Official C12 Clone - Build and Support Thread

[Banzai]

The stock T11 screws have heads that strip easily, so definitely an issue worth addressing. But tbh, there's no mechanical advantage to gain by re-tapping perfectly good threads.

Just upgrade the screws to M2 stainless steel (A2), and save yourself the headache! Easily available in the US.

Well that didn't go to plan.

 

[saxmonster]

Banzai,
I think i will just save the tap if i need to fix a stripped one.  Thanks. What place do you get your M2 screws at and what does A2 mean is that the code for stainless steel?

 

[Banzai]

Exactly, A2 is the quality grade of the Stainless Steel (most common standard is A2-70). A4 comes with additional corrosion protection for use on boats etc.

Based in Europe so we mainly use Bossard; the cheapest place we found to get them from is TME in Poland. For the US we've ordered from Fastener Express in CA in the past, and the service/quality was excellent. They have everything you need:

http://www.fastener-express.com/metric-pan-head-phillips-machine-screws-stainless.aspx

Banzai,
I think i will just save the tap if i need to fix a stripped one.  Thanks. What place do you get your M2 screws at and what does A2 mean is that the code for stainless steel?

 

[andyfromdenver]

Hi good people of C12 land.
I got my package (thanks chunger and matador).  most of the resistors supplied for the power supply fall far outside the values in the schematic/ are absent.  I have lots of resistors from guitar amp land.  Question, and sorry if it's been clarified elsewhere, do I shoot for the schematic?  is there a wide variance d/t the bias adjustments of the trim pots and I mostly hit the numbers when testing?
Just checking before I do any soldering to the power supply pcb.  Plus, I have several nos 12at7s and am going that route, if that's a consideration.  Also also, along that line would ~60k be good for R1 and R2 to swap between 12at and 12ay?

Thanks!
what a fun project 
Andy

 

[Matador]

Hi good people of C12 land.
I got my package (thanks chunger and matador).  most of the resistors supplied for the power supply fall far outside the values in the schematic/ are absent.  I have lots of resistors from guitar amp land.  Question, and sorry if it's been clarified elsewhere, do I shoot for the schematic?  is there a wide variance d/t the bias adjustments of the trim pots and I mostly hit the numbers when testing?
Just checking before I do any soldering to the power supply pcb.  Plus, I have several nos 12at7s and am going that route, if that's a consideration.  Also also, along that line would ~60k be good for R1 and R2 to swap between 12at and 12ay?

Thanks!
what a fun project 
Andy

Most values?  Can you give an example?

I made some BOM changes a few months ago and may have not updated the schematic on the first post properly.

 

[andyfromdenver]

Hi good people of C12 land.
I got my package (thanks chunger and matador).  most of the resistors supplied for the power supply fall far outside the values in the schematic/ are absent.  I have lots of resistors from guitar amp land.  Question, and sorry if it's been clarified elsewhere, do I shoot for the schematic?  is there a wide variance d/t the bias adjustments of the trim pots and I mostly hit the numbers when testing?
Just checking before I do any soldering to the power supply pcb.  Plus, I have several nos 12at7s and am going that route, if that's a consideration.  Also also, along that line would ~60k be good for R1 and R2 to swap between 12at and 12ay?

Thanks!
what a fun project 
Andy

Most values?  Can you give an example?

I made some BOM changes a few months ago and may have not updated the schematic on the first post properly.

Ahh.
Perhaps there's a new scheme or something?
As far as what was sent (besides the mic pcb resistors which are all there, 2 x 1M, 2 x 4.7k 5W, and the switch resistors)
2 x 33.2k
2 x 221ohm
1 x 499k
2 x 68.1k
1 x 47k
2 x 400k

Thanks!

 

[chunger]

Hello,

We recently made a few BOM changes that are reflected in parts kits.  I need to update the first posts to reflect these changes.


