Official C12 Clone - Build and Support Thread

[Mikael-ange]

Ok so heater is correct (off course you mesure it with one probe of you multimeter on pin 4 in your case, and the other on a ground plane like the support rail of the mic for exemple.).
And btw your tube pinout seem correct.
Now as far as b+ and bias go, you mesure it at the psu, and adjust it with the mic connected.
I saying that because you mention b+ 120v unloaded.

Now for the transformer, xp1 and xp2 are your primary (xp1 is audio + and xp2 is audio -).
The secondery side go to the xlr.
Have you mesured what side is the primary and what side is the secondery btw?
I know stupid question but just to be sure.

 

[DuBmastah]

Yes, all voltages mesurement are made beetween each mesured point and chassis ground. I also checked any point that should be grounded for continuity to the chassis (hoping i didn't forgot one).

Regarding the transformer :
- One side has a black and a red wire. i could read 714Ω beetween them so i guess this is my primary.
I connected the red to XP1 and the black to XP2
- The other side read 50,3Ω so it should be my secondary, right ? I connected those wires to pin 5 and 6 of the XLR, without taking care of what should be + or -... thinking that would just influence the phase witch is not an issue at the moment.

 

[DuBmastah]

Maybe this build is not for me, but as i already built something like 30 mics with differents diy "kits" so far, and because this one looks like pretty easy to do comparing to some others, i feel pretty confused i can't manage to make it work.

 

[Delta Sigma]

Do you get audio when the body isn't assembled? It will hum, but it's a way to make sure you're not getting a short when the body is assembled.

 

[DuBmastah]

No, unfortunatly i have no audio at all, tested opened or closed, with 2 different capsules, 2 different PSU and 2 different 6072A tubes (all of them working previously). Cables are OK.
I get hum in the audio (when the mic is open), but no sound from the capsule. At least, this mic was working perfectly until i changed the board for the matador (there was a Microphone-parts "Fox 460" kit in there that i built some times ago and i just wanted to change to try something else, keeping the Peluso capsule, the GE 6072A tube and the transformer from the Microphone-parts kit).
Imo, the problem should mostly come from the Matador board or some faulty component on it...

 

[DuBmastah]

I didn't find any short in there, but maybe i'm not looking closer enough ? any idea of mesurements i could make to be sure ?

 

[JeffKall]

Is the cable pinout the same? From the Fox PSU to the Matador.

About 6 months ago … I did 2 of Matador/Chunger/Studio 939 C12’s … which included 2 of their PSU’s upgrades of the original Apex 460 PSU’s …

Since I had new C12 bodies and head baskets from 939 … my Apex 460’s … which I had originally intended as donors … remained largely intact …

So … I performed the Fox Mini Mod to the 460’s … upgraded them with Advanced Audio capsules, tubes and transformers … and I power them (when I use them) with the Matador upgraded Apex supplies …

All my issues with the Fox upgraded 460’s … which were all related to the original Apex PCB’s and cheap wire and poor factory soldering … were minimal and they work great with Matador’s upgraded PSU’s …

So … there was no wiring compatibility issues between my new C12’s and my Fox Mini Upgraded 460’s with the Matador PSU’s …

The beauty of the Matador’s Universal Tube PSU’s is they are well-designed … easy to build … and adaptable (voltage tunable) to virtually any tube microphone !!!

I recently did two of Dan’s (poctop) D-67’s and I used Matador’s Universal Tube PSU PCB’s (with R1 & R2 changed to 18K) in Thomann t.bone Retro Tube II enclosures (keeping the AC inputs and removing the Pattern Selector switches) for that “retro supply look” …

It was a bit of a chore to fit Matador’s PCB’s … and I ended up having to cut off the fuse holder wing of his PCB’s (sorry Matador) … but it was well worth the effort !!!

I am hoping some day Matador will consider designing a slightly smaller rectangular PCB to fit in the more traditional enclosures !!!

Best Regards …

 

[Delta Sigma]

No, unfortunatly i have no audio at all, tested opened or closed, with 2 different capsules, 2 different PSU and 2 different 6072A tubes (all of them working previously). Cables are OK.
I get hum in the audio (when the mic is open), but no sound from the capsule. At least, this mic was working perfectly until i changed the board for the matador (there was a Microphone-parts "Fox 460" kit in there that i built some times ago and i just wanted to change to try something else, keeping the Peluso capsule, the GE 6072A tube and the transformer from the Microphone-parts kit).
Imo, the problem should mostly come from the Matador board or some faulty component on it...

