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[Vam zi]

Hello everyone,

Im a silent guest in this forum for one year and a half and been studying as much as I can. been keen with this mic for all known reasons
now its time for me to build one, including all the metal work. its not my first project but the first to exhibit pristine metal work in order for it to work properly.
right now I have the top plate, the body tube and the lower bell quite ready to be used, accept that I'm missing a few important details:


I know the overall length of the mic is 240mm aprox. how long is the body tube itself and the mic head seperatly?
Ive used an old VCR head as top plate and lower bell, the diameter is 62.5mm which is pretty close to original.
the body tube is carved from 3.18kg Aluminum diaginol block and is 1.5mm thick, which makes is less resonate.
but with the top and bottom attached to it, which have quite a mass, it doesnt resonate at all



I made the tube 240mm length in order to be able to cut it when I'll have a clue about the real measurement.
third question if i may-
I have as you can see the inside head of a vintage U87 which is a bit damaged. thought about  using it as a pattern selector
for  this built. is KK47 can fit in this capsule holder? may I dare to dream that theres an M7 capsule holder that is compatible
with U87 head and shockmount? or should I just make my own and keep it for a U87 build?

thank you guys, you made me allot smarter over past years

[Vam zi]

2nd pic

[Vam zi]

3rd pic

[Vam zi]

4th and last. sorry for the mess.

[klaus]

That's quite the project.
I notice that you seem to concentrate on the metal work. Among other reasons, because you wish to suppress resonances. In my experience, audible artifacts from resonating components WITHIN the metal construction of the mic (housing tube, head basket, amp frame, etc.) are quite a bit more audible than the material of the mic construction.

Besides, what about the really important positive audio generators for your mic: capsule, tube, transformer, components?

P.S.: K87 and K47 are identical in outer diameter. There are plenty of aftermarket M7 capsule mounts, complete with threaded rubber column, available. Check Thiersch, FLEA, BLUE, Telefunken N.A.

[Vam zi]

Thanks for your reply Klaus.
the reason Im so concentrate about the metal work is because it is new to me and Im trying not to make a mistake, since the costs of good materials. there must be some sort of components that i would have to buy instead of making
it by myself, I thought about the internal tube socket and suspension from AMI. Im planing on making the ribs and the head+grill myself, and maybe the transformer plate. as to the transformer I chose Oliver's BV8R, capsule is planed to be Neumann's (if so than a K47+good service for it), though I heard good things on Thiersch's M7
As for the tube- my preferred way is to go for original- but if there will be none of the good ones in an affordable price I'll have to check for replacements (maybe EF800 as Oliver suggested at his site, E88cc maybe, amongst glass tubes).
if you have suggestions regarding this issue-including other metal tubes- by all means share
as much as I want to learn I wish to have a decent mic evetually- so if there will be stuff to buy, like a mic head or any other in order for it to sound good thats what Im up for.
Is the info Im looking for is confidential regarding the parts measurements?

Thank you for your answers

[klaus]

Dimensions of existing microphones are public knowledge and not proprietary.  All you need to do is ask here what dimensions you need to know, and they will be posted.

...but I still have to ask:
If all the components are going to com from existing U47 "kits" or copy parts, why not go to these suppliers and buy the whole thing? Aside of extra work, what exactly do you expect will be different in your approach from buying the whole set ready-made?

[Vam zi]

Thats very good to know, thank you
the dimensions that is missing is:

Body tube length
Body ribs height
Headbasket length from the very connection to the mic body
if there are any documents regarding angles and radius of the head frame
or the wire mesh since Im completely new to this.

the reason for doing this is because it was very easy available parts beside the body tube, and I think I can build a very heavy duty body but not heavy weight for a bit of work and not so much money involved. I can buy the whole thing as a kit, theres lots of them out there but I wanted to try it for myself and make as much as I can with my own hands. and if something is wrong, I can buy a part very easily.
I wish to make my own capsule and transformer too, but thats a few mics ahead of me
I also have a PSU rack for it that I made (Im making racks for other stuff that I build).

[Kai]

As for the tube- my preferred way is to go for original- but if there will be none of the good ones in an affordable price I'll have to check for replacements

I have very good sound results with the EF14.
The circuit I use makes the tube work under the same conditions as the VF14.
Even the same amount of underheating works reliable for some years now.

The only real difference is, that I use a separate heating supply.
This needs to be stabilized and filtered to very low noise in the PSU, because it is coupled to the audio part of the tube, like in the VF14.
With modern voltage regulators this is a quite easy task.

Regards
Kai

[Vam zi]

Thank you for replying Kai. Did you had the chance to compare a EF14-VF14 in the SAME mic with documented results perhaps? or any other comparison for that matter?
To your knowledge is there a reliable service place to offer good specs EF14s? I know they need to be more hand-piked then VFs in order to stand to good amplification standards. 
my intention is to go for VF14, if its not to much trouble to get a decent one
(I see on EBay non-M versions around 1300$). the problem is that I have no idea how this particular tubes sounds and how it handles noise and microphonic. and the  price is quite high for "experimenting"...

Does anybody know the answers to my questions from my previous post?

Thank you for your help guys

[Kai]

Did you had the chance to compare a EF14-VF14 in the SAME mic...To your knowledge is there a reliable service place to offer good specs EF14s? I know they need to be more hand-piked

No, they don't.
I didn't ever have a VF14 equipped mic in my studio.
All I can say is, that I built this mic (EF14, new Geffel M7 from the time when they still had the full bass, Cinemag transformer).
It stands on par with other high class mic's I have, giving me a rich, full sound with soft but not underrepresented treble.
Noise is a least as good as my Neumann U87 1st generation, much better then other tube mics I have.
It was much easier to make it work then some of my other projects, and I have a bunch of EF14's here that don't differ much in noise, not at all in sound.
There's a distinct difference in microphonie between the specimen, but non of the ones I have is unusable.

What needs to be payed attention to is:
All isolating materials in contact with the capsule signal (tube bottom, tube socket, switches etc.) need to be perfectly clean.
If not, you will suffer from noise.
Of course no normal circuit board can be used here, like the original you should use direct wire connections.

Regards
Kai

[Vam zi]

Thank you for all your help Kai ,and the useful information, Im having thoughts on which route to go regarding the tube and the capsule. will go and listen to an alternative design using Tektronix 12AU6  and Dale M7 made by Igor (IJ Research) this week for further investigation

in the mean time-
can anybody here share the info regarding body tube length, head basket measurements (as many as possible) and body ribs height?

Thanks all

EDIT: I just found a post by Klaus at neumanns forum regarding some dimensions but im a bit confused with other information previously found at http://recordinghacks.com/microphones/Neumann/U-47 :
overhaul length= 232mm vs. 240mm
internal diameter= 57mm vs. 63mm (63mm - maybe external diameter?)

Is this a normal difference between two hand made pieces? seems a bit big
from the same post I also found the body tube length (145mm).
does anybody knows where can I find as much info as I can regarding the head basket and its materials?
and what is the length of the ribs?

[klaus]

U47 housing dimensions

1. Short Body:

Housing tube
length: 128 mm
O.D.: 60 mm
I.D.: 56.8 mm

Capsule head basket
height: 83 mm ± 1 mm
(depending on individual dome flatness)

Capsule head basket O.D. at switch window: 63 mm


2. Long Body:

Housing tube
length: 145 mm

All other dimensions: see Short Body