Neumann Vintage U87 Clone : Build Thread.

[wave]

Matador,
I looked at a datasheet for a Toshiba 2SK170BL on Mouser and I couldn't tell if the orientation of the FET would be the same looking at the diagram on the sheet. What do you think?

Dave

 

[Matador]

The SK170 has the same pinout as the 2N3819 that's stock in the circuit: it's a drop in replacement (other than the rebias of course).

 

[kante1603]

The SK170 has the same pinout as the 2N3819 that's stock in the circuit: it's a drop in replacement (other than the rebias of course).

Why not give it a try?Matador,do you think we must tweak anything around the fet then or simply swap and re-bias it?

Thanks,

Udo.

Edit:I tried to get some more infos from the both schemos:The 1972 version says it was a "S2436".Tried to google it but only found out that it is either a zip code or an indian flight number etc. so far.....hmmmmmmpfffffff......
In the 1980s version only this number can be found:8280800006.6 which seems to be an internal parts number at the neumann company.On the neumann homepage there´s a button for spare parts but there´s only a blank field showing up.

Edit#2:Found them here in germany and ordered some of them,let´s wait and check it out.

 

[geekmacdaddy]

Go Udo! I have 1 spare 2SK170BL here, wondering if i should pull the 2N3819 and put it in....

 

[poctop]

Hi All,  i am currently working on a u67 pcb but i am starting to wonder if i should have made a version of the u87ai as well question of having the DC-DC converter for the capsule as it will put out the same gain as the aI,  just a tought  :-\ ,

Cheers ,

Dan,

 

[kante1603]

Go Udo! I have 1 spare 2SK170BL here, wondering if i should pull the 2N3819 and put it in....

I would say do it.What's the situation with your capsule,have you received it?
I bet some guys here will give it a try because they're not lucky with the gain situation.
In my case it will take a while,my "real live/life work" gets me back from tomorrow on,some shows here in germany and then in vienna austria.I'm thinking about swapping it in my build or even build another one to have a comparison.Not sure yet.And I will also try a styrene in the c3(10pF) position and see- pardon-hear what happens.As said mine sounds really like a neumann in the complete mid range,so I'm pretty close to get what I want.
Thinking the 2sk170bl will give me some more output and c3 softens the highs just a very small bit
would end up in a nearly perfect clone soundwise and will make me really happy!

Cheers "brother geek",

Udo

 

[kante1603]

Hi All,  i am currently working on a u67 pcb but i am starting to wonder if i should have made a version of the u87ai as well question of having the DC-DC converter for the capsule as it will put out the same gain as the aI,  just a tought  :-\ ,

Cheers ,

Dan,

Hi Dan,

Any solution in getting more gain from the mic would be wonderful at the moment because it offers the use of way more "old"preamps with lower available gain therefore more "colours" soundwise.
If so you should call it something like "u1621v2" or so,the u87Ai is still in production.

Just a thought,

Udo.

 

[geekmacdaddy]

Udo,
My capsule won't be shipped until monday, but that still leaves the host aurycle, and the cinemag. And my rat-trap car that is late for inspection (they fine you here) which needs a muffler. So I'm 2-3 weeks away. Excited, but patient.

Tell it from the mountain, brother Udo!
Geek

 

[poctop]

Any solution in getting more gain from the mic would be wonderful at the moment because it offers the use of way more "old"preamps with lower available gain therefore more "colours" soundwise.

Thanks Udo, great wisdom as usual.

i will give it a tought as well ,  question ? can i be in the brothers Club too,  8)

Best ,
Dan,

 

[saxtim]

I've been thinking about building one of these U87's for quite a while, but I'd be more interested in the u87ai.  I tried to DIY one some years ago. There will be a couple of threads on it somewhere, probably around 2004. I got the DC-DC converter going - it does have an autotransformer on it but I managed to scramble wind one that did the job fine and got around +/- 50V. These voltages were loaded down by my meter, I didn't have a scope but I'd be guessing they were closer to +/-60V without the meter loading them down.

I never got the actual head amp going properly though - I was using a cinemag 2480 transformer and a 2N3819 FET. I think the FET may have been the problem - I couldn't get it biased right (I probably needed to buy 100 or so of them and hand pick one that would bias well, but at the time I gave up). It may have been something else though, I never finished it and pulled the circuit apart and built something more simple.

The other advantage of the U87ai is that you don't need isolated backplates for the capsule to get the polar patterns.

But anyway - a definite vote for the U87ai here!

Tim

 

[kante1603]

Welcome brother Dan! ;D

@Brother geek:Won't a new muffler bring it down soundwise?Is that what you want? ;D

Hallelujah,praise the board!

Udo.

 

[Matador]

The 2SK170 has about 4-8 times the gm as the 2N3819, but much higher input capacitance.  This will also be multiplied by the Miller effect.  I'll have to run some sims to measure the effect, but since the mike is low pass filtered anyway it might not be so bad.

But higher gain means less headroom for loud sources...no free lunch here!

I would say if there's a V2 of the PCB, one might want to add a provision for a PNP follower for those that struggle with the gain and want to use a lower ratio transformer.

 

[geekmacdaddy]

can i be in the brothers Club too,  8)

We are all brothers of the solder fume. You are the FATHER figure...(at least in this thread) as well as a brother.  ;D

 

[kante1603]

But higher gain means less headroom for loud sources...no free lunch here!

Hi Matador,

Thanks a lot for the infos!
Thinking the mic wasn't designed to pick loud sources it might be a way to go.
As you are our "transitor guru" we all would be grateful if you can run the simulations and then tell us the results.
It would be great if this works out good because most of us have spent certain amounts of money for the transformers,buying new ones again would make this project a bit expensive......

Thanks for all your efforts,keep up your good work please!

Udo

 

[Matador]

You bet:  I finally got my Teflon standoffs so I can build two more mikes
...I'll try both FETs and see how much gain I can squeeze from each one.

 

[kante1603]

You bet:  I finally got my Teflon standoffs so I can build two more mikes
...I'll try both FETs and see how much gain I can squeeze from each one.

GREAT!
Teflon standoffs?That means a different project,no?

Thank you in advance,

Udo

 

[kpearsall]

Dan I almost had a heart attack when you said u67 PCB. I had to concentrate on fixing my car before hand, which I've just finished thankfully, but I know a guy who has two 67's I was going to work on cloning. Seriously my favorite mic ever and it's been a dream of mine for years to own one. Please make that board!!!! I was just going to try to perf board it but... Definately count me in for at least TWO whenever that's read. And I'll cross my fingers that it's ready soon  ;D

 

[tskguy]

Hi all,

Good stuff, especially the u67 board!! I may have a capsule that will just be fine for that.... Anyway, I just finished a good old fashined 3 day recording session using my u87. I am pretty pleased to say the least.  Here is a link to a Very ruff mix, try not to be to critical all of the vocals as well as a few other tracks were recorded with my u87 and my capsule. Listen to the end it rocks ;D
http://dl.dropbox.com/u/55530129/who%20you%20want%20me%20to%20be_Mix.wav

The chain is U87, access 312, LA2A, RME fireface.
Eric 

 

[spase]

i will take 2 - u67 boards depend on the price

 

[poctop]

Work in progress Sneek Peek , 

D