Official C12 Clone - Build and Support Thread

[Matador]

Does anyone knows what is the voltage on both 5000pF capacitors?
Is there any existing voltage chart for C12 clone?
I have two 5000pF Siemens styroflex caps, unfortunatelly rated for 160V (pink ring marking).
I know that the genuine were at least 250V, but if the voltage isn't floating at those points, maybe 160V would work?

C10 (the tube bias cap) will only ever see perhaps 2 or 3V across it.  C11 (the polarization voltage filter) has max about 120V.  So in short, 160V is fine.

 

[chunger]

Sorry for the confusion.  I believe I have always been clear to cease perpetual email attempts with tim AFTER confirmation that you are in his build queue.  Prior to that point you are not officially in line.

Chunger, thanks for responding to my earlier venting. 
I am willing to wait as long as it takes, but I'm still confused about the "process" of getting in Tim's queue.  In my case, I sent an email requesting a capsule about two weeks ago.  Since I have not heard back from Tim, does that mean that I will need to try again with another email in the future, OR does it mean I'm in the "pre-queue queue" and may still hear from him at some point?

I understand that he is a busy man who is making a great contribution to the DIY community.  I don't want to bug him with too many emails.  Whatever the procedure it, I'm happy to follow it. 

My intention has always been to build the mic with the original capsule and then upgrade once everything else is right.  So, I can wait as long as I need to get the right capsule.

You would need to continue contacting him until he confirms you are in the queue.  Unfortunately, if be is severely backlogged and is receiving high volumes of new inquiries, he is not able to respond to emails in a timely manner and you emails may go unresponded to and float to the abyss of the bottom of the inbox.  Really not a good situation for anybody which is why I am working to confirm another viable capsule for the build.  Once demand loosens up a little bit on tims capsules he will likely get back to normal response times.

for now, it is a bit of a brick-wall.  I just shipped out a ton of mics and kits as they were recently restocked and many people prefer a campbell capsule in their builds.

we are working diligently on an alternate solution and I will be receiving a trickle of campbell capsules at some point but I do not know when.

 

[ln76d]

C10 (the tube bias cap) will only ever see perhaps 2 or 3V across it.  C11 (the polarization voltage filter) has max about 120V.  So in short, 160V is fine.

Thank you very much

 

[teacat]

Regarding cheaper capsules, (since I might as well not worry about getting a CT12 for a while) I read a lot of folks install and like the RK-12. What about AA's AK12? Anyone install that one in this mike? I had a Stellar CM-5 that I liked quite a bit and I think they use those.

 

[chunger]

Regarding cheaper capsules, (since I might as well not worry about getting a CT12 for a while) I read a lot of folks install and like the RK-12. What about AA's AK12? Anyone install that one in this mike? I had a Stellar CM-5 that I liked quite a bit and I think they use those.

Matador built the first prototype with an AA AK12 capsule and the microphone sounded nice although we did not subject that original prototype to extensive audio tests.  Dave Thomas (CEO at Advanced Audio) has contributed a great deal of knowledge to the DIY community.  He is a die-hard advocate of the CCDA "cathode follower" circuit in the original HT-11A microphone  . . . so hopefully he doesn't get too upset about our plate follower layout.  I know his capsule is a 6 micron as opposed to 5 micron in the Microphone-parts.com unit.  Beyond that, since I don't have direct experience with the microphone-parts rk12, I cannot comment. 

 

[Matador]

Regarding cheaper capsules, (since I might as well not worry about getting a CT12 for a while) I read a lot of folks install and like the RK-12. What about AA's AK12? Anyone install that one in this mike? I had a Stellar CM-5 that I liked quite a bit and I think they use those.

Matador built the first prototype with an AA AK12 capsule and the microphone sounded nice although we did not subject that original prototype to extensive audio tests.  Dave Thomas (CEO at Advanced Audio) has contributed a great deal of knowledge to the DIY community.  He is a die-hard advocate of the CCDA "cathode follower" circuit in the original HT-11A microphone  . . . so hopefully he doesn't get too upset about our plate follower layout.  I know his capsule is a 6 micron as opposed to 5 micron in the Microphone-parts.com unit.  Beyond that, since I don't have direct experience with the microphone-parts rk12, I cannot comment.

Indeed I thought it sounded fine:  it wasn't in TC's level of quality (and probably not up to tskguy's either, if his 47-type is any indication).  However it had very smooth highs and a balanced sound all-around.

I think it's hard to beat for the price (which I think is about $30 cheaper than the RK12, which I don't have any experience with).

 

[Woot]

Hi, what is the minimum voltage for C12? Can I get away with 200v?

I presume so as the B+ is 120v but I thought I'd double check.

Cheers,

Matt

 

[JessJackson]

It sounds like a grounding issue to me.

Please confirm the following:

1) On your 7-pin XLR connector into the mike, that you have whatever wire is carrying ground also bridges over to the brass lug that connects with the XLR screw.  You can clearly see it in Chunger's build pic:

2) That you "loosened" the XLR screw which actually tightens it against the bottom housing.

Barring that, solder a ground wire to the mike PCB right at the tube pin 9, and feed it up through the top plate, and out of the head basket's mesh.  The set your meter to ohms, and ground one side to the PSU right where it comes out of the 5-pin header, and then connect the other side to your new wire.  Then watch the reading and you assemble the housing and tighten it.

Thanks brother,

You were absolutely right. the moment i tightened that screw into the base, the problem went away and my voltage stays at a nice solid 120v now.

