C12 DIY Kit - Complete Build Guide
« on: December 31, 2013, 05:46:52 AM »

Welcome to this build guide step by step of our C12 DIY Kit.

Here is our Webstore : www.micandmod.com

WARNING! The construction process of this tutorial is only for educational purposes.
Everything must be done only by qualified technicians and electronicians. This DIY project
involvesto work with the circuit of the Power Supply which has lethal voltages. A very good
knowledge of electronics and soldering is required before starting the project.

 Step by step: (choose your chapter)


To make this microphone, you will need:

- Our high quality PCB, a perfect recreation of the Vintage C12 circuit: purchase here

- Or our full kit C12 DIY Kit : available here


- An electronic or analog multimeter to calibrate the microphone.



- A quality soldering iron with a fine tip. We recommend our soldering irons Weldteam: available here



- Tin of quality. We recommend Weldteam tin: available here


- A small cutting pliers special electronic

- Set of precision screwdrivers. Available here

- Possibly a desoldering pump, if ever you need to desoldering a component misplaced: available here

- Cleaning solder flux. Isopropyl alcohol to about 90% with a toothbrush and cotton swab will do the trick.
It is important to clean your welds and remove the flux which may interact with the circuit.

Once you are ready, that you have gathered all the necessary materials and that you are now aware risks, we can begin.
« Last Edit: December 31, 2013, 06:41:56 AM by micandmod »


Re: C12 DIY Kit - Complete Build Guide
« Reply #1 on: December 31, 2013, 05:48:46 AM »
1 - Assembling the Power Supply

Start by the Power Supply of microphone. Take the Power Supply box.

Remove the 4 lateral screws.

Remove the cover of the box.

Now take the C12 printed circuit.

Detach gently the "Power Supply" circuit.

Remove with pliers the remaining plastic.

File down if necessary.

Check that the circuit fits perfectly in the diet without fixing.


Start with the resistors of the circuit:

- R1, R2 : 75k
- R5, R11 : 1M
- R6 : 470k
- R9 : 392ohm
- R10 : 1k


Place them in the locations indicated in the direction you want (resistors are not polarized).

Bend the leads and solder them to the circuit.


Then cut them out.

Continue with 10 diodes.

Place the diodes in observing the direction of orientation of the printed circuit like this example :

Check several times that your Diodes are not installed backwards before moving to the solder.

If everything is OK, bend, solder carefully (without too heating, these components are fragiles!) And cut.

A little cleaning is required. This is not obligatory, you can achieve the cleaning at the end.

Now, resistors R7 and R8 4.7 ohm.

Install the two resistors to locations noted in the direction you want (non-polarized components).

It is the turn to trimmer pots to be installed.

To help you solder these components, we have included to kit an alligator clip.

Simply pinch the legs of a component using the alligator clip, and solder the other leg.
Then remove the clip and solder the other legs.


The Terminal Blocks are now appearing.
The bag consists of three different blocks (2P, 3P, 5P)


Install them as in the following pictures.

Solder them to circuit, always using the very useful alligator clip.

Now let's look at the voltage regulator and heat sink.

Optional Note: We strongly recommend that you use some thermal paste for this step.

Make sure you have all the elements of bag

Begin by placing the insulating layer on the second hole of the heat sink.

Optional Note: You can put some thermal paste between the heatsink and the insulating layer.

On the voltage regulator, install the plastic washer.

Then, insert the screw.

Install all the previous assembly.

Optional Note: You can put some thermal paste between the regulator and the insulating layer.

On the back side, place the large flat washer first.

Then, the small lock washer.

Finally place the nut by hand without loosely yet.

Install the final assembly on the printed circuit.

Solder the fasteners of heat sink by pressing firmly on your soldering iron.

Put your soldering iron to maximum power.


When positioning has been verified, you can securely tighten the regulator to the heatsink
taking care that the insulating layer remains in its place.



Use the multimeter to check that there is no conduction between the top of regulator and heat sink.
If you get a conduction, insulating layer has probably been moved or breakthrough


Solder now the regulator to the PCB.

