Neumann U 47 Clone - A DIY Bachelor Thesis

GroupDIY Audio Forum

Help Support GroupDIY Audio Forum:

This site may earn a commission from merchant affiliate links, including eBay, Amazon, and others.

Zottel

Well-known member
Joined
Aug 15, 2015
Messages
73
Location
Leipzig
Hello folk!

I'm Max, an audio engineering student.
In the next 6 month i will build a DIY U 47 and im hoping to gain some interesting results for my bachelor thesis.
When im finished with building I'd like to do some testing and measuring in a anechoic chamber and also a A/B hearing test to see how close i could get.

I'd like to build this microphone as close as possible (without original parts).
I already ordered a body from Andriejus: http://groupdiy.com/index.php?topic=58609.0

And now I'm a little bit puzzles about how to go on.
--------------------------------------------------------------
I think i will go with a Tiersch capsule.
and if its possible the "VF14" from Andreas Grosser.

As these two are replacement parts.. does anybody know if there have to be some changes done at the schematic?
http://www.gyraf.dk/gy_pd/g7/u47.gif

Does annyone know where to get a PCB for this build?

And I'm still not sure about which BV08 Replica I’ll take. Peluso? AMI? etc.?
And... Whats Haufe? Cant find anything about them.

I'will have to do some additional research about what kind of resistors and capacitors, etc. have been used in the U47.

Hope you can help me out.  :)

All the best,
Max.


P.S. This Forum is a gold mine! :)
 
Hi Max,

what a great endeavor !
i'll try to briefly resume my U47 cloning situation.

the most important part is obviously the capsule .The best options are Thiersch M7 PVC or Mylar, or genuine Neumann K49.
Dale and Poctop capsules are also an option but i didn't try it...
For the body , you can go with Flea for the best overall recreation.
the output transformer can be sourced directly from Haufe or AMI.
The only part that you can't easily get is the tube.
I think it's better to install metal tube from the same era.
The VF14 was declined in 3 heater voltages : EF14 6,3V, UF14 25V,VF14 60V
You have to pick a quiet one.
VF14 in the U47 is vastly underheated , and it's a part of its sound signature, as well as the biasing method.
they all have the same electric characteristics but even if you apply a proportional underheating, the sound is not exactly the same.
You have to find a compromise.
my personal tests reached that an EF14 with H=5,3v and a self bias with suppressor at ground, sounds fine and balanced.
An EF12 with fixed bias can be fine as well , but can sounds a bit thin, it could be fine for a heavy low mid / low end sounding capsule.Ef13 can be use also.EF8XX can be a option but with an output impedance adaptation.Parallel 408A is the commonly used option but i had microphonic and noise issues...
You have to carefully design a quiet power supply as well, avoid if possible integrated regulators...

keep in mind that all parts are more or less important, and have more or less their sound signature.

If you want more accurate details, then PM me.
Good luck !

Cheers
Fred
 
If you want to build the microphone with A.Grosser's VF14 substitute tube -contact Andreas, because you can't buy his tubes on free market. Also, Haufe transformers are not presented on the market. Haufe makes bv08 transformers only for A.Grosser, as far as I know. Andreas tested AMI bv08 and Peluso Bv08 at his lab and concluded that Peluso is bit better for U47.
 
Thanks for the fast reply!  :)

I've already written an email to Andreas asking about his VF14 substitute tube.
I will also ask him about the BV08 from Haufe and the testing he has done with other tubes.
Depending on what he may say I will think about EF 14 etc.  :eek:

granger.frederic: You say its possible to buy the BV08 directly from Haufe? Do you have a link to the website? Because there are many Haufes around here in Germany :D
If there is no way in getting the bv08 from Haufe I will go with the Peluso. Maybe Andreas can present some results of his testings to me.  8)
 
Hello,
The Haufe Webside.
http://haufe-uebertrager.de/mobil/
Contactdata
http://haufe-uebertrager.de/mobil/kontakt.html
It would be interesting If You could  post the Answers from Andreas and Haufe.
About the Tube and all other Parts You will find lot s of Information If You use the search Funktion or Study the Micmeta
Here is for Example a very  interesting Discussion about the VF 14 and possible more or less useable Subtitutes.
http://groupdiy.com/index.php?topic=53620.0
Happy studying
Lothar
 
http://www.haufe-uebertrager.de/HP%20Englisch_/Formulare%20englisch/Uebertrager_englisch_pub_0001.pdf

you have the email at the end.
they were usually selling transformers to private customers , but they may have changed their policy.

i don't want to say that one transformer sounds better than another, they 're just different , and you have to experiment a lot to find your optimal chain : capsule / tube / electronic parts / transformer

i forgot EF42/UF42 that sounds gorgeous in a U47, but you have to pick the less microphonic one and  achieve a special mechanical decoupling to avoid bad ringings...

