Official C12 Clone - Build and Support Thread

[jrmintz]

I think I answered my own question:

http://vintagemicrophone.com/JShop/product.php?xProd=18&jssCart=60c6cb4ac8b0e8a4ae959b9a4bbb4564

Will an Apex 460 fit in a C12-sized box?

 

[HellfireStudios]

You can find Telefunken R-F-T style boxes on ebay for a decent price. The ones with the red and yellow velvet are the ones that should fit the Apex 460.

-James-

 

[pmcorbett]

Just got my kit and I'm looking forward to building the mic. I'll be using a CEK-12 capsule and a cinemag 2480 transformer... are there different functioning parameters (metering, voltages...etc) I should be aware of when testing and tuning the mic? Let me know when you can. Thanks!

 

[ruairioflaherty]

... are there different functioning parameters (metering, voltages...etc) I should be aware of when testing and tuning the mic? Let me know when you can. Thanks!

This whole thread is dedicated to those questions - read it in it's entirety before you start to gain an understanding of what's involved.

 

[tonycamp]

been using this mic, getting to know her at bit, It's clearly getting better as she's breaking in, and her bottom is surprisingly large! My kind woman! still much learn Kemosahbee

 

[jrmintz]

Matador, in the 251 variant would the 20uF cathode bypass cap have been a Tantalum electrolytic in the original?

 

[strangeandbouncy]

Hi,



    pretty sure it was an electrolytic . . . . anyone?


  Not sure what would be gained by using a Tant here(?)



    ANdyP

 

[Matador]

I honestly don't know.  The size of the cap puts the gain step way down near DC anyways (like 4Hz):  I can't imagine the cap type would make that much of a difference.

 

[jrmintz]

Thanks gents. Matador, the board design is elegant, easy to build. I love the plated through-holes.

 

[drumminkiger]

Well, I pulled the trigger today and bought all the remaining kit components to make my c12 clones after sitting on my mic bodies and tim's capsules for about 6 months now. The only thing I have left to buy is the tubes. I emailed Christian at pro audio tubes, and he recommended two tubes to me. One of them is a vintage GE and the other is a vintage mullard. He said the GE seems to be the choice tube for most folks, but he said the mullard had a more defined mid prescense and is also about half the price. I'm just curious if anyone has tried the mullard, I'm even somewhat curious if it kinda tilts the mic more towards a 251 response. It might be kinda cool, what do you guys think? Anyone tried it?

 

[tonycamp]

Well, I pulled the trigger today and bought all the remaining kit components to make my c12 clones after sitting on my mic bodies and tim's capsules for about 6 months now. The only thing I have left to buy is the tubes. I emailed Christian at pro audio tubes, and he recommended two tubes to me. One of them is a vintage GE and the other is a vintage mullard. He said the GE seems to be the choice tube for most folks, but he said the mullard had a more defined mid prescense and is also about half the price. I'm just curious if anyone has tried the mullard, I'm even somewhat curious if it kinda tilts the mic more towards a 251 response. It might be kinda cool, what do you guys think? Anyone tried it?

I put a nos mullard in my K2, sounds smoother than the stock tube in that mic, so?? You're building a pair  right?, are your campbell capsules a matched pair? if so, wouldn't you want a couple tubes that are identical? just curious.

 

[drumminkiger]

Yes, I would be buying a matched pair of tubes, so one kind or the other.

 

[tonycamp]

Yes, I would be buying a matched pair of tubes, so one kind or the other.

Gotchya, i got the 6072 $100+ ge from christian, it keeps sounding better and better, this mic is real impressive. As a matter of fact, i can't believe how great the matachung c12 and the ioaudio Mk47 sound! Both these mics are quite literally a dream come true for me ;D

 

[baadc0de]

hi matador, i have the dale 100k resistor there

i have ddm oscilloscope and sine wave gen

Ok, let's try this:  disconnect the capsule lead connected to FB (the one that leads to C13).  Inject a ground-referenced 1V peak-to-peak sine wave into this node (right at the teflon standoff labeled "FB").  Then read the peak-to-peak voltage coming out of the XLR jack that goes to your preamp.

You should be about 5-6dB of gain through the entire chain to the output jack.  If the signal is way low, move the injection point right to the tube grid (pin2 or pin7 depending on which half of the tube you picked).

Let's start there and we'll debug from there.

I did this, and unfortunately the amp is alright, working as it should, identically between the bad and good mic. So... that means the capsule, right? Darn...

 

[Tim Campbell]

Disconnect the mic from audio, remove the headbasket and turn on the mic while looking at the membrane. Is it collapsing? Try the mic with the original capsule. If the problem disappears then it is the capsule. I have never heard of this problem with one of my capsules but there's always a first time.

 

[baadc0de]

Disconnect the mic from audio, remove the headbasket and turn on the mic while looking at the membrane. Is it collapsing? Try the mic with the original capsule. If the problem disappears then it is the capsule. I have never heard of this problem with one of my capsules but there's always a first time.

It's not one of yours, Tim. But thank you for the tips nevertheless..

 

[jrmintz]

Matador, is there any reason I can't mount the board to the underside of the rails rather than the top? I'm using a fatter output cap and I might need more room for clearance. I was thinking about mounting in the center of the rails using nuts as standoffs.

Thanks

 

[drumminkiger]

Gotchya, i got the 6072 $100+ ge from christian, it keeps sounding better and better, this mic is real impressive. As a matter of fact, i can't believe how great the matachung c12 and the ioaudio Mk47 sound! Both these mics are quite literally a dream come true for me ;D

Oh yeah, I hear ya there, I think an MK47 is going to be my next project after these bad boys. I don't have a super solid all around type condenser yet so I figured I would build a pair of c12's so I have something good to kinda stand in that role first and then branch out. I don't doubt that the GE is worth every penny, and I'm sure I'll end up with a pair at some point, but I guess I'm kinda curious because of how christian described the mullards having a little more 47ish mid presence. Will that might give me a little more of a 251 style mic? That might be kinda cool.

 

[chunger]

Be aware that the 12AT7 will shift some of your voltages and you may need to adjust a few values to optimize the PSU and audio circuit.  Details have been discussed earlier in this thread.

 

[Matador]

Matador, is there any reason I can't mount the board to the underside of the rails rather than the top? I'm using a fatter output cap and I might need more room for clearance. I was thinking about mounting in the center of the rails using nuts as standoffs.

Thanks

It was mounted to the top to give clearance for the tube:  if you can fit in the tube and the output cap, then really any arrangement is fine.