Official C12 Clone - Build and Support Thread

[granger.frederic]

yes it has !
the HiZ is in a sealed acrylic chamber and is point to point.
it has the U47 rubber damped capsule mount
the components under the PCB are point to point and the PCB is fixed through the BV11
the vibrations are reduced by the mass of the big heavy transformer
no contact between the components/capsule and the body/headbasket, except with the bottom/base through a non resonant material
the tube is damped with an absorbing mat
there's a lot to say about the design....

i was not mainly talking about resonances coming  from the mount (easy to fix...), but mostly about resonances generated inside the mic due to the source .

 

[Matador]

I think we've exhausted this topic in this thread, and we're just spinning in circles now:  the last two pages have hardly even touched on the subject matter and intent of this thread.

Granger, since you feel so passionate about this, I suggest you start a different thread about what (in your opinion) you think just can't possibly work, and it can be debated there.

Fair enough?

 

[granger.frederic]

Matador,

Politeness, respect, tolerance and moderation are the hallmarks of a civilized society.

you could just call me  "Frederic", that would be better.

I think we've exhausted this topic in this thread, and we're just spinning in circles now:  the last two pages have hardly even touched on the subject matter and intent of this thread.

Granger, since you feel so passionate about this, I suggest you start a different thread about what (in your opinion) you think just can't possibly work, and it can be debated there.

Fair enough?

You ask me to leave this thread (a bit sternly)  but :"Are you a Moderator in this Forum ?"

The subject is C12 clone.

You have presented here your production to us, even if it's not a white market thread.

I just gave my opinion about your internal mic kit design , which is, for me, a  complete redesign more than a clone.

i thought that wasn't off topic.

With one aim in mind : improvements and sharing/debating knowledge

i tried to illustrate my point of view with some other mics designs ( but the principle is the same ).

All  i have said here, is perfectly transferable to the all the cloning mic threads

But don't worry , i stop posting here, i would not want to jeopardize your business ...

 

[Matador]

If it's my capsule please use a pop filter and move it further away.
If it's another manufacturer's please continue using it on loud source so that in the future if it fails you can replace it with mine  ;D

Tim, do you have a gut feeling about what kind of SPL your capsule can tolerate?  It's something I've wondered about in the past.

 

[Melodeath00]

If it's my capsule please use a pop filter and move it further away.
If it's another manufacturer's please continue using it on loud source so that in the future if it fails you can replace it with mine  ;D

Tim, do you have a gut feeling about what kind of SPL your capsule can tolerate?  It's something I've wondered about in the past.

Hopefully Tim can answer, but for what it's worth, the C12 sounded clean as a whistle during my snare test, and another mic (an SDC, with a published Max SPL of 126dB) was very obviously distorting at the  same position.

That being said, as per Tim's recommendation, I wont be using the C12 on bottom snare, even with the pop filter I was using. It sounded much better than anything else I tried, but it's not worth the risk to me.

 

[chunger]

Hello Mr. Granger,

I do not understand your persistence in re-stating the same arguments continuously here as it only serves to dilute the content of a thread expressly designed for assisting in the assembly of a particular kit. . . one that you do not have any direct problems with, intention of building, or any interest other than to point out your objections to the design.  This is classic trolling behavior.

You have made your points, and I personally feel you you have had ample space to air your objections.  Everyone understands your position.  There are plenty of people who frequent these forums who adhere to the belief that ONLY traditional methods, materials, and component layout qualifies as acceptable.  I personally feel many of those familiar traditional features are simply the most expedient production methods at the time given the economics, resources, and materials of the era. . . or just stubborn German adherence to established conventions for no apparent reason (we often see this in car designs). . .  catastrophic failure in some of these designs (ie. decomposition over time of the plastic frame in ELA M251) do happen.  At any rate, you have Flea, Shaggy, and other suppliers who will gladly provide components to build mics to your sensibilities. 

Matador has always maintained that this is HIS implementation of the original C12 circuit with noted changes to the PSU topology and BOM adjustments to utilize readily available modern components.

