Neumann Vintage U87 Clone : Build Thread.

[Drosselmeier]

Are you sure everything is assembled correctly?
If not, you will need a lot of clear pictures.

 

[Greenie]

Ok then, it was the pair of electrolytics that where somehow not working, so now it seems to be working. Thanks for helping out,

 

[RBeTT]

Hello everybody,

I must start by saying that I'm very new at this kind of builds. I have the intention to DIY 4 U87 mics but still wondering about the PCB's from PocTop.

With that in mind, aside from aesthetics and ergonomics, what is the difference between D-87L, D87-M, D-87T ? Sonically is it the same?

Cheers

RB

 

[doqmemory]

aside from aesthetics and ergonomics, what is the difference between D-87L, D87-M, D-87T ? Sonically is it the same?

Yes, the same circuit, to fit different size bodies. If you order the nice SYT-5 bodies from Chunger, then the blue PCB (D-U87M) is best. The D-87T is for smaller, tapered bodies, like the MXL 2010 (my favorite for this purpose), Aurycle, etc..

You will also need to source a proper capsule with isolated backplates, such as from Mic Parts dot com, 3U Audio (my favorite), Dachman Audio (same as 3U Audio capsule), Maiku, etc.

There is an official build thread that covers these things.

 

[RBeTT]

Yes, the same circuit, to fit different size bodies. If you order the nice SYT-5 bodies from Chunger, then the blue PCB (D-U87M) is best. The D-87T is for smaller, tapered bodies, like the MXL 2010 (my favorite for this purpose), Aurycle, etc..

You will also need to source a proper capsule with isolated backplates, such as from Mic Parts dot com, 3U Audio (my favorite), Dachman Audio (same as 3U Audio capsule), Maiku, etc.

There is an official build thread that covers these things.

Thank you!

I'm more inclined to use Aurycle bodies and make a cutout for the switch or use a jumper...what do you think?

Yes, I love 3u audio too...I have contacted them already.

Thanks for fast response!

 

[Ricardus]

Hi,

A quick question:
I had biased my U87 clone for symmetric clipping, but measured a drain voltage of only about 8.7 Volts. Since it sounded fine, I didn't worry too much about it. But in a recent vocal session I had the feeling that the microphone started distorting a bit when the vocal became really loud. Can somebody comment on whether both issues could be related and whether it is an indication that something is wrong in my built?

Best regards,
Waldemar

This is an old post but I figured I'd reply to it. I built 2 of these a couple years ago and just biased the FET to 10.5 volts as many people in the thread were saying to do (although other places say 11.5 volts).

Anyway. I wanted to do a biasing with a scope for a long time, then life hit and all sorts of crap happened. Anyway, I landed in a good place and decided to do this today. When I bias them and get the sine wave where I want, I also ended up with a voltage of about 8.5 on both mics just as this person did.

Later in his responses people thought that indicated a problem. Is it?

 

[doqmemory]

I'm more inclined to use Aurycle bodies and make a cutout for the switch or use a jumper

I've done cutouts several times on the Aurycle bodies. It works best to offset the pattern switch to one side of the centerline, directly across from one of the included switches.

 

[RBeTT]

I've done cutouts several times on the Aurycle boddies. It works best to offset the pattern switch to one side of the centerline, directly across from one of the included switches.

Thanks for the info!

I have found some these bodies at WGT Center U87 body , Have you tried them out?

Thank you for your time and knowledge!

 

[doqmemory]

I have found some these bodies at WGT Center U87 body , Have you tried them out?

Yes, I got one and it is crap. The silly rail design is something like 33 25mm wide--way too small.

The Aurycle bodies are nice brass and ship fast (or used to, anyway).

Chunger's SYT-5 are great, BTW.

 

[RBeTT]

Yes, I got one and it is crap. The silly rail design is something like 33 25mm wide--way too small.

The Aurycle bodies are nice brass and ship fast (or used to, anyway).

Chunger's SYT-5 are great, BTW.