If you get hum that is louder when the body is open, then I would re-check your capsule wiring. If the hum does not change when the body is open, I would check the audio connections inside the power supply. Also, make sure that your audio pins on the cable are 1:1.

 

[drtechno]

Maybe this build is not for me, but as i already built something like 30 mics with differents diy "kits" so far, and because this one looks like pretty easy to do comparing to some others, i feel pretty confused i can't manage to make it work.

Don't get bent out of shape too badly over this because this one and the other 6072 mic circuit, the elm251 clone are junk designs to begin with.

Happy new year everyone

I'm definatly stuck with this build.
There was no problem builind the PSU, but for the mic itself its another story
After spending numerous hours trying anything i could to make it work, my last option is to gather help from the community...

- First, the mic itself was previously working perfectly (microphone-parts "Fox 460" kit + peluso capsule + GE 6072A NOS tube).
- After building the Matador PSU kit, it was still working perfectly with it.
- Then i removed the Fox 460 stuff and keeped the capsule and transformer.
- I populated the Matador V1.4 PCB from 2021 with the provided components
- I putted everything together and... Get NO sound at all !

I then tested everything i could like : exchanging the capsule for a chinese Apex 460, exchanging the tube for a EA 6072A, Exchanging the power supply, cables... all for "known as working" ones...
Still no sound.

I checked the voltages at the mic and got (with modded PSU) :
- Pin 1 -> P5 (B+) = 120V
- Pin 2 -> P8 (heater) = 6,3V (6,6V with other PSU)
- Pin 3 -> P3 (polar pattern) = 0V to 96V (about 44V at cardioid position)
- Pin 4 -> P4 (bias) = -1.03V (0V with other PSU)
- Pin 5 and 6 are the audio from the transformer secondary, i could read 50,3Ω beetween them
- XP1 and XP2 are linked to the transformer primary, i could read 714Ω beetween them

From what i understand, those values might be correct, right ?
So what am i doing wrong? I'm not absolutly sure about the tube socket wiring, so i attached detailled pics of the build, maybe you could see something wrong somewhere ?

Many thanks in advance.

So what schematic you are using? Because all of them are wrong that I'm finding online for a 6072 tube.
For like a 120B+, self Bias should have a 220K plate resistor& 3.8K for cathode for around -4 grid voltage for class A.

-1 at the grid would be for more like a 12AX7 or a 12AU7 on self bias.

 

[Mikael-ange]

If you get hum that is louder when the body is open, then I would re-check your capsule wiring. If the hum does not change when the body is open, I would check the audio connections inside the power supply. Also, make sure that your audio pins on the cable are 1:1.

Agree
I misread and understood he've go nothing at all (no audio, no hum).

Don't get bent out of shape too badly over this because this one and the other 6072 mic circuit, the elm251 clone are junk designs to begin with.

So what schematic you are using? Because all of them are wrong that I'm finding online for a 6072 tube.
For like a 120B+, self Bias should have a 220K plate resistor& 3.8K for cathode for around -4 to -8V grid voltage for class A.

-1 at the grid would be for more like a 12AX7 or a 12AU7 on self bias.

Are you sure you speak about a c12 clone?
Just asking because in a c12, cathode is connected direct to the ground with no cap in between.
Maybe I misunderstand something...

 

[Delta Sigma]

...

Are you sure you speak about a c12 clone?
Just asking because in a c12, cathode is connected direct to the ground with no cap in between.
Maybe I misunderstand something...

And it is a 1.1V bias for 6072 in a C12.

https://coutant.org/akgc12/c12schem.jpg

 

[drtechno]

Agree
I misread and understood he've go nothing at all (no audio, no hum).

Are you sure you speak about a c12 clone?
Just asking because in a c12, cathode is connected direct to the ground with no cap in between.
Maybe I misunderstand something...

I remembered, the 6072 when direct biased should be ~ -40V. Self biased is -4V class B -8V Calss A.

He's getting -1V at the bias test point (grid). I know 251ELM clones are using the wrong resistors because they are saying that instead of normally is biased -4V with the tube.

C12 has always been badly engineered. But the guy probably has the tube base not wired correct either.

 

[DuBmastah]

As long as his could make a difference, the two PSU i use are not the same.
While the Matador modded one use pin 4 of the XLR for bias, the other one doesn't have such a fonction and pin 4 is linked to ground.
I don't think plugging the microphone to the other PSU would damage anything, right ?

