Neumann Vintage U87 Clone : Build Thread.

[kante1603]

Congrats!

About lowish level,I don't know the bluebird.
But you can compare the technical data of both and see what the results are on your mic-pre,look for sensitivity.

Udo.

 

[spudstyle]

The gain knob on my Steinberg is at 3/4 to have a -14dB in cubase. For the same recording level, bluebird is at 1/4 max.
The level of my DIY looks like a sm57 level.

 

[HellfireStudios]

The gain knob on my Steinberg is at 3/4 to have a -14dB in cubase. For the same recording level, bluebird is at 1/4 max.
The level of my DIY looks like a sm57 level.

Did you bias the FET with an oscilliscope?

-James-

 

[spudstyle]

Yes, with the software scope. And my dmm find 11.3v on the drain. Bad adjustment you think ?

 

[late]

Same here. Get hum when i remove the tube from body. It is normal?

 

[atticmike]

http://www.thiersch-mic.de/en/estm_produkte.html

thanks eric, the mounts are too high though (50 mm)

Try to fit that in any donor body

 

[Matador]

Same here. Get hum when i remove the tube from body. It is normal?

Yes.  The high impedance circuits are antennas for hum pickup.  You must have the head basket, body tube, and bottom cap on (and they all need solid connection to circuit ground) in order for the mike to work properly.

 

[herrmann]

Hello all
Just finished my mic, all is working good. But I get much noise floor than other mic : http://herrmann.records.free.fr/diy/u87-noise.mp3
Could it be related to that "high impedance" area ? I have not cleaned my boards.

 

[HellfireStudios]

Hello all
Just finished my mic, all is working good. But I get much noise floor than other mic : http://herrmann.records.free.fr/diy/u87-noise.mp3
Could it be related to that "high impedance" area ? I have not cleaned my boards.

Yes you absolutely need to have the high impedance section clean to reduce noise. 91% isopropyl alcohol and a clean tooothbrush will do the job nicely. Be careful, if you've used styrene caps, as they can be damaged by the alcohol.

-James-

 

[spudstyle]

Some pictures of my microphone work:

https://www.facebook.com/media/set/?set=a.413027982101765.98307.139235492814350&type=1

 

[3nity]

Wow!
I had the chance to test the u87 with Dany vs a genuine U87 and it kinda sounds similar.
D-U87 had a peluso? so it sounded a bit different but surely sounds the same ballpark...same league.
I need a pair of those.

Really this are a must to all studio!
Thanks,

 

[spudstyle]

Any idea for the low output level ? The bias seems to be ok :/

 

[poctop]

can you check all the reference voltage including 40V polarisation and also the capsule connection
hope this helps,
Dan,

 

[spudstyle]

Ok so:

my +48v = 46.6v

I've 11.47 on the drain

22.93v on the zener

and 39,95v on the backplates.

The level is more like a dynamic microphone.

Fet is bad ?

 

[spudstyle]

Add informations:

CineMag transformer wiring is: RT = Red, SW = Brown, BL = Orange and WS = Yellow.

It's correct ?

The pad can not be activated because I don't have the cap for this, it was not included in the mouser bom.

 

[spudstyle]

I try again to bias the fet and it's impossible !!! The bottom never clip... The curve change and looks like this:

and if i want something symetrical, i've this:

Why ? I'm lost, i try 2 different fet but the same thing

 

[Matador]

What value pot is your source resistor?  Where are you measuring the signal?

 

[Hank Dussen]

I try again to bias the fet and it's impossible !!! The bottom never clip... The curve change and looks like this:
Why ? I'm lost, i try 2 different fet but the same thing

Did you measure without the transformer?

 

[spudstyle]

What value pot is your source resistor?  Where are you measuring the signal?

Something around 12k. I measure on the drain of the jfet. The signal is injected on R6.

Did you measure without the transformer?

Yes.

 

[HellfireStudios]

Was R6's orientation reversed on the PCB?

-James-