Neumann Vintage U87 Clone : Build Thread.

[poctop]

...connected the switches directly to the main board.

Thanks!
I'll try to get the orientation of the switches correct, not sure how to tell though.

Make sure your switch board is just a switch board you could be surprised some model require you to modifiy it
read post from Kante1603 in the build thread , (Thanks Udo)

Or use the Jumper to start with and then you see if everyting is in order to begin with ,

 

[sr1200]

On that model that hes working with, if you remove all the components the switches are all insulated from one another.

 

[kevinkace]

Thanks for the info, hope to finish the build this weekend.

 

[Spencerleehorton]

Hi guys,

first of all big thanks to dany and all the other guys for putting this all together.
I want to get 10db approx more output from the U87 clone, im using the following:
microphone parts RK87 capsule, Sowter 9610 transformer, i am aware that an original U87 has a low output but i want to mod mine to get more output.
Brian Sowter has offered up the following and i wanted to hear what people had to say about it:
we talked about changing the 9610 which is a 10:1 ratio to something else to get more output

1303 (U47) has a step down ratio of 7:1 (-16.9 dB)  and 1304 (U67) is 9:1 (-19.1 dB).  9610 is 10:1. (-20 dB)
6.5:1 is -16.4 dB.

So if you use a 6.5 :1 instead of 9610 you will get a level improvement of 3.6 dB.  To get a 10 dB lift you would need a 3.2:1 ratio.  Not a good idea.

I do not recommend reducing the step down ratio too much because the reflected impedance of the mic cable and the input impedance of the desk will be reduced to a point where the loading on the anode spoils the frequency response and the linearity.  Generally these triode mic amps need to see as high an anode as possible which means a high step down ratio for the transformer.

I suggest you try the difference between 1303 and 9610 before deciding what to do.  You can also try increasing the anode load resistor and/or reducing the anode current to increase the gain.

I am afraid there is no magic fix with the transformer but there is plenty of scope for optimising the overall circuit which may or may not include changes to the transformer.

if someone could help me understand the anode resistor and what value would be a good way to go i would very much like to experiment.

thanks in advance.

 

[kante1603]

On that model that hes working with, if you remove all the components the switches are all insulated from one another.

Yes,and after cutting a trace because one had an unwanted connection to ground.This refered to a B2Pro build.
Just make sure all switches are floating,everything else is an easy one.Dan´s suggestion to build it with just the headers/jumpers first if you´re unsure is pretty good,this way you set up the mic to a working condition  (easier to troubleshoot then).When everything is working fine just hook up the switch wires.

Cheers,

Udo.

 

[kevinkace]

For the jumper suggestion, I assume that for the pad/LC it's just a matter of shorting the 2 pins of either/both header?
What about for the 3 pins for the pattern?

 

[poctop]

For the jumper suggestion, I assume that for the pad/LC it's just a matter of shorting the 2 pins of either/both header?
What about for the 3 pins for the pattern?

for the pattern  leftmost 2 pin short = 1 pattern and rightmost 2 pin = other pattern ,
No Jumper at all = cardiod,
Hope this helps,
D

 

[atticmike]

are there actually low end mic mics with a body diameter of 60mm?

Mike

 

[wave]

what auricycle body were you using for your build? Any additional stand you got for the capsule?

Well, if they prefer it over an original neumann, it must be good sign.

You know I started to cudgel my brains over the sonic injury I'd be having if I didn't use the original headbasket and so on. Now that you've told that story, which I hope is true to its core, things won't be as bad as I thought they'd be.

Looks like most of you guys were drawn to the switchless body whysoever? I guess you chose by the headbasket shape?

--

In addition to that, I've checked geekmacdaddy's samples and I gotta say that the clone completely lacks the sheen created by the U87.

--

What are your thoughts on using a U47 type of body / headbasket for the microphone? Wouldn't it grand the mic a little more hf which the U87 could use?
I don't think it'd destroy the mic's vibe since there've also been U47 in u87 type of bodies by Neumann.

Yes this story is true. This was when I had an RK-87 in the mic. The mic was quieter than the Neumann but it sounded really good.
One thing I see on the forum when talking about cloning mics is the headbasket and mesh issue. For me, I think the Aurycle is a fine donor body and a really good sounding mic can be built.
The old samples from geek were before Eric fixed his capsule. There was a problem with the mid spacer and now that that issue has been worked out, Eric's capsules sound incredible. Geek posted a new sample somewhere I think and the mic def sounds much better.

