[FEELER] C12 Clone Project

[0dbfs]

Headbaskets have incurred delays. . . well, figure it couldn't all be smooth sailing.  They like their holidays over in China.  Feb. 19 is the new ETA for samples.

PCB's and parts kits should be online pretty soon.

Chinese New Year! Hooray!

Cheers,
jb

 

[chunger]

OK. . . most electronic components are in-hand for 50 C12 kits and 10 psu only kits.  Just a couple little details to wrap up like a knob for the pattern switch and the isolating pads for the LM317 heatsink.

I'm also trying to figure out which output capacitor to include in the kit. . . internet hearsay abounds in this department and I don't believe any production microphone company including AKG used esoteric/expensive parts for their mics. . . well, at the time anyways.  They may have become esoteric and expensive over time.  We have opened up a lot more possibilities than the standard HT-11A mod, but are still constrained to ~16mm diameter with perhaps a hair of wiggle room.

I don't really buy into the hype of magic capacitors so my inclination is to use a reasonably priced good-quality polypropylene cap in this position close to the .5uF original value and am leaning towards the .56uF 630V Erse, but in the interest of being thorough, I have purchased the following capacitors between .5 and 1.5uF to test:

Erse .56uf 630V
Erse 1uf 630V
Erse 1.5uf 400V
Solen .56uf 630V
Solen 1uF 630V
Mundorf M-CAP MKP .56uF 630V
Mundorf M-CAP MKP 1uF 400V
Mundorf Mcap ZN KP Tinfoil .68uF 250V
Sonicap Gen 1 1uF 200V
Sonicap Gen II .68uF 600V
Sonicap Gen II .82uF 600V

and, the only new production oil-ish type cap that I have found fits even thought the cost is a bit on the silly side.
V-Cap OIMP 1uF 250V

Again, the test mic we have up and running is using a JustRadios.com .5uF polyester cap, and it sounds fantastic so far.  I'm fairly certain a reasonably priced high quality polypropylene should also sound great and the Erse caps are known to work in Apex 460 mods, but those mods had a very narrow set of caps to try because they were space constrained to about 13mm diameter.  Reading forum postings by folks like Klaus, I gather caps with the same material/construction can sound quite different in microphones when using different voltage types. .  and well, he was not very forthcoming with specifics as to which specific caps he recommends (industry secrets kept to retain market edge) so I decided to pretty much carpet bomb the thing and try a big pile of viable options and determine for myself if something really special emerges. .  . or, to know for certain with my own ears that my original idea is on the right track and there is not that much difference.

The only way to know for sure is to put them side by side on the same source in the same recording environment and get audio data.  I will also need to rig something up to run signal through the test capacitors to settle them a bit prior to testing.

 

[micaddict]

Some fragments here from Jim Jacobsen's comments regarding the innards of the JJ Audio Dutch. That's a C12-like circuit in a gutted Apex with modified headbasket. The microphone has an open sound but with some real character, too, to my ears.

The following is just for some possible component inspiration and FWIW. Ignore if need be.

Campbell CT12 capsule
Tab Fukenwerk T14
C12 circuit
GE NOS tube
Phillips and Mundorf film capacitors
Nichicon and Elna electrolytics
Modded headbasket
Rebuilt power supply

I also have a paper in oil option for this mic. I have found some vintage capacitors similar in construction to the Siemens capacitors in the C12.
That option is for a .5uf/1uf vintage MP capacitor and PIO for all of the film caps.

C12 circuit
6072a tube GE
Tim Campbell's CT12 capsule
Tab T14 transformer
Mundorf capacitor
Custom power supply
Teflon / Silver wire
Headbasket mod
Takman audio resistors

I am always trying to improve the mic. I use Axon, Mundorf and PIO (paper in oil) capacitors. I am currently testing some MP Russion an German capacitors that are from the early 50's that will give a more vintage tone than the modern film caps.

I use vintage Phillips or Russian PIO.

The poly caps will work well on decoupling.

The larger the cap the more bass can be had out of the circuit. Also the larger the capacitor the slower it reacts to HF and transients.

