause all sorts of erratic images on a scope if they are at all compromised.

I noticed you said you zoom in to get a closer look, have you tried not zooming in and just pushing your level up higher until you see the wave?
is it possible your not using enough level to cause viewable clipping?

Have you any way of listening to whats coming through the scope so you can get more idea whats going on?

I'm only guessing but i think there maybe some minor thing your overlooking.


Mick
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: HellfireStudios on July 06, 2012, 01:08:20 PM
I thought by "sync" you meant like A/D sync issue. It seems like it may be losing sync (the trigger threshold is set to 0.000 Pa) as I increase the volume. The wave begins to shift up and down a little. Then, it begins to shift out of control, clip wildy, and move accross the screen. The best way to describe the chaotic nature of the movement is to equate to Bugs Bunny, after he sees a monster, when he walks away muttering nonsensicals and generally freaking out. Spastic comes to mind. I'll give it another go soon.

I'm going to spend some time learning exactly what all those little menu options mean in SignalscopePro. Can anyone recommend a good place to learn the intricacies of the oscilliscope? Thanks.
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: kante1603 on July 06, 2012, 04:25:06 PM
@ Hellfire,

the more I follow your posts the more I bet it's just your scope showing weird things.I also don't get these "pa" scalings same as mukole.As I don't know your program,can you say it is approved by the manufacturer that it is running stable on an alesis io dock?
I have read somewhere that it tends to do some nasty things when running different programs on it,for example randomly swapping inputs ans so on.Maybe it is really only a sync/trigger issue.
Can't you borrow a scope from a friend or so?

Just an idea,

Udo.
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: HellfireStudios on July 06, 2012, 04:56:18 PM
@ Hellfire,

the more I follow your posts the more I bet it's just your scope showing weird things.I also don't get these "pa" scalings same as mukole.As I don't know your program,can you say it is approved by the manufacturer that it is running stable on an alesis io dock?
I have read somewhere that it tends to do some nasty things when running different programs on it,for example randomly swapping inputs ans so on.Maybe it is really only a sync/trigger issue.
Can't you borrow a scope from a friend or so?

Just an idea,

Udo.

Unfortunately, I'm the only person I know who does this type of stuff around me. So no scope to borrow, that I know of.
On the other hand, Signalscope Pro is not a cheap program by the Appstore's standards ($75).  It has calibration controls that haven't been set beyond default. There are probably a lot of little things that need to be set appropriately before the scope will work correctly in my case.
FWIW, I use the Pa setting on the scope because it gave me a sine wave on the direct in test. There is also a FS setting, but I remembered seeing mV/Pa used for mic sensitivity, so I used it on the scope. I feel like I have a lot of reading to do before the scope will be my friend.
Which test is 2nd on list for effective biasing, and where amongst this plethora of information could I find the specifics? I'd like to test the mic audibly to make sure the electronics work before I go further with the scope. Thanks in advance. You have all been so helpful and quick with responses.

-James-
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: kante1603 on July 06, 2012, 06:04:16 PM
Hi James,

I can not find a manual for signalscope pro,so it´s hard for me to help you.
At least you should try to change the y-axis to read mv.
"Pa" means "Pascal" and is relating to the sound pressure level through the air,"Pa/mv" is the result in Millivolts on the output of the measured microphone in relation to a defined acoustic signal source in a defined distance given a defined sound presure level and so forth.
We don´t need it for this measuring,just the amplitude on the y-axis in Millivolts and the time on the x-axis,that´s all.
Next I would check is the trigger modes,I´ve seen from the program´s description there are several options like these:

Auto, normal, and single-shot triggering
Trigger slope and threshold options


Just try these settings,it is nearly impossible to explain all the functions of a scope in a short way.
Swapping the settings on the fly doesn´t hurt,so it´s "trial and error-time" now,hahahaha........

Biasing should be done first,then give it a listen.You can try the mic for functionality of course,but depending how far the exact bias point is off to what it should be you might end up in pretty bad results.

Good luck,

Udo.
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: Matador on July 06, 2012, 06:52:05 PM
What kind of gain are you seeing?  Before it goes crazy, what are the input and output amplitudes?
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: HellfireStudios on July 06, 2012, 08:57:40 PM
I would have to perform the tests again to be sure, but it is just a tiny bit above the solid sine wave pic from the mic. I'm going to try using the I/O Dock as the signal generator, and run the oscilliscope program from the iPod Touch via my iRig "interface." We shall see if Alesis Dock is to blame for my strange readings. I'll report back ASAP.
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: tskguy on July 07, 2012, 08:33:16 PM
 :) Hi all,

Doing a small run of capsules, thought you guys might enjoy a picture.

(http://i280.photobucket.com/albums/kk187/tskguy/20120707_191651.jpg)
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: HellfireStudios on July 08, 2012, 11:48:33 AM
After trying to run the scope again last night, the readings were stranger and totally different. The sine wave looked "fuzzy" at normal levels and oscillated at higher levels. My points of contact were correct in this test, and it acted similarly to when I was doing it wrong earlier. If my scope doesn't give me consistent output, I'm afraid I will have to find some other way to bias it. Does any one know where in Central Florida I could find a scope? Is craigslist a feasible place to ask about using someone's scope to test some stuff? Would an electronics repair shop have a scope on hand I could rent? I'm so close to a completed mic I can taste it (electricity is tangy).

It can't hurt to put it out there. If anyone on this thread is in Florida, and has a scope, I'd be willing to drop a few dollars to "rent" it long enough to bias this mic and two preamps (Neve 1290 clones). PM me. Thanks.
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: kante1603 on July 08, 2012, 12:30:44 PM
James,

Shops for electronics repairs like radio and tv certainly have scopes.
What just came to my mind was:why not ask a teacher at a lokal school,normally they have one for physics lessons!Would be perfect during the holidays,no?

Cheers,

Udo.
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: HellfireStudios on July 08, 2012, 02:16:43 PM
I know that the high school I went to had no scope to speak of (and the school was fairly well equipped), but it couldn't hurt to ask. If schools in your part of the world have scopes, it shows just how sad American/Florida education have become. I'll check around for a scope soon. Thanks again for all the help.

-James-
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: Matador on July 08, 2012, 02:48:00 PM
After trying to run the scope again last night, the readings were stranger and totally different. The sine wave looked "fuzzy" at normal levels and oscillated at higher levels. My points of contact were correct in this test, and it acted similarly to when I was doing it wrong earlier. If my scope doesn't give me consistent output, I'm afraid I will have to find some other way to bias it. Does any one know where in Central Florida I could find a scope? Is craigslist a feasible place to ask about using someone's scope to test some stuff? Would an electronics repair shop have a scope on hand I could rent? I'm so close to a completed mic I can taste it (electricity is tangy).

It can't hurt to put it out there. If anyone on this thread is in Florida, and has a scope, I'd be willing to drop a few dollars to "rent" it long enough to bias this mic and two preamps (Neve 1290 clones). PM me. Thanks.

It's possible the scope probes themselves are causing the problems, especially if they aren't high impedance.  Since you are looking at the drain, it's possible the scope may be putting hash into the ground connection which feeds back to the gate causing the oscillation.

I just purchased a Rigol DS1102E from Saelig for about $400, which is good to 100MHz.  If you plan on doing a lot of stuff like this in the future it's money well spent (along with a decent function generator that can do sine and square waves).

Aside from that, you should be seeing a gain of about 6-9 with reasonable input levels (say starting at about 100mV peak-to-peak).  After biasing, you should be able to put in nearly a volt peak-to-peak before you clip both sides of the waveform (assuming a normal gm FET, of course).  The output should be able to swing 7V or so peak-to-peak before you start pinching off the FET (again, assuming a FET in the middle of the specs).  Higher gm FETs will clip with less input signal, however will be "louder", all other things being equal.

And tskguy, stop showing those capsule pics!  I'm nearly to the point of replacing a laptop after all the drool in the keyboard!  ;)
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: wave on July 10, 2012, 05:47:59 PM
For the record Matador, Eric's capsules definitely have a high drool factor!
I have 2 RK-87s and one of Eric's K87s that I have swapped through one mic. The RK-87s sound good and have a nice quality on the high mids that brings a lot of presence.
That being said, Eric's K87s have an incredible midrange response as well as a very nice hi end (we're talking in the 16K-20K range).
I have spent a lot of time recording different vocals through the capsules and the RK-87 is a great capsule, especially for the price range.
Eric's capsules are worth every extra $115. I have tried different combos of caps (styrenes and pulse films) and Eric's K87s sound great through either. I think if one wants to go the RK-87 route, using the styrenes is what I would do. I notice an openness and depth with the styrenes but it comes with a cost. They seem to be a bit noisier than their pulse film counterparts and as has been documented by myself and saxmonster, they are very sensitive when it comes to being installed. I had to replace the 2 470pF and the 10pF today as I think that I applied too much heat when I initially installed them. You really gotta be quick with the iron. I also changed the way I installed them from the orientation like the resistors to bending the leads down and in and orienting them horizontally.
When I first built the mic, it sounded great and in hindsignt, I think I would have left it alone. However, since I'm building them for other people now I wanted to fully educate myself as to what the sonic differences are with the different component combos.
The only thing I stillneed to try is the combos with a Cinemag. I have been doing all my experimentation with the AMI T-13.

