UEC-14 microphone experiment

Recently I have constructed a couple of microphones based on the cheap UEC-14 electret microphone capsules.
I decided to give them the shape of tube microphones (20 mm.- 4/5")



The electronics were placed on a small PCB:



Because the build-in sourcefollower had a rather high noise level, I only used the bare electret capsule.
I used a low-noise 2SK170BL for the impedance transformation.
It is relatively easy to remove the capsule from the metal enclosure:



Closeup of the small PCB in the original microphone (removed):



The schematic used in the prototype.
Input impedance is 1 G.ohms. The junction of the gate and the 1 G. resistor is 'floating' (not on the PCB) to avoid leak current and disturbance due to moisture.



The 500 ohms mini pot sets the bias for the FET.
The circuit can deliver 600 mV. at a distortion of only 0,01%
At 1,5 Volts output the distortion rises to 0,1%.



Some details: the wire mesh used was taken from old kitchen equipment! The mesh used on the front opening was formed on a piece of wood with a diameter of 18 mm.

The results:

A first quick comparison with a Sennheiser MKH416 showed that there was not a big difference in sound. The low end sounds deep and the treble end is slightly brighter than the Sennheiser.
Directivity is good, sounds from the sides and behind are well suppressed. Soon I will perform accurate measurements on the prototypes.

The finished microphones:

very nice... Really cool idea.  I've never thought of removing the excisting FET from an electric capsule.  I just always thought it couldn't be done because of the design.

How much did this build cost you? And could one use that capsule in a tube circuit.  Forgive my ignorance.

Cheers and cool way to think out of the box for this project,
Marcos

I don't see any reason why you couldn't use this capsule in a tube circuit.
You don't need a polarisation voltage, so the way you would like to do the impedance matching is up to the user!
About the total costs: I think the most expensive part was the aluminium tubing... It was difficult to find the right diameter and I had to order it from a specialized metal company.
I needed a tube with an inner diameter of 18 mm. A (threaded) standard 3-pole DIN connector fits exactly inside.
I had all the electronic part laying around, so this did not cost me very much. (Couple of Euro's.)
The electret capsules were something like 7 Euro. ($ 8.80 US.) The result is not exactly Neumann, AKG or Sennheiser, but certainly good value for money.
Anyway: I am very happy with the results.

These capsules are actually quite good (for the price), also used in Audio-Technica ATM-31 and Line Audio CM2(3) microphones.

Where did you find these for 7-8 Euros? Elfa wants about 18 Euros without VAT... 

Distrelec for us non-vikings .


@RuudNL: great work, really lovely!

volker said:

Distrelec for us non-vikings .

Click to expand...

Great, thanks!  ELFA always had hefty prices, one reason for us vikings to emigrate!  ;D

I have used these capsule (violin mic) together with this:
http://sound.westhost.com/project93.htm

Wow! That looks great! Very nice work indeed.

Looking for an other nice enclosure to mount my electret capsules in, I found this type of microphone...



I found them by chance in a Dutch textiles supermarket ("Wibra"), where they were sold for 2,99 Euro (=$ 3.88 / GBP 2.49)
Of course they sound like crap (I didn't have the courage to try one yet!), but they have a nice metal head basket with a pop screen, that can easily be screwed off the body.
Inside is a cheap dynamic microphone capsule, that can be removed without any brute force.
The grip of the microphone is big enough to hold a male XLR connector.
They come with 4 m. "High grade low noise microphone cable" and a 1/4" mono jack plug.
They don't look too bad, for a price as low as this I am very happy with my new DIY microphone shells!

RuudNL said:

Looking for an other nice enclosure to mount my electret capsules in, I found this type of microphone...

I found them by chance in a Dutch textiles supermarket ("Wibra"), where they were sold for 2,99 Euro (=$ 3.88 / GBP 2.49)
Of course they sound like crap (I didn't have the courage to try one yet!), but they have a nice metal head basket with a pop screen, that can easily be screwed off the body.
Inside is a cheap dynamic microphone capsule, that can be removed without any brute force.
The grip of the microphone is big enough to hold a male XLR connector.
They come with 4 m. "High grade low noise microphone cable" and a 1/4" mono jack plug.
They don't look too bad, for a price as low as this I am very happy with my new DIY microphone shells!

Click to expand...

I run there but they were already ended

It as very good solution for me

Hi all

I posted previously this post in a wrong topic. I'm sorry for that.
I removed it from that section and I post it here.

I know it was a bunch of time ago.
however: I built my mic Let's say it works.
The issue is that I don't find the 1G or 5G resistance to put in parallel to the capsule a TSB165A
This bring a not very stable working.

In the shops I don't find such resistances
on "farnell.be" they want a minimum order of 50 euro from privates and it's exceptional. Indeed they wrote me telling me that they sell only if I have VAT.
dgkey.be has not and has the same rules of farnell.be
RS-COMPONENT the same with a variant: I cannot order 2-3 pieces of that resistances but minimum 500

What a situation.

Prosperous 2013 to everybody

Violinist,

I haven't read the whole thread but are you just looking for a single 1 gig resistor?

If so I can let you have one for the cost of one, plus the price of posting an envelope from UK to Belgium. I buy from Farnell all the time, and I'm sure I have some in stock.

Send me a message if that helps

Happy 2013

Stewart

Oh that's will be great!
Thank you Zebra50



i will write you a Personal Message in few minutes

Dear all

I finally finished my little project ) I would like to share with you this moment because your Forum was really a support for that.

First of all i would like to post the schematic I used, which is not different form many other ones, having Shoeps architecture.
here you finde pictures and schematics
http://www.flickr.com/photos/92089816@N04/sets/72157632487688033/

Audio sample:
https://soundcloud.com/violinist-belgie/sdc-small-capsule-microphone

Diagram:


Top side:


Rear side:


Principle:


Construction:


Body:




Please your feedback is much appreciated