Creation CK12 capsule and power supply question

[Putchy]

Hello,

For a student project I chose to build a condenser microphone. For the capsule, I took inspiration from a CK-12, which was the least difficult to make. So I machined it from brass in x2 scale. For the membrane, I chose aluminum mylar (the only one I could find).

Now that I've got the model, I need to make it work. And that's where my knowledge ends. I know I need to use a Phantom power supply, but I don't know which one (voltage and current), given that my capsule is twice the size of the normal one. As for the electronic wiring, I have very little precise documentation.

I know that with my capsule I might not get the audible frequencies, but that's okay, as long as I get a response to a signal I'll be happy.

Information about the capsule :
- S = 1260 mm² (area of the membrane)
- Cmeasurement = 101.6 pF
The only value I can modify is the spacing between the diaphragm and the backplate. At the moment it's 80 μm, but I'm thinking of reducing it to 40μm.

If you can help me with any information (documentation or diagram) I'd be grateful.
I'm always open to help.
Sorry if my English isn't good, I'm still learning.

 

[pasarski]

Wow, respect! You started making mics other way around than usual. Capsule is the most difficult part. And CK12 is the most difficult capsule to make, at least if you want it to sound good. But yeah I understand that that's not the point of this project.

You need an enclosure and an impedance converter for the capsule. Lot's of information here if you do the search.

 

[Putchy]

Wow, respect! You started making mics other way around than usual. Capsule is the most difficult part. And CK12 is the most difficult capsule to make, at least if you want it to sound good. But yeah I understand that that's not the point of this project.

You need an enclosure and an impedance converter for the capsule. Lot's of information here if you do the search.

Thanks, I know it's not going to be easy but I like a challenge.
In this case I'll try to find a simplistic impedance converter schematic.

 

[OneRoomStudio]

You're probably going to have to arrive at the right values through experimentation. If I were you, I'd try polarizing it with something around 60V to start, and see what that gets you. The current will be negligible (<1mA). Make sure you keep the high impedances in mind when you're building up your circuit, and keep it simple.

Regular CK12's are around 80pF, so 100pF isn't far off.

 

[Tim Campbell]

Please show us your delay network. To begin with you can simply polarize it using 48v phantom power. That's what Haun and AKG did on some of their models

 

[Khron]

I could be wrong though, but that looks to me a lot more like the Chinese edge-terminated K67's..? Rather than the dozen-component CK12...

 

[soapfoot]

I suggest doing what many young engineers do--investigate prior work done by others, copy it, and then make your own refinements.

Do a search on this forum for terms like "schoeps circuit" "transformerless" or "active-balanced" condenser microphone circuits. Choose a simple one, build it, and analyze the schematic. Try to isolate different functional sections or 'building blocks' of those circuits and see where you can make adjustments to optimize performance.

Good luck!

 

[Recording Engineer]

I could be wrong though, but that looks to me a lot more like the Chinese edge-terminated K67's..? Rather than the dozen-component CK12...

I had pretty-well assumed that when I saw the picture. Didn’t say anything though. Great DIY regardless!

 

[Putchy]

Thank you for your many replies.
In this case, I will try to find a 48V power supply, otherwise I will try with a 12V hex inverter circuit to obtain a voltage of 80V and maybe the preamplifier that goes with it.

 

[Tim Campbell]

Well you can easily find stand alone phantom power supplies but every mixer supplies 48v phantom

 

[Putchy]

Hello,
After building a 130pF capsule, a DC power supply from 40V to 400V and buying 1GOhm resitance, I'm now looking for a simple preamplifier to try to observe a response of our capsule on an oscilloscope and/or to be able to record and listen to the sound. I've scoured several forums, but haven't found a simple preamplifier. I've often seen a Jfet transistor used, but I don't understand what it's for.
If anyone can shed some light on these grey areas, and if you have any schematics, I'd be infinitely grateful.

Please note that this is a school project and I only wish to observe a response from the capsule.

 

[Khron]

I know I need to use a Phantom power supply, but I don't know which one (voltage and current), given that my capsule is twice the size of the normal one. As for the electronic wiring, I have very little precise documentation.

Well, "phantom power" is a pretty standardized concept by now - the preamplifier you connect the complete microphone to, feeds 48V through a pair of 6.8k resistors onto the two signal lines coming into the input XLR socket.

Regarding the impedance adapter (which is what you need / want for this), one of the simplest ways to go would probably be a "FET847" / KM84 type circuit, assuming you can get your hands on a half-decent 10:1 ratio transformer (Neutrik NTE10/3 is a pretty low-cost and accessible solution, if nothing else).

I'm now looking for a simple preamplifier to try to observe a response of our capsule on an oscilloscope and/or to be able to record and listen to the sound.

If you also wanna record, in addition to viewing waveforms (plenty of ways to do that on a computer), you'll probably want to score a used, if possible reputable brand, 2-channel USB audio interface.

 

[alphasnk]

Hello,
After building a 130pF capsule, a DC power supply from 40V to 400V and buying 1GOhm resitance, I'm now looking for a simple preamplifier to try to observe a response of our capsule on an oscilloscope and/or to be able to record and listen to the sound. I've scoured several forums, but haven't found a simple preamplifier. I've often seen a Jfet transistor used, but I don't understand what it's for.
If anyone can shed some light on these grey areas, and if you have any schematics, I'd be infinitely grateful.

Please note that this is a school project and I only wish to observe a response from the capsule.

Buy a used behringer umc22 soundcard on vinted / leboncoin, or amazon second hand.. You'll have a working preamp and a way to record / listen and observe a response from the capsule.

 

[Khron]

You'll have a working preamp

While that's true, i believe the OP is also looking for a circuit to put between the capsule and the XLR input of the preamp.

 

[Putchy]

While that's true, i believe the OP is also looking for a circuit to put between the capsule and the XLR input of the preamp.

Yes, that's exactly what I want, a simple, uncomplicated assembly that fits between the capsule and the preamplifier (I'm thinking of using Opa for this one).
According to The Microphone Handbook [1], this circuit might be suitable. It's simple, but I have no indication of which Jfet model it uses.
On another documentation I have a similar schematic but no specification on the components. [2]
On another forum I also found this concept [3] which I like because it uses an opa stage as an amplifier. However, I can't get it to work properly.

 

[Khron]

According to The Microphone Handbook [1], this circuit might be suitable. It's simple, but I have no indication of which Jfet model it uses.

Regarding the impedance adapter (which is what you need / want for this), one of the simplest ways to go would probably be a "FET847" / KM84 type circuit, assuming you can get your hands on a half-decent 10:1 ratio transformer (Neutrik NTE10/3 is a pretty low-cost and accessible solution, if nothing else).

https://cdn.imagearchive.com/groupdiy/u/39511/58d1402a088f4.jpg

 

[Putchy]

https://cdn.imagearchive.com/groupdiy/u/39511/58d1402a088f4.jpg

I looked at the KM84 circuit, and it mentions a transformer to avoid impedance problems. Is it really necessary to observe a response on an oscilloscope or to connect the suite to an opa amplifier ?