Sorry this post was so long
DAve
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: HellfireStudios on July 10, 2012, 06:42:31 PM
Well, I went to my local TV repair shops today (all two of them), and was graciously turned away by people who seem to have less electrical knowledge and more oscilliscopes than I do (which is none). I don't know if was fear of "new" 1967's technology or my long hair that did me in with these backwoods types. Unfortunately, this leaves me without a cheap scope option yet again.
When/if I ever get this scope problem sorted out, I'll post pics of the finished mic (at least I know the outside looks pretty. Now, if only the mic sounded as pretty as it looks...).

-James-
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: tskguy on July 11, 2012, 08:18:13 AM
Thanks for the kind words guys! Interesting suff Dave, I am glad you figured out the issues with the styrenes.  I have to admit i am glad I went with the pulse films on my mic. ;D

Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: geekmacdaddy on July 12, 2012, 10:22:54 AM
Cinemag FINALLY shipping! Should have it tomorrow or Sat. Will be putting it together on Sunday. I hope. Damn.
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: tskguy on July 12, 2012, 02:56:24 PM
Sweet!

Cant wait to hear it... ;D
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: HellfireStudios on July 12, 2012, 03:52:16 PM
Just an update on my lack of a scope. I've got a customer of mine that does ham radio stuff for a hobby. Unfortunately, he is out of town until next week, and there is no guarantee he will have acces to an oscilliscope when I do hear back from him. With my patience wearing thin, I'm considering buying one myself. The only thing I need it for is transistor biasing. Can anyone recommend a dirt-cheap-but-will-get-the-job-done oscilliscope? Keep in mind, I'll only likely be biasing a few mics and preamps. I guess I could also use it to detect DC ripple in power supplies and the like. Thanks.

-James-
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: 0dbfs on July 12, 2012, 04:00:45 PM
A simple dual channel scope is awesome for comparing signals in circuits. I bought one off clist for $50. You can get SW scopes, hw scopes, recording scopes, and newer/better/faster if you want to spend more and more. Something simple, used, and cheap works well for most general tasks.

The one I picked up is a 20mhz model which may be a little low for detecting some oscillations but works well for poking around.

Cheers,
jb
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: 0dbfs on July 12, 2012, 06:51:51 PM
A simple dual channel scope is awesome for comparing signals in circuits. I bought one off clist for $50. You can get SW scopes, hw scopes, recording scopes, and newer/better/faster if you want to spend more and more. Something simple, used, and cheap works well for most general tasks.

The one I picked up is a 20mhz model which may be a little low for detecting some oscillations but works well for poking around.

Cheers,
jb
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: kante1603 on July 13, 2012, 11:38:50 AM
Yes,I bought a nice used Hameg for less than 100 EUROs an evilbay.
Very usefull for most of our audio stuff.
James,maybe someone in your area from this forum can do the biasing for you.Sending just the pcbs in a flat envelope can't be too expensive,and-given the circuit is working-it's just a work of 5 minutes.

Udo.
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: HellfireStudios on July 13, 2012, 04:00:56 PM
Yes,I bought a nice used Hameg for less than 100 EUROs an evilbay.
Very usefull for most of our audio stuff.
James,maybe someone in your area from this forum can do the biasing for you.Sending just the pcbs in a flat envelope can't be too expensive,and-given the circuit is working-it's just a work of 5 minutes.

Udo.

I would be up for that, but my previous experience with unwilling people won't leave me holding my breath anytime soon... Not to mention I have more to bias than just the mic (two KM-84's I've yet to build, two Neve 1290 clones, and possibly a pair of Trident A-Range clones in the future). Maybe my luck will change. Thanks for the suggestions, guys.
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: HellfireStudios on July 16, 2012, 05:28:55 PM
Hmmm... I've been over at evilbay trying to make sense of all the oscilliscopes they have to offer. My question are:

-What is the MHz range I should be shopping in for FET biasing and the like?

-Which probe should I be using 10x or 100x?

-Is the dual channel worth the extra monetary outlay for simple electronics testing?

Sorry, if my questions are telling of my ignorance. I appreciate any help. Thanks.

-James-
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: berkleystudios on July 17, 2012, 11:39:51 PM
Hmmm... I've been over at evilbay trying to make sense of all the oscilliscopes they have to offer. My question are:

-What is the MHz range I should be shopping in for FET biasing and the like?

-Which probe should I be using 10x or 100x?

-Is the dual channel worth the extra monetary outlay for simple electronics testing?

Sorry, if my questions are telling of my ignorance. I appreciate any help. Thanks.

-James-
im in the market for one as well, will similar needs, and i have on good authority that this one should do us just fine, and its not to bad of a price either!
http://www.saelig.com/PSBEB100/PSBEB100009.htm
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: kante1603 on July 18, 2012, 02:25:20 AM


-Is the dual channel worth the extra monetary outlay for simple electronics ?


Hi James,

I say yes,this way you can do comparisons pretty easy,e.g. ingoing to outgoing signal.
This way matador was able to tell us the actual gain for example.He measured the input (coming from the signal generator) on one channel and the "biasing point" (fet) and the other.You then have several informations at one time:the amplitude or gain,if the sine is looking o.k.(distortion),and others like if you have a phase shift on an eq or the frequency etc.

Cheers,

Udo.
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: HellfireStudios on July 18, 2012, 08:55:08 AM
Thanks for the suggestions. I'd like to keep the scope price between 100-200 dollars, but the PDS5022T is a great fall-back, if my endeavours to find one used don't pan out. I will be looking for a dual channel model. Is the suggested 25MHz enough, or should I try to go higher (like 100MHz)? Thanks again.

-James-
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: mrc on July 18, 2012, 07:12:22 PM
I bought a 100mhz 2235 dual, 2 probes, HP tone generator and 2 Fluke bench dmm's from a military surplus guy in Ft. Worth on evil bay 4 yrs ago for $300 for the whole shootin' match and every item worked/works perfectly.  Took a few weeks of looking but it paid off 8)
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: 0dbfs on July 19, 2012, 10:11:44 AM
I've got a 20mhz which works well for scoping audio and control signals. I would recommend higher though for the purpose of scoping and troubleshooting oscillations and such in audio circuits. I'll eventually end up with a nicer one but the used 20mhz has served quite well and is easily replaceable should it fail. Some of the digital ones have a nice small footprint which would help out on my ever-cluttered bench.

-jb
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: HellfireStudios on July 19, 2012, 12:37:59 PM
Since my unit MAY be oscillating, if I am to stay under budget, I will need to find a hamfest or scientific/military surplus to pick up a higher MHz scope on the cheap. Off to google I go... Wish me luck (preferably good luck this time). I may have to lurk around the internet for awhile until the next hamfest in August. Any other ideas? Thanks.

-James-
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: Matador on July 22, 2012, 09:52:06 PM
I finally got some time to solder some parts onto these boards.  I'm making a matched pair.

I made a few changes to the BOM:  I subbed in my favorite Nichicon UVZ electrolytic caps where appropriate (they are rater to 105C), and replaced all of the resistors with the Vishay RN55D series of epoxy coated precision 1% resistors.  I went with the Styrene caps and mica's along with Dany's recommended Wima's.