Aurycle would be great, but i live in Europe so would need to wait a little longer I guess..

I have contacted Chunger via email, but no response until now..or should i contact him here?

 

[Dimon]

D-U87 How about an electrical scheme ? Due to IP blocking and shipping in shops, I'm unlikely to buy a board and a set of parts. (

 

[JimSalabim]

I have a problem with Figure-8 mode. Cardioid and Omni are working just fine, but in Figure-8 the signal is very low, and the rear side has much lower sensitivity than the front side.
It makes no difference in any of the modes which side of the capsule is wired as front and which side as rear, they’re both working equally fine (and they’re technical identical anyway as far as I know), so I think the capsule itself is probably not the problem.

I built the mic from a complete kit from Mic & Mod a few years ago. The issue has been there all the time, but I didn’t have time to address it yet.

Any ideas what could be wrong?
Pictures and audio file attached. The capsule is installed just as described in the guide (picture also attached).
View attachment U87.wav

 

[TLRT]

I have a problem with Figure-8 mode. Cardioid and Omni are working just fine, but in Figure-8 the signal is very low, and the rear side has much lower sensitivity than the front side.
It makes no difference in any of the modes which side of the capsule is wired as front and which side as rear, they’re both working equally fine (and they’re technical identical anyway as far as I know), so I think the capsule itself is probably not the problem.

I built the mic from a complete kit from Mic & Mod a few years ago. The issue has been there all the time, but I didn’t have time to address it yet.

Any ideas what could be wrong?
Pictures and audio file attached. The capsule is installed just as described in the guide (picture also attached).
View attachment 103649

If the fig8 is not working means you backplates are not isolated correctly.(or circuit issue) To proof it you need to remove the capsule and measure isolation resistance between the copper plates with a good meter above 1gigohm.

 

[JimSalabim]

Thanks! I have removed the capsule and the resistance between the backplates is close to 0 Ohm. So it’s the wrong type of capsule?

 

[Ricardus]

Thanks! I have removed the capsule and the resistance between the backplates is close to 0 Ohm. So it’s the wrong type of capsule?

What exact capsule did you use? You need a capsule specific to the U87i design which means no eletrical connection between the backplates. So either you have the wrong style capsule, or you have a U87i style capsule but it's defective.

 

[JimSalabim]

The capsule was sent to me with the full kit back then. They have changed the design of their kit to work with a capsule with uninsulated backplates later, so maybe they accidentally sent me one of these capsules?
It looks like this:

 

[TLRT]

Thanks! I have removed the capsule and the resistance between the backplates is close to 0 Ohm. So it’s the wrong type of capsule?

Yes you need isolation between the backplates, so anything under gigohm ranges wont be ok.

 

[Ricardus]

The capsule was sent to me with the full kit back then. They have changed the design of their kit to work with a capsule with uninsulated backplates later, so maybe they accidentally sent me one of these capsules?
It looks like this:
View attachment 103656

I always thought the capsule HAD to have insulated backplates to work in figure-8 mode in the U87i because phantom voltage was essentially so low. You should probably reach out to the people you bought the kit from and discuss this. Sounds to me like they might need to send you the proper capsule.

 

[JimSalabim]

In their current kit there’s a dual voltage converter (+/-60V) in the circuit and as far as I can see figure-8 mode is achieved by switching a 470pf cap between front and rear capsule? Anyway, unfortunately I don’t have enough understanding of how it works. But the backplates of the K87 capsule are connected together on the PCB in their new design, that’s for sure.

 

[Ricardus]

In their current kit there’s a dual voltage converter (+/-60V) in the circuit and as far as I can see figure-8 mode is achieved by switching a 470pf cap between front and rear capsule? Anyway, unfortunately I don’t have enough understanding of how it works. But the backplates of the K87 capsule are connected together on the PCB in their new design, that’s for sure.

Yeah, that sounds like the U87ai design, not the U87i. The 87ai uses a DC to DC converter for higher voltage and a different capsule.