Official C12 Clone - Build and Support Thread

[stelin]

The voltages are fine:

B+ 120V
Bias -0,983V
Heater 6,42V (at the PSU, that’s 6,3V in the mic)
Polar 51V for cardioid

I have seen no sign of that the membrane is collapsing.

But, I think I’ve found an explanation: When I just assemble the mic loosely, there’s no problem. When I screw on the bottom cap hard there is sometimes a drop in volume (4-5 dB).

I noticed that the screw holes in the rails is not a flat surface.  There’s some bending and tension on the board when I’m tightening the screws. There is additional tension added when I screw on the bottom cap hard (a pulling action on the rails).

I probably have a fracture in a solder joint somewhere on the board. I will re-solder everything and then make sure I don’t fasten the board down so hard that it’s bending.

Thank you all for your suggestions and your kind help!

- Stefan

 

[Matador]

The voltages are fine:

B+ 120V
Bias -0,983V
Heater 6,42V (at the PSU, that’s 6,3V in the mic)
Polar 51V for cardioid

I have seen no sign of that the membrane is collapsing.

But, I think I’ve found an explanation: When I just assemble the mic loosely, there’s no problem. When I screw on the bottom cap hard there is sometimes a drop in volume (4-5 dB).

I noticed that the screw holes in the rails is not a flat surface.  There’s some bending and tension on the board when I’m tightening the screws. There is additional tension added when I screw on the bottom cap hard (a pulling action on the rails).

I probably have a fracture in a solder joint somewhere on the board. I will re-solder everything and then make sure I don’t fasten the board down so hard that it’s bending.

Thank you all for your suggestions and your kind help!

- Stefan

Check the 7-pin connector, and make sure that the brass retaining screw is fully "loosened", meaning you have to "unscrew" it counter-clockwise in order to make sure it's tight against the brass end-bell.  This is the only way to make sure you have good ground continuity throughout the system.

 

[stelin]

Thanks, I've checked that.
I started using Switchcraft XLR connectors for mic cables in the seventies. 

 

[Category 5]

Anyone with ht-11a transformer shield bell housings?  I need a few more. 

Also interested in your stock pattern switches if you don't need em.  Pm me.

 

[kidvybes]

Fresh from the powder-coat shop!

 

[MicDaddy]

Fresh from the powder-coat shop!

siiiiiick

now you have me wanting to blast mine and redo white, c'mon spring

 

[micaddict]

Like a virgin ...

 

[vinylwall]

Some pics of my build.  Alctron HT-11A body, C12 single layer headbasket, MP RK12 capsule, cinemag CM-13114 transformer, ElectroHarmonix 6072A tube, silver teflon wire

 

[vinylwall]

Inside

 

[vinylwall]

tube side

 

[vinylwall]

PSU

 

[lampas]

I just finished the build but instead of PCB version I did P2P in Flea body but with Chunger PSU. Everything is good, but I found that the gain is not the same as with my U87 or TLM103 and I also notice small but audible hum around 50hz. If I turn off PSU the hum stays until mic went off .... I try to connect grid to earth and then hum went away... It's really small hum but I didn't notice it on the Neumanns... Would something with wire cage ? The housing is connected to ground... Tube is GE 6072A ... I try with a few others GE and RCA 6072, but result is the same ... Capsule is MBHO C12 copy ...
Thanx.

 

[lampas]

... and inside ...

 

[lampas]

Ok I found that behavior of the mic I post before is normal... I put it on the car (Faraday shield...) and hum disappear ... It appear that it is a lot more sensitive for background and electrical noise than the Neumanns... Otherwise incredible microphone.

 

[beatnik]

i've almost finished building the mic

i have checked power supply voltages with no load everything seems fine. i also strapped the 180k resistor between B+ and ground and pre-trimmed B+ to 120V as recommended in the build guide

triple checked the wiring between power supply through the 7 pin xlr connectors and everything is good

because i only have tim campbell capsule and nos 6072 tube i want to be 100% sure that everything is good before putting them in the circuit

is there any test i can do without tubes and capsule plugged in ?

 

[Tim Campbell]

If all your voltages are correct put the tube in it but use  a 70-90pf capacitor in place of each capsule half to make sure everything else is OK.

 

[beatnik]

thanks Tim, will do

looking forward to trying your capsule !

 

[mica]

Finally got to test my C12 with Beeskneez capsule yesterday on vocals with some other mics, including my U47 (Beeskneez capsule),  and the results for the C12 are very disappointing. Dark and muffled. Is it the capsule or can something else be wrong: ?

1. C12:
http://soundz.dk/C12.wav

2. U47
http://soundz.dk/U47.wav

3. Manley C-Ref
http://soundz.dk/Manley.wav

4. U87
http://soundz.dk/U87.wav

 

[Tim Campbell]

Check that the capsule isn't collapsed by powering it up without the headbasket on. Make sure you haven't put too large avalue capacitor somewhere.

 

[mica]

Hi Tim. I re-adjusted the voltages and the capsule looks fine:

I dont think i have too large values anywhere.. ?