We take all input into consideration and test for problems.  If you would like to assist and come back with actual data illustrating within normal operating conditions which frequencies in our microphone design are resonant beyond the baseline behavior of a "proper" traditionally designed C12 implementation (including vintage original) and provide your test methodologies so we can independently confirm data, please do so.  If you have NEW points to make (ie. ones that you have not stated already several times in this thread), please make them concisely.  Otherwise, you are simply diluting the content of a build and support thread.

You are welcome to make a "Frederic Granger guide to properly designed microphones" thread to evangelize your preferences, criticize our futile efforts, and provide as many pictures as you like of various approved microphone designs, all within the purity of your 100% economic-interest-free development ecosystem, by all means do so.  We will enter into the discussion respectfully and with data  to advocate our position if relevant and when we are able to set up /execute tests as we develop our kit.

I do not understand your insistence upon diluting this thread further having no direct problems with building or using the kit, no assistive information for those who are (besides using the platform to dissuade people from trying it, and advocating other parts/ kits), and repeating ad nauseum the same positions that we have already acknowledged and understood.

Many times with these complex systems, it is difficult to absolutely prove a definitive opinion, but in general, large-scale implementation will reveal faults in a system or at least point to weaknesses, and we do have many hundreds of these microphones in use across the entire spectrum of amateur and professional applications.  The feedback we have been getting as to microphone performance as prescribed (short of build faults) has been stable and positive.

Either we, in our blind pursuit of economic exploitation of the audio community, have coerced and deceived a great number of people and tricked them out of their hard-earned dollars. . . or, people genuinely find the kit accessible, educational, and the end performance exceeds expectation in the real world.

 

[granger.frederic]

This is endless ! My intentions weren't thread dilution...

i think it's the first time in this forum, that we're talking about something unusual : internal design/resonances of the HiZ sections

it wouldn't cost a lot to rework the HiZ sections of your kits, and the result would be greatly beneficial , but if don't want to, or if you don't even think about it, you are not obliged, off course ....

rest assured, i won't open a "guide", i don't want to develop or sell some kits ,  I do not profess to have the universal knowledge ,i just want to share my humble experience and my microphones passion freely, and that's the biggest difference between us ...

PS: Do you have pictures of ELAM internal parts "decomposition"  ?    i'd like to see that !

Now it's time for me to leave , and get a tan at Marrakech  8)

 

[Matador]

One of the main design goals for this project is ease of assembly.  The previous version has only 4 wires that need to be run on the board, and the new version reduces this down to 3.  Provided you use some IPA and some elbow grease, you can assemble the entire kit within 1 hour and not have any problems.

In terms of 'improving the HiZ section':  I don't see what else there is to optimize without damaging the design intent above.  The design has exactly 4 HiZ nodes (my definition for HiZ is an impedance wrt. ground above 1M).  All are contained at the top of the board, with a combined area of about 4 square inches:  not terribly different from the cross sectional area of an ELA M251!  The only exception is about 1.2 cm of trace that extends below the tube PCB attachment point.  All of the nodes that are in contact with PCB have at least 1 cm of clearance to nodes that are at different potentials, and all are shielded to ground via planes as well throughout most of their length.  The total calculated parasitic capacitance comes to under 1pF, which is tiny compared to that of the capsule and the tube grid itself.  The total length of all HiZ PCB traces is 1.8 inches, or about 4.5 centimeters.  I think this pretty well optimizes the trace length versus wiring / assembly complexity.

What can be problematic with HiZ is EMI, which is why all of these designs are stuffed into conductive/shielded tubes, and will hum like crazy if operated 'outside'.  With that regard, I feel the PCB implementation is superior to point to point, as we can shield the board with planes, and reduce the cross sectional area of the wiring in the process, and reduce the total wiring length, and make it repeatable from build-to-build.

 

[granger.frederic]

Maybe it would be judicious to disassociate the lowZ and HighZ sections
You could keep the lowZ as it is, and rework the highZ with , for example ,with  thick plates of acrylic/point to point (or equivalent) , hermetically sealed if possible,  including a shock mount/damping system  , and holding the capsule wires and the capsule mount also, without any contact ( except wires)  with the body and the the LowZ section.
And you could also find a way to damp the tube in the same time...

