Official C12 Clone - Build and Support Thread

[chunger]

First thought: Awesome!!!

Second Thought: Is the back plate assembly similar to the original multi part assembly?

The back plate and internal chamber structures are true to the original C12.  The response characteristics should properly reflect the original design.

 

[TLRT]

Last weekend we checked around 30pcs of NOS and EHX 6072 tubes, 1980's GE6072a's, older triple micas, GE12ay7's. In the end I could select only 3 tubes from my friend's NOS collection(all of them are the newer 6072's). I grounded one my modded mics' grid, then we set up a reference gain on the preamp and monitored the noise results in the RME's Totalmix software(spectrum analyser, peak and RMS), it was a very nice experiment,btw the EHX 6072's cryo version won in the end for noise,but it has different sound then the GE6072,I need another mics to build to compare them by ear.

 

[micaddict]

In the end I could select only 3 tubes

Why was that, if I may ask?

 

[TLRT]

Because they were the least noisiest - I could not judge by ear as I still don't have 2 identical mics.

In the end I could select only 3 tubes

Why was that, if I may ask?

 

[trans4funks1]

Thanks for sharing your experience with this. Did you just use a small wire with alligator clips to ground the grid?

It occurs to me that I have frequently read that noise tests should be made after burning the tubes in for an extended period of time. (24 to 72 hours) I wonder if the older tubes would have quieted down after a while?

Have you made a complimentary test to determine if the NOS GEs and the new EH tubes have the same gain?

 

[TLRT]

Thanks for sharing your experience with this. Did you just use a small wire with alligator clips to ground the grid?

It occurs to me that I have frequently read that noise tests should be made after burning the tubes in for an extended period of time. (24 to 72 hours) I wonder if the older tubes would have quieted down after a while?

Have you made a complimentary test to determine if the NOS GEs and the new EH tubes have the same gain?

Yes,I prepared the alligator clip what Matador mentioned. I know that tube need some burn-in time, but I travelled 150km from my home and we had a half day only - I tried to select the least noisiest tubes from the stock.
In May I'll make another tests with Mullard E81CC's and GE6201's, now here are the printscreens of the 6072's(fixed gain during all the measurements):
EHX Cryo:

GE 12AY7:

GE6072 used one- probably burned inThe scale moving automatically in Totalmix, i could not adjusted it to be more sensitive at this measurement)

 

[trans4funks1]

Thanks for posting the screen shots. It is interesting to see the left right imbalance on what would seem to be a mono source. Are both channels getting signal from the mic output or is one channel just the self noise of the I/O device?

In any case, the RMS difference seems to be about 0.1dB.

The question about gain was regarding the mu inherent to each tube in the specific circuit. In other words, if a test tone at some specific level was introduced to each tube's grid would one tube exhibit more gain than some other. Would that effect the Signal to Noise ratio and the practical applicability of the tube?

 

[TLRT]

Thanks for posting the screen shots. It is interesting to see the left right imbalance on what would seem to be a mono source. Are both channels getting signal from the mic output or is one channel just the self noise of the I/O device?

In any case, the RMS difference seems to be about 0.1dB.

The question about gain was regarding the mu inherent to each tube in the specific circuit. In other words, if a test tone at some specific level was introduced to each tube's grid would one tube exhibit more gain than some other. Would that effect the Signal to Noise ratio and the practical applicability of the tube?

No, you have to see the left channel values only as the mic/preamp is mono only There is at least 4-5db difference in RMS  between the tubes. (EHX -74.7, 12AY7 -70.1, old GE -75.3db) As I had half a day only, this was the simliest method what I could find out, the next method would be to substitute the capsule with an approx 80pf cap and injecting  different types of signals with the signal generator.

 

[trans4funks1]

Ah OK, thanks, I see that I misread the meter display. Now I see that it is a dual display showing Peak and RMS simultaneously on the left channel.

It appears that the used 6072 was the quietest of the 3 shown here.

 

[dmp]

Has anybody replaced the 7 pin XLR on the PSU?
I didn't at first, but the stock one is pretty crappy. Touching the mic cable causes the audio to go out.
Anyway, it seems the stock one mounts with a switchcraft layout (like D7F), but has a 7 pin layout like a Neutrik (I don't think they are interchangeable). I don't see a Neutrik that will drop in for the screw holes that are there.

 

[shabtek]

switchcraft inserts can be interchanged

 

[dmp]

Well, I already made a Neutrik cable, so I was hoping to stay with a Neutrik 7 pin.

 

[trans4funks1]

The Neutrik P series is described as being interchangeable with some Switchcraft chassis hole dimensions:

http://www.neutrik.us/en-us/industrial/xlr/p-series/nc7fp-1

 

[Category 5]

The connectors in the stock mic are fragile but perfectly adequate if you clean and solder them carefully.  The plastic that holds the pin will melt under heat if you keep the iron on too long and the pins can shift when this happens.  A good way to keep everything aligned is to connect the cable to the connector while you are working on the pins to hold them in perfect alignment.  Without an adequate rework station I used solder wick to clean mine before re-wiring them which meant I had to keep heat on them a little longer than I'd have liked.  Mine stayed perfect using this trick.

