Official C12 Clone - Build and Support Thread

[aaquilato]

So was I. My friend could be mistaken. I hate to spread rumors.

 

[Biasrocks]

Hello All,

Having an issue with one of my two C12 clones which worked flawlessly for years.

One has anemic output, the other is normal.

Powered both up on the same power supply, cable.

Swapped tubes with no change, the problem did not follow the tube.

I would like to isolate the circuit from the capsule for testing. Is there any easy way to inject a test tone to measure the circuit to see if I can find the problem.

 

[Matador]

Is there any easy way to inject a test tone to measure the circuit to see if I can find the problem.

Inject an AC test signal right into the grid of the tube through a 50pF capacitor. You can disconnect the capsule as well. Depending on the tube, you should see around 6dB of gain from the grid of the tube to the output (2 to 3) on the output XLR.

 

[Tim Campbell]

Hello All,

Having an issue with one of my two C12 clones which worked flawlessly for years.

One has anemic output, the other is normal.

Powered both up on the same power supply, cable.

Swapped tubes with no change, the problem did not follow the tube.

I would like to isolate the circuit from the capsule for testing. Is there any easy way to inject a test tone to measure the circuit to see if I can find the problem.

Check that the connections to the capsule are tight and check that the capsule is not collapsing.

 

[johnsonic]

You can find a step-by-step testing I did while trying to troubleshoot a 251 I had built - starts here: ELA M251 Inspired Microphone - Build Thread

 

[Biasrocks]

Inject an AC test signal right into the grid of the tube through a 50pF capacitor. You can disconnect the capsule as well. Depending on the tube, you should see around 6dB of gain from the grid of the tube to the output (2 to 3) on the output XLR.

Great, I will give this a try. I wanted to test the circuit separately from the capsule before I went there

 

[Biasrocks]

Check that the connections to the capsule are tight and check that the capsule is not collapsing.

Will do Tim, both capsules are your great work and have sounded great aside from this issue

 

[Biasrocks]

You can find a step-by-step testing I did while trying to troubleshoot a 251 I had built - starts here: ELA M251 Inspired Microphone - Build Thread

Awesome, will have a look

 

[JeffKall]

I had #84, I believe it was, that I bought new. Sold it back in 2015 along with most all my gear.

Excellent mic all-around! However, no good at all for acoustic guitar in my experience. There, it’s way too dull!

If you can buy a pair for a fair-price, I wouldn’t hesitate. I haven’t heard anything about a supposed “safety-circuit” problem, but I never looked at the power supply. I know the CS1 is self-biased and use a single transistor buffer in its supply.

The capsule is a custom CK12-type, MBHO-manufactured and spec’d by David Bock of Bock Microphones. I’d find out for sure if the pair you’re considering are original capsules or Tim’s capsules… I wouldn’t hesitant with either, but I’d want to know for sure either way.

Lucas LMG-95-ES tube (made by Mullard), and labeled as such. AMI has replacements. Both sides are ran in parallel. There are arguments on whether other 9-pin tubes will work good-enough.

Super tiny, AMI T-1 transformer.

Dennis at AMI is super helpful and responsive. Don’t hesitate to ask him for any help!

I have a pair of CS-1 -inspired mics, made for me by Chris at Barbaric Amplification, with original tubes (bought from AMI when I still had the CS-1) and transformers (bought from AMI in 2020).

I just finished building my pair of Chunger Matador C12’s … with AMI T-14, NOS 6072a and MAIKU K-12 capsules (sorry, Tim … I can’t afford yours … YET … but as you have stated here previously, I can always upgrade!)

Anyway … this past Tuesday … I finally got around to doing a test session with them … and chose acoustic guitar as my maiden source …

The guitar was recorded flat in stereo about 10” from where the neck joins the body …

My fretless bass is custom built with a Warmoth neck … it was recorded direct with a SansAmp Bass DI … and a “touch” of Fairchild 660 to even out the notes … but no EQ …

The only processing is a touch of reverb and mix bus internet compression …

Kudos to Chunger and Matador for an AMAZING product !!! Thank you !!!

Jeff

https://www.dropbox.com/s/gyjx56eh64atqqk/DanC12ClonesMixA.wav?dl=0

 

[DuBmastah]

Hey there

I have a question regarding the trimmer pots on the PSU.
On the PCB values are indicated for the 3 of them :
- R2 (heater adjust) = 2K
- R3 (Bias adjust) = 5K
- R4 (B+ adjust) = 100K
But, in the bag, i had 2x5K and 1x100K, no 2K trimmer pot at all.
Am i correct to think i should then put 5K at R2 instead of the pcb claimed 2K, or will i just burn everything down ?
Sorry for the newb question...