 

[Matador]

Maybe it would be judicious to disassociate the lowZ and HighZ sections
You could keep the lowZ as it is, and rework the highZ with , for example ,with  thick plates of acrylic/point to point (or equivalent) , hermetically sealed if possible,  including a shock mount/damping system  , and holding the capsule wires and the capsule mount also, without any contact ( except wires)  with the body and the the LowZ section.
And you could also find a way to damp the tube in the same time...

I'll repeat again:

In terms of 'improving the HiZ section':  I don't see what else there is to optimize without damaging the design intent above.

Also again: the soldermask/board combo has similar impedance as air, so why would we ask builders to assemble a point-to-point version to get exactly the same performance?

'Hermetically sealed' for DIY? Really?

 

[granger.frederic]

because point to point is the only solution on acrylic
building a HiZ sealed chamber with 3 acrylic parts (2 plates and 1 tube) could be easy...
the capsule mount could be fixed on top
a rubber (or equivalent) shock mount around it could be also quite simple
Same for a shock mount around the tube socket

 

[Tim Campbell]

Tim, do you have a gut feeling about what kind of SPL your capsule can tolerate?  It's something I've wondered about in the past.

It's not a criteria that I've worried excessively about. I've tried to recreate the performance of a vintage capsule which are more sensitive. Perhaps Eric has an idea about SPL's and his capsule or Ben his.

At the current exchange rate my capsule only costs about 300 dollars so it's in the price ballpark with selected Chinese capsules not the plus 400 dollar range. I'd say abuse them and buy more

 

[granger.frederic]

I measured the CT12 regular version (Sinus 1KHz/OMNI/1m), around 130db in a C12 clone and around 135db in a ELA M 251 clone for 2-3%THD

(measures are not ultra accurate because of the non negligible THD of my 2KW sound system)

more than enough ! (you can't stay in the room)

 

[Category 5]

At the current exchange rate my capsule only costs about 300 dollars so it's in the price ballpark with selected Chinese capsules not the plus 400 dollar range. I'd say abuse them and buy more

Getting an email that your capsules are ready to ship from Tim is like getting a visit from Santa Claus.  Definitely one of the nicest sounding capsules I've ever heard, and I do think Matador's project showcases it beautifully.

Any ETA on the new boards Matador?  I'm eager to try them.

 

[MicDaddy]

I just want to say that when this mic is "working" (performing adequately?) with a proper capsule it is more than sufficient, however I do feel there is some value in some of the criticisms, if that's what you want to call them.

I chased "noise" in this mic for a good few months, hell it might have been a year or better. 

It came down to proximity to RF/EMI sources... the usual suspect donor body (at least the one I use) is not a great shield.  Being aware of that and working to keep the mic away from those sources and the issue is no more.  It was first noted while using the mic in a position raised several feet above a cellist, was just close enough to the flouro lighting in the 12' ceiling.

I've had issues with capsules, to the point that I'm exhausted in trying to remedy. 

Maybe this is just me... but I work mostly in dynamic microphones.  My "field" of battle is within an air-gap that is very very tight and unforgiving.  Any debris in the air-gap after a diaphragm is installed and we're in for a bad day and lots of cussing.  One has to be absolutely ruthless in cleaning the air-gap, (positive pressure room helps) prior to installing a voice coil.  Anyone that has re-coned a speaker knows what kind of clearances we're talking... now scale that down to a microphone.  My point is debris, at what point is it a problem when it's under the diaphragm of a condenser capsule?

On more than one occasion with more than one Mfr, I've observed what looks like debris under gold sputtered diaphragms.

They show as bumps, or convex spots on the diaphragm.  Sometimes it's groupings of bumps or debris.  Sometimes it's observed with not polarization voltage present, meaning the capsule on its own as is is clearly visible to see these bumps.  Other times only when polarization voltage applied (and if the diaphragms collapse) are the debris/bumps visible under the sucked in diaphragm.

I've seen these bumps on Neumann capsules so it's not exclusive to the Chinese or any particular 3rd party builders.  (Tim I have only seen one of your capsules and neither diaphragm shows debris underneath)  I don't want to slight or sully any product, that's not my intent, but only to maybe pose a question as to what is acceptable for debris under a condenser capsule? ?

Anyways I'm selling my c12 in the black market if anyone wants to pick one up for much less than what is in it for parts.

I floated most of the HiZ nodes from the PCB via p2p wiring.  It's very very ugly,  I was determined to weed out the futzy noise floor... I've taken this into consideration in the asking price.