There's also the nuvistor 13CW4 (used by Neumann) but it's hard to find a non microphonic one.The impedance is not mismatched with the BV08 like you could read around the web ...It is a usable replacement but i find the sound a bit unnatural/metallic with it...not my taste.

cheers
Fred
 
Haufe never sold Bv08 to private persons. More of that, Haufe produced Bv08 as special order for A. Grosser.  They never produced output transformers for U47 before Andreas order, as far as I know. Btw, nuvistor is not bad tube. Neumann made a mistake with cathode resistor value for nuvistor version of U47 modulation. Andreas explained it to me. If you are interested- ask him. Andreas is a very sympathetic person and knows a lot about the correct connection of the lamps, the correct choice of optimum modes of operation, etc. Many myths have time, although I agree that sound quality is a matter of taste.
 
i must say that :

-1: here's a copy of an email i've received from Haufe, it was for a T14 :

"Hello,
the price for 1 pce of T14/1 is 43,15 Euro/pce, packing cost: 5,00 Euro and shipping costs: 34,12 Euro.
Total price: 82,27 Euro + 19% MwSt = 97,91 Euro total costs
Is this ok for you? Then I will provide you a proforma invoice and tell you how you have to pay.

Mit freundlichen Grüßen/Kind Regards

Michaela Knoth

Vertriebsinnendienst/Export

Haufe GmbH & Co. KG

Weilburger Str. 14

61250 Usingen

Phone: 0049 6081 9153-40

Fax:    0049 6081 9153-20

E-Mail: [email protected]


-2 : BV08 by Haufe is produced for various  mics manufacturers , example : http://blackspademics.com/pages/um-17b-microphone-1

Thus you can ask for example Haufe , Blackspade , or Grosser to source a Haufe BV08...

-3: 13cw4 is a good tube, i didn't say the opposite , i just that i don't like the sound even with the hot biasing trick.Neumann didn't made a "mistake" , they just choose to bias the tube at their specs/taste.And, I must admit that i find the sound difference between the two biasing method, minimal.The sound is not very pleasing for me .
in the end , it's always a matter of taste....
 
Fred, maybe you may order big quantity of the Bv08 directly from Haufe? For example, if you are company which is building a bunch of the microphones. Is it interesting for us, here, on forum? I don't think so. Anyway, I just shared what I heard directly from Andreas.
And I agree with him:  Neumann made a mistake with nuvistor biasing method, because of wrong operation point. The impedance was not optimal,  low end  was too small, sound too surgical. I will not argue with you again( good point: we all have different ears, is not it?) but i heard it with my own ears at Andreas lab. Ok, forget it.
I know, that underheating is bad way to use for very, very long list of the old and modern tubes.  Ef14 is  not excluded from the list, from that point of view.. and : VF 14 has much thicker low mid freqs and softer high freq-s than Ef14, for my ears anyway, so I exclude Ef14 from my list of good tubes for U47. And G.Wagner, and A.Grosser.
BTW: We forget to include in the list of available transformers for us: Ioaudio B08.  Who knows, maybe Max can sale one-two transformers for suffering people who can't afford to buy his kit?
 
Haufe sells their own line of transformers to anyone (minimum order €120), EXCEPT for the BV-08.

Business or no business, it's only available through AGES Berlin.

Edit: If ever, the AGES model is the Haufe T-7853.
Any company using that, bought it directly from Grosser. You see a different code, then it's a different spec/transformer.
 
AGES Berlin ??? what's that ? do you have a link ?


I source my BV08 type from another manufacturer (Flea) ,  but i'm quite sure Haufe would accept to sell for less than 100€ (read my previous post).
i don't see why they would sell a T14/1 (used by telefunken) and wouldn't for a BV08 or equivalent...