Granted I have built a cardioid only circuit on this board. (I'll take some pics of my mods) here are my voltages. Mic has never sounded better!

B+ 120v
Heater 6.3v
Plate 67.5v
Front Capsule 33.3v
Front Backplate -0.025
Cathode 1.171v

Cheers J

 

[teacat]

Regarding cheaper capsules, (since I might as well not worry about getting a CT12 for a while) I read a lot of folks install and like the RK-12. What about AA's AK12? Anyone install that one in this mike? I had a Stellar CM-5 that I liked quite a bit and I think they use those.

Matador built the first prototype with an AA AK12 capsule and the microphone sounded nice although we did not subject that original prototype to extensive audio tests.  Dave Thomas (CEO at Advanced Audio) has contributed a great deal of knowledge to the DIY community.  He is a die-hard advocate of the CCDA "cathode follower" circuit in the original HT-11A microphone  . . . so hopefully he doesn't get too upset about our plate follower layout.  I know his capsule is a 6 micron as opposed to 5 micron in the Microphone-parts.com unit.  Beyond that, since I don't have direct experience with the microphone-parts rk12, I cannot comment.

Indeed I thought it sounded fine:  it wasn't in TC's level of quality (and probably not up to tskguy's either, if his 47-type is any indication).  However it had very smooth highs and a balanced sound all-around.

I think it's hard to beat for the price (which I think is about $30 cheaper than the RK12, which I don't have any experience with).

Thanks for the input, guys.
(...and the project!)

 

[kcatthedog]

Hi everyone,

My voltage readings are off.  I tested the trimmers before installing them and believe they are correctly placed and I have reviewed the entire pcp:

b+  28.7
H      6.3
B        .31
P    22.1

Typically I can turn the trimmer screws many times to little effect.

Suggestions ?

Thx !

 

[Christopher L]

I understand how to determine where the blue and red wires go on the t14 transformer but still am unsure of how to determine the positive and negative leads.  There is no explanation in the thread. 

 

[Reverend]

The volt reading from my B+, with the stock Alcatron capsule is about 150 volts. However, when I try to adjust the trim pot on the B+, it just turns and turns and turns. Does this mean that it's broken?

 

[Reverend]

"Carefully install the capsule and solder the four connections to the proper lugs on the microphone pcb" is what the instructions say. I'm sorry. I can't figure out which lugs do what. Could you post a little bit more in depth instructions for mounting the capsule. What are the "proper lugs?"
FYI, I'm trying to do this with a Peluso CEK12 capsule. Thanks.

 

[chunger]

RB rear backplate
FB front backplate
RC rear capsule
FC front capsule

The particular capsule screw terminals will vary between capsule manufacturers.  Use a multimeter to confirm connections.

 

[Reverend]

RB rear backplate
FB front backplate
RC rear capsule
FC front capsule

The particular capsule screw terminals will vary between capsule manufacturers.  Use a multimeter to confirm connections.

OK. Thanks. I see where they are marked now with closer inspection. But I still may need to know how to use the DMM on the capsule to determine.

 

[Matador]

Hi, what is the minimum voltage for C12? Can I get away with 200v?

I presume so as the B+ is 120v but I thought I'd double check.

Cheers,

Matt

Any rating over 160V will work fine (which is about as high as you can trim B+).  Most film types carry a 250V rating but 200V will also work.

 

[Matador]

Hi everyone,

My voltage readings are off.  I tested the trimmers before installing them and believe they are correctly placed and I have reviewed the entire pcp:

b+  28.7
H      6.3
B        .31
P    22.1

Typically I can turn the trimmer screws many times to little effect.

Suggestions ?

Thx !

Need more input.  Is this without a mike installed?  Start at the basics...no mike installed, what are all of the voltages as measured right at the PSU 5-pin terminal block?

 

[Matador]

I understand how to determine where the blue and red wires go on the t14 transformer but still am unsure of how to determine the positive and negative leads.  There is no explanation in the thread.

In this design, such a distinction doesn't matter.  Once you know primary from secondary you are good.

EDIT:  this statement is true unless you consider matched pairs of mikes.  The phase on both should be consistent to each other.  Easy way to tell is to set up two of them, and then clap a few times (providing something near an impulse response) while recording on your DAW.  Zoom way in to the sample level, and you should see the transients move in the same direction on both channels.  If one "goes up" while the other "goes down" you should swap the secondary wires on one of the mikes.

 

[Matador]

The volt reading from my B+, with the stock Alcatron capsule is about 150 volts. However, when I try to adjust the trim pot on the B+, it just turns and turns and turns. Does this mean that it's broken?

No, it just doesn't feature a hard stop.  Once you go back "the other way" it will start to change back again.

 

[Reverend]

The volt reading from my B+, with the stock Alcatron capsule is about 150 volts. However, when I try to adjust the trim pot on the B+, it just turns and turns and turns. Does this mean that it's broken?

No, it just doesn't feature a hard stop.  Once you go back "the other way" it will start to change back again.

Ok. But, with the stock Alcatron capsule and a good 6025 tube, turning the B+ trimmer still does nothing to the voltage. Is this a problem?

Another question. I'm getting hum when I listen. When I touch the top of the capsule or another part, the hum goes away, but I can't hear the capsule. Could I have a problem? Could it be the same problem with a cap (C10 or C13?) as described in earlier posts?

Sorry. Ha Ha. Chunger calls himself a newbie....I'm the real deal!