Neumann Vintage U87 Clone : Build Thread.

[spudstyle]

Was R6's orientation reversed on the PCB?

-James-

Yes

 

[HellfireStudios]

When I was trying to bias my mic, I could never get the software-based oscilliscope to work correctly. I finally bit the bullet, and bought an analog o-scope (a Tektronik 454). It biased easliy after that. Just remember, like all analog gear, let it warm up for at least twenty minutes before trying to use it.

-James-

 

[spudstyle]

I don't have enough money to buy a scope but I will try to Take an analog scope at work :/

 

[spudstyle]

Again a question: you think the bad biasing is the reason for the low output level ? With the first fet, biasing was ok and voltages too but the output level was low. See precedent post for the voltages etc.
The CineMag wiring can't be the problem ?

 

[HellfireStudios]

The people who have biased with an o-scope say the output was higher than biasing it with some of the other methods mentioned (I only tested the mic after I got it properly biased w/ the scope).
This being a vintage mic circuit, the output is going to be lower than most modern condensers (10-11dB less than a modern U-87ai). If your mic preamp can't give the extra dB without excessive noise, you may need a better preamp

A simple way to test the transformers wiring is to put a small AC voltage across the primaries (I used a 9VAC adapter). Test the adapter voltage with your DMM (mine was at 10.6 volts unloaded). Then, test the secondaries. If all is well, you should see a major step-down in voltage (just over 1 volt for my particular circumstances). I do not know if this harmful to transformer or not. It worked on my Cinemag 2480, but your mileage may vary...

-James-

 

[spudstyle]

Ok, thank you You answer my question for the level ! So I think my level was not too bad before :/
For my preamp, I only have my Steinberg mr816 but after a gssl, I will try to make a 1073

 

[Sredna]

A simple way to test the transformers wiring is to put a small AC voltage across the primaries

Why not just use a DMM and measure the resistance? The lowest side is the output (XLR-side).
For example the AMI transformer has ~ 22 Ohms on the secondary and ~ 440 Ohms on the primary.

 

[poctop]

Thanks Guys to help out here  ,  sometimes i have to travel in remote places for job can't catch everything for a while
This forum is great

Best To All,  and Merry Xmas at the sametime  ;D
Dan,

 

[spudstyle]

Merry Xmas Dan and thanks for all

 

[evanmurphy]

Hi folks,
Trying to get John's P-T87 wired up to the board and can't find a definitive color code chart for it. How far off am I ?

RT = red
SW = yellow
WS = Black
BL = green

I'm basing that off of the aurycle trafo so I could be totally wrong? Anyone?

Thanks in advance, and thanks Dany for such a cool project!

 

[HellfireStudios]

Hi folks,
Trying to get John's P-T87 wired up to the board and can't find a definitive color code chart for it. How far off am I ?

RT = red
SW = yellow
WS = Black
BL = green

I'm basing that off of the aurycle trafo so I could be totally wrong? Anyone?

Thanks in advance, and thanks Dany for such a cool project!

Call or email John over at Peluso. He should send a wire color chart for your particular transformer.

-James-

 

[poctop]

I was requested to post some sample in another thread so here it is again ,
Enjoy,

Here is what my Clone sounds like the clip is very raw ( No pop filter to have an idea of the proximity effect ) but at same gain setting
D.
https://cdn.groupbuilder.com/groupdiy/u/39511/58d02819939b3.wav

Edit : when i say it is very very flat i am tlaking about the extra sweetness with the original capsule.
Got the year october 1979 
Dan,

 

[evanmurphy]

Call or email John over at Peluso. He should send a wire color chart for your particular transformer.

-James-

Dropped him a line yesterday. I'll update this thread when I hear back, I'm sure I'm not the only one looking for this info since I don't recall it being included in any correspondence or the packaging.

 

[Biasrocks]

I was requested to post some sample in another thread so here it is again ,
Enjoy,

That request was made by me. Here is the full context of that request, in related posts.

http://www.groupdiy.com/index.php?topic=49389.msg642539#msg642539

Regards,
Mark

 

[kante1603]

Have read through the above mentioned link some minutes ago.
Seems he stops posting here finally.
And it doesn't make me sad at all......

Back to topic,o.k.?

Cheers,

Udo.

 

[andyfromdenver]

Hi folks,
Trying to get John's P-T87 wired up to the board and can't find a definitive color code chart for it. How far off am I ?

RT = red
SW = yellow
WS = Black
BL = green

I'm basing that off of the aurycle trafo so I could be totally wrong? Anyone?

Thanks in advance, and thanks Dany for such a cool project!

Poo, I just ordered his and figured it'd be in there.
Would appreciate this info or I can obtain and post

 

[Sredna]

The lowest side is the output (XLR-side).
For example the AMI transformer has ~ 22 Ohms on the secondary and ~ 440 Ohms on the primary.

Should be about the same values for other T87-clones as well...

Dont be afraid to check things yourself, the low output problem some here had was because of following the colour codes blindly! 8)

 

[andyfromdenver]

The lowest side is the output (XLR-side).
For example the AMI transformer has ~ 22 Ohms on the secondary and ~ 440 Ohms on the primary.

Should be about the same values for other T87-clones as well...

Dont be afraid to check things yourself, the low output problem some here had was because of following the colour codes blindly! 8)

true-ché

 

[atticmike]

Gonna start building my stereo pair today but there are some questions left:

What is the FET measuring gonna give me? I guess it for finding a matching pair in a stereo situation but not helpful if you go mono? Whereas I'll be building a stereo set so it is important to me. Is it better that I measure a bigger or lower voltage drain? I guess lower is better right? Any references value like 10.5V ?

And what does it mean to install R6 backwards? Doesn't it matter to what side i solder the resistor to the board? Or is this just a facility to support the measuring ergonomics?

I mean, I read through the thread and as this being the first time mic build I'm doing, I've got easily lost. Can someone post a quick succession of what's supposed to be done in a numeric order after stuffing the boards?

i suppose it is to measure the drain with a 9V battery and put this in the math form provided by the author which gives me the resistor value then?

 

[poctop]

Gonna start building my stereo pair today but there are some questions left:

What is the FET measuring gonna give me? I guess it for finding a matching pair in a stereo situation but not helpful if you go mono? Whereas I'll be building a stereo set so it is important to me. Is it better that I measure a bigger or lower voltage drain? I guess lower is better right? Any references value like 10.5V ?

A: it is the IDSS of the FET that you want to be low but arround 10ma you should be all fine , you can determine it with the 9V battery procedure has been posted by matador and it is on the first page of the build thread

And what does it mean to install R6 backwards? Doesn't it matter to what side i solder the resistor to the board? Or is this just a facility to support the measuring ergonomics?

A: yes easier to inject signal from the top of the board for biasing

I mean, I read through the thread and as this being the first time mic build I'm doing, I've got easily lost. Can someone post a quick succession of what's supposed to be done in a numeric order after stuffing the boards?
1- stuff it
2- bias it
3-use it

i suppose it is to measure the drain with a 9V battery and put this in the math form provided by the author which gives me the resistor value then?
see Matador procedure for IDss ,

Hope this helps,