(http://www.musicalsparks.com/images/u87/IMG_0591.JPG)

I started by labeling all of the parts by reference designation so I could keep track of where I was:

(http://www.musicalsparks.com/images/u87/IMG_0592.JPG)

I clamped the boards into my Panavise PCB holder jaws and started soldering in all of the resistors:

(http://www.musicalsparks.com/images/u87/IMG_0593.JPG)

I checked the values as I stuck them in to make sure Mouser didn't mess anything up when packing (totally worth the extra 15 seconds per part to save headaches later!):

(http://www.musicalsparks.com/images/u87/IMG_0595.JPG)

Pretty simple just going part by part, soldering and clipping each pair of boards:

(http://www.musicalsparks.com/images/u87/IMG_0596.JPG)

A little electrical tape holds in devices that want to fall right out, like the Wima caps and electrolytic caps:

(http://www.musicalsparks.com/images/u87/IMG_0597.JPG)

And the B boards are stuffed:

(http://www.musicalsparks.com/images/u87/IMG_0600.JPG)

For the bias resistor R11, I cut off one outside leg, then bent the other two to fit the layout, then dialed them up to 25K maximum before stuffing them in:

(http://www.musicalsparks.com/images/u87/IMG_0601.JPG)

And finished up the rest of the components:

(http://www.musicalsparks.com/images/u87/IMG_0603.JPG)

Somehow I messed up my Mouser order and ordered 51pF mica's instead of 560pF styrenes, so I'll have to wait until my next order comes in before I can move on to biasing and stuffing the rest of the components.
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: kante1603 on July 23, 2012, 02:41:21 AM
Hi Matador,

Cool pics!
For building a matched pair,how will you manage to get matched capsules and transformers?
I'm quite interested in this topic.Found out that my T14s have slightly different dcr readings (not too much,but measurable).
Which parts are you going to use for these positions by the way?

Keep up the good work,maybe you should reserve some place here posting some "reserved for build pics" or so like e.g. our friend chunger does?This way your infos can be kept together....just an idea....

Cheers,

Udo.
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: berkleystudios on July 23, 2012, 08:36:57 AM
nice stuff matador. i cant believe i never thought of the tape for mica caps! duh! totally using that haha

and i agree with udo, we should have a reserved place for all finished builds! that would be nice
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: Matador on July 23, 2012, 11:39:57 AM
For building a matched pair,how will you manage to get matched capsules and transformers?
Which parts are you going to use for these positions by the way?

For matching, 90% of it is in the capsule, so I ordered a matched pair of them.  The next most important part is the 220pF cap, so I ordered 20 of them and hope to find two that are reasonably close.  Last is the FET's however different FET's of the same part number don't really sound all that different, there just might be a slight difference in volume (as opposed to frequency response).

I'll be using Cinemag CM-2480's for these.  Primary inductance is the most important part, but I think C7 is large enough that the response difference will be way down near DC, so even if they are slightly different it will be inaudible.
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: kante1603 on July 23, 2012, 11:52:45 AM
Thanks for the infos!
I meant which capsules and transformers you will use,pardon my bad english,still learning.... :)
O.K.,cinemags and ...?
Udo.
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: HellfireStudios on July 23, 2012, 11:57:57 AM
I don't know what Matador is using, but microphone parts sells matched pairs (for a little extra).
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: Matador on July 23, 2012, 01:54:26 PM
I meant which capsules and transformers you will use,pardon my bad english,still learning.... :)

Oops, my fault you asked very clearly. ;)

I'm using two K67 type capsules matched by Dave Thomas at AAMicrophones.  They are essentially the same as those sold by Microphone Parts, but they are re-skinned with 6 micron Mylar.  They should have slightly less high frequency lift in the 7-9kHz range as a typical K67 type capsule.  Since I already have two "dark" versions using K47 type capsules, I'm hoping this pair has slightly more "air".

More sonic crayons to add to the box!
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: kante1603 on July 23, 2012, 02:05:09 PM
Cool,thanks!

Udo :)
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: poctop on July 23, 2012, 04:19:59 PM
+ 1 Matador for Matador  :)

Dany,

Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: sr1200 on July 24, 2012, 04:53:04 PM
I know this is almost blasphemy, but I used mine in front of a kick drum (with the pad on about a foot infront of the front skin) HOLY HUGE KICK DRUM SOUND!!!!
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: kante1603 on July 24, 2012, 05:03:15 PM
I know this is almost blasphemy, but I used mine in front of a kick drum........
Yes.
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: HellfireStudios on July 24, 2012, 06:15:13 PM
I know this is almost blasphemy, but I used mine in front of a kick drum........
Yes.

Not when used with a pop filter in front of it...
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: kante1603 on July 25, 2012, 01:50:29 AM
Not when used with a pop filter in front of it...
Right,and one can use a U47 as a salt shaker and a CMV3 as a rolling pin......
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: HellfireStudios on July 25, 2012, 03:20:53 AM
Not when used with a pop filter in front of it...
Right,and one can use a U47 as a salt shaker and a CMV3 as a rolling pin......

Even a ribbon, which is known for its fragility, can be used in front of a kick, if the air blast is properly dissipated/absorbed, and can take the SPL. A pop filter does the former very well. Notice how I didn't say INSIDE a kick drum? The pressures all around the capsule would be ridiculous for a condenser mic, and no pop filter is going to be sufficient for the job.

-James-

P.S.- The badge on a CMV-3 would make it difficult to use it as a rolling pin, and the U-47 would require a total redesign to implement a salt shaker-style operation. :)
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: kante1603 on July 25, 2012, 03:51:55 AM
Even a ribbon, which is known for its fragility, can be used in front of a kick, if the air blast is properly dissipated/absorbed, and can take the SPL. A pop filter does the former very well. Notice how I didn't say INSIDE a kick drum? The pressures all around the capsule would be ridiculous for a condenser mic, and no pop filter is going to be sufficient for the job.
I know how to choose and use microphones....
P.S.- The badge on a CMV-3 would make it difficult to use it as a rolling pin,
...but makes pasta dough quite unique....
and the U-47 would require a total redesign to implement a salt shaker-style operation. :)
...leave out the innards,especially the mounting plate for the capsule,fill in the salt before assembly,done....

Completely OT again.....
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: HellfireStudios on July 25, 2012, 04:07:07 AM
Wouldn't salt leak from the side grills, as well? :)

Let's move on to more relevant topics. Like the thread at hand.

-James-
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: kante1603 on July 25, 2012, 04:57:57 AM
Wouldn't salt leak from the side grills, as well? :)

Let's move on to more relevant topics. Like the thread at hand.

-James-
Yes. ;D
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: Hank Dussen on July 26, 2012, 07:46:10 AM
I think I managed to bias the FET. But since the IDss of all (5) my FET's are rather high (around 12) the voltage at the drain is rather low.
Maybe it would be better to to have some FET's with a lower IDss.
Instead of having to buy another 50 or so is anyone willing to sell me 2 of their leftover but 'within specs' FET's?

Pieter
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: kante1603 on July 26, 2012, 09:24:18 AM
I think I managed to bias the FET. But since the IDss of all (5) my FET's are rather high (around 12) the voltage at the drain is rather low.
Maybe it would be better to to have some FET's with a lower IDss.
Instead of having to buy another 50 or so is anyone willing to sell me 2 of their leftover but 'within specs' FET's?

Pieter
PM sent!

Udo ;)
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: geekmacdaddy on July 26, 2012, 07:30:41 PM
Got the mic together sans capsule (I'll do that last, as I don't want to keep it exposed any longer than needed), here's some photos;

(http://i52.photobucket.com/albums/g9/geekmacdaddy/U87%20II/1.jpg)

(http://i52.photobucket.com/albums/g9/geekmacdaddy/U87%20II/2.jpg)

(http://i52.photobucket.com/albums/g9/geekmacdaddy/U87%20II/3.jpg)

(http://i52.photobucket.com/albums/g9/geekmacdaddy/U87%20II/IMG_2877.jpg)

(http://i52.photobucket.com/albums/g9/geekmacdaddy/U87%20II/IMG_2880.jpg)

(http://i52.photobucket.com/albums/g9/geekmacdaddy/U87%20II/IMG_2881.jpg)


Having a problem biasing. I have one audio track in logic with a tone recorded to it. This is being outputted via out 1, which has a mono 1/4 in plug going into 2 wires w/alligator clips. Those are connected to; a) rail of the mic chassis, b) R6 directly. The mic is routed to track 2's input. I have pulled up a software oscilloscope in track 2. Problem? No signal in to track 2. Just a bit of low level hum. I'm doing something stupid, I'm sure...(Yes, track 2 is in record) Thoughts?

Thanks in advance
Geek
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: tskguy on July 26, 2012, 07:37:14 PM
Geek,

Have you set the voltage at the drain? I would start with around 11.5v or so. Its a good place to start. It will also verify that the circuit is working.

Eric
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: HellfireStudios on July 26, 2012, 09:19:56 PM
Geek,
You are not supposed to use the mic's XLR output for biasing. Make another gator clip cable, and attach the positive side of the cable to the drain of the FET. The negative to the mic's ground. That should help. This info alluded me too.

