Neumann Vintage U87 Clone : Build Thread.

[Wordsushi]

I'm finally putting together my game plan to build a D87 in the not too distant future and I had some questions and wanted to confirm a couple of things.

1) Swapping 330pf for the 220 at C6 will smooth the top end a bit, correct?

2) Going with 22uf at C9 will give it more low end, yes?

3) Will pulse film instead of polystyrene give it a more modern sound?

4) Will electrolytics instead of Tantalums give it a more modern sound?

I'm leaning toward wanting it to sound more modern rather than vintage because my sole use for it would be commercial voice over and detail and brightness are things I'm looking to get dialed in just right for my particular voice.

For me, it doesn't have to sound exactly like an authentic vintage 87, just a great 87-style mic. My main VO mic for work is a transformerless Sennheiser 416 shotgun which works great for most jobs, but there are certain commercial reads like car spot jobs that I think a transformer-fed 87 would be better suited for and I'd prefer to build one myself and customize it for my personal work use.

 

[hugo]

I'm finally putting together my game plan to build a D87 in the not too distant future and I had some questions and wanted to confirm a couple of things.

1) Swapping 330pf for the 220 at C6 will smooth the top end a bit, correct?

2) Going with 22uf at C9 will give it more low end, yes?

3) Will pulse film instead of polystyrene give it a more modern sound?

4) Will electrolytics instead of Tantalums give it a more modern sound?

I'm leaning toward wanting it to sound more modern rather than vintage because my sole use for it would be commercial voice over and detail and brightness are things I'm looking to get dialed in just right for my particular voice.

For me, it doesn't have to sound exactly like an authentic vintage 87, just a great 87-style mic. My main VO mic for work is a transformerless Sennheiser 416 shotgun which works great for most jobs, but there are certain commercial reads like car spot jobs that I think a transformer-fed 87 would be better suited for and I'd prefer to build one myself and customize it for my personal work use.

Modern ?...i dont think it is the right project...it is not the AI version, which delivers more gain for modern use

 

[Wordsushi]

I know. I'm not looking for more gain, just a more detailed sound vs a vintage sound.

 

[hansen]

Hi guys,

I noticed the BOM has the L1 and L2 (Fixed Inductors 47uH). The Mouser BOM tells it's only possible to order a minimum of 100 of those components. Is there a workaround?

 

[poctop]

Hi guys,

I noticed the BOM has the L1 and L2 (Fixed Inductors 47uH). The Mouser BOM tells it's only possible to order a minimum of 100 of those components. Is there a workaround?

Just bought this:
542-78F470-RC
MFG Part No: 78F470J-RC
Bourns 47uH 5% / Fixed Inductors

 

[hansen]

Thanks, that worked. I'm about to buy wires. Will any wire do? I read a DIY guild from someone who used 22awg silver stranded teflon wire. Also, does cable voltage matter for this particular project?

 

[TillM]

they are good, but u can nearly use every wire you want.

 

[hansen]

they are good, but u can nearly use every wire you want.

Sorry for my ignorance, but would't quality in cables affect quality in the audio? Or is this to neglect?

 

[winner]

Jumpered? From the pics i see that you used jumper base connector - are these two points connected to eachother?
Measure voltage in these points:
-both sides of R14
-both sides of R2
-c9/c7 point
-R19/R18 point

Hello guys, excuse me, I built the microphone everything is normal, but the output level is too small, I browse a lot of information, whether the resistance of the R8 1M cut out, or switch to smaller resistance, its output will become big? Hope to get your answer, thank you

 

[hugo]

Hello guys, excuse me, I built the microphone everything is normal, but the output level is too small, I browse a lot of information, whether the resistance of the R8 1M cut out, or switch to smaller resistance, its output will become big? Hope to get your answer, thank you

It is normal. You built a vintage version, the level is low. Level of modern U87 is higher, but your mic is working fine. Close that project and start to enjoy using it ;-)

 

[zaraxisof]

Just finished population and transfo,xlr wiring, capsule not connected, phantom power ON and took these weird measurements:
With phantom power: 43,8V
Voltage Drain: 0,14V.
Zener: 0,67V
Pad XLR2: 43V but clipping a bit at soundcard's meter when probe of multimeter touches the pad.
Ωtest transfo pri&sec normal (950Ω pri and 90Ω sec).
R18,R19(resistors near inductors): 30,4V .
But the most weird thing was that when i turned phantom power on (mic connected of course), input channel at inteface peaked(at reds) for a bit and then went to its normal silence/zero meter. The same when turned off phantom. And thats the reason i dint tried anything like insert sine wave etc...
Checked for wrong components,bad connections,connectivity probs with multimeter, all OK.

