Neumann Vintage U87 Clone : Build Thread.

[PG_Sax]

Also if anyone is interested, I have run a couple of sweep tests on the D87 and my friends old U87 which used to belong to me.

The D87 spec is,

HK87 capsule
Sowter 1303 Transformer.

U87 is from the 1980s I think its 1987.

I couldn't exactly match the input level of both mics so the D87 is 0.5db louder than the U87.

Low end is pretty spot on taking this into account.

 

[PG_Sax]

Here is U87.

Will post the results of the C6 change, when I've done it.

 

[PG_Sax]

I just finished up another one of these and it sounds great except for the figure 8 pattern. I just get a very big volume drop when in that pattern. Everything else works great. Any ideas where to look? Switch PCB or Output transformer wiring?

Are you getting a volume drop on just one side? Or both sides? I would definitely check pattern selection switch wiring.

 

[Haoxian]

Also if anyone is interested, I have run a couple of sweep tests on the D87 and my friends old U87 which used to belong to me.

The D87 spec is,

HK87 capsule
Sowter 1303 Transformer.

U87 is from the 1980s I think its 1987.

I couldn't exactly match the input level of both mics so the D87 is 0.5db louder than the U87.

Low end is pretty spot on taking this into account.

What software is used for such tests? Can I test the capsule with it?

 

[HosaMogami]

Are you getting a volume drop on just one side? Or both sides? I would definitely check pattern selection switch wiring.

Definitely both sides equally. No distortion, just a volume drop. Will check switch switch wiring soon.

 

[PG_Sax]

What software is used for such tests? Can I test the capsule with it?

I'm using a program called Fuzz Measure by Rode to perform sweep tests. With my setup its far from scientific but I'm using an old U87 I know to be good as a reference.

 

[PG_Sax]

Definitely both sides equally. No distortion, just a volume drop. Will check switch switch wiring soon.

Yeah I'm not knowledgeable enough to be that helpful unfortunately. Maybe also check C2? And go over the boards.

 

[PG_Sax]

I realised that I made a mistake yesterday with my measurements, so I remeasured.

Here are the two mics on the same graph. This time they are matched to within a tenth of a db.

 

[Haoxian]

Thanks for replying!

Its a 25k pot, I have another one but they both seem to be working when I hook up them up to the meter.

I forgot to mention I can also see the sine wave on scope and it looks normal. Ive also been able to hear it on headphones although the ground noise is quite bad without body.

Could it be FET?  Is the source voltage 2.1v ok?

When the mic is first supplied with phantom fet voltage is around 12-13v but it moves around a lot and gradually starts falling?

How did you solve the problem? My FET will not work for 5 minutes after starting up because the voltage is too low, but will slowly rise to 9V after 5 minutes and maintain a perfect sine wave. It makes me sad

 

[PG_Sax]

How did you solve the problem? My FET will not work for 5 minutes after starting up because the voltage is too low, but will slowly rise to 9V after 5 minutes and maintain a perfect sine wave. It makes me sad

For me the was a electrolytic capacitor that was orientated the wrong way. Think it was C8.

 

[TillM]

as far as I understand you was able to fet the bias ?
what happened with an installed capsule ?
Do you get sound ?

 

[SparkleBear]

Has anyone sketched up an exact schematic of this circuit with all the connections?

 

[Ricardus]

So I'm about to begin building two D87s, and I have a question or two. Is the BOM on Dany's site still accurate? It seems like it calls for more components than it appears the build requires. I haven't actually counted components on the built examples I've seen but it seems smaller.

For example, the BOM calls for 3 2N3819's. Doesn't the mic only need one?

 

[fsalter]

There is redundancy in the BOM to give you options. Some resistors like the 2.2 k ones have to be closely matched. Buying many will permit you to find a matching pair. Also, there  are Polypropylene options to the Styroflex caps if you chose to go that route. You have to find a 2N3819 with a low Idss.  Ideally below 10ma. You may find it hard to find those jfets. Let me know if you want any, i have a few.

 

[Ricardus]

I found some 3819s and bought a dozen from a reputable site (not ebay!) so I should be fine. OK. I didn't realize there was redundancy built into the BOM. I bought the BOM from Mouser and the styroflex caps from Dany's site.

I also found another supplier for 3819's that a friend hipped me to. A place that supplies educational institutions. Not sure if they're as high quality as the dozen I bought. They didn't ship after 2 days though, so I suspect they have no inventory. I'm going to call tomorrow to see.

 

[Ricardus]

..the last two batches of 2N3819 I bought turned out fake, just some rebranded generic NPN transistor..

They were branded, with laser marking:

(Fairchild-Logo-F)
BJ12
2N3819

Yeah, I bought some of those myself and some fairly well known mic techs I know on FB guaranteed me they were fake. I actually made a claim with ebay and they refunded all of my money!

 

[Ricardus]

I was looking at the build thread for the D87M and when he mounts the switch PCB he was using some sort of spacers or offsets. I don't think those are part of the BOM. Does anyone have a part number for those?

 

[TillM]

I was looking at the build thread for the D87M and when he mounts the switch PCB he was using some sort of spacers or offsets. I don't think those are part of the BOM. Does anyone have a part number for those?

You don’t need them

 

[Duizels]

Hello,

I am preparing to build this u87 clone mic.

When trying to order this BOM http://www.mouser.com/ProjectManager/ProjectDetail.aspx?AccessID=1AD602D54E
the website gives me an error with the 610-2N3819 RF JFET Transistors N-CH -25V 10mA > I need to order 5.000 or more
Is there a comparable component I can get that is not the bulk pack? Im having a hard time figuring out which one is the correct one to order, since I am not experienced with this and the mouser website is huge.

thanks

Chris

 

[TillM]

There are some things you can change.
The 150k resistor shows 5€ in your BOM.
Change it to another.
Decide whether you take 68Mohm or 60 Mohm resistors. You dont need booth.
Also there a two 25k trimmer in the BOM.
Just choose one.
For the 2N3819 ask in the black marked.
I also have some, but I’ve first to look on which builds I need them.