Official C12 Clone - Build and Support Thread

[Category 5]

Barboja, try flipping the capsule around and see how it sounds.  Also make sure your capsule leads are short, cleanly attatched and free of any flux residue.  Those steps helped mine with the same issues.  Now front and back sound about the same. Before the back side was completely dark and veiled.  Also, remember the rear is out of phase so in headphones it will always sound different.  You can invert phase on the pre to alleviate this. 

 

[kidvybes]

...just to put the value and importance of this MataChung C12 project in perspective, this is what was done previously (by respected audio engineer Doug Sax) to build an improvised C12-type microphone:

http://www.ebay.com/itm/Rare-Handmade-Sheffield-Labs-Tube-Microphone-C12-Capsule-And-Custom-Tube-Preamp-/301257336152

Copied directly from the eBay ad:
"Extremely rare and sought after microphone. handbuilt by Doug Sax from the mastering labs, around a dozen of these mics were made for the industry changing Sheffeild Labs direct to disk recordings. the capsule is a hand picked C12 cap chosen after exhaustive shoot outs. the preamp ids custom made for the mic allowing you to come line out directly in to a console or converter if desired. the preamp offers line out and test out, which is a slightly less hot signal. a detented DB attenuator controls the output from the preamp. proprietary cable is include . this is as high end and esoteric as it comes. the serial # is 9. don’t be foole by the radio shack project box housing, this is one of the finest mics in the world. all of the other ones are represented in world class collections by Bill Schnee, Blackbird studios etc. they come on the market very rarely and chances are you will never see one on ebay again. the mic just came back from Toby Foster and it is in premium ready to go condition. He even took it over to Schnee’s studio for a blind listen to make sure it was 100%. This mic has been featured on uncountable master recordings and as the vocal mic for Keith Urban, Rascal Flatts, Kenny rogers and many more over the years. it comes in a professional foam lined case with the PSU/preamp. This your chance to own a piece of recording history and to never second guess your microphone again."

 

[stelin]

Have just finished the build of my second C-12 clone. Both nr 1 and 2 worked the first time I plugged them in. No problems.
I have measured the noise level (subjectively), and if we can trust that a Neumann TLM 103 has a noise level of 7dB, then the C-12s has a noise level of about 16 dB (with the difference in sensitivity accounted for). That’s good for any tube microphone.
I’m using Beesneez capsules and Mullard 12AT7 tubes for the (first) two microphones. They do not sound exactly the same: The first one is a bit darker. I have measured the (relative) frequency response (with FuzzMeasure on my Mac), and both have a dip around 7KHz and a resonance peak around 10-11KHz. The dip is 3-4 dB’s deeper on the first microphone.
I’m thinking of building two more. I’m on Tim’s list for two capsules and I’ve got two GE 6072A tubes (Thank you Christian Whitmore!). It would be great fun to compare that configuration to the Beesneez/12AT7 ones.
At last, I have to thank Matador and Chunger for an excellent project. I’ve been building (audio) things since the seventies, and I remember how hard it was in those days to get anything done. Today, because of the Internet and folks like Matador, Chunger and Christian, we can do things we could not even dream about in the olden days!

 

[Pip]

...just to put the value and importance of this MataChung C12 project in perspective, this is what was done previously (by respected audio engineer Doug Sax) to build an improvised C12-type microphone:

http://www.ebay.com/itm/Rare-Handmade-Sheffield-Labs-Tube-Microphone-C12-Capsule-And-Custom-Tube-Preamp-/301257336152

Copied directly from the eBay ad:
"Extremely rare and sought after microphone. handbuilt by Doug Sax from the mastering labs, around a dozen of these mics were made for the industry changing Sheffeild Labs direct to disk recordings. the capsule is a hand picked C12 cap chosen after exhaustive shoot outs. the preamp ids custom made for the mic allowing you to come line out directly in to a console or converter if desired. the preamp offers line out and test out, which is a slightly less hot signal. a detented DB attenuator controls the output from the preamp. proprietary cable is include . this is as high end and esoteric as it comes. the serial # is 9. don’t be foole by the radio shack project box housing, this is one of the finest mics in the world. all of the other ones are represented in world class collections by Bill Schnee, Blackbird studios etc. they come on the market very rarely and chances are you will never see one on ebay again. the mic just came back from Toby Foster and it is in premium ready to go condition. He even took it over to Schnee’s studio for a blind listen to make sure it was 100%. This mic has been featured on uncountable master recordings and as the vocal mic for Keith Urban, Rascal Flatts, Kenny rogers and many more over the years. it comes in a professional foam lined case with the PSU/preamp. This your chance to own a piece of recording history and to never second guess your microphone again."

CIRCUIT SCHEMATIC ANYONE?

