Neumann Vintage U87 Clone : Build Thread.

[patxiplg]

Hello everyone! This is my first post and first of all I'd like to thank you for all the great info you're all sharing here.

I'm currently building an u87 and when I ordered the bom long time ago, I don't know why but I didn't order the 2x 0.01uF film WIMA caps! (C2 and C14 of the u87M blue PCB). But I've found some KEMETs laying here around (www.mouser.com/Search/ProductDetail.aspx?R=PHE426HK5100JR05virtualkey64600000virtualkey80-PHE426HK5100JR05) which I think is a perfect equivalent, but I'm not 100% sure since it is rated for a 250V, and it's "AC and Pulse Film Capacitors" vs "RF Microwave Film Capacitors" (WIMA). I'm looking for the best audio quality possible (fidelity to the original desgin), so if it could replace the WIMA in terms of functionality but compromises the sound quality then...

Thanks for your help!!

PD: I also have both the 60 and 68MOhm resistors. I installed the 60M (metal oxide vishays) because in the PCB the spot was marked as 60M but, again, is there any difference in sound quality-fidelity to the original design? Thanks!

 

[fazeka]

Hi,

Finally getting around to building but fearing I made an error.

I am biasing the FET (measured in the low 10s) and yes, I could see the waveform clip on the bottom part of the sine waveform on my scope when I increase the amplitude of 1kHz. Then I tweak (had to tweak both the bias pot and the pot I subbed for R11) and I get the nice sine waveform again. Keep doing a couple of times as per instructions, OK. However, I get to a point where the bias pot and R11 pot are at the end of its travel and I cannot get it to smooth out on the bottom of the waveform. Just to see how close I am, if I increase the amplitude slightly at this point, I see that both the top and bottom waveforms start to "square", so I know I am close, just that the pots are "maxed"... and sure enough, when I remove the R11 pot and measure, I get 22.83k ohm, quite a bit off from the 7k-12k ohm range spec per the schematic. BTW, my drain voltage is measuring at 10.48.

FWIW, I am using Dany's new blue D87-M PCB:

Any ideas/tips?

Cheers,
Chris

 

[poctop]

Hi,

Finally getting around to building but fearing I made an error.

I am biasing the FET (measured in the low 10s) and yes, I could see the waveform clip on the bottom part of the sine waveform on my scope when I increase the amplitude of 1kHz. Then I tweak (had to tweak both the bias pot and the pot I subbed for R11) and I get the nice sine waveform again. Keep doing a couple of times as per instructions, OK. However, I get to a point where the bias pot and R11 pot are at the end of its travel and I cannot get it to smooth out on the bottom of the waveform. Just to see how close I am, if I increase the amplitude slightly at this point, I see that both the top and bottom waveforms start to "square", so I know I am close, just that the pots are "maxed"... and sure enough, when I remove the R11 pot and measure, I get 22.83k ohm, quite a bit off from the 7k-12k ohm range spec per the schematic. BTW, my drain voltage is measuring at 10.48.

FWIW, I am using Dany's new blue D87-M PCB:

Any ideas/tips?

Cheers,
Chris

FYI,  the Bias Pot and R11 are the same thing ,  i would not suggest that you use both at the same time
the R11 location is only if you want to remove the pot from there ,  i usually leave it on the board. but it can be replaced by R11 ,
you should have plenty of room then to bias Properly.

BEst,
Dan,

 

[fazeka]

FYI,  the Bias Pot and R11 are the same thing ,  i would not suggest that you use both at the same time
the R11 location is only if you want to remove the pot from there ,  i usually leave it on the board. but it can be replaced by R11 ,
you should have plenty of room then to bias Properly.

Dan,

OMG, I feel so stupid! Shoulda checked the schem more closely... :

Biasing up nicely now! Thank you!  ;D

 

[rob61]

Ordered a pack of 25. I only need 8, so if anyone needs some, hit me up.

I have the parts ordered, so I'll probably need screws for 1 build. Are you in the U.S.?

 

[dreadheaded]

I have just finished putting together 2 of these, one of them is working perfectly, the other has a rather odd problem.

It seems no matter what I do there is a full polarization voltage to both sides of the capsule. I disconnected the switch to try and force it to cardiod and it still has a full 40v to the back diaphragm. I havent put it through its paces like the other one but it seems to sound fine

 

[patxiplg]

Hello everyone! This is my first post and first of all I'd like to thank you for all the great info you're all sharing here.