The workmanship on Tim's capsules are amazing. His customer service is outstanding. The detail that is captured by these capsules are second to none. ... These are authentic reproductions of the CK12. The fact that he has the original Gold Mylar shows the length that he goes to, to attain the best sound. I have had them side by side with real CK12 capsules and the frequency response and tone were very close. They were as close as two AKG capsules would be o each other. The consistency of the original AKG builds on the CK12 varied daily. So no two capsules would sound exactly alike.
These are the best of the best for the ultimate build.

The Cinemag is a good sounding transformer that is clean and transparent.

Tab Funkenwerk T14 is my favorite for these builds. This transformer has the most character and warmth. I like it with the Plate Follower circuit because it can be driven harder than in a Cathode Follower. This is a copy of the Hiller transformer that was in the early C12 mics.

We already knew about the goodness of Tim's capsule and Oliver's tranny, but hey, a little confirmation never hurts. 

(In general

The components I use in my microphones are some of the best available. All of the electrolytic capacitors are high grade Nichicon, Elna, and Rubycon. The film capacitors i use are high quality Wima, Phillips mustard caps, Paper in oil capacitors, Seimans (Siemens? -micaddict-) Elco and many other brands. I use the polystyrene and Silver Mica in critical locations.

There's much more, but to keep things in perspective, I'll stop here.

There's just so much to choose from. And as always, there's the dilemma between modern, high quality parts (or microphones for that matter) and vintage ones. The first might be unbeatable on paper and lack the possible problems like worse reliability, leakage, size, poor availability and possibly higher cost etc. But on the other hand, when using too many modern components at critical places the end result could be too sterile sounding, lacking the original vibe one tries to capture.

 

[mwrichardson]

Hi Chunger

Can you tell me what capsule you are using to test the prototype mic?  Any idea when PCB's might be available?  Thanks

 

[chunger]

Hi Chunger

Can you tell me what capsule you are using to test the prototype mic?  Any idea when PCB's might be available?  Thanks

Test prototypes to date are using Tim Campbell's CT12 capsule built to his "stock" specification.  200 PCB's will be arriving this week.  Matador will construct one more test microphone to confirm function and performance of the final revisions PCB.  We are ~99.52% confident it will work just fine.  Once function is verified, the boards will be updated to my webstore and posted in the white market for immediate distribution.  Complete electronic parts kits will be available shortly after as well as T14 transformers.  Donor bodies are currently available and custom headbaskets will likely become available mid-march at the earliest.  Removal of the inner 2 mesh layers on the Alctron HT-11A or Apex 460 donor microphones is very straight forward and in our testing, completely functional.

The test microphones built on the 1st and 2nd revision pcb's are running without any issues whatsoever in production environment, so we are confident these kits are on the right track!

 

[buildafriend]

So are the PCB's first come first serve or are there reservations? Count me in for 1 maybe 2.

 

[chunger]

So are the PCB's first come first serve or are there reservations? Count me in for 1 maybe 2.

We will not run out of pcb's. . . there's no way we'll sell through 200 units anytime soon and if we do, it's only a 9 day turn-around for new batch.  I'm just going to post them up on the webstore.  The boards have landed.  Now, I'm just waiting for one more prototype build from Matador to confirm there are no problems and we'll make them available for purchase.

 

[chunger]

OK. . . the good news from the Motherland is we have headbasket prototypes!!! These are officially not vaporware anymore.  The bad news is the tooling cost was about 2.5x the original quoted price    Well, done is done.  From the pictures the factory provided, this looks on target.  I will need to get hands-on to confirm.

Here is the single layer C12 variant

And the 2 layer Ela M251 variant

If there is a complaint on my end, it would seem the headbasket feels a little bit on the high side.  I did tweak the dimensions a few iterations before settling in on the final sizing so I need to confirm that the factory used my latest revision drawing to generate their tooling, but it does appear to be correct to my specification.  Because the HT-11A body tube is wider and shorter than the original C12 tube, it's a compromise fudging the headbasket proportions.  From the pictures that I squinted at continuously while doing the design, it seemed the C12 placed the capsule low in the headbasket which is why I favored taller on the headbasket in the end.

For the 2 layer Ela M251 configuration, it seems my meshing at least on the outermost layer may need to be tighter than the current 12x12 material.