 

[TillM]

Just use the 5k for the 2k trimmer.

 

[DuBmastah]

Ok, thx, i will try that.

 

[DuBmastah]

Hello
I didn't manage to find a step by step building guide for the 2021 (V1.4A) revision of the Matador (microphone) PCB.
This board has quite a few differences from the one presented at first page in this topic.
I feel well confortable with soldering things, but when it comes to understand schematics it's another story and i could struggle quite a lot trying to figure how this thing should be put together without an updated guide to help :-/
Maybe this issue has been debated elsewhere beetween the 145 pages of this topic, but it would be a real live savior if someone could point me to the right direction ?
Many thanks in advance.

 

[DT_Music]

After letting it sit while for months while I've been sidetracked by project after project, I finally finished my C12!!! It's got an Advanced Audio AK-12 (although I'd love to put in a CT12 if Mr. Campbell ever offers them again) and it currently has a cheap JJ test tube in it but I got a NOS Mullard from Christian Whitmore that I'll put in this week. Even as it is it sounds amazing!

My only concern is that I can't quite get the bias down to -1v. The lowest I can get it is around -1.34. Is this ok or will it be a problem? I'm using a 12at7 so I don't know if that changes anything where the bias is concerned. The B+ is right where it should be at 120.
EDIT: I got it sorted, just a dumb user error.

@DuBmastah I agree about getting a better guide for v 1.4 (or at least moving it to page 1). There are some pretty good pics of Chunger's prototype v1.4 build on page 93.

Thanks @chunger and @Matador for providing such an amazing DIY product and all the help putting it together!

 

[C12VR]

After letting it sit while for months while I've been sidetracked by project after project, I finally finished my C12!!! It's got an Advanced Audio AK-12 (although I'd love to put in a CT12 if Mr. Campbell ever offers them again) and it currently has a cheap JJ test tube in it but I got a NOS Mullard from Christian Whitmore that I'll put in this week. Even as it is it sounds amazing!

My only concern is that I can't quite get the bias down to -1v. The lowest I can get it is around -1.34. Is this ok or will it be a problem? I'm using a 12at7 so I don't know if that changes anything where the bias is concerned. The B+ is right where it should be at 120.

@DuBmastah I agree about getting a better guide for v 1.4 (or at least moving it to page 1). There are some pretty good pics of Chunger's prototype v1.4 build on page 93.

Thanks @chunger and @Matador for providing such an amazing DIY product and all the help putting it together!

The bias point was chosen because it was the best for the 12ay7, not a 12at7. Will it work? Yes. Is it optimal? Maybe not. They are two different tubes. I say spring for a 12ay7.
That being said, good CK12 capsules are available for about 400-550 USD from MBHO (canford carries the KA1000) and OPR.

 

[Delta Sigma]

The bias point was chosen because it was the best for the 12ay7, not a 12at7. Will it work? Yes. Is it optimal? Maybe not. They are two different tubes. I say spring for a 12ay7.
That being said, good CK12 capsules are available for about 400-550 USD from MBHO (canford carries the KA1000) and OPR.

And Beesneez

 

[11Schotter]

Just finished 2 builds - one C12 and one 251 both with @Matador PCB and they work just fine! Great layout and information in this thread. Thanks a ton for that.

I have some questions to maybe improve the builds further:

1. I used an AMI transformer for the C12 and a Haufe Telefunken T14/1 for the 251. The AMI measures ~1,4kohm to 32ohm; while the Haufe measure ~3kohm to 64ohm. Does this affect the circuit in terms of sound in a relevant way to try to swap both to check for the best combination?

2. The 251 noise floor seems to be a tiny bit higher or it least in a higher frequency. I swapped around tubes without improvement. Is to be expected? The biggest difference is otherwise the capsule - a Haun MBHO for the C12 and a OPR for the 251. Both capsules are tuned to 115V following an advice from Mr @Tim Campbell in another thread to improve capsule lifetime.

 

[mrgrooves666]

Higher noise floor in high frecuency in 251 also was my experience with mine, both with Tim's excellent capsules. I also swapped tube in that one and still the same. Nothing to worry about though. I guess its normal?

 

[johnsonic]

I wasn't getting the output I expected from the 251, had to use more gain on preamp = more noise. Even built it twice after tracing the circuit just to be sure it wasn't me! How does your gain look?

 

[Roxxy]

Hello,

I’d like to build one or maybe two c12 clones with Matador’s PCB. Does anyone know a good source for c12 body kits? It seems they are quite hard to get these days. Sure I would also like Tim’s CT12. However it seems really impossible to get one:-/

I live in Europe, but don’t bother importing from somewhere. Thanks!