If someone in this forum needs a BV08 at that time, please send an email to Michaela Knoth at Haufe Gmbh !
we'll see the answer ...

misha, i can't see the relation between making a electronic design mistake,  and choosing the operation point...
if you decide to bias "hot" or "cold" some 6V6s in a fender amp, it's a choice, not a mistake. in this case the sound change is significant .
But, if the inner impedance of the 13cw4 is low enough to drive correctly the BV08 (around 6,5kohms ...VF14 around 8k ),  you may agree that the biasing marginally changes the overall sound of a U47 headamp (if you stay whit-in -1,1v and -1,7v) .The change occurs mainly on the THD gradient measures, and in a moderate way.
When i did the tests, it was hard to hear it, for me and for that tube.
probably because of the weird "metallic" coloration, maybe microphonic issues...i picked however the best from a batch of a dozen!

Remember also , that the bias voltage, defines the input tube voltage headroom.
if you lower it too much, the capsule could saturate the tube too quickly.

datasheets: http://frank.yueksel.org/other/RCA/RCA_Nuvistors.pdf
 
Ok, I understand your point of view. No problem. Forget about nuvistor, - its not your choice. Fred, I can't on the forum to disclose the Andreas schematic for nuvistor, without his permission. You will agree it's dishonest. I can only say that the mistake is not only in the value of the cathode resistor. There are some nuances. In general : less current= less low end, earlier distortions. I wrote in another topic that it is best to contact Andreas directly if there is a desire to clarify.
about bv08: the reason why Haufe does not sale Andreas's bv08( keep in mind, that it was special order for Andreas with his specifications) to private persons is - bv08 is not Haufe serial product, they never made U47 transformers before. Andreas paid for exclusive production. BTW,  if you're interested, Neumann officially confirmed the status BV08 Haufe transformer, suitable for repair of old U47s.  None of the modern manufacturers of transformers for U47 has received such status. T14- is another story. This is historical Haufe transformer.
 
I'm quite sure that if you kindly ask them for a historical Neumann BV08 equivalent transformer, they will be glad to produce " some samples" for a fistful of hundreds euros...
after all, it doesn't matter if it's written another product number on it...

About the Andrea Grosser's BV8 mods , do you have details?
 
granger.frederic said:
I'm quite sure that if you kindly ask them for a historical Neumann BV08 equivalent transformer, they will be glad to produce " some samples" for a fistful of hundreds euros...
after all, it doesn't matter if it written another product number on it...
it's a fair point for most Chinese, often unscrupulous manufacturers, but not so serious that cares about the reputation of the firm as Haufe. And then, what kind of problem contact Andreas? He's not some unreachable person. You mentioned American mics with transformers from Andreas ( yes,  I can see on the photo typical Haufe bv08 print). Great example.
Info about Andreas bv08? No, I have not got information. But  I know that Andreas helped Flea with their Bv8, I think they have necessary information.
PS: You mentioned that Flea sold you Bv08 separately from FleaU47 microphone?  Wow, they changed their policy. Thats good news for DIYers.  :)
 
Hmmmmm !
I would not bet my last dime on it ...( for Haufe)

For Flea i didn't have any issue  to order parts in the past.

i even have in stock a Flea K49 skinned by Thiersch !

maybe they've changed a bit their policy , but i would be surprised...

i have one FLEA BV08 in stock ,  great finition , and i like the sound a lot...
 
o3misha said:
BTW: We forget to include in the list of available transformers for us: Ioaudio B08.  Who knows, maybe Max can sale one-two transformers for suffering people who can't afford to buy his kit?

Transformers are now back in stock ---> http://groupdiy.com/index.php?topic=35667.0

-Max
 
Hey folks!

Great and interesting discussion's going on here :)
It helps a lot because I  miss the forest for the trees! :D

Just to update my status. I send an Email to Haufe and to BSA Microphones. Let's see what they may say. ( Funny "y's"  ;D)
Still didn’t get a reply from Andreas, maybe he is on vacation :)

And i fought trough the big post's about this topic in the last month. It's just crazy how many way's can be taken! Even the tubes are like an own martial arts form  ;)
 

Latest posts

Back
Top