CAn someone confirm 14x14 .020" diameter outer layer mesh configuration for the Ela M251?  I think that's where this is headed.  Also, I have no clue as to the inner mesh specification.  Internet data to date is chirping birds.

 

[HellfireStudios]

It looks killer to me. Is there an estimated price for headbaskets yet? I just want to know how much money to allot for the near future.
Also, will there be any indicator for the front of the mic (like the cardioid symbol on the original Apex headbasket)? Thanks.

-James-

 

[mwrichardson]

Hi. I would say you are close to the right capsule position. Look at the images on the Flea site ..The images in the gallery with the whole mic for sale web page show the capsule low in the basket and the images in the C12 kit web page show the reason why.  The C12 capsule is suspended from the top which places it low in the basket.  Also the Saturn Sound pics seem to show the Flea capsule mounting system looks like the original one. There is another good image at funkyjunk.it which shows the capsule mount. If these are accurate reproductions of a C12 , there is a vertical metal strap/post that holds the capsule mount up in the basket. Wonder what that does to reflections in the basket? Maybe ask Tim Campbell as he seems to have several of them.  Basket looks great!!

 

[Melodeath00]

Hi. I would say you are close to the right capsule position. Look at the images on the Flea site ..The images in the gallery with the whole mic for sale web page show the capsule low in the basket and the images in the C12 kit web page show the reason why.  The C12 capsule is suspended from the top which places it low in the basket.  Also the Saturn Sound pics seem to show the Flea capsule mounting system looks like the original one. There is another good image at funkyjunk.it which shows the capsule mount. If these are accurate reproductions of a C12 , there is a vertical metal strap/post that holds the capsule mount up in the basket. Wonder what that does to reflections in the basket? Maybe ask Tim Campbell as he seems to have several of them.  Basket looks great!!

The mount covers a small portion of the back of the capsule. This has an effect on the high end and response in certain polar patterns. To quote Klause: "Capsule mount on C12 interferes with direct signal path to the diaphragm on rear access (especially of concern in omni and figure eight) altering the acoustics inside the head basket"

I thought I saw a post online somewhere with more details about the c12 mount. I thought Oliver made a post that included exactly how much of the capsule is obscured by the mount, but I can't seem to find it.

C12 capsule position looks pretty good, although it's not the traditional C12 mounting system with the "hugging" felt bar.

Another thing is that the C12 "pedestal" in the headbasket is flat, whereas the 251 pedestal is angled. The angle is meant to break up high frequencies.

 

[lolo-m]

Chunger,
You're killing me  ... I'm already in for a C12 headbasket + PCB... but now I would like to add an ELA-M251 donor microphone + PCB+ headbasket + Tim's C12 caps or a full kit depending on price...
Please stop, my wallet is empty  ;D !!!

 

[Winetree]

Upper capsule mount Like this

 

[micaddict]

For this project's purchases I decided to start with the heart.

And it arrived yesterday. 

Thanks Tim!



Henk

 

[Scrappersa]

I would love to get three headbaskets if possible. They're beautiful.

 

[Volume11]

For this project's purchases I decided to start with the heart.

And it arrived yesterday. 

Thanks Tim!



Henk

What was the turn around time for this capsule?

 

[micaddict]

What was the turn around time for this capsule?

About three months.

 

[chunger]

A bit more hacking on my end. . . it's a little behind in terms of the overall development of this project, but I've grown quite fond of my little frankenstein hack-job prototype built on the Rev. 1 pcb, so I figure I should finish it.  This will be a nice test platform to hear oil-type capacitors in this circuit.

The V-Cap OIMP is the only current production oil-ish cap that I found to fit our physical layout . . . but, it needs the cutout to clear the tube. . . so I use some tape and a pen to mark my cut on the pcb.

Cutoff wheel on the dremel seems as good a plan as any. . .

Poof!  Humans Win.

And on a more relevant note, I now have final revision PCB's in hand and ready to ship. . . just waiting for final confirmation from Matador that the latest revision board runs before releasing.

 

[manulaudic]

Yellow is the final word !

Nice !
I'm taking one

 

[kevinkace]

Looks great, I'll be in for 1, maybe 2.

Why are there 3 tube mount PCBs?