R1, R2 = 68.1K
R9, R10 = 221R
R6 = 499K
C1, C2 = 47uF 350V

All other components are the same as 1st revision.

The 2x 33.1K resistors are for use in the R1, R2 position of the PSU if you use 12AT7 tube instead of the original 6072A.

 

[Winetree]

Banzai,
I think i will just save the tap if i need to fix a stripped one.  Thanks. What place do you get your M2 screws at and what does A2 mean is that the code for stainless steel?

Bought some at the local "True Value Hardware"

 

[geebeeVIE]

Hi,

I have built two of these kits, and basically they work very nice.

There are just some oddities:

- I replaced the XLR 7 with Neutrik gold plated connectors. Now everytime I touch the connector at the power supply and move it a tiny bit (there is some play in the fit), I get some scratching noises.... I guess this is because of the DC passing and some changes in resistance. Any ideas how to cure it?

- When I connect the PS to my Madiface XT, it sounds fine and clean. But as soon as I connect the Madiface XT to a Laptop, and the laptop to its power supply, I get to hear "computer noises".... THis does not happen with P48 powered microphones.
I already added a ground lift switch to the powersupply, which opens the GND connection between XLR and XLR7, which makes it better, but does not completely cure it.

- The mics work fine in omni and figure of eight, but in cardioid, it seems that the back diaphragm is still active..... Any ideas on that?


Thank you!!

Gee

 

[andyfromdenver]

Hello,

We recently made a few BOM changes that are reflected in parts kits.  I need to update the first posts to reflect these changes.


R1, R2 = 68.1K
R9, R10 = 221R
R6 = 499K
C1, C2 = 47uF 350V

All other components are the same as 1st revision.

The 2x 33.1K resistors are for use in the R1, R2 position of the PSU if you use 12AT7 tube instead of the original 6072A.

Perfecto!
Thanks chunger

 

[Tim Campbell]

geebeeVIE
If the back membrane is still active then it would remain in fig 8 or omni. If you mean you still get signal through the back membrane in cardiod it should sound darker and weaker on the back side. This is normal. If you look at cardioid fig pattern you'll see capsules are not really unidirectional . If the signal from the back membrane sounds more like omni then you have a short or a problem with your capsule.

 

[geebeeVIE]

Thanks Tim,

i will keep that in mind.  I know that and (ideal) cardioid has a 30dB reduced sensitivity on the backside.
ANd yes, if I talk into the mic from the backside, it sounds muffled and lower in level. However if I check with very quiet sources, e.g. rubbing one finger against another, at a very short distance in front of the capsuel, i hear basically no difference between front and back.... Oh well. Some experimenting has to be done

Any ideas regarding the hum or noises?
Might it help to hard ground the sleeve from the 7pin xlr to the central ground point at the chassis and remove the direct connection of Signal GND and Housing?

Any ideas are very much welcome.

 

[Matador]

Check your polarization voltage at the P4 node right where it enters at the base of the mike.  It should be very close to half B+ (or 60V).

 

[geebeeVIE]

Thanks Matador,  voltages seem correct (omni 0, cardioid 60, fig 8 120). I cleaned the high ohm section and that seems to have cured it.

What a stunning microphone. Just tried it on my Steinway D grand... full and rich, but silky and smooth withoud sounding dull....

Thanks all for the inputs and help! And thanks matador & chunger for that great mic!

 

[icemanaman]

Hi there! Bought a pair of these from Chung when I was in California last fall (I live in Norway).
Started building them about 10 days ago, and Im almost done!
Such a fun and good looking build!

Just a question..

Can someone point me to instructions on how to hook up the capsule??

I am unable to find pictures or description of this.
I have the Eric Heiserman Capsule. I just need to screw the supplied cables to the capsule, and solder them to the correct pins.
I have no idea what configuration it should be.

Thank you!

 

[saxmonster]

Bridge front and rear backplate either at the capsule or at the PCB.

