Official C12 Clone - Build and Support Thread

[micaddict]

Is it fit a MXL V67I body? I'm asking that because they are really similar of the AKG C12 (gold headbasket and mesh, green body). Just a matter of look hahaha. Awesome work by the way

The original C12s (the early ones anyway) were gray or silverish with a polished nickel ("chrome") headbasket:

The C12VR ("vintage re-issue", albeit with a totally different circuit) is a bluish green with a gold plated grill:

The MXL V76i does copy the colors of the latter, though not the shape:

http://www.realmusic.ua/images/catalog/products/12833563157893img1_big.jpg

The colors on the T-Bone SCT800 are even more complementary (blue/gold). This is the actual Alctron HST11A (Apex 460) body I think, so the PCB should fit perfectly. Unfortunately the PSU is cardioid only:

http://www.thomann.de/gb/the_tbone_sct800_tube_mic.htm

 

[Matador]

Hi mate, where is it grounded? There doesn't appear to be a trace from pin 9 on my board to ground. Theres no continuity unless it bridge it myself.

The plated through hole itself attaches to the ground plane on the tube board via a thermal relief (which are just small traces around the circumference of the pin to the plane).  If you look closely you should see them.  I can upload a zoomed in shot of that area of the PCB if you are interested.

The lack of continuity is puzzling.  Ground is provided to the main PCB via two methods:  the first is the ground wire in the XLR socket, which attaches down at the bottom of the main PCB via the "P6" node.  Additionally, the shield of the cable is shorted to the brass body right at the 7-pin jack, which them transmits ground to the mike PCB via the PCB screws directly in to the body.  This ensures that the body is a solid ground at multiple places.

Ground moves over to the tube PCB via the two outside pads that hold the tube PCB in place.  The heater voltage appears via the middle one.  Pin 9 should show 0 ohms between itself (right at the tube socket), and any ground connection on the board or even the mike body itself.  If not, I would revisit the tube pcb and socket soldering and check it.

 

[JessJackson]

Hi mate, where is it grounded? There doesn't appear to be a trace from pin 9 on my board to ground. Theres no continuity unless it bridge it myself.

The plated through hole itself attaches to the ground plane on the tube board via a thermal relief (which are just small traces around the circumference of the pin to the plane).  If you look closely you should see them.  I can upload a zoomed in shot of that area of the PCB if you are interested.

The lack of continuity is puzzling.  Ground is provided to the main PCB via two methods:  the first is the ground wire in the XLR socket, which attaches down at the bottom of the main PCB via the "P6" node.  Additionally, the shield of the cable is shorted to the brass body right at the 7-pin jack, which them transmits ground to the mike PCB via the PCB screws directly in to the body.  This ensures that the body is a solid ground at multiple places.

Ground moves over to the tube PCB via the two outside pads that hold the tube PCB in place.  The heater voltage appears via the middle one.  Pin 9 should show 0 ohms between itself (right at the tube socket), and any ground connection on the board or even the mike body itself.  If not, I would revisit the tube pcb and socket soldering and check it.

Thanks mat,

I think i see the tiny trace on the underside of the tube board but not on the top side. In my build i only soldered the top side of ground plane (outer pads) i left the bottom side un-soldered, this is probably the issue or did you also provide a trace from pin9 to pad on the top side also?

Cheers

 

[Matador]

Thanks mat,

I think i see the tiny trace on the underside of the tube board but not on the top side. In my build i only soldered the top side of ground plane (outer pads) i left the bottom side un-soldered, this is probably the issue or did you also provide a trace from pin9 to pad on the top side also?

Cheers

Ahh yes, this is the issue, good catch!  The "top" pads (or the pads that are on the opposite side as the tube and socket) are there only for mechanical attachment.  The plane on the top of the board is only to make the soldermask color more consistent and there are no thermal reliefs or ground traces on the top side either.  There has to be a solder connection to the "bottom" pads in order to complete the ground circuit (like you can see in Chunger's build guide, as he actually always solders both sides):

I will add a pour and second thermal relief to the next run of boards as a safety measure.  I had assumed that people would always solder both sides but never explicitly called it out.

 

[JessJackson]

Thanks mat,

I think i see the tiny trace on the underside of the tube board but not on the top side. In my build i only soldered the top side of ground plane (outer pads) i left the bottom side un-soldered, this is probably the issue or did you also provide a trace from pin9 to pad on the top side also?

Cheers

Ahh yes, this is the issue, good catch!  The "top" pads (or the pads that are on the opposite side as the tube and socket) are there only for mechanical attachment.  The plane on the top of the board is only to make the soldermask color more consistent and there are no thermal reliefs or ground traces on the top side either.  There has to be a solder connection to the "bottom" pads in order to complete the ground circuit (like you can see in Chunger's build guide, as he actually always solders both sides):

I will add a pour and second thermal relief to the next run of boards as a safety measure.  I had assumed that people would always solder both sides but never explicitly called it out.