-James-
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: geekmacdaddy on July 27, 2012, 06:48:32 AM
Thank you James and Eric. Back to the "real" world for another couple of days, then I will have at it again. Eric, I may collect on that phone call sometime soon... ;)
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: tskguy on July 27, 2012, 08:03:23 AM
Anytime,
I will be around all weekend! ;D
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: HellfireStudios on July 30, 2012, 09:32:17 AM
None of the good deals on evibay for oscilliscopes include probes (I will be lucky, if I get a power cable), and the probe selection on evilbay is somewhat slim at the moment. Which probe (10x or 100x) do I need to bias this mic? Does the MHz rating on the probe need to match the scope (150MHz)? If I get a Tektronix scope, do I need Tektronix probes? If there are "universal" probes, where do I find them as cheaply as possible (my budget is strained at the moment)? Thanks.

-James-
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: Beeswax on July 30, 2012, 01:54:50 PM
Would the Mxl V6 body accommodate the build? 
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: signalflow on July 30, 2012, 02:03:03 PM
Would the Mxl V6 body accommodate the build?

The V6 looks like it would be better suited for a G7 build rather than the U87.  The mounting brackets are set for a rectangular PCB where the U87 has angled boards. And it does not come with any switches for pattern, pad or hpf.  If your looking for a body try the white market there is a reasonably priced one there.

-Casey
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: HellfireStudios on July 30, 2012, 02:26:17 PM
Check out http://recordinghacks.com/microphones/MXL/V6 for information that may make you rethink gutting that mic. Mainly it is designed and built in California, and gets decent reviews. The mic this project was originally built into was a bottom-dollar Aurycle. Just something to think about.

-James-
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: HellfireStudios on July 30, 2012, 03:59:47 PM
I just bought a Tektronix 150MHz Dual Channel Scope, but it has no probes (which doesn't suprise me). When I saw how simple they seemed, the idea came to me to make my own probes. After some searching, there is still debate on whether a DIY probe is viable, but I came across this site: http://emcesd.com/1ghzprob.htm He seems to know more techno-jargon than I care to wrap my head around at the moment, but says it can be done. Any thoughts? Thanks.

-James-
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: kevinkace on July 31, 2012, 05:11:30 PM
Would Mouser part 270-330K-RC (http://www.mouser.com/ProductDetail/Xicon/270-330K-RC/?qs=yxsGOJNBReJeHa1cOCVr14qrKQ1RotsotPExWpHY3tE%3d) be a reasonable replacement for RN55D3303FB14 (http://www.mouser.com/Search/ProductDetail.aspx?R=RN55D3303FB14virtualkey61300000virtualkey71-RN55D-F-330K) (which is out of stock)?
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: wave on July 31, 2012, 05:15:54 PM
Would Mouser part 270-330K-RC (http://www.mouser.com/ProductDetail/Xicon/270-330K-RC/?qs=yxsGOJNBReJeHa1cOCVr14qrKQ1RotsotPExWpHY3tE%3d) be a reasonable replacement for RN55D3303FB14 (http://www.mouser.com/Search/ProductDetail.aspx?R=RN55D3303FB14virtualkey61300000virtualkey71-RN55D-F-330K) (which is out of stock)?

Yes

Dave
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: Matador on July 31, 2012, 05:25:40 PM
While I wait for my styrene caps to show up, I was thinking about breadboarding up the front end of the circuit to show how the JFET parameters (like IDSS and VP), the source and drain resistors, and Zener voltages all played together in this simple voltage amplifier stage.  Is there any interest in me doing this and providing the scope shots?  I could test both the 2N3819 as well as the 2SK170BL.
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: wave on July 31, 2012, 06:08:47 PM
Matador,
I would like to see your results, especially the difference between the 2 FETs. I'm doing a build for a client and I'm trying to decide if I should go with the 2SK170. Since you have way more tech expertise in this, your tests could be very helpful to me.
By the way, is it better to have a low idss? I'm still confused as to what is better in the way of gain and noise. I picked the lowest in my bacth of 2N3819 fets but didn't some people use higher number idss fets with better gain results? As you can probably tell, I really don't understand how the idss and Vp relate to what I should be looking for to achieve good results in the amplifier.

Thanks,
Dave
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: 0dbfs on August 03, 2012, 09:58:08 AM
+1 Matador!

That would be very interesting and useful for many in selecting and understanding what the FET is doing here and how the various parameters affect the operation in the circuit and ultimately the sound and capability of the microphone.

the FET does appear to be a slightly important component since it's the only active component in the ckt, all the signal goes through it, and the part also appears to vary significantly from piece-to-piece regarding the critical parameter ranges.

Thx,
jonathan
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: geekmacdaddy on August 03, 2012, 03:28:54 PM
Wanted to thank Eric (tskguy). I sent him a capsule from an old U87 who's diaphram was stretched and sounded like it. Eric reskinned it, and all I can say is, I have a guy who thought his Neumann was dead, and he is now screaming over the phone, "It's alive!!!". Apparently, he is a happy recording engineer. He said that he'd give me mp3's of voice and acoustic guitar. I'll post them when I get them. Still haven't biased mine.
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: tskguy on August 03, 2012, 05:10:09 PM
Sweet!! I am glad he is happy so far. Can’t wait to hear the clips.
Eric
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: geekmacdaddy on August 06, 2012, 10:55:08 AM
Ok. Clips (Done by my friend, who's U87 it was) of the U87 I pulled the K87 out of, and sent to tskguy for a re-skin.

1st clip is voc and acoustic guitar. both were recorded separately, no eq, through vintek pre's into an mBox3

https://dl.dropbox.com/u/87086401/Acoustic%20and%20Vocal%20no%20eq.aif

2nd is the same w/eq

https://dl.dropbox.com/u/87086401/Acoustic%20with%20vocal%20eq.aif

Vocal, no eq

https://dl.dropbox.com/u/87086401/Vocal%20no%20eq.aif
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: tskguy on August 06, 2012, 11:36:27 AM
Sounds pretty darn good if i do say so myself  ;D ;D ;D

Geek, how does your 87 sound?? wink wink nod nod.. :P :P :P

E
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: geekmacdaddy on August 06, 2012, 11:43:49 AM
It doesn't. I'm not smart.
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: tskguy on August 06, 2012, 07:00:32 PM
Geek, I know thats not true, your very smart!! :D
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: geekmacdaddy on August 07, 2012, 09:36:37 PM
It's alive. Definitely darker than the U87 I a/b'd it with, and a heavy 1k bump, bit honky, but could be good in a mix. Here's photo's and 3 clips.

The first clip is of the real U87 (re-skin by tskguy). 2nd clip is my clone, no eq. 3rd with eq. Thanks for the help Eric.

https://dl.dropbox.com/u/87086401/U87.aif

https://dl.dropbox.com/u/87086401/CloneNoEq.aif

https://dl.dropbox.com/u/87086401/Clone%20EQ.aif

(http://i52.photobucket.com/albums/g9/geekmacdaddy/U87%20II/IMG_2888.jpg)

(http://i52.photobucket.com/albums/g9/geekmacdaddy/U87%20II/IMG_2889.jpg)

(http://i52.photobucket.com/albums/g9/geekmacdaddy/U87%20II/IMG_2890.jpg)

(http://i52.photobucket.com/albums/g9/geekmacdaddy/U87%20II/IMG_2892.jpg)
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: kevinkace on August 07, 2012, 10:21:53 PM
Looks nice!

I have a Pacific Pro Audio LD-One and actually like it stock! Didn't find it usable?
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: geekmacdaddy on August 07, 2012, 10:27:00 PM
Looks nice!

I have a Pacific Pro Audio LD-One and actually like it stock! Didn't find it usable?

Usable? Yes. Brittle? Yes. I took the chance that having it as a donor for a U87 clone would make it eminently more usable.  ;)
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: wave on August 07, 2012, 11:26:53 PM
Yo Geek,
I listened to your samples and  I'm hearing (at least I think) that your fet isn't biased correctly and there's some distortion in the signal. Did you just set it at 11.5V and roll with it?

Dave
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: geekmacdaddy on August 08, 2012, 06:20:23 AM
Dave,
 Good ear. I had 2 XLR wires backwards so I didn't get too far trying to bias, at which point I just popped on the capsule. Eric diagnosed the problem quickly, so I didn't bias, just  set it for 12  volts.  I'll go back in and try again.