Just got caught up on all of the capsule drama.  Seems these CK12's are indeed difficult to do right.  The one I had that was muffled on the back went back to Tim with another and he sent them back to me as matched.  Both of the matched capsules sound better to me than the one that didn't go back, but all three sound excellent.  Even the matched pair doesn't match exactly, but both sound beautiful to me.  I didn't try flipping either around, they are installed with the backplate screws to the right on both.  I did notice after soldering the backplate wires to teh capsule that the tabs moved freely and were a hair loose so I gently screwed the screws back down to make good contact.  I did not notice this on my first capsule so perhaps this contributed to the issue I had.

I had thought the stock capsules were sounding good before Tim's were installed, but now I can't even listen to those samples.  These are the capsules that belong in these mics.  Here are samples of the two capsules.  This is the "matched" pair Tim sent me.  The tubes are 1954 GE triple Mica and were matched for transconductance and are two of the best samples I have listened to.  I acn not say enough good stuff about the older GE's.  Ignore the crudity of the recording. These samples are simply from a function test after installing the new capsules.  The fan noise is my PC server tower about 6 feet from the mic.  Sorry about singing a little flatter in the first sample.  Did I mention it was late?  lol  Preamp was the stock PGA2500 based pre in my UA Apollo.  Gain set about 49 dB.  Both mics output similar level.  After installing the new capsules figure 8 mode produces a "normal" signal on both mics, front and back diaphragm.

They sound a little bit different still.  I am guessing it's impossible to get a perfect match with all for the variables in the manufacture of these capsules.  That said, both sound super to me and I can't decide which I like best.

https://soundcloud.com/shane-bushman/newcaps-triode-2-revolution

https://soundcloud.com/shane-bushman/newcaps-triode-1-revolution

One mic uses triode 1 and the other triode 2 as you can guess from the filenames.

https://soundcloud.com/stream

 

[Melodeath00]

Category, did you just send the capsules back to Tim, or did you confirm with him first that he could look at them?

I emailed Tim about a slight retuning, and while he replied asking why I wished for a retune, ultimately I never heard back when I told him why. I didn't feel comfortable sending in my capsule without direct confirmation from him that he would address my issue, and I also had no idea how much time it would take, which was a concern.

So, did you just send it in, or did he give you info on sending it in? How long did it take to get the capsules back?

Thanks

 

[Category 5]

Yeah.  I sent mine in at his request.  I think one was actually defective.  In short i think that we have to expect slight variances in these capsules.  Heck the originals were like that too.  All three of mine sound superb but each has is own personality.  It's kind of like a premium piece of wood or granite.  Each piece looks the same as a whole but the grain and structure varies.  That's the best analogy I can come up with.  I still think I could get great stereo recordings from my pair but they are definitely different.  That said I love both and with time getting to know the nuances of each I could use that to my advantage.  Also I think finding perfectly matched tubes is impossible as well so on light of that I think my pair matches pretty well. 

 

[dmp]

The Neutrik P series is described as being interchangeable with some Switchcraft chassis hole dimensions:

Thanks - those look like they will fit.

 

[Tim Campbell]

Melodeath, since I can't guess your name I can't be sure exactly about the scenario with your capsule.  I get a gazillion emails so sometimes it's hard to remember all of them.
Anyone is welcome to send a capsule of mine to me for adjustment. This has always been my policy.
I must have just assumed you'd send them .
I have gladly made capsules brighter simply because an owner compared them to a TLM103, never having heard a CK12, but was sure that since a CK12 is a bright capsule it should sound as bright as his TLM103.

 

[Biasrocks]

I have gladly made capsules brighter simply because an owner compared them to a TLM103, never having heard a CK12, but was sure that since a CK12 is a bright capsule it should sound as bright as his TLM103.

My god, what a shame!

I would not call a C12 bright.

I would say, as at least one other person has pointed out on this thread, that it's a fairly neutral sounding microphone that takes EQ or any additional processing really, really well.

If you've ever been in "TLM-HELL" you'll know that no amount of EQ, Compression or De-essing can make those microphones sound good.

My pair of microphones sound superb, with a lot of the heavy lifting being done by your superb capsules.

Thank you again Tim.

Mark
Sharktankpro.com

 

[Tim Campbell]

Well I'm sorry my capsules have  been so unavailable in the last few months. During that time I've aquired some new CNC equipment and changed some of the mechanical assembly of my capsule in order to make my parts interchangeable with AKG's.
I do a lot of repair work on original capsules and so it's advantageous to have my parts interchangeable with theirs.
More capsules should begin being available for DIYers. The price is still 2000 danish kroner ( around 370 dollars) and I have a cadiod only version available for 1500 danish kroner (around 290 dollars).