Your right thats the issue, cheers mate… do the 45 degree angled struts pass ground because I have one of those soldered through to the underside of the tube board?

Any knowledge on the different ratings of left and right sides of the tube?

J

 

[chipss36]

it indeed does ground there, take a meter to one of your extra tube pcbs....and check it out , its where i thought he was running ground, didn't  meter the back side of the PCB, 4 different areas that  run to ground....

 

[Pip]

On matador circuit you have pin 4 or 5 (whatever side of the tube you are using) connected to heater with the additional pin left floating. While Pin 9 is also left floating. Is this something you consciously decided to implement?

I'm not sure where this is coming from:  on my build, pin 9 is grounded, and is not left floating.  You can attach either pin 4 or pin 5 (or both!) to the heater supply to light up each half of the tube (or both!).  Whatever side (pin 4 or pin 5) is left floating will definitely not be heated.

Think of the heater as two resistors, which happen to share a common node (pin 9).  So long as you put 6.3V across either pin4 and pin 9 or pin5 and pin 9, each half will light up (respectively).

If you declare pin9 as ground, then 6.3V on pin 4 or pin 5 will light each half.
If you declare pin9 as 6.3V, then you must ground pin 4 or pin 5 to light each half.

Hi mate, where is it grounded? There doesn't appear to be a trace from pin 9 on my board to ground. Theres no continuity unless it bridge it myself.

cheers

J

Yes I did not mean to imply that Matadors schematic or PCB was wrong quite the opposite. What does intrigue me is why the original design shows the other half of the tubes pins referenced to ground? Yes also it does not matter one bit how you get the 6.3 volts into the heaters.

 

[Matador]

Yes I did not mean to imply that Matadors schematic or PCB was wrong quite the opposite. What does intrigue me is why the original design shows the other half of the tubes pins referenced to ground? Yes also it does not matter one bit how you get the 6.3 volts into the heaters.

No worries!  Perhaps it was to minimize the chance of the internal nodes floating to weird voltages and causing noise?  I did try grounding the unused pins and couldn't notice any difference.  But it's certainly easy to do with a few wires if you want to experiment.

I did confirm the tube support pins are grounded as well.

 

[sr1200]

I want another one sooo bad... Used mine this week for some stuff, its so pretty.

 

[JessJackson]

I was getting 160v at b+

so i increased r1 and r2 to 160k each and now still getting 134v

both measurements with trimmer pot all way down.

weird huh

 

[Matador]

I was getting 160v at b+

so i increased r1 and r2 to 160k each and now still getting 134v

both measurements with trimmer pot all way down.

weird huh

Was it working properly before and now it's changed?

 

[JessJackson]

I was getting 160v at b+

so i increased r1 and r2 to 160k each and now still getting 134v

both measurements with trimmer pot all way down.

weird huh

Was it working properly before and now it's changed?

No it was always high, I just tried to bring it down now.

The trimmer pot is definitely the 100k. I'll try two 200k resistors in r1 and r2

 

[Matador]

I was getting 160v at b+

so i increased r1 and r2 to 160k each and now still getting 134v

both measurements with trimmer pot all way down.

weird huh

Was it working properly before and now it's changed?

No it was always high, I just tried to bring it down now.

The trimmer pot is definitely the 100k. I'll try two 200k resistors in r1 and r2

This is with a tube?  What kind?  Did you try the 180K resistor trick?

 

[JessJackson]

yeah when its loaded.

Whats strange is I'm getting the higher voltages when the mic is open and exposed but the moment i slide the body sleeve up the cable and over the mic the voltage drops slightly and then as I tighten the bell connector on the bottom, the voltage drops dramatically further to my specified 120v.

Ive repeated this over and over and literally changes the moment I tighten or loosen the bell. Ground has continuity over entire body and frame from PS regardless of bell being tight or or even slid down cable.

odd findings huh

 

[originalmusician]

I ordered all the parts for this except for the capsule. I had planned on buying the Tim Campbell CK12. I emailed Tim on August 14th and asked to be put on his waiting list. But I never got a reply from him. So I emailed him again a few weeks later at his other email address but still haven't heard back (checked my spam filter and no return emails were in there).

Has anyone else ordered one of his capsules, and is it typical for it to take a month or more to get an email response when trying to get a spot on the waiting list? I'm not trying to be critical of Tim, as I know he's probably tremendously busy. I'm just trying to figure out if my experience is typical, or if the emails are getting hung up somewhere or something? Or maybe my emails are getting redirected to his spambox? My main concern is, I don't want to bother Tim with relentless repeat emails if it normally takes some time for him to catch up with his inbox.