Jeff
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: poctop on August 08, 2012, 10:37:27 AM
+1 For Geekmacdaddy,  i specially like the place when we hear " Its Hotter Now"  8)

Good Job ,  thanks For you nice Picture,

Dany,
Best,

 
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: geekmacdaddy on August 08, 2012, 05:18:27 PM
+1 For Geekmacdaddy,  i specially like the place when we hear " Its Hotter Now"  8)

Good Job ,  thanks For you nice Picture,

Dany,
Best,

Thanks to you, my solder sniffing brother, for all of your hard, brilliant, wonderful work. The feeling of accomplishment in orchestra with beating the system by about 2,800.00 USD is quite envigorating. I'm all over the '67 when it's ready. 2 probably. Sniff on!
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: geekmacdaddy on August 08, 2012, 07:44:50 PM
Went back in, Swapped out the 220pf (C6) for a Wima 100pf, and hopefully biased at 13.7 volts and here's a clip

https://dl.dropbox.com/u/87086401/Clone1stTweak.aif
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: poctop on August 08, 2012, 08:46:24 PM
I can see the smile on your Face  :),
Nice Tweak !,

D
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: wave on August 09, 2012, 12:52:43 AM
Geek,
You made the right move. It's totally sounding better and I don't hear any more distortion. What do you think?

Dave
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: geekmacdaddy on August 09, 2012, 07:45:54 AM
I did think I heard something towards the end...back down to 10v....I needed to do this to match the real U87

(http://i52.photobucket.com/albums/g9/geekmacdaddy/U87%20II/ScreenShot2012-08-09at74304AM.png)
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: tskguy on August 09, 2012, 08:23:04 AM
That's strange, I really don't hear the bump in the 1k that you do.
I also liked the way your tweak sounded better than the original its smoother. And as for biasing  the scope its really the best way to be sure!
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: sr1200 on August 09, 2012, 10:26:40 AM
Hmmmm i have some 100p wima's layin around.... suggested mod?  I like the way your clip sounded.
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: saxmonster on August 09, 2012, 11:25:36 AM
Hi Guys,
Ok so I have not used my Mic in a bit and when I took it out today I noticed that the capsule was leaning to the left quite a bit because of the way it was in the case and how the case was stored. 

My question is what kind of mounts are you guys using in the aurycle body?  Obviously this plastic mount that comes with it bend easily and doesn't hold its form.

Would I be able to get one of Peluso's mounts in there?

What are you guys using?

-Scott

Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: wave on August 09, 2012, 03:02:28 PM
Hi Scott,
I'm using the stock Aurycle mount but I noticed mine wasn't molded correctly. One half of the mold was a bit higher than the other half so I took my Dremel to it with a sanding drum. After I sanded it flush, the mount holds the capsule correctly.

Dave
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: Cgaines on August 10, 2012, 01:15:06 AM
Can a noob ask for a little troubleshooting help? I got the mic all put together but I'm just getting a faint sound. I have to turn up the gain all the way before I hear anything. And then it's just handling noise. Or I can tap on the head basket and hear the tapping sound. I checked all of the voltages before I hooked up the trafo and capsule and everything looked great. I had trouble biasing the Fet since I had never done it before but after several tries I finally got even clipping on the scope. So now I don't know where to take it. Any ideas?
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: sr1200 on August 10, 2012, 11:20:21 AM
im gonna guess the capsule is not wired to the board correctly.  I did this the first time too with the same results :)
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: HellfireStudios on August 10, 2012, 01:01:52 PM
Can a noob ask for a little troubleshooting help? I got the mic all put together but I'm just getting a faint sound. I have to turn up the gain all the way before I hear anything. And then it's just handling noise. Or I can tap on the head basket and hear the tapping sound. I checked all of the voltages before I hooked up the trafo and capsule and everything looked great. I had trouble biasing the Fet since I had never done it before but after several tries I finally got even clipping on the scope. So now I don't know where to take it. Any ideas?

What capsule are you using? Does it have the isolated dual backplates?
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: Matador on August 10, 2012, 03:51:14 PM
Here is some data I took on a few FET's.  The plan is that I'll mock up the front end of this circuit so we can see how these parameters play into the operation of the circuit.

I started by breadboarding up a simple test rig:

(http://www.musicalsparks.com/images/curve_tracer/test_setup.jpg)

You first dial in the pot (a multi-turn precision type works best for this so you can dial in voltages accurately) to show 0V on the voltmeter.  This should happen roughly half way through the range of travel.  You can then connect the JFET and read the IDSS on the ammeter directly.  Note this value down.

Now we want to figure out VP:  dial the pot so that the voltage becomes negative.  As you make the voltage more and more negative, you'll see the current drop as the device becomes more and more pinched off.  What you want to do is lower the voltage until the current drops to 10% of it's IDSS value.  Note this negative VGS value down as well.  Repeat these two measurements for all the devices you want to measure.  Here are results for the first three JFET's I had in my stash:

(http://www.musicalsparks.com/images/curve_tracer/measurements.JPG)

Now VP is difficult to measure exactly, as it's defined as the gate-source bias that results in zero drain-source current.  It's difficult to measure no current, but we can use the characteristic equation of the JFET to get very close:

ID = IDSS * [1 - VGS/VP]2

If you solve for VP, you get:

VP = VGS/(1 - SQRT(ID/IDSS))

So you have all the above information from your measurements, which results in the following data for these three devices:

Code: [Select]
IDSS ID VGS VP
-----------------------------------------------------
10.79 1.079 -3 -4.387425887
13.51 1.351 -3.41 -4.987040758
9.33 0.933 -2.45 -3.583064474

This way of calculating VP is not perfect but I've found it gets pretty close.  In general, IDSS and VP track together very well, meaning that the higher the current, the more negative the pinch-off voltage.

So I'm going to pick through 20 or so 2N3819's and 20 or so 2SK170BL's, and find one of each at the high and low ranges of these parameters, then I'll construct the front end of the circuit so we can see what the gain and input ranges look like.

As a primer:  gm (or transconductance) is defined as the delta change in ID with a delta change in VGS.  Mathematically, this is just the derivative of the ID equation above with respect to VGS.  The result is this equation for gm:

gm = | 2 * IDSS/VP * [1 - VGS/VP]

The first interesting result is that gm is a linear function of VGS (and the other parameters as well, which are generally constants).  People tend to think of transconductance as a constant but it isn't in this case!  It also means that the transconductance is maximum the closer VGS is to zero.  These equations can be found in any standard text on amplifier circuits BTW.

For the U87, the basic gain equation for the front end (assuming bypassed source resistor) is:

AV = - gm * RD

So gain is maximized when gm is maximized, which means we should keep VGS as high as possible and operate the JFET as close to IDSS as possible.
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: poctop on August 10, 2012, 04:16:45 PM
Hey Mike , this is awesome ,  i have to say i do like the Math and derivative, 
can't wait to see Gm versus Gain and go back in the lab with this ,
Thanks For taking the times to reveals such a wonderfull door as this one ,  8)
Best ,
Dan,
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: wave on August 10, 2012, 06:48:04 PM
I agree with Dany that this is awesome. Honestly though it's a bit beyond me. Is there a simple explanation of what we want to
look for? That's some complicated math for me  :)

Thanks for doing this! Hopefully the penny will drop for me at some point.

Dave
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: tskguy on August 10, 2012, 06:58:20 PM
ummm.....what number makes it sound better  :o

Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: Cgaines on August 10, 2012, 08:23:16 PM
Can a noob ask for a little troubleshooting help? I got the mic all put together but I'm just getting a faint sound. I have to turn up the gain all the way before I hear anything. And then it's just handling noise. Or I can tap on the head basket and hear the tapping sound. I checked all of the voltages before I hooked up the trafo and capsule and everything looked great. I had trouble biasing the Fet since I had never done it before but after several tries I finally got even clipping on the scope. So now I don't know where to take it. Any ideas?

What capsule are you using? Does it have the isolated dual backplates?


I'm using Dave Thomas' AK67 capsule
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: tskguy on August 10, 2012, 08:51:50 PM
If your using a 67 style capsule it will only work in this mic as cardiod, How do you have it wired?

Eric
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: Cgaines on August 10, 2012, 09:31:42 PM
If your using a 67 style capsule it will only work in this mic as cardiod, How do you have it wired?

Eric


Well I actually thought I could wire it as a multi pattern so that's where my stupidity lies... I added a fourth wire and wired it like the multi pattern should've been. Capsule wires in the appropriate places and the body wires in the appropriate places but reversed for the figure 8 pattern. How would I wire it for cardioid only?
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: Marcocet on August 10, 2012, 10:35:44 PM
Thanks Matador! Extremely well put. I can't wait to see what your results come to.
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: HellfireStudios on August 10, 2012, 10:46:35 PM
If your using a 67 style capsule it will only work in this mic as cardiod, How do you have it wired?

Eric


Well I actually thought I could wire it as a multi pattern so that's where my stupidity lies... I added a fourth wire and wired it like the multi pattern should've been. Capsule wires in the appropriate places and the body wires in the appropriate places but reversed for the figure 8 pattern. How would I wire it for cardioid only?