The issue with this microphone is driving me mad.
I'm just a few mns away from trashing this Matador PCB and putting back the MicParts Fox460 PCB in there !

At least, any idea what to do in such case ?
Is there a possibility to send the mic to someone in the EU who could service it ? What are the options when things goes wrong with a kit like this and you're a newb in electronics ?
I've spent COUNTLESS hours trying to fix it, but now i'm done, i'd better go back to my studio and make music.

 

[drtechno]

And it is a 1.1V bias for 6072 in a C12.

https://coutant.org/akgc12/c12schem.jpg

And its always been badly designed for a 6072
https://frank.pocnet.net/sheets/049/6/6072.pdf

 

[drtechno]

As long as his could make a difference, the two PSU i use are not the same.
While the Matador modded one use pin 4 of the XLR for bias, the other one doesn't have such a fonction and pin 4 is linked to ground.
I don't think plugging the microphone to the other PSU would damage anything, right ?

The issue with this microphone is driving me mad.
I'm just a few mns away from trashing this Matador PCB and putting back the MicParts Fox460 PCB in there !

At least, any idea what to do in such case ?
Is there a possibility to send the mic to someone in the EU who could service it ? What are the options when things goes wrong with a kit like this and you're a newb in electronics ?
I've spent COUNTLESS hours trying to fix it, but now i'm done, i'd better go back to my studio and make music.

Grounding pin 4 is not going to do anything to the tube even if it was directly connected to the grid of the tube. If it was connected to the tube grid, it would only turn off the tube and get nothing but maybe a hum.

 

[DuBmastah]

At least, those are the symptoms i experiment with this build.
But... from the other (matador modded) PSU, pin 4 is not grounded and i still have the same issue with the mic...

 

[drtechno]

At least, those are the symptoms i experiment with this build.
But... from the other (matador modded) PSU, pin 4 is not grounded and i still have the same issue with the mic...

Ok, first thing in tube kit flop is check the tube connections.
First thing to do is check the tube base to see if its connected correctly. In post #2954 has the datasheet.
The pinout is illustrated as if you were looking at the pins/solder side.
Check this and we continue.

 

[Delta Sigma]

To be honest, I'm still not clear on the power supplies, their differences, and the pinouts.

All your tube voltages seem fine, so while it doesn't eliminate the tube wiring, I'd troubleshoot elsewhere first.

Please make sure that
-your front facing diaphragm is connected to 0V
-your backplates are connected together
-the two backplates both connect to the voltage divider via R14 (this supplies the 50-60V to the capsule)
-the two backplates also connect to the tube grid via C13 (C13 isolates the 60V capsule bias from the -1.1V tube bias)

If you didn't tie your backplates together, and only connected it as the Matador schematic could be misinterpreted to show, you would have 60V only on your rear backplate. The front backplate would be floating, and you would get no audio from the front diaphragm. The rear backplate would have no connection to the tube grid, so you would get no audio from the rear diaphragm.

-1.1V is fine for the C12 bias. You'll make hit records with -1.1V.

 

[rock soderstrom]

-1.1V is fine for the C12 bias. You'll make hit records with -1.1V.

 

[DuBmastah]

To be honest, I'm still not clear on the power supplies, their differences, and the pinouts.

All your tube voltages seem fine, so while it doesn't eliminate the tube wiring, I'd troubleshoot elsewhere first.

Please make sure that
-your front facing diaphragm is connected to 0V
-your backplates are connected together
-the two backplates both connect to the voltage divider via R14 (this supplies the 50-60V to the capsule)
-the two backplates also connect to the tube grid via C13 (C13 isolates the 60V capsule bias from the -1.1V tube bias)

If you didn't tie your backplates together, and only connected it as the Matador schematic could be misinterpreted to show, you would have 60V only on your rear backplate. The front backplate would be floating, and you would get no audio from the front diaphragm. The rear backplate would have no connection to the tube grid, so you would get no audio from the rear diaphragm.

-1.1V is fine for the C12 bias. You'll make hit records with -1.1V.

Many thanks Delta Sigma for helping me figuring out what the problem might be.
As for the points you enumerate, everything is OK.
(and for the capsules, the peluso uses 2 cables for the backplate wich are linked, and the RK12 from MicParts, there's only one, but the backplates are linked internaly).
At this point i'm checking back all the voltages and will post results in next comment.