Neumann Vintage U87 Clone : Build Thread.

[wave existence]

anyone got mouser links for the toggles used for the switch pcb? guessing they are SPDT on on and on off on, cant seem to wade through all the switches to find the correct orientation, thanks.

 

[wave existence]

this fit btw: https://www.mouser.com/ProductDetai...FHHLLKGh0DA==&countrycode=US&currencycode=USD

 

[wave existence]

peluso only sent me 1 backplate wire, but most builds i have show 2 (4 wires in total from the capsule) any ideas for what i should do?

 

[wave existence]

ok so i noticed there is a place to solder? a wire to a hookup on the backplate on one side. my gut says dont put any heat on this sensitive part. any recommendations?

 

[fauxjazz]

Oops, my fault you asked very clearly.

I'm using two K67 type capsules matched by Dave Thomas at AAMicrophones. They are essentially the same as those sold by Microphone Parts, but they are re-skinned with 6 micron Mylar. They should have slightly less high frequency lift in the 7-9kHz range as a typical K67 type capsule. Since I already have two "dark" versions using K47 type capsules, I'm hoping this pair has slightly more "air".

More sonic crayons to add to the box!

Hiya, I'm in the process of building a pair of U87s and wondered how you rate the AA capsules (if you used them)? The bodies I have are quite small, so I think I am going to go for cardioid only (no switches/single back plate). Also considering the microphone parts K87 as I'm trying to keep costs down. Many thanks.

 

[Matador]

I thought they were fine, although I found when using them I needed to low-pass shelving filter them as their high end was a bit exaggerated (I LPF'ed 3db at 10 kHz if memory serves).

Once I switched to Eric Heiserman's 87 capsule I never looked back however. Both of those mikes record perfectly.

 

[benqbasic]

Hiya, I'm in the process of building a pair of U87s and wondered how you rate the AA capsules (if you used them)? The bodies I have are quite small, so I think I am going to go for cardioid only (no switches/single back plate). Also considering the microphone parts K87 as I'm trying to keep costs down. Many thanks.

See 3u audio for a good cheap K87 capsule.

 

[wave existence]

is there a troubleshooting guide? ive not no audio and flipping the switches makes a big pop on my preamp. don't really know where to begin

 

[wave existence]

ok so i had the front/back diaphragms mixed up. now i get sound but its very faint, have to crank my pre up all the way to hear anything. also when i switch to between different patterns there is a kind of loud stuttering, any ideas?

 

[doqmemory]

ok so i had the front/back diaphragms mixed up. now i get sound but its very faint, have to crank my pre up all the way to hear anything. also when i switch to between different patterns there is a kind of loud stuttering, any ideas?

Have you checked that the transformer is wired correctly? Very weak signal is a symptom of wiring the transformer backwards.

 

[wave existence]

Have you checked that the transformer is wired correctly? Very weak signal is a symptom of wiring the transformer backwards.

it appears to be: p+ and p- are wired to primary + and -, same for s+ and s- -> secondary + and - from data sheet

 

[catapultedplastic]

I cannot find anywhere Bourns PV37X253C01B00 trimmer, so my question is may I use Vishay T93YA253KT20 as a replacement?

P.S. Please know that mouser isn't an option because of the very high costs of the transport.

 

[Ricardus]

I cannot find anywhere Bourns PV37X253C01B00 trimmer, so my question is may I use Vishay T93YA253KT20 as a replacement?

P.S. Please know that mouser isn't an option because of the very high costs of the transport.

It should be fine. If the pins don't line up exactly you can bend them a bit.

 

[gearhunter]

Hi!

I'm attempting to finish my u87 build but I'm stuck trying to get optimum voltage when I bias the FET.

When I thought I had the mic finished in the biasing stage the DMM was showing 4V maximum. I measured all the voltages I could and the answer I had was that the FETs were bad.
Then I ordered some J112's because of the availabilty where I live (they have lower IDSS than 2N3819's) and replacing it now I'm obtaining around 8.64V maximum at the Drain (6.90V FET Gate) which is not sufficient to be able to do the symmetrical clipping procedure.

Could please someone bring me some light to know where more I have to look at?

I'll leave the schematic with the values I obtain. It's from when I had the 2N3819's so now the FET values are larger as C4, R7, C7 now is good, R7=6,89V R1= 0V?

Thank you!!!!

 

[fauxjazz]

Hello all, I have just assembled my D87, however I am experiencing some issues and wondered if someone can help me? I'm using the tapered circuit and using a cheap Chinese body with no cut-outs for switches (figuring I could just use the jumpers when required). The jumpers seem to work as expected in all positions. I'm using a 2n3819 FET from the Mouser BOM which measured 8.4mA and I was able to get 11.5V from the trim pot adjustment. I'm using a Maiku K87 capsule and 3U GZT-87 transformer.

Mic is passing sound but output is very low. I have to have my gain almost maxed-out on my interface to get a reasonable vocal level.
Have taken voltage measurements (below), which seem WAY off:

top of L1 - 42.5v
top of L2 - 42.5v
top of R18 - 42.5v
top of R19 - 42.1v
bottom of R17 - 20v
top of R17 - 22.5v
Zener 22.5v
FET drain pad 2.3v
FET source pad 8.8v
top of R12 8.7v
top of R13 25.9v
top of R14 20v
top of R8 16.1v

One thing I forgot to do was cut one leg of the trimpot, so I soldered all three legs in circuit. Is it necessary? I have reheated all joints and given the boards a clean. Any ideas on what could be the likely culprit?

Cheers,

Ben

 

[fauxjazz]

Deleted

 

[fauxjazz]

Finished my first U87. Managed to find some Motorola 2N3819s with low Idss. Went for 7mA in the end and this seemed to improve the output and quality of the sound in general. Sounds quite dark with the Maiku capsule but seems to take EQ very well. Thanks to Dany and all the contributors for this amazing project! This has been a great learning experience for me and I'm looking forward to building some more mics in the near future.

 

[AV]

Hello
Could I use a K67 capsule (non-isolated black plates) with D87 circuit?

 

[dmp]

Short answer is no, you need isolated backplates the way the front end in designed in the u87

 

[AV]

Thank you a lot for the answer.
Do you know any U87, U67 or similar project compatible with my non-siolated capsule?