Wire up the front diaphragm to FC Cap and the backplate to FC Body. Leave the other pads (RC) empty.

-James-
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: Cgaines on August 10, 2012, 11:46:48 PM
If your using a 67 style capsule it will only work in this mic as cardiod, How do you have it wired?

Eric


Well I actually thought I could wire it as a multi pattern so that's where my stupidity lies... I added a fourth wire and wired it like the multi pattern should've been. Capsule wires in the appropriate places and the body wires in the appropriate places but reversed for the figure 8 pattern. How would I wire it for cardioid only?

Wire up the front diaphragm to FC Cap and the backplate to FC Body. Leave the other pads (RC) empty.

-James-

Ok cool thanks for the help! But one more thing... What about the third wire connected to the rear diaphragm? Do I disconnect it? Or just let it be?
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: poctop on August 11, 2012, 12:26:04 AM
you can let it be,  ;)
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: Cgaines on August 11, 2012, 12:49:48 AM
Hey thanks for the help HellfireStudios and Poctop! I took on this project as a learning experience and I believe I succeeded. This forum is a great tool for people who actually know what they are doing, to help out people who don't. I still have only grazed the surface but I'm sure this site will help me dig deeper. I would like to understand a little more why Dave can use this capsule in his 87 mic and have polar selections. Does his circuit have jumpers somewhere, that the other diaphragm is attached to, that allows the pattern selection? And this circuit doesn't?
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: HellfireStudios on August 11, 2012, 01:21:18 AM
The U-87 used a derivative of the K67 capsule that was used in the U-67. The only real difference is the backplates are electrically isolated from each other by a plastic spacer. The vintage U-87 circuit requires this isolated backplate design for polar pattern selection. Dave Thomas is probably not sticking as closely to the original U-87 circuit as this project does. Most other U-87 style mics use the K67 style capsule.
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: tskguy on August 11, 2012, 09:28:16 AM
Cgaines

Hellfire is correct the 67 and 87 are very close in terms of construction and hole pattern. For some reason on the 87 type Neumann decided to isolate them, so if you take your dmm to check continuity you wont see a connection from one backplate to the other. this is done with a plastic spacer and some very odd screws. The screws that hold the backplates together are sheilded so when they pass through the plate it doesnt touch the brass. I actually am building both 67 and 87 style capsules. If you want I could turn your 67 to an 87 pretty quickly. Send me a pm if your interested.

Eric
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: HellfireStudios on August 11, 2012, 02:26:22 PM
Tskguy, the AK-67 capsule is 35mm in diameter unlike the Peluso's, etc. that are 34mm. Are your plastic spacers the right size to modify Cgaines' capsule? I would hate to see all that shipping/labor paid for, with nothing in return.

-James-
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: tskguy on August 11, 2012, 02:58:09 PM
Thanks for the heads up! But its no big deal, I can always cut larger ones.  ;D
offer is still open
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: HellfireStudios on August 11, 2012, 03:17:18 PM
I'm glad to hear it. I hope it works out. On another note, could you do reskins of chinese capsules that have been damaged, or is the inconsistency of chinese stuff a deterrent? Thanks.
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: tskguy on August 11, 2012, 09:34:48 PM
Sure I can reskin it no problem as long as the traget of gold on the mylar is 23mm thats the only mylar other than completly coated like a c12 style capsule.
Send me a pm if your interested.
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: Cgaines on August 12, 2012, 04:28:13 PM
I got back in town last night and rewired my capsule and it worked! Sounds very cool and dark. Darker than anything I have. I am having some low level hum that's bothering me. Its only when I have to really crank the amp. Any Ideas? It looks as though the boards are grounded to the body well. The mounting screws are snug and making contact. I tried adding a wire from the "gndlink" to the screw but that didn't help either. Now I'm out of ideas...
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: dandeurloo on August 12, 2012, 04:43:15 PM
I just finally built up one of my 2 mics.  I used vintage capsule and transformer.  I did a small vocal test comparing it to a 414 EB and a Sony c 38.  Both mics that are very nice.  I have to say the 87 sounds wonderful.  I can't wait to give it some use and see how I like it in day to day work. 

Thanks Dan and everyone else who has been so helpful in making this happen. 
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: poctop on August 13, 2012, 05:25:18 PM
I got back in town last night and rewired my capsule and it worked! Sounds very cool and dark. Darker than anything I have. I am having some low level hum that's bothering me. Its only when I have to really crank the amp. Any Ideas? It looks as though the boards are grounded to the body well. The mounting screws are snug and making contact. I tried adding a wire from the "gndlink" to the screw but that didn't help either. Now I'm out of ideas...

"Swapped out the 220pf (C6) for a Wima 100pf," quote from GeekMacdaddy this is likely reduce negative feedback and undarken a bit if you would like to try ,
the Value of C6 is based on the original K87 sound. As for the hum check your ground scheme and mic shielding and bottom base nut to be tight
Cheers,
Dany,
 
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: Matador on August 13, 2012, 07:32:14 PM
Ok here are some more notes about this circuit that I've formulated over the last few days.  The equations that govern JFET behavior (and this circuit as an extension), are non-linear and difficult to summarize succinctly.  However there are a few broad generalizations that can be made.

First off, we can reason a bit about operating points based on the original Neumann design.  First off, it stands to reason that the target was that the drain voltage would sit at roughly half the supply voltage (in this case, this is the voltage coming out of R14, and shown to be 21V).  If this is true, then half of this is 10.5V.  With a 47K drain resistor, this gives a quiescent bias current of 223uA.  I'm guessing Neumann selected 225uA which is really close.

With the drain bias and drain resistor selected, we need to figure out the idling point next.  I'll spare the detailed math, but you essentially look at the VGS / IDS transfer curve, and find a point roughly around the point that intersects 225uA.  I've found for the nominal 2N3819, this voltage is roughly -3.4V (but given JFET parameter swing, can be anyplace from -0.2V up to damn near -7V!).  If you measure the IDSS and IDS points you can calculate VP, then use the equations I provided earlier to find the VGS that intersects with the 225uA point with a spreadsheet.

So if the nominal 2N3819 has a VGS at -3.4V at a quiescent current of 225uA, then the source resistor needs to be 15.2K.  This will place the source voltage at 3.4V.  With a 47K drain resistor, the drain will idle at 10.5V given these nominal JFET conditions, which I have confirmed with a SPICE simulation.

Herein lies the first problem with this circuit:  in order to be in the saturation region, the VDS voltage must be held above VP, otherwise the JFET is operating in it's ohmic (or triode) region.  In this region, the drain->source current starts to depend on VDS (and not just on VGS).  As the VDS falls, the transistor impedance rises, which can be thought of as a "softening" of the pulling ability of the JFET down towards it's source terminal (it essentially becomes a VCR, or "voltage controlled resistor").

In any case, we must maintain VDS at greater than VP (which in this case is 4V for the nominal 2N3819).  Now while the trouble is on the downward slope for output (meaning on the upward slope on the input, given this is an inverting stage), due to the action of gm against RD, the drain voltage will fall "faster" than the source voltage.  If this difference falls below VP, the waveform will start suffering a lot of THD.

You can see this for the nominal U87 circuit with a nominal JFET in the SPICE plot below:

(http://www.musicalsparks.com/images/curve_tracer/u87_bias_nominal.jpg)

which is a plot of VDS with an input signal of 1kHz, 200mV peak to peak.  You can see that as the output signal falls below the 4V threshold, the signal flattens out.

This means that the VP level greatly reduces the amount of gain we can realize while still maintaining low distortion.  Although the gain calculates at roughly 35, we can really only make use of the first 88mV of input signal before the stage begins to run out of signal swing headroom.

There are two ways this can be mitigated:  the first is to run higher quiescent current.  This has the effect of reducing the VGS bias, which means that the source resistor can be smaller.  With less VGS bias, we can swing more signal.  This has the secondary effect of reducing gain however, but we do get more input headroom.

The other way is to jack up the VDD voltage from 21V.  For example, if we raise this up to 30V, and idle at 15V, then we can raise up the drain resistor to 67K and have a few more volts of headroom before we start to run into trouble.  We have to be careful however, as if we exceed the maximum drain to gate voltage (25V for the 2N3819) we get into more trouble.  30V is about as high as one can go.

Here is the same plot with 30V VDD, 15V idle:

(http://www.musicalsparks.com/images/curve_tracer/u87_bias_nominal_30V.jpg)

Looks much cleaner, gain is slightly higher as well (50 versus 35, with a larger input swing too).  Output impedance is higher however, which means we have to think about dampening into the output transformer too!