I'm currently building an u87 and when I ordered the bom long time ago, I don't know why but I didn't order the 2x 0.01uF film WIMA caps! (C2 and C14 of the u87M blue PCB). But I've found some KEMETs laying here around (www.mouser.com/Search/ProductDetail.aspx?R=PHE426HK5100JR05virtualkey64600000virtualkey80-PHE426HK5100JR05) which I think is a perfect equivalent, but I'm not 100% sure since it is rated for a 250V, and it's "AC and Pulse Film Capacitors" vs "RF Microwave Film Capacitors" (WIMA). I'm looking for the best audio quality possible (fidelity to the original desgin), so if it could replace the WIMA in terms of functionality but compromises the sound quality then...

Thanks for your help!!

PD: I also have both the 60 and 68MOhm resistors. I installed the 60M (metal oxide vishays) because in the PCB the spot was marked as 60M but, again, is there any difference in sound quality-fidelity to the original design? Thanks!

Sorry to ask again but could you help me to ensure if this one is equivalent to the WIMA, please? I received poctop's U87M PCB last week and this capacitor has stuck my build...!

Thank you in advance!

 

[Krumlee]

Yes, use the Kemets - they'll sound fine.

If you've installed the 60M resistors then stick with them - they'll also be fine. I think the 68M ones were only specified because the 60M ones were unavailable or expensive - see way back in the thread. There's no difference in sound quality.

Enjoy your build...

 

[fazeka]

Hi all,

Am having more difficulty, so another stupid question for y'all...  :

I have tskguy's (Eric's) K87 capsule and am trying to determine front and back...

The hole orientation of my capsule doesn't seem to match that of the diagram. Hard to describe but the holes seem to almost be offset... see below:

Maybe the diagram above is for the Peluso capsule and not Eric's?  ???

Anyway, any help would be appreciated to make out which end is which...

Thanks,
Chris

 

[wave]

Hi all,

Am having more difficulty, so another stupid question for y'all...  :

I have tskguy's (Eric's) K87 capsule and am trying to determine front and back...

The hole orientation of my capsule doesn't seem to match that of the diagram. Hard to describe but the holes seem to almost be offset... see below:



Maybe the diagram above is for the Peluso capsule and not Eric's?  ???

Anyway, any help would be appreciated to make out which end is which...

Thanks,
Chris

Chris,
There is no pre determined front or back. Just pick one side to be the front and wire that "front" backplate to the corresponding pcb point

Dave

 

[fazeka]

Chris,
There is no pre determined front or back. Just pick one side to be the front and wire that "front" backplate to the corresponding pcb point

Dave

Hi Dave,

OK, that makes sense. I read too much into it. 

Thanks for the feedback! I will give it a shot and report back. 

Cheers,
Chris

 

[Spike TheMan]

No word from TSKGuy,
Is there anyone that has contact with Eric, as I am trying to buy a U87 capsule from him?

I want to order all the parts for my U87 but I don't want to do it without knowing I can get TSKGuy's capsule.

I have $250 waiting aside just for Eric!

 

[fazeka]

Ordered a pack of 25. I only need 8, so if anyone needs some, hit me up.

I have the parts ordered, so I'll probably need screws for 1 build. Are you in the U.S.?

I am, but the M1.6 screws I ordered are too small... I'll have to find out what size I need... sorry about that.

 

[fazeka]

Yes m1.6, and I had exactly the same problem, I have ordered 200 m1.6's now because it was the only place I could find them, otherwise I was cannibalizing an old hard drive for them to temporarily hold my first one together!!

The M1.6 screws I bought did NOT fit the mic chassis... I will have to scrounge for some that will fit. Thinking to take the mic to the local hardware store and pray that they have metric...

 

[dreadheaded]

I apologize mine have yet to arrive but I did measure the ones provided with calipers!!! I guess my calipers need recalibrating  :

 

[fazeka]

I apologize mine have yet to arrive but I did measure the ones provided with calipers!!! I guess my calipers need recalibrating  :

Maybe the vendor I bought from (McMaster) got the order wrong/mixed up?

 

[fazeka]

Note: screw in the hole, too small

 

[poctop]

Note: screw in the hole, too small

IIRC those screw are M2,
Best,
DAn,

 

[kante1603]

Yes,sounds familiar to me and looks like M2.
The before mentioned caliper must be very far off[font=verdana, arial, helvetica, sans-serif].[/font]

[font=verdana, arial, helvetica, sans-serif]Udo[/font]

 

[fazeka]

IIRC those screw are M2,
Best,
DAn,

Yes,sounds familiar to me and looks like M2.
The before mentioned caliper must be very far off

M2 it is. Thanks guys!

I have ordered 200 m1.6's now

Oh my!