Clean it, it is ready for the next step.


Now let us tackle the mounting of capacitors.
Firstly small electrolytic capacitors C5, C9 and C11.



Warning, these capacitors are polarized.
The big lug is positive, the small is negative.


Place the capacitors on their respective housing.

Capacitor C5

Capacitor C11, note the direction.

Capacitor C9.

Once you have verified that the direction is complied with, solder and cut.

Now the capacitors C1, C2, C3, C4 100uF polarized also.

Install them in the same way, checking the direction of each.

After verification, solder and cut.

Then the capacitors C6, C7, C8, C10 4700uF.

Install, check their direction.

Always after checking the proper positioning, solder.

And cut.


Solders are now finished for this circuit. Therefore perform a complete cleaning.
Do not hesitate to put a good quantity of cleaner and perform this cleaning under a fume hood or outside.



Last Power Supply part, the fuse holder.

Install to the position indicated on the circuit. Put the screw.

On the back, place the washer and nut.

Tighten all.

Congratulations! You have completed the assembly of the circuit of the PSU.

Install all in the case of PSU.

Note: Do not connect the PSU to your outlet for the moment!

Start by unscrewing the 3 screws of the support.

Lay out the circuit of PSU.

Insert the previous 3 screws and attach the PCB.

Connect the wires of pattern switch as follows :

- 1=POLV=Red
- 2=PMic=Green
- 3=PGND=White

Then insert different wires of XLR 7-pin connector as follows :

Pin 1=B+=Red
Pin 2=H+=Yellow
Pin 3=Bias=Blue
Pin 4 = Pol=White
Pin 5=A-=Black
Pin 6 = A+=Green
Pin 7 = GND=Brown

Check the connection of the XLR output :

Pin 1=Ground (GND)
Pin 2=Hot (A+)
Pin 3=Cold (A-)

Connect the transformer 200V (blue wires) in the corresponding block.
As the current is alternating (AC), there is no direction of connection wires.

Then the same thing with the current 9.5V (yellow wires).


Connections of the high voltage input fuse.

Insert first the 2 heatshrink sheaths.

Make sure to place them as far as possible from your soldering iron for the future.

Position the two wires on the fuse holder.

Solder them.

When solders are cooled, move the two sheaths on the Connectors.

Warm the sheaths a few seconds without damaging other components.

Then install the fuse in the direction you want.

Your PSU is now ready to be "pre-calibrated".

« Last Edit: December 31, 2013, 05:59:11 AM by micandmod »


Re: C12 DIY Kit - Complete Build Guide
« Reply #2 on: December 31, 2013, 05:51:48 AM »
2 - Precalibration of Power Supply

Before you start assembling the microphone circuit, it is best to check the proper functioning
of PSU and make a first calibration.

The first calibration is important for not distribute a too high voltage to the microphone.
We will simulate the mic connection with a 180k resistor.

The kit comes with the following resistor

Bend both legs

And insert into the pins 1 and 7 of the 7-pin XLR connector.

Select the voltage according to your country with the switch, then plug the power cable and turn on the switch.

dentify the different connections and their meaning.

Connect your multimeter to DC mode.

To measure, you will need absolutely put the plug point "COM" to the ground (GND screw)
then place the other on the screw where you want to know the value.

To make the adjustments, then it will suffice using a screwdriver to turn the screws of different Trimmer pots:

B+ adjust=R4
H+ adjust=R12
Bias adjust=R3


B+ must be set to 120V

H+ must be set to 6.30V

Bias must be set to -1.1V

Attention Bias setting changes the value of B +
So you will return to B +, then the Bias and B + ...
For now, make an approximate measure.

« Last Edit: December 31, 2013, 05:59:40 AM by micandmod »


Re: C12 DIY Kit - Complete Build Guide
« Reply #3 on: December 31, 2013, 05:52:31 AM »
3 - Microphone assembly

As earlier, remove the last parts of the circuit.

Install the 4 PCB turrets to points BD, BG, Grid et BP.