The fundamental problem here is that with a nominal JFET, we are operating too far away from IDSS.  With IDSS also comes lower VP, which means less headroom.

Here is the same idea with a minimal JFET (2mA IDSS, VP of -0.22V).  Gain is up another full order of magnitude (around 100), and we have tons more output swing to use up because VGS is so low (about -0.15V).  Gain is up because we are so much closer to IDSS in the quiescent state.  The simulation shows that 30mV at the input swings nearly 7V at the output.

However input headroom is tiny:  roughly 50mV will take the output to the rail.  This may be ok if you are only room miking at a distance, but this would distort heavily on loud sources I am guessing.

What I'll do next is post a chart of IDSS and VP, and what the gain and headroom look like.  That way, you can hand select a JFET to go with whatever operation you like.  I'll also post the source resistor values so that those without a scope can get very close to the ideal value.
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: Marcocet on August 14, 2012, 01:24:49 AM
Thanks Matador! You have once again significantly increased my understanding of a circuit.
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: kante1603 on August 14, 2012, 01:37:56 AM
Thanks Matador! You have once again significantly increased my understanding of a circuit.
Same here,thank you so much matador for your deep and well documented investigations!
Interesting how complex this little fet circuit can be and to see (and learn in my case) what it is doing under different circumstances.I'm really curious now what the results may be with a minimal fet at low Idsss.

Cheers,

Udo.
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: poctop on August 14, 2012, 02:31:50 AM
There is no words to say how well Matador has explained all of this ,
Thanks a million ,   i am printing this and will put it with my precious file....

My precious.... ;D

Best ,
DAn,
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: dissonantstring on August 14, 2012, 03:52:22 PM
thank you matador! your explanation is so well prepared and makes things so understandable.  one of the best tutorials i've seen here that is so project specific and yet yields such a great amount of knowledge as well about JFETs.  looking forward to your next installment.
kindest regards,
grant
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: Matador on August 14, 2012, 03:57:42 PM
Thanks for all the kind words!

I created a simple PHP script to do all the calculations for everyone.  It's located here:

http://www.musicalsparks.com/images/curve_tracer/jfet_bias.php (http://www.musicalsparks.com/images/curve_tracer/jfet_bias.php)

You plug in the two values that you measure for your JFET, and it will do all of the math and tell you the values of all the resistors, the gain, and calculate the maximum input signal before clipping.  If you have a handful of JFET's (even different types), you can plug in the data and see what it gives.

For example, if I use my nominal JFET that I have (IDSS = 10.79mA, VGS at 1% IDSS = -3.4V), this is what is spit out:

VP = -3.77777777778 V
gmo = 5712.35294118 µmho
β = 0.756046712803m
VDD = 21 V
VD = 10.5 V
IDQ = 225 µA
RD = 46.6666666667 kΩ
VGSQ = -3.23224990585 V
RS = 14.3655551371 kΩ
gm = 824.889108622 µmho
AV (gain) = 38.494825069
Headroom Analysis

Output swing headroom (positive) = 10.5 V
IDO (ohmic) ≤ 282.182455648 µA
Output swing headroom (negative) = 6.72222222222 V
Maximum input signal before clipping = 174.626646833 mV

For those of you without a scope and only a simple DVM, this calculation for the source resistance should be VERY close to the optimal value for that JFET.

I went through most of my stash of 2N3819's and have a few near the extremes of the ranges.  I'll breadboard up the circuit and inject a test signal and we'll see how close the math is to reality.
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: wave on August 14, 2012, 04:06:57 PM
Matador,
You rock! This will help me out as I don't have a scope yet and I do the listen method which is hard in it's own right.

Thanks!
Dave
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: Studio Mollan on August 14, 2012, 05:26:33 PM
Hi,
I just came back to this discussion having had some issues with my mics.
I've used them on a lot of different instruments. On louder sources they tend to distort in a very strange way. Hard to describe but the mik looses headroom and also starts to modulate. Especially hearable when in front of electric guitar cabinets. I can also see something's wrong when looking at the waveforms in ProTools. The waveforms are uneven.  Only the positive (upward going) side of the waveform looks "healthy". The negative looks to be clipping and shows minimum dynamics.
Anyone else having the same or similar problem?
I'm using peluso capsules and ami transformers.
/
Emil
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: wave on August 14, 2012, 05:32:01 PM
Emil,
Are you using the pad when using the mic on loud source? What about the biasing? Were you able to use a scope of did you use the listen method?
I used the listen method and I did notice that before I got it in the sweet spot, some of my louder vocal tests had a bit of distortion. Much like what geekmacdaddy had on his initial tests before he dialed his bias in better.

Dave
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: Cgaines on August 14, 2012, 10:55:10 PM
Hello all,

I still seem to be having a grounding issue somewhere that I can't find. I did notice today that before I apply phantom power, I can hear the hum. I thought it might be my preamp but I checked it against some other mics and it didn't hum. I am literally out of ideas... Can someone smarter than my point me in the right direction?
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: HellfireStudios on August 14, 2012, 11:20:30 PM
Hello all,

I still seem to be having a grounding issue somewhere that I can't find. I did notice today that before I apply phantom power, I can hear the hum. I thought it might be my preamp but I checked it against some other mics and it didn't hum. I am literally out of ideas... Can someone smarter than my point me in the right direction?

Is your mic body painted?
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: Cgaines on August 15, 2012, 12:09:53 AM
Hello all,

I still seem to be having a grounding issue somewhere that I can't find. I did notice today that before I apply phantom power, I can hear the hum. I thought it might be my preamp but I checked it against some other mics and it didn't hum. I am literally out of ideas... Can someone smarter than my point me in the right direction?

Is your mic body painted?


No I haven't painted it. It's still just the stock aluminum finish
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: kante1603 on August 15, 2012, 01:16:31 AM
Matador,this is nothing but great!
Even scope users can cross-check now what is happening,sometimes it occurs that measuring errors happen when not being concentrated.This is a perfect way to confirm it.
Thank you very much indeed!

Udo.
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: kante1603 on August 15, 2012, 01:19:48 AM
Matador,this is nothing but great!
Even scope users can cross-check now what is happening,sometimes it occurs that measuring errors happen when not being concentrated.This is a perfect way to confirm it.
Thank you very much indeed!

@Dany,can you put the calculators link to the compiled info page please?

Thank you!

Udo.
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: HellfireStudios on August 15, 2012, 08:33:23 AM
Hello all,

I still seem to be having a grounding issue somewhere that I can't find. I did notice today that before I apply phantom power, I can hear the hum. I thought it might be my preamp but I checked it against some other mics and it didn't hum. I am literally out of ideas... Can someone smarter than my point me in the right direction?

Is your mic body painted?


No I haven't painted it. It's still just the stock aluminum finish

You mentioned earlier that it only hums when you turn up the gain really high. When you checked the preamp/XLR cable (by using a different phantom powered mic), did you turn up the gain like you did with the U-87? The hum could be the preamp's noise floor rearing its ugly head. It could also be the XLR cable. Did you use the same cable when you switched mics?
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: Studio Mollan on August 15, 2012, 08:39:58 AM
Emil,
Are you using the pad when using the mic on loud source? What about the biasing? Were you able to use a scope of did you use the listen method?
I used the listen method and I did notice that before I got it in the sweet spot, some of my louder vocal tests had a bit of distortion. Much like what geekmacdaddy had on his initial tests before he dialed his bias in better.

Dave
Hi Dave and thanks for your input! Your contributions here are much appreciated!

I did not use the pad. I'll give it a try with the pad the next time i use them. I'm still not sure if all the microphones behave this way. I built three. I'll post my results here.
Having read Matadors latest posts I'll also try to do that. I have no scope so i biased them by ear.
Thanks again all!!
/
Emil
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: Cgaines on August 15, 2012, 10:21:34 AM
Hello all,

I still seem to be having a grounding issue somewhere that I can't find. I did notice today that before I apply phantom power, I can hear the hum. I thought it might be my preamp but I checked it against some other mics and it didn't hum. I am literally out of ideas... Can someone smarter than my point me in the right direction?

Is your mic body painted?


No I haven't painted it. It's still just the stock aluminum finish

You mentioned earlier that it only hums when you turn up the gain really high. When you checked the preamp/XLR cable (by using a different phantom powered mic), did you turn up the gain like you did with the U-87? The hum could be the preamp's noise floor rearing its ugly head. It could also be the XLR cable. Did you use the same cable when you switched mics?