Thanks to Chunger and Matador

 

[Matador]

It came down to proximity to RF/EMI sources... the usual suspect donor body (at least the one I use) is not a great shield.  Being aware of that and working to keep the mic away from those sources and the issue is no more.  It was first noted while using the mic in a position raised several feet above a cellist, was just close enough to the flouro lighting in the 12' ceiling.

Sorry to hear about this trouble:  what did the noise sound like?  Did it change as you touched the body?  Did it have a clear 60Hz signature?

I floated most of the HiZ nodes from the PCB via p2p wiring.  It's very very ugly,  I was determined to weed out the futzy noise
floor... I've taken this into consideration in the asking price.

Thanks to Chunger and Matador

Unfortunately floating stuff won't help (much) with EMI:  however sanding the top and bottom of the outer shell does help with this, as the metalwork relies on metal-to-metal contact to transmit the shield up from the connector to the capsule.  Generally the headbasket isn't an issue as it screws directly into the top plate, but the outer shell relies on press fitting via the bottom threaded end bell.  If you coated the end shell with some kind of paint this can be greatly exacerbated.

 

[MicDaddy]

I media blast and powder paint microphones using the appropriate masking where needed to ensure a proper electrical continuity throughout the housing pieces.

I will post the audio.  It sounded of 60Hz & harmonics, not a clean sounding waveform but a complex ugly one... more fuzzybuzzy than hum.  Once I realized the Mic was sensitive it was easy to forecast which placement might not be ideal or otherwise possibly susceptible to emissions. 

Not related to intermittent or non connecting or conducting pieces of the body which a change in noise from touch would suggest, which this microphone does not exhibit.

I agree with your Hi Z assessment.  Any improvement from floating those nodes was negligible, possibly nil, and any improvement credited to floating was most likely from not putting the microphone in a situation where it was smothered in interference.

I'm exaggerating the shielding, it's adequate, (the donor body), but will not put up with interference as well as other microphone that I have extensive practical experience using.

What material is the mesh made of is it brass or other alloy?  What was 251/c12 original mesh material and mesh count?  The Chunger I have is only single layer with a large mesh count 10x10?  Easily pliable, you can't do that with SST mesh with wire OD the same. Maybe using stainless steel, a tighter count(throws historically accurate out the window) , multiple layers, combination of would help... Not that it's a problem, just that it's not ideal.

**without losing scope of the intent of my initial post on this page...

Debris under condenser diaphragms... issue, non-issue?thoughts?

 

[Matador]

Hmmm - a harsh buzz sounds like ballast hash.  If you post an audio file I can take a listen too.

I'm wondering if perhaps the mesh itself is making poor contact with the shell pieces:  that would explain it.  Even the more open mesh sizes look like ground planes to audio wavelengths, so the mesh size shouldn't be as critical here. 

Did you try measuring the resistance between the mesh and the bottom of the 7-pin connector (or even the ground node in the PSU) at various places?

My SOP these days (as I've pointed out previously in the thread) is to re-tap the internal hardware from M2 to 2-56 or 4-40 stainless steel hardware.  In the 7 or 8 prototypes I've built, I've never had any EMI issues, and I wonder if that was because the new hardware held the internal pieces together much tighter.

 

[Banzai]

This advice risks people ruining their body-kits and wasting an enormous amount of time: there's zero mechanical benefit in re-tapping perfectly good threads.

Just use stainless steel screws in metric M2 to improve structural strength. They are just as easily available in the US as your standard imperial sizings.

My SOP these days (as I've pointed out previously in the thread) is to re-tap the internal hardware from M2 to 2-56 or 4-40 stainless steel hardware.  In the 7 or 8 prototypes I've built, I've never had any EMI issues, and I wonder if that was because the new hardware held the internal pieces together much tighter.

 

[Matador]

This advice risks people ruining their body-kits and wasting an enormous amount of time: there's zero mechanical benefit in re-tapping perfectly good threads.

The key phrase being "perfectly good":  I had more than a few that just spun forever.

The 5 stages of Bolt Tightening

[list type=decimal]
[*]Loose
[*]Tight
[*]Tighter
[*]Really Tight
[*]Loose
[/list]