Any thoughts?

PS. I used all "normal" values as included in BOM.

 

[TillM]

That the level can go up to red when you turn on phantom power is normal.
Even my original Neumann TLM102 do it.
Your zener has to low voltage.
Change it.
Look for polarization of your caps.
Maybe a connection cable from the PCBs is broken, also check this.
Cost me a while to find this failure, when my mic doesn’t work.

 

[zaraxisof]

You wil not believe if i tell u what the prob was actually. .  I had wired wrong the XLRs lool

Thank u TillM and Khron as always for your help, appreciated!

Just for the record, Zener is now 23,6V.

Peace.

 

[zaraxisof]

Pff now i have another (but small) prob here. TrimPot cannot goes above 7,30V. so i cannot reach the  ~11,5V. value.

Idss value (out of circuit) of JFET was about 6,5mA.
Starting value for Drain Voltage was 4,5V, so i started give turns to Trimpot, it went well until 7,30V and then it becomes difficult to turn more, its like you need 20 full circles or so to increase just 0,01V. and it makes these "limit clicks"/hard to turn it"...

2N3819
Phantom: 43,8V.
Zener: 23,6V.

I found some threads with similar prob, it may be wrong transfo wiring?
I used the 3U 87 transfo,  here's the wiring diagram. I wired from front side, like that: 
Red to RT , Brown to SW(gnd) ,  Yellow to XLR2+Hot ,  Orange to XLR3-Cold. 

Is this right, or this is for backwards wiring?
Any thoughts on this low  drain voltage issue?

 

[RuudNL]

Use another FET. (The one you are using now is too much off spec.)

 

[zaraxisof]

If you read on what it finally was, you will not believe it. When i unscrewed all pcbs and looked back to swap the jfet for a new one, there was a f**kin cutted solder leg just exactly between the two jfet's legs (drain and source), causing a short between them lolol. It was found there probably after a cutting of a soldered leg  with scissors
Had never experienced smthng like that haha.

Finally all is OK, i did properly FETbiased it,  with simple multimeter and digital scope. In the begining  drain voltage was 7,9V. , i turned the trimpot so  to achieve 11,5V. drain voltage. After that there was scope biasing time, so i used the 1kHz input digital scope method. Signal generator from DAW to interface's output and from that cable, connected signal with input signal resistor (iso pin - styro capacitor)  and ground with mic's chassis body via alligator clips.
Important NOTE here and maybe useful for you : After Khron's useful advise as always, he motivated me to check how  my alligator clips were connected and see if they were soldered or just tightened up. And guess what, the uninsulated piece of wire was bent back parallel with the rest, and just tightened/crimped into  this metal clamp /cable holder with no solder at all! I guess that explains the extremely low cost i bought them for.  Sooo ultra important: When buy all these alligator cheap stuff check first  their  inside connections !!

At  the end of the day  all is fine , having  learned some useful and interesting things here.
My U87 clone is ready and waiting for a K67 capsule but for the time i have to be patient for a good opportunity  at about 50 bucks. My goal is the common  34mm 797 Beijing K67 double sided 6 micron Mylar capsule but people of 797 Audio that i spoke with staright away, accept only DHL (50 euros shipping) and not Simple China Post (low shipping cost/free shipping). 

Happy Christmas

 

[rockinrob86]

Just FYI, I've noticed (and heard from others) that a FET that was shorted can become noisy later in life - so you may want to at least keep some other fets around and remember this if you notice your mic getting noisy down the road

 

[zaraxisof]

Yeap i know, i had replaced it with another one just to be sure, forgot to mention above, thanks for the add btw  8)
My only concern now is how could i find a 797 K67 capsule for it, as shipping  is too much for one caspule from 797 company,  plus, i read somewhere here that buying straight from them could not be the best solution, as they may want to sell out any problematic/not 100%  perfect capsules that they didn't sell to big mic companies out there -just an opinion though- , so my other option is to buy a used  Behringer B2 Pro, NT1/2 early models or SP C3 that uses the 797 6 micron K67. But even with this last option i cannot be sure as you can never know the real condition and previous use of a used capsule ... 

Maybe the best bet here is to  do a groupbuy from 797 Audio, but dont know how many heads here are interested in ...

 

[Khron]

I hope you're aware none of those mics have isolated-backplate dual-diaphragm capsules, so the pattern selection won't work.

 

[zaraxisof]

Right. I will turn it to cardioid only use till i find an appropriate K87 with isolated backplates ...