Yeah I did all I that as well. That's why I'm stumped. I tried different cables, used the same gain structure and every other scenario I could think of. I used the stock analyser in my daw on all of the mics and my 87 is the only one with the 60hz wave. I checked the wire coming from the xlr pin and it looked ok as well. I wonder if the xlr jack isn't grounded to the body very well? I'll double check that this evening and see if that could be the issue.
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: Matador on August 15, 2012, 12:05:39 PM
I've found that certain mike bodies rely on a tenuous connection from XLR pin 1 to the bottom shell, to a lower screw bracket and THEN to the body.  In fact someone struggled with this previously in the thread.

One thing you can try:  stuff a cable into the XLR jack, then attach a wire to pin 1 on the other end of the cable and attach it to a meter to measure continuity.  If the body is unpainted, you should be able to touch the various parts of the body and read low resistance.  Barring that make sure if the body is clear coated that you scratch of areas where such ground connections are made.
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: DUDE GUY on August 15, 2012, 07:44:27 PM
Hello All,

I finally received my RK-87, but I'm unclear as to where exactly I should attach the backplate terminations on the capsule (I know where all the termination wires need to be soldered on the PCB). I've seen a couple diagrams for capsule wiring on the forum, but they all refer to the peluso 87 capsule. From what I can tell from poctop's diagram (first page of the initial thread, not the build thread), the FC (front capsule) backplate termination wire connects to one of the diaphragm clamping ring screws on the BC (back capsule). I'm assuming this is specific to the Peluso 87 because Matt at microphone parts said i should never touch any of the diaphragm clamping ring screws. So, I've attached a small diagram of the RK-87 (side view) and I'm hoping someone can show me exactly where to attach the backplate termination wires for each diaphragm (to be clear, "FC WHITE" and "BC WHITE" refer to the white termination wires connected to the center of the front and back diaphragms. I understand what to do with these white termination wires, but I'm unclear about the blue backplate termination wires). Referring to my diagram, does the FC backplate termination wire connect to screw hole #1 and the BC backplate termination wire connect to screw hole #2? This seems logical to me, but then again I've never wired a dual capsule and I want to be 100% of what I'm doing.

I really appreciate the help. I'm sooooo close! Thanks.

-DUDE GUY

(http://i99.photobucket.com/albums/l306/opistyles/9a8c89e4fbf95675020a68f8eced886f.jpg)
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: poctop on August 15, 2012, 08:34:45 PM
So to make this simple in this circuit the capsule has 2 backplate and 2 diaphrgame , the 2 backplate are isolated so it connects to the circuit separately you would normally use the saddle screw for on of those backplate and the other one another screw with a little terminal to solder on a wire that will go to the PCB   and then each side of the diaphragme ,

Let me know if this helps,
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: DUDE GUY on August 15, 2012, 08:55:04 PM
Dan!!!!!! Thank you!!!!! Finally, it's clear to me! Sorry that I PM'd you and posted, but I'm sure you can understand how badly I want to test this thing out. Hopefully other noobs like me can get some clarity from your additions to my diagram. Feel free to add it to the other diagrams seeing that the wiring for the RK-87 is different than the Peluso 87. Or better yet, I'd be happy to create a higher quality diagram with real pictures that you could post at the beginning of the white market and build threads, if you like. Anyway, thanks again for all your help. By the way, I'm really looking forward to your U67 as well! Happy building/creating.

-DUDE GUY
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: poctop on August 15, 2012, 09:15:18 PM
Quote
seeing that the wiring for the RK-87 is different than the Peluso 87.
Just a quik note,

The Wiring for the Peluso or the RK-87 should be the exact same principle  :)

I would be more than happy to share your picture and put them in the forum and build thread for sure ,  if it can help this is fantastic  8)
Keep me posted,

Best,
Dan
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: poctop on August 15, 2012, 09:19:18 PM
Matador,this is nothing but great!
Even scope users can cross-check now what is happening,sometimes it occurs that measuring errors happen when not being concentrated.This is a perfect way to confirm it.
Thank you very much indeed!

@Dany,can you put the calculators link to the compiled info page please?

Thank you!

Udo.

Added To First Page of White market  8)  Thanks Matador And Udo,
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: DUDE GUY on August 15, 2012, 10:56:40 PM
U87 COMPLETE!!!

It sounds damn good, but I want to A/B it against the real thing. All original BOM, RK-87, and AMI T13. My donor is half Gauge ECM87 and half MCA SP-1. No switches, so for now I'll just use the internal jumpers. I'm going to buy a body from Cathedral Pipes at some point. Thanks everyone for your help and a special thanks to poctop for making this available!

(http://i99.photobucket.com/albums/l306/opistyles/2b63d255c446aeb0249eb1bf95729add.jpg)
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: Cgaines on August 16, 2012, 02:35:22 PM
I've found that certain mike bodies rely on a tenuous connection from XLR pin 1 to the bottom shell, to a lower screw bracket and THEN to the body.  In fact someone struggled with this previously in the thread.

One thing you can try:  stuff a cable into the XLR jack, then attach a wire to pin 1 on the other end of the cable and attach it to a meter to measure continuity.  If the body is unpainted, you should be able to touch the various parts of the body and read low resistance.  Barring that make sure if the body is clear coated that you scratch of areas where such ground connections are made.


Thanks for the tip matador! I hooked the mic up to my DMM and it shows have continuity from pin one to the mic body. So I guess maybe I need to check elsewhere for the problem. I just don't know why else it could be.
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: HellfireStudios on August 16, 2012, 02:44:17 PM
I've found that certain mike bodies rely on a tenuous connection from XLR pin 1 to the bottom shell, to a lower screw bracket and THEN to the body.  In fact someone struggled with this previously in the thread.

One thing you can try:  stuff a cable into the XLR jack, then attach a wire to pin 1 on the other end of the cable and attach it to a meter to measure continuity.  If the body is unpainted, you should be able to touch the various parts of the body and read low resistance.  Barring that make sure if the body is clear coated that you scratch of areas where such ground connections are made.

Make sure your headbasket, body sleeve, and end cap are all showing continuity with XLR pin 1. Make sure the inner rails, that the PCB's are attached to, are showing continuity to pin 1, as well. Check your ground connections on the PCB's too.

-James-


Thanks for the tip matador! I hooked the mic up to my DMM and it shows have continuity from pin one to the mic body. So I guess maybe I need to check elsewhere for the problem. I just don't know why else it could be.
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: 0dbfs on August 17, 2012, 08:14:15 AM
Hello all,

I still seem to be having a grounding issue somewhere that I can't find. I did notice today that before I apply phantom power, I can hear the hum. I thought it might be my preamp but I checked it against some other mics and it didn't hum. I am literally out of ideas... Can someone smarter than my point me in the right direction?

Is your mic body painted?
if you are getting it without 48V applied it's not the electronics.

Try holding the mic near sources of emf like a lightbulb or something. If the hum get's louder and you can change it be reorienting the mic it is likely a transformer issue where the transformer isn't humbucking properly. I have had these issues where the trafo had shorted windings and was able to measure the DCR of the various windings to confirm they didn't match where they should. Which transformer are you using?

Thx,
jb
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: Cgaines on August 18, 2012, 12:05:35 AM
Hello all,

I still seem to be having a grounding issue somewhere that I can't find. I did notice today that before I apply phantom power, I can hear the hum. I thought it might be my preamp but I checked it against some other mics and it didn't hum. I am literally out of ideas... Can someone smarter than my point me in the right direction?

Is your mic body painted?
if you are getting it without 48V applied it's not the electronics.

Try holding the mic near sources of emf like a lightbulb or something. If the hum get's louder and you can change it be reorienting the mic it is likely a transformer issue where the transformer isn't humbucking properly. I have had these issues where the trafo had shorted windings and was able to measure the DCR of the various windings to confirm they didn't match where they should. Which transformer are you using?

Thx,
jb

I'm using the AMI T13. I've used their products in other mic mods and loved them. That's why I went with this route again.
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: poctop on August 19, 2012, 01:06:39 PM
I have 9 sets Left as of today.
Dan,
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: Marcocet on August 19, 2012, 04:52:22 PM
Hey Matador,

Are you by any chance closer to determining an "ideal" Vp and IDSS are for this circuit? I have a bunch of fets which I'm now capable of testing, but I'm not sure exactly what it is I should be looking for. Thanks again for all your help!
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: bigswole on August 19, 2012, 06:43:19 PM
Im about to start stuffing this board, i was wondering could i use the behringer B2 capsule to test the circuit once it is done?
Title: Re: Neumann U87 Vintage Circuit Build Thread.
Post by: HellfireStudios on August 19, 2012, 06:58:45 PM
Only in Cardioid. Hook the front diaph