Thanks 

 

[chunger]

I ordered all the parts for this except for the capsule. I had planned on buying the Tim Campbell CK12. I emailed Tim on August 14th and asked to be put on his waiting list. But I never got a reply from him. So I emailed him again a few weeks later at his other email address but still haven't heard back (checked my spam filter and no return emails were in there).

Has anyone else ordered one of his capsules, and is it typical for it to take a month or more to get an email response when trying to get a spot on the waiting list? I'm not trying to be critical of Tim, as I know he's probably tremendously busy. I'm just trying to figure out if my experience is typical, or if the emails are getting hung up somewhere or something? Or maybe my emails are getting redirected to his spambox? My main concern is, I don't want to bother Tim with relentless repeat emails if it normally takes some time for him to catch up with his inbox.

Thanks 

Hi,  I know a lot of people have been frustrated lately trying to get into Tim's build queue.  I spoke with him recently regarding sustainable sourcing of capsules moving forward, and as of right now, given his OEM commitments, this project has completely exceeded his current production capacity.  As Tim is a one-man operation hand-building these fine capsules, he is not set up to track many emails and inquiries above his previous baseline of communication volume.  While maintaining his current production volumes, he is working diligently to tool up and increase his production capacity, but this takes significant investments in tools and streamlining of production processes.  This will take time, and he must weigh the long-term prospects of my little DIY venture.  My view is I can continue to bring in new DIY customers and expand the market and make kits essentially perpetually available.  For now, once Tim is finished shipping capsules to his current queue of non-commercial DIY customers (people who he has confirmed), I have let him know I will buy every "extra" capsule he can produce and make them available as they trickle in to kit customers.  Hopefully, once some new production processes come online, Tim will be able to incrementally increase his monthly production volume.

That being said, there is currently a shortage of backplate-correct C12 capsules for this project.  I am now working with tskguy to finalize his C12 capsule in hopes that he will be able to fill the gap with a capsule that is true to the vintage AKG capsule's internal construction and frequency response.  His initial tests and prototypes have been very promising and he is basing development on a pristine vintage C12 that he has access to.  For people who require a premium capsule for their builds, I would wait for these units to hit production.  I am sure tskguy will not release anything that he does not feel 100% about, but his production process for these new capsules is conducive to production volumes that can meet the current demand.  I am hoping to finally be able to stock complete turn-key kits when these come online.

 

[maq3396]

Thanks Chunger

Hats off to yourself, Tskguy and Tim for helping to not only sustain, but make major contributions to this DIY world. Without the tremendous efforts made by the members of this forum, many of us would never have an opportunity to own microphones such as the U67, U47, C12 and ELAM 251.

Thank you all
Mac

 

[Woot]

Chunger -  Sorry if I missed the point of your reply but is Tim still putting DIY people on the list, or are you saying he has suspended this availability for the DIY'ers until his current OEM/DIY backlog is sorted?

Originalmusician - I had a similar experience to you. Additionally, there's a bit of a discrepancy between some peoples reported experience in ordering capsules and what Tim has said to me. ie there were people saying that they sent an email, received no confirmation but received a request for payment and shipping details when the capsules were ready some 8 weeks later. Tim has told me categorically that everyone who has been placed on his list has received email return confirmation of this fact. So unfortunately if he hasn't replied with confirmation then you're not on the list. It took me a few emails over 3 months to receive a reply (not complaining as we know Tim is very busy, just stating facts).

I am going to build a MataChung c12 today, with a Beesneez K12 capsule. Anyone know if they are considered backplate-correct? Anyone elaborate on what backplate-correct means?? I'll post some samples with this combo if anyone interested.

Lastly, I echo the the sentiments from Mac... it's an awesome service you guys provide (and an addictive one).

Cheers,

Matt

 

[Matador]

I'm not an expert, but I have seen a real one apart so can give a general impression.

So a k67 type capsule has a single backplate element per side.  The number and spacing of the holes determine the amount of resistance between the air in front of the capsule and the inside of the sealed chamber.

C12 capsule have a screw in chamber which makes yet another resonance chamber inbetween the front and middle of the capsule.  A large number of C12 clones are simply k67 type backplates that are reconfigured to utilize an edge terminated diaphragm.

I would construe "backplate correct" to indicate the presence of the isolated resonance chamber.  Both tskguy's and Tim's capsules feature this chamber.  Many/most of the clones do not.

 

[StaticRick]

Well that stinks. I had read a couple of different times here that the process to get one of Tim's capsules was to email him, don't expect any response from him, and wait until you get an email from him saying your capsule is ready.  I sent my email and respected his wishes by not peppering him with followup emails. Now, I read that since I DIDN'T get a response from Tim that means that I WON'T be getting one of his capsules?

I understand that he's busy, but I don't understand operating a business when your policy is to never communicate with customers who contact you.

I guess I'll be looking for other options, but a definitive response from Tim would seem to be a common courtesy.