You can adjust the value of C4 to gain or lose some HF (at the expense of some volume tho)
As far as sticking the mic in a 47 style headbasket, I think it could work but if you want to have a body that is really close get the U87-67 style body that ChuckD and Chunger are offering.
The circuit in an Aurycle DIY FET mic and using styrenes tantalums and the T-13 in conjunction with a capsule like the RK-87, you will have plenty of high end - and I thought that, when compared with Eric's final K87, maybe there was too much high.

I hope that some of this info helps you

Dave

 

[MicDaddy]

I have 3  2 sets of these pcbs, untouched, asking original price.

 

[geekmacdaddy]

PM sent

 

[geekmacdaddy]

In addition to that, I've checked geekmacdaddy's samples and I gotta say that the clone completely lacks the sheen created by the U87.

NEW CLIPS w/New Capsule from tskguy (got buried on page 60) I am sooooo happy!

real U87a
https://dl.dropbox.com/u/87086401/U87.aif

my clone
https://dl.dropbox.com/u/87086401/Capsule%202%20U87%20Clone.wav

 

[0dbfs]

Hey Guys, I biased my u1621's up via scope method with capsule installed (instead of 51pf cap)... Just un-soldered pad1 of the transformer to disconnect primary and temp soldered signal-wires to the designated calibration pads and measured for symmetrical onset of clipping at the drain. Seemed to work as expected and sounds nice.

I had temp set the drain to 10.5V and after cal it was about 11.6V so.... At least on one unit. Doing three more now.

Any thoughts on that method (not disconnecting the capsule)? There wasn't any significant interference to speak of on the waveform.

Thought I would share that if it saves someone a step and potential flux contamination by re-soldering the capsule connections.

Also, if leaving the tweaker-pot installed instead of replacing with a precision resistor how-much / how-often should we check for pot-drift? I'll check it on a semi-regular basis and see how it goes but you know some of those pots can drift and would be nice to never have to worry about it again once in-service...

Cheers,
jb

 

[poctop]

In addition to that, I've checked geekmacdaddy's samples and I gotta say that the clone completely lacks the sheen created by the U87.

NEW CLIPS w/New Capsule from tskguy (got buried on page 60) I am sooooo happy!

real U87a
https://dl.dropbox.com/u/87086401/U87.aif

thanks  for the nice comments and also ,  really neat Job ,
always appreciated,
Dan,.

my clone
https://cdn.groupbuilder.com/groupdiy/u/39511/58d0281993897.wav

 

[Hank Dussen]

To bias the FET's I'm injecting a sine wave at the top the reversed R6 and measure the voltage at the drain of the FET.
But I find that the volume (amplitude) of the sine wave effects the reading at the drain.
Is this normal and should I read the drain voltage without any injected signal?

Pieter

 

[HellfireStudios]

It sounds to me like you are confusing the two methods of biasing. No sine wave is needed to bias it by voltage. If you own, or can borrow, an oscilliscope you will need the sine wave for biasing.

-James-

 

[mukole]

I just wanted to thank Poctop and everyone else who has contributed and made this project possible.

I built 5 of these using Styrenes/Tantalums, the AMI transformer and Tskguy's capsules (thanks Eric) which i chose after listening to Wave's samples.
I used ISK BM600's for the doner bodies with all 3 switches working. Also I set the bias using a scope.

Recently I started tracking some drums with the drummer from my band and used the clones for overheads and room mics.
I had two on overheads in an ORTF setup in cardioid pattern, one on either side of the kit in omni, and the last one about 2 inches away from and pointed toward the doorjam in cardioid pattern at the entrance to the room. The room only measures around 10 by 20 foot and is heavily insulated.

I haven't used a real u87 so i don't know how they compare to the original but the amount of detail these mics add to my mix compared to previous recordings i've done is amazing.

Here's a sample i recorded when we were setting up. It's a mix of all five mic's together, all tracked through jlm audio baby animal preamps into an apogee ensemble. I haven't added any eq or compression.

https://dl.dropbox.com/u/107261645/u87%20test.wav

 

[mukole]

And another pic

 

[tskguy]

Sounds great!!

Glad you are happy.  ;D

 

[kevinkace]

Nice sounding drums!

I'm wondering about epoxying/hot gluing the transformer in place, just a couple dabs between each side of the transformer iron and the mic body rails. Recommendations?