zebra50

1932 DIY tube condenser mic document - group translation!
« on: March 22, 2008, 02:34:02 PM »
EDIT: The group translation is HERE

I found this whilst researching old bottle mics. I've put it into pdf format!

Some interesting stuff about capsule building. We'd be grateful for a native German speaker to translate.

Cheers!

Stewart

 :thumb:
Ribbon microphone services
http://www.xaudia.com
Microphone blog


EZ81

1932 DIY tube condenser mic document - group translation!
« Reply #1 on: March 22, 2008, 07:47:57 PM »
Hi Stewart,
thanks, that was an interesting read.
I gave the first page a try, maybe someone can add more (or turn the denglisch writing into real english :oops:. ).

Quote from: "Eugen Schachta"

Condenser Microphone
by Eugen Schachta

Building microphones in the style of Reisz has been described repeatedly; and with clean work one will have gotten decent results, but every carbon microphone has the disadvantage of high self noise, which is irritating especially with high gain. This was the main reason for me to start constructing a condenser microphone. The result of my experiments are described here. A note in advance: it takes extreme accuracy to get a decent result, but afterwards one will have fun with the device. The microphone is designed in a way to allow the DIYer to experiment with improvements.

Abb. 1 shows the working principle and the schematic of the microphone. C is the microphone capacitor, cap plate 1 is a perforated disc  which lets sound pass to cap plate 2, a membrane (very thin metal foil). The sound hitting plate 2 changes the capacity of C, and these tiny changes of charge are amplified by the first amplifier stage which is set up the usual way. This connection is naturally the most susceptible one in the whole circuit. Let me add here that this small amount of amplification is usually not enough, it is recommended to add two more resistance stages (i guess he means tube stages with plate resistors as opposed to interstage transformers that were not uncommon at that time). It is appropriate to supply the preamp from batteries only, this also prevents noise.

Abb. 2 shows a cross section through the DIY microphone. The capacitor is resting inside a brass enclosure a. Inside the latter is a isolating pertinax (= FR-2) ring b, which surrounds a contact ring c, which is connected to the terminal screw m by a wire. Next to this contact ring c is the membrane d and the distance ring f, which sets the distance between the membrane and the fixed cap plate e (a perforated disk). This disk is conected to the enclosure a by the second contact ring g. The end ring i fixes the construction on the front side, the disk k closes the back side.

After this description of the  microphone the parts are to be described in detail. As most DIYers do not own a lathe, it is recommended to have parts a, c, e and g made by a precision mechanic. The latter will also happily provide proper screws for the terminals and for fixing the end rings. It is advised to wait for the metal parts to be ready before building the other parts to make sure everything can be fitted together.


A wiki might be nice for things like this...

PRR

1932 DIY tube condenser mic document - group translation!
« Reply #2 on: March 23, 2008, 12:48:09 AM »
There is nothing unclear about your denglisch.

"pertinax" is, I think roughly Perspex in British and Plexiglas in American. A high purity plastic with high electrical resistance (including resistance to dampness), which can be machined, and will hold its shape under pressure (hopefully years of pressure). As you say, good PCB stuff will work.

The amplifier passage is in context of replacing a Reisz microphone, which was a high output Carbon mike. Also the tube and other parts are very antiquated. Instead, use any modern capsule amplifier.

What is the diaphragm material? Is it tensioned? How?

zebra50

1932 DIY tube condenser mic document - group translation!
« Reply #3 on: March 23, 2008, 06:21:23 AM »
Thanks for the comments and the translation, which is very good and really helpful.

I liked the wiki idea. I've set one up to see if it works. Check out:

http://microfonica.wetpaint.com

I haven't done a public wiki before so it will be interesting to see if it works. You should be able to see and edit without registering, although I may need to change the security settings at some point if we attract unwanted attention.

I'll upload all the pictures to the wiki.
Ribbon microphone services
http://www.xaudia.com
Microphone blog

guitarbill55

1932 DIY tube condenser mic document - group translation!
« Reply #4 on: March 23, 2008, 10:13:59 AM »
Thanks Stewart for the hosting and translation!   I have just a couple of bone headed questions:   How thick is the distance ring "f" ; I assume it must be the insulator?   Also I'd like to hear someone chime in for what exact materials were used for each part; and possibly where they might be available, ect.      And finally I'd really like to know the answers to PRR's question.

