Microphones - Homebrew DIY Condenser Mics - Here

If anyone is interested, we have an old JEOL JEE 4C thermal evaporator free to whoever wants to pick it up (near Chicago). The only thing wrong with it to my knowledge is a hole in the cooling line for the diffusion pump that needs to be brazed. However, when it blew water sprayed everywhere, so I'm not sure if any of the electronics were damaged, but I don't think so. It is huge, weighs a ton and you'd need a new rotary backing pump as I'm going to keep the one that is on it now. PM me for more details. If you google it, ours it the first one that shows up.

I'd love to see pictures of your capsule... How about a sound clip?

What are the dimensions on the pump?

Don´t have a digital camera,but at least i can post my dimensions now:

the brass pull is 1 inch diameter,then the pvc tube is 1-5/16 diameter,finally the outer rings are 2 inches ...i know it's big...the height is 13/16 ...

I'll try to record something through it...i'm happy that it sounded,as i said...i'm starting to build my second one...i'm using coppered fiberglass for the outer rings and the back surface,the membrane is held between the two outer ring,no spacer...

[quote author="northsiderap"]
You can adjust the diaphragm tension by tightening the rear nuts in a star shape[/quote]
Ha ha ha... To adjust some mike properly (without using some that hell
like electrostatic calibrator) you need electronic measuring instrument -
bridge.
Yes, bridge for ribbon dynamic mikes, was published a long ago by
M.L.Gayford. I named it "Gayford bridge". There must be minimally
two pieces of that bridges. One is in the Coles factory and one at my
bookshelf.
But what about electrostatic mics bridges? At some fotos from Neuman
factory there is only one wire (and ground) going out from the mic.
Yes, it is bridge, not so complicated, but nowhere published.
I then named it "Neumann bridge". There are minimaly two that bridges
on the world. One on my bookshelf, one in Neumann factory(ies).

What is in the Neumann bridge??? If someone knows, then
can know, that inventor of bridge is not Neumann, maybe Braunmuehl?,
Then I will rename it, I don t know. Help me, please

xvlk

[quote author="xvlk"][quote author="northsiderap"]
You can adjust the diaphragm tension by tightening the rear nuts in a star shape[/quote]
Ha ha ha... To adjust some mike properly (without using some that hell
like electrostatic calibrator) you need electronic measuring instrument -
bridge.
xvlk[/quote]

Please,don´t laugh that way at me...i'm humbly trying to experiment :sad: :sad: :?

That single-wire test jig that Neumann uses does two things - it measures the capacitance of the capsule, and applies an adjustable DC polarizing voltage. The assumption is that by design you are supposed to know the capacitance of the capsule (by the diaphragm gap and area), and the proper diaphragm tension (by change in capacitance when the polarizing voltage is applied). That tester is used to verify proper assembly and diaphragm tensioning, and can also be used to sort capsule halves for matching of the assembly dimensions and tensioning.

This is what they say they do in their published documentation, anyways.

[quote author="maneco"][quote author="xvlk"][quote author="northsiderap"]
You can adjust the diaphragm tension by tightening the rear nuts in a star shape[/quote]
Ha ha ha... To adjust some mike properly (without using some that hell
like electrostatic calibrator) you need electronic measuring instrument -
bridge.
xvlk[/quote]

Please,don´t laugh that way at me...i'm humbly trying to experiment :sad: :sad: :?[/quote]I think that xvlk is perhaps not laughing, but rather means "aha" instead of Ha-ha... I know that English is not his first language, but I'm very interested to learn more. certainly in his posts to date, he's not made fun of people, rather he's been very educating!

Keith

Oh! i was confused them,and i agree with the amount of information he shares here,so,thanks for the clarification,my apologies,and peace and fun here!
:thumb: :thumb: :grin: :grin:

Here's an update on my mic...

Still have to work the noise floor down, but perhaps I'll bring up the polarization voltage. The space between diaphragm and backplate was done by eye, not spacer, so cutting spacers will help dramatically too as the backplate spacing is HUGE.

I'm happy with the sound! It already sounds more 'open' than those factory stamped capsules. Then again, maybe I'm a little biased. Get it? Biased? :wink:

This is my cheap-o guitar with a little bit of digital reverb and no EQ preamped through a Studiomaster mixer.

http://northsiderap.com/DIY/MyCapsule030306.mp3

Geez, Where do you folks come up with this knowledge ?

This is far beyond the typical DIY , I'm still in awww.
I'd love to learn more but where , how ?

great thread :thumb:

Really, really impressing :shock:
Sounds good :thumb:

Keep up the good work :!: :guinness:

[quote author="maxwall"]Geez, Where do you folks come up with this knowledge ?

...I'd love to learn more but where , how ?
[/quote]

Google It!

[edit] ...Although half of the links will lead you back here :grin:

Here is my testing rig. It is an octal socket and a breadboard screwed to a log. The transformer is a University Sound @3.9:1.

I blocked out the amp, because I've never seen one like it. Well, I think AKG has dabbled in something kinda similar.



I am the Faraday shield, as I have a ground strapped to my toe. What's the worst 48VDC @ 15ma could do? At worst it would probably cure my manic depression for a few weeks. Come to think of it, I should strap that ground right on to my bean.

This particular capsule came out wrinkled :?

Thanks again for the mic meta!