Introduisez complètement les fiches.

Then the turret FD (=Front Diaphragm)

Solder on the circuit.

Then, the resistors R12, R13 and R17 (not polarized).

Check, solder and cut.

Resistors R14 et R15.

Do not hesitate to take resistors with the alligator clip if you have trouble to soldering.

Solder the first legs on the turrets.

Then the second on the circuit. Cut.

Resistors R11 et R16: 30M.

Solder and cut.

Do the same on the back of the circuit.

Continue with the capacitors Styroflex C10 et C11: 5000pF.


Note: Styroflex capacitors must not be heated too long.
We recommend that you use the alligator clip as a heat sink.


Check, solder and cut.

And the last capacitor Styroflex.

Bend the capacitor in this way.

Place it on BG and Grid turret.

Solder being careful not to touch the components.

Clean circuit with isopropyl alcohol.

Note: do a good cleaning! Some solders are not accessible later.

Proceed to Tube Socket installation.

Gently bend the legs of the socket and install into the circuit.

By pressing down on the circuit, solder the different legs.

Clean soldering.

Place the assembly on the microphone circuit and align it.

Solder one leg that will guide you.

Use a square to make a right angle between both circuits.

Take care to keep the two well perpendicular circuits, solder the last 3 legs.

Cut a wire of about 2.5cm.

Solder it to the second leg of tube named "Grid"

Then the second on the turret of circuit "Grid"

Cut and prepare a cable about 2cm.

Place it and solder it between BG and BP turrets of circuit.


Now, the output capacitor C12.


2 options available to you :

- Capacitor NOS Russian PIO 0.47UF: capacitor "Vintage" oiled paper.
Its value is close to the original capacitor C12 and agree to the purist

- The capacitor 1uF JFX Premium: very high quality Polypropylene capacitor.
With its 1uF value, the sound will be slightly slower transient response and more bass extension.


Place the capacitor as you see fit.

Solder and cut.

Transformer Cinemag CM-13114


Pass orange and yellow wires in the back.


Install the "Zip" to fix the transformer.

Do not put the wires under the "Zip".

Locate markings 1, 2, 3 and 4.

onnections with transformer Cinemag CM-13114 are as follows :

- 1=Red
- 2=Brown
- 3=Orange
- 4=Yellow

Prepare to present the 7-pin XLR connector.

Take a leg of a component.

Create the Ground between pin 7 and chassis. Solder and trim the surplus.

Prepare a brown wire about 4.5cm.

Connect this wire to pin 7 and solder.

Prepare 6 other wires and solder them to the corresponding pins :

Pin 1=Red wire of 8.5cm
Pin 2=Orange wire of 4.5cm
Pin 3=Blue wire of 4.5cm
Pin 4=White wire of 4.5cm
Pin 5=Black wire of 4.5cm
Pin 6 = Green wire of 4.5 cm


Place the 6 shrinkable sleeves and heat them.


Install the XLR connector in the body.

Unscrew the base and remove the microphone body.

Enter the connector on the below.

Loosen the screw to wedge the connector into place.

Clean up remaining solders of circuit.

Put the complete circuit in the microphone body.

Screw the 2 small screws at the top of the PCB.

Then the 2 screws from the bottom of the PCB.

Short screw to left, long screw to right.


Solder the wires of the XLR connector as follows :

Pin 1 = Red=B+
Pin 2=Orange=H+
Pin 3 = Blue=Bias
Pin 4 = White=POL
Pin 5=Black=A-
Pin 6=Green=A+
Pin 7=Brown=GND


The B+ connection is between the transformer and the capacitor C12.

Clean your solders with a toothbrush and/or cotton swab.

Then unscrew the two screws holding the microphone head.

Let us install and connect the capsule MK-12.


Do not touch the membrane front and rear of the capsule, you could damage it.
Handle the capsule gently and only by holding its edges


Remove the capsule from its protective box.

Drill 2 holes for the screw with a screwdriver.

Screw the capsule on the holder with the blue wire to the left.