Thanks again!
gb
"Eat your sockeye with wild blueberries" - Copper River Red

zebra50

1932 DIY tube condenser mic document - group translation!
« Reply #5 on: March 23, 2008, 11:02:45 AM »
Thanks for the support gb.

EZ81 contributed the translation to P1 of course. Hopefully all these questions will be answered as the translation to P2&3 unfolds.

If anyone else can help, please do, even if you only have time to contribute a paragraph or two.

The wiki software is quite good, but please note that not all of the editing features work with the Safari browser.
Ribbon microphone services
http://www.xaudia.com
Microphone blog

zebra50

1932 DIY tube condenser mic document - group translation!
« Reply #6 on: March 24, 2008, 06:09:03 PM »
It seems that the actual retyping is an obstacle to this kind of thing.

Does anyone have any OCR (optical character recognitions) software that would help with this?

This would also give us the opportunity to at least run it through some translation software and giggle at, then correct the results.

Any help gratefully accepted.

Stewart

Stuff at http://microfonica.wetpaint.com
Ribbon microphone services
http://www.xaudia.com
Microphone blog

EZ81

1932 DIY tube condenser mic document - group translation!
« Reply #7 on: March 25, 2008, 04:45:16 PM »
@PRR + guitarbill:
The membrane is made from 0.07mm sheet metal (i guess copper, but this is not clearly stated in the article) and is not tensioned. The spacer is made from wax impregnated paper. Pertinax is actually the trade name common in .de for the dark brown phenolic PCB material with the nasty smell.

HTH
Matthias

clintrubber

1932 DIY tube condenser mic document - group translation!
« Reply #8 on: March 25, 2008, 04:54:11 PM »
Quote from: "EZ81"
Pertinax is actually the trade name common in .de for the dark brown phenolic PCB material with the nasty smell.

It's the word used in the Netherlands as well. Lots of older Philips gear used it.
Indeed a not too pretty smell, and I know how it smells; ripping pertinax PCBs & tagstrips was my first source of components.

I don't think it looks very cool, a bit cheap actually, unless for tag-boards & p2p.

zebra50

1932 DIY tube condenser mic document - group translation!
« Reply #9 on: March 26, 2008, 04:11:50 AM »
Hey,
Thanks for the extra information.
And thanks for updating the wiki too! I just checked and it is coming along nicely.

http://microfonica.wetpaint.com/
Ribbon microphone services
http://www.xaudia.com
Microphone blog


zebra50

1932 DIY tube condenser mic document - group translation!
« Reply #10 on: March 26, 2008, 04:28:12 AM »
I just cleaned it up a little.

"A piece of high frequency litz is soldered to the inside of the first contact ring":

http://en.wikipedia.org/wiki/Litz_wire
Ribbon microphone services
http://www.xaudia.com
Microphone blog

emorysmith

1932 DIY tube condenser mic document - group translation!
« Reply #11 on: March 26, 2008, 09:33:58 PM »
Looks like a good CNC project.
Any idea on where to get super thin metal plated Mylar type material?
Free/cheap samples, maybe???
A square yard would be enough for many of us to make pairs of
U47-esque mikes.

OOPS, I used a real model name and ancient spelling in one sentence!

My 2 nonCents worth
  :guinness:

EDIT:
A friend turned me on to some kind of "emergency space blanket" thing.
Feels Mylarish, is very thin, shiny as the Chrome on my Mom's 1960 Buick and reads good continuity with an Ohmmeter.
He got it at a Bass (as in the fish) Pro something.

zebra50

1932 DIY tube condenser mic document - group translation!
« Reply #12 on: May 01, 2008, 04:33:33 AM »
Hi!

Thanks to everyone who has contributed so far. We're about 80% through the document.

It would be nice to get this finished so that I can make up a nice PDF and share it. If anyone has good German, and a little free time, please have a look at the wiki at http://microfonica.wetpaint.com/

The next untranslated bit is on the third page towards the bottom left, starting "Dann wird diese Scheibe...

We're grateful for all contributions, however large or small

Cheers!

Stewart
Ribbon microphone services
http://www.xaudia.com
Microphone blog

Marik

1932 DIY tube condenser mic document - group translation!
« Reply #13 on: October 28, 2008, 02:44:31 PM »
Here is a little bit more organized .pdf of what we had so far:

http://home.comcast.net/~markfuksman/DIYCondencerMicTranslation.pdf

Could someone confirm if this is translation of entire document, or we still have untranslated parts?

Best, M
Samar Audio & Microphone Design

www.samaraudiodesign.com

The Art of Ribbon Microphones


 

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