Neumann Vintage U87 Clone : Build Thread.

[kante1603]

yes, i bought inkjet printable decal paper. It's pretty straightforward to use. but i think i'll have to give it at least one cote of clear to make it last.....

-Leifur

Thanks Leifur,

I have tried things with water decal for inkjets,same as you.But I failed most of times applying it,so I gave up,hahaha.....looking nice btw.,

Best,

Udo.

 

[mus1k_freak]

just finished a u87 build inside a mxl v250! it was tight but i got it all in there, ill try to get pictures up tomorrow

 

[sr1200]

Stepped away from this thread for a while.  Just saw the posts about the AMI transformer wiring mis labeling.  AWESOME!!!!!  Mic level is SOOOO much better now, (dont have to crank the hell out of the pre to get a usable level)

I am noticing something new now though.  After being on for a while, the mic starts to get a crackle, almost like when a tube is going on a tube mic.  I cleaned the connections around the capsule wires, theres no residue or flux or anything there.  Any thoughts on what it could be (im guessing i could never hear it before i flipped the trafo). 
And could the fet bias have anything to do with it?

 

[phonofranz]

Hello again,

just finished my 87  ;D Strangely enough: it works at first try!
B2 body (non "pro", 2 switches!), cinemag 2480, Microphone Parts RK87.
Pictures will be uploaded as soon as I stop sucking at painting...

Observations and small issues:

- cardioid: great!

- fig 8: back side is sounding noticebly different (duller, softer) Is that to be expected?
I'm going to switch the diaphragms to check the capsule asap, but I suspect the switch and related cables to play a role in this... possibly some capacitive effect ?
In omni a similar effect to fig 8, but way less significant.

- microphone is dead quiet; I'm very satisfied with the noise floor, but touching the switches cause a loud hum. Bet I have to check switches' grounding ?

- pad seems to raise the noise floor. I'm not talking about signal to noise ratio: when I switch it on I can hear a little more "white" noise. Is that to be expected?

 

[pasarski]

- fig 8: back side is sounding noticebly different (duller, softer) Is that to be expected?
I'm going to switch the diaphragms to check the capsule asap, but I suspect the switch and related cables to play a role in this... possibly some capacitive effect ?
In omni a similar effect to fig 8, but way less significant.

How did you check? If by speaking to the mic with headphones on they'll sound different because of the bleed and opposite polarities of the sides.

 

[phonofranz]

- fig 8: back side is sounding noticebly different.

How did you check? If by speaking to the mic with headphones on they'll sound different because of the bleed and opposite polarities of the sides.

Doh! I feel so dumb: I did not recall I fell into this already with another project: recording and playing back "fixed" the non-issue. Thanks Pasarsky!

 

[Deepdark]

Congrats phonofranz!

I tried the mic last sunday and it sounded awesome. We did some classical female vocal and everhting works just perfectly. A really great microphone.

 

[phonofranz]

and here's the pup:

 

[poctop]

and here's the pup:

Congrats , on the mic and the paint Job,
Best,
dAN,

 

[mus1k_freak]

can you use a k47 style capsule with only 2 leads and just wire into one side of the boards? I tried this on one set I have using a stock capsule and got no sound, didn't know if I had to have a capsule with both sides hooked up
thanks guys!

 

[poctop]

can you use a k47 style capsule with only 2 leads and just wire into one side of the boards? I tried this on one set I have using a stock capsule and got no sound, didn't know if I had to have a capsule with both sides hooked up
thanks guys!

you can do it with one connection on the backplate and one on the front diaphragme and it will work fine , the thing is the capacitance of a K47 is rated at 72 pf and the K87-67 is 50pf so the overall output will be compromise,
Best,
Dan,

 

[phonofranz]

Hey, an update on my build:

have just compared sound and noise floor between the clone, a c414b-uls and a Beyer m260.
Rme UFX preamps.

Noise floor (white-ish high freq noise): the clone, as expected, sits between the c414 and the Beyer. Totally usable even if I wish I could optimize something  to push it down a bit.
I bet I should spend more time learning how to select a better FET....? ... or a better Zener...?

Gain: clone needs 4 to 6 db more gain than the c414 to get a comparable level with speech.
Not really problematic. Fet: 7,6 IDSS. Bias with scope method. Cinemag 2480.

Sound: "Neumanesque" as I wished. Totally different beast than a ck12-based microphone.  Mid forward with some sweetness at the extremes... IMHO the best things about this mic is the wider directional pattern in the lower range and a more usable proximity effect...

More tests in a real scenario asap. Wish I could find someone nearby with an original u87 (non AI) to compare...

 

[phonofranz]

Hello again,

further tests, recording quiet stuff in omni and fig8, revealed that I have some low level "pops!" and crackling coming from the 180° side.  :'( I need some help troubleshooting.

Already done so far:

- ruled out a possible capsule contamination: swapped sides and the issue still persist only in omni/fig8

- ruled out a switches' issues: desoldered cables/cleaned pads/phisically removed the switches' assembly from mic body, keeping it in fig 8 with a direct solder.

- cleaned both pcbs again and again/checked for solder spats, etc etc...

What's the next clue?
- 1G/68M resistors R3 to R7?
- Styrene caps ?

Any hint would be much appreciated...  ;D

 

[pasarski]

What's the next clue?
- 1G/68M resistors R3 to R7?
- Styrene caps ?

The styrene cap that connects the the other side of the capsule in fig8 and omni would be my guess. Or the switch.

 

[phonofranz]

The styrene cap that connects the the other side of the capsule in fig8 and omni would be my guess. Or the switch.

Thanks Pasarsky!

You mean C1:470p that connects to the backside diaphragm, right? I was going to try that ...
Switches have been removed already.

EDIT:  exchanged C1 and the pops and crackling seem to be gone!

Bad cap indeed!

 

[gary o]

I see in some U87s L1 L2 caps 16 / 17 330p are not used ..... is there purpose RFI ? do they effect the sound or sound level ....

Thanks

 

[poctop]

I see in some U87s L1 L2 caps 16 / 17 330p are not used ..... is there purpose RFI ? do they effect the sound or sound level ....

Thanks

RF Rejection , this has been implemented after version Circuit diagram 16

best,
DAn ,

 

[gary o]

Thanks Dan whats version circuit diaphram 16 ? ..... & do they effect  the sound or level of the mic ?

Thanks again

 

[poctop]

Thanks Dan whats version circuit diaphram 16 ? ..... & do they effect  the sound or level of the mic ?

Thanks again

Hi Gary ,
diagram circuit 16 refers to neumann version of the u87 schematic ,
here is version 16 wich the RF rejection input modification was not present a the time , it came in a little after version 16
https://cdn.groupbuilder.com/groupdiy/u/39511/58d0281993f21.jpg
to answer your question it does not affect the sound or level  but it will affect the noise floor , so this is considered as an improvement made after rev 16 for busy electromagnetic enviromment,
Best,
Dan,

 

[gary o]

Brilliant info thanks for that.