Insert the white and blue wire on the front.

Insert the small screw in the ring of second blue wire.

Screw it beside the first.

Insert the white wire from the rear and the second blue wire in the back holes.

Replace the microphone head and tighten it.

Prepare the cables to the correct size.

The white wire from the front of the capsule will be solder to FD = Front Diaphragm.

White wire from the back of the capsule to BD=Back Diaphragm

Blue wire from the front to BP=Backplate 1

Blue wire from the rear to BG=Backplate 2

Clean all connections with isopropyl alcohol.

Tube installation.

Insert the tube gently in the right direction.

You're almost done. Now to the final calibration of the microphone.

« Last Edit: December 31, 2013, 06:00:16 AM by micandmod »


Re: C12 DIY Kit - Complete Build Guide
« Reply #4 on: December 31, 2013, 05:53:24 AM »
4 - Final microphone calibration

The microphone calibration is relatively simple.

Connect the 7-pin XLR microphone cable, then connect it to the power supply.
Remove first the 180K resistor.

Connect the "COM" of multimeter to ground microphone.
We will use in our case, a clamp connected to the microphone body.

Then turn on the Power Supply.

The advantage of calibration with the microphone is to quickly check each voltage from the circuit board.
The B+ is verified directly top right of the capacitor C12.

With our pre-calibration with resistor of 180k, we have now 121.1V, connected microphone.

So we need to decrease the value using the small screw Trimmer B+.

Here is the required value for B+=120V

The value of "bias" is checked directly at the top left of the capacitor C12.

With the microphone connected, we now have a value of -1.110V.

Reminder: Changing the value of B + changes the value of "Bias".

So you must go back to one then the other, until the two values agree.

The correct value of "bias" is -1.100V.

The value of H+ is verified directly above the tube.

Our value, connected microphone, is 6.03 V. So we have to increase the H+ with Trimmer.

The correct value of H+ is 6.30V.

Once the calibration is complete, it'll just close the Power Supply with the 4 screws.


Plug your XLR to preamp, and do not activate the +48V phantom power.

"Check, Check, Waouh !"

And voila, you are now the owner of a C12 !

All pictures in this tutorial are subject to the right of the author

2014 © Mic & Mod
« Last Edit: December 31, 2013, 06:00:48 AM by micandmod »

Re: C12 DIY Kit - Complete Build Guide
« Reply #5 on: February 22, 2014, 11:55:16 PM »
There was no brown ground wire from the 7 pin input connector to the PCB in my unit.  I have added one, but, also, there is an existing connection between pin 7 and pin 4  - I assume this link should this be removed?


Re: C12 DIY Kit - Complete Build Guide
« Reply #6 on: February 23, 2014, 05:17:54 AM »
There was no brown ground wire from the 7 pin input connector to the PCB in my unit.  I have added one, but, also, there is an existing connection between pin 7 and pin 4  - I assume this link should this be removed?

Yes sorry for this mistake.
You must remove the ground connection between pin4 and pin7.

Re: C12 DIY Kit - Complete Build Guide
« Reply #7 on: February 23, 2014, 03:18:38 PM »

I thought I stuffed this thing carefully, but now I can't get the b+voltage to adjust beyond 35V with or without the temporary load resistor.  Ugh.   :'(

I must have stuffed a resistor or trimmer incorrectly.  Although I can get the other voltages to trim out ok.  I stuffed the trimmers per the silkscreen NOT per the build guide pictures in the build thread - I suspect they work in either direction. ?

How long does this thing take to discharge the caps?  I've left the loading resistor in there but it isn't discharging very quickly.   Can someone clue me into a quicker way?  I'd rather not get zapped.  :P

Also any heads up on where I should be looking would be dearly appreciated.


Re: C12 DIY Kit - Complete Build Guide
« Reply #8 on: March 03, 2014, 02:04:28 PM »
What a joke, nice PSU, it must have taken u a long time to change matadors pcb color?? you even used Chingers head basket, how do u sleep at night you fraudulent twit! It's an outrage!