Troubles to build mic body

[Violinist]

Ok I found the solution of the "ahrshing sound".
It was due teh resistance on the gate of the first fet.
It was 1M.
I put 10M but I have the same issue.
I need to buy the 1G  (7 euro each resistance)

I found also the Pipe but the trimmer is blocking the insertion of the cirtuit. i will go to change the trimemr with  resistances.

For the pipe I followed your suggestion and I found one very beautiful for the curtains

 

[zephyrmic]

You should be able to get 1G resistors from Element14 much cheaper than that. I bought 5G SMD resistors for less than $3AU. Then soldered thin flexible leads to each end to put them in the gate circuit. Check them out.

Kindest regards,

zephyrmic

 

[Violinist]

You should be able to get 1G resistors from Element14 much cheaper than that. I bought 5G SMD resistors for less than $3AU. Then soldered thin flexible leads to each end to put them in the gate circuit. Check them out.

Kindest regards,

zephyrmic

I think I'm condamned to pay a lot for that resistors:

I went on Element14 then clicked on STORE and they gave me the following webstie where I found the 1G. Look the prices, please ...

http://be.farnell.com/jsp/search/browse.jsp;jsessionid=LIQXGC1IMBPHCCQLCIRJN4Q?N=203074&Ntk=gensearch&Ntt=1G&Ntx=mode+matchallpartial&displaytext=&_requestid=304541

 

[zephyrmic]

The SMD resistors are the ones to get. Just over 2 Euro. And they are not too bad to use by soldering a fine flexible lead either end and then use in the circuit. I use the SMD resistors - 5G - in my mics and have them to work perfectly. Hope that helps.

zephyrmic

 

[zephyrmic]

Go for the SMD resistors displayed in the link- just over 2 Euro each. I use them in my mics, and they work perfectly. I use 5g resistors. Just solder a fine flexible lead to either end and then from FET gate to resistor divider across the source resistor.

zephyrmic

 

[Violinist]

Excellent! I found the 5G ones and the 10G ones . They are selling it also in 1 unit.
I will buy these resistors buying also the component for the second microphone 

Today I will work on the mechanical support and I will get some picture to post here

In IKEA I found the Cap of the pot (een deksel) made by network. 4 euro. I got it in order to ge the network. It's exacly what I needed for the microphone

 

[RuudNL]

I've got my 1 G.ohm resistors from RS Components (€ 0.74)

Recently I have made some more DIY microphones with the same electret capsules (UEC-14).
I stuffed the pipe behind the capsule with cottonwool. I have the impression that this improves the sound, because resonances in the pipe are damped.
Keep in mind that for low frequencies, you will get an acoustic 'short circuit' between the front and the back of the capsule.

 

[RuudNL]

The new version (20 x 110 mm.)

Referring to the 'thin' sound:

Ok I found the solution of the "ahrshing sound".
It was due the resistance on the gate of the first fet.
It was 1M. I put 10M but I have the same issue.

I found that the capacity of my capsules is in the order of 20 pF.
That means the reactance at 50 Hz. will be around 160 M.ohms.
So: if you would have a gate resistor of 160 M.ohms, the lower -3 dB point would be at 50 Hz.
If you use a gate resistor of 1 G.ohms, the -3 dB point shifts to  160/1000 x 50 = ~ 8 Hz.
But with a 10 M.ohms resistor, the lower -3 dB point is at 800 Hz! (Maybe nice if you are recording birds!... )