FB = front backplate
RB = rear backplate
FC = front capsule
RC = rear capsule

 

[icemanaman]

Bridge front and rear backplate either at the capsule or at the PCB.

FB = front backplate
RB = rear backplate
FC = front capsule
RC = rear capsule

Thanks for that saxmonster! but being a total newbie to microphones.. how do I identify front backplate, rear backplate, etc on the Heiserman capsule? I'm sure it's self explaining for some, but I wouldn't want to make any mistakes..

 

[saxmonster]

Once you determine which side is your front thats the front capsule.  The wire attaches to the rims of the front and back.  Not sure if Eric denotes which one is the front.  You could try it one way and then reverse it and see if it sounds better.  Most of the time they are tuned the same so it doesn't matter.  You'll have to ask him, the backplates are the two brass disks behind the capsule skins with the holes in it.  When you attached the wires and screws to the sides of the capsules you are attaching them to the backplates.  The backplates need to be electrically connected  somehow either soldered at the capsule or down on the pcb.  There needs to be continuity between both backplates and the pcb RB&FB.  HTHS

see photos below for how FC is hooked up to solder tab on front rim, two black wires(without red heat shrink) go to the side for backplates.  Did he provide soldering tabs and screws to connect everything.  I'm looking to get one of his capsules too.


 

 

[icemanaman]

Thanks saxmonster, that explains a lot! Really appreciate you showing me with picture and all!
I bought the Heiserman capsules from chunger.
I don't have the capsules in front of my right now.. but as I can remember, this is what came with the capsule:
Capsule, 4 leads with solderpads, 2 screws, 1 capsule mount.

So, I can just remove one of the screws from the rim of the front capsule, put in on lead, and then screw that screw back in??

Regarding the bridging I think I'll just solder a short wire between the RB and FB pins on the PCB. Sound OK? Not sure how other people solve this. Question: Why isn't this done in chungers tutorial?

Also, the capsule mount I was supplied with, is just a tiny hair to wide to fit slot in the stock microphone post. Also, it has two small tabs that limits the capsule mount from lying flat in post. Do I simply just cut the tabs off the capsule mount and maybe shave some material off from one side to make the capsule mount fit in the post slot? I can upload a picture if that was hard to picture..

Thank you!

 

[saxmonster]

Thanks saxmonster, that explains a lot! Really appreciate you showing me with picture and all!
I bought the Heiserman capsules from chunger.
I don't have the capsules in front of my right now.. but as I can remember, this is what came with the capsule:
Capsule, 4 leads with solderpads, 2 screws, 1 capsule mount.

So, I can just remove one of the screws from the rim of the front capsule, put in on lead, and then screw that screw back in??

I would double check with Eric on taking out the screw,  I wouldn't want to change the tension on the membrane but if it has to be done then kind of feel how tight it is when you first take out the screw so you can get it somewhat close to the original tension that the screw originally had.  I never had to do this so not too sure about it yet, on another mic I have one of tim's capsules and he had the solder tabs already installed on the rims of the capsule so all I had to do with solder my connections to that.

Regarding the bridging I think I'll just solder a short wire between the RB and FB pins on the PCB. Sound OK? Not sure how other people solve this. Question: Why isn't this done in chungers tutorial? 
I'll look through the tutorial again but what I did was bridge it at the capsule and then run one wire down to the pcb and bridge again at the pcb.  This way only uses one wire and to me looks less cluttered and less soldering to do.

Also, the capsule mount I was supplied with, is just a tiny hair to wide to fit slot in the stock microphone post. Also, it has two small tabs that limits the capsule mount from lying flat in post. Do I simply just cut the tabs off the capsule mount and maybe shave some material off from one side to make the capsule mount fit in the post slot? I can upload a picture if that was hard to picture..
Yes its probably made for a different post so I would just get it to lay flat and level and as clean as can be.  Use locking washers so it doesn't get loose from handling and what not.
Thank you!