 

[barbaroja]

Barboja, try flipping the capsule around and see how it sounds.  Also make sure your capsule leads are short, cleanly attatched and free of any flux residue.  Those steps helped mine with the same issues.  Now front and back sound about the same. Before the back side was completely dark and veiled.  Also, remember the rear is out of phase so in headphones it will always sound different.  You can invert phase on the pre to alleviate this.

Thanks, Cat, helped a lot.

Now, I know that high impedance part is highly delicate, sensitive. Could you theoretically place a switch between the posts and capsule that would let you select the side of the capsule you would use? Well all capsules have some variance between their front and back sides, so being able to use that difference to your favor, makes sense, and make the mic more versatile. Main concern is the switch affecting the sound.

 

[Category 5]

Barbaroja,  not sure id want to put a switch in there but if you have a reasonably deadened environment you can use figure 8 mode and invert the phase to use the rear diaphragm.  It sounds pretty much the same except for the increased room sensitivity.

 

[barbaroja]

Quite dead. Yours seems like a better solution.

Thanks!

 

[kidvybes]

...just to put the value and importance of this MataChung C12 project in perspective, this is what was done previously (by respected audio engineer Doug Sax) to build an improvised C12-type microphone:

http://www.ebay.com/itm/Rare-Handmade-Sheffield-Labs-Tube-Microphone-C12-Capsule-And-Custom-Tube-Preamp-/301257336152

Copied directly from the eBay ad:
"Extremely rare and sought after microphone. handbuilt by Doug Sax from the mastering labs, around a dozen of these mics were made for the industry changing Sheffeild Labs direct to disk recordings. the capsule is a hand picked C12 cap chosen after exhaustive shoot outs. the preamp ids custom made for the mic allowing you to come line out directly in to a console or converter if desired. the preamp offers line out and test out, which is a slightly less hot signal. a detented DB attenuator controls the output from the preamp. proprietary cable is include . this is as high end and esoteric as it comes. the serial # is 9. don’t be foole by the radio shack project box housing, this is one of the finest mics in the world. all of the other ones are represented in world class collections by Bill Schnee, Blackbird studios etc. they come on the market very rarely and chances are you will never see one on ebay again. the mic just came back from Toby Foster and it is in premium ready to go condition. He even took it over to Schnee’s studio for a blind listen to make sure it was 100%. This mic has been featured on uncountable master recordings and as the vocal mic for Keith Urban, Rascal Flatts, Kenny rogers and many more over the years. it comes in a professional foam lined case with the PSU/preamp. This your chance to own a piece of recording history and to never second guess your microphone again."

CIRCUIT SCHEMATIC ANYONE?

...no circuit schematic, but go to 6:35 in this video shot at Bluebird Studios:

http://youtu.be/-8E0GwS9Ywc

 

[Reverend]

I finished my second C12 clone by Matador/Chunger and this one sounds as amazing as the first. Thanks to Chunger and Matador. I've already started buying bits and pieces to start on the ELAM 251 clone project. But as a super-noob, it would be best for me to wait until there's a page with extreme details and Chunger photos. Does anyone know when or if a page dedicated to the ELAM version of this clone will be up. Thanks also to everyone on this thread who helped me through my issues.

 

[Spack]

200vac secondary voltage full wave rectified is 282vdc.  This voltage is placed directly across C1 which is only rate for 250 volts.

 

[barbaroja]

200vac secondary voltage full wave rectified is 282vdc.  This voltage is placed directly across C1 which is only rate for 250 volts.

Interesting. You sure? Mine has not exploded yet...

 

[Matador]

200vac secondary voltage full wave rectified is 282vdc.  This voltage is placed directly across C1 which is only rate for 250 volts.

This was already covered a few times:

As for the B+ supply:  the Nichicon caps we use have quite a high derating factor when used near room temps.  The manufacturers have a lot of margin built in to these parts (especially the high temp parts).  I stayed with 250V because the next size up is 315V, which only specifies 47uF instead of 100uF for the same package.  Also the preliminary transformers I tried seemed to have higher core loss, and I didn't see average DC reading up near the 270V mark in any case.

If you want to be extra conservative, you can sub in a 47uF/315V variant of the VZ line which is in the same package size.  Sonics would (probably) not be impacted to any audible degree (the filter pole is already sub 1Hz in any case).

 

[Spack]

Oh they won't blow up (for awhile).  And I figured somebody brought it up.  Did they also bring up the margin on the transformer?  Mine's 225vac or 320vpp.  (and yes the line is 115Vac).  That's a lot across that cap.  This was discovered because B+ is too high.

 

[Matador]

Oh they won't blow up (for awhile).  And I figured somebody brought it up.  Did they also bring up the margin on the transformer?  Mine's 225vac or 320vpp.  (and yes the line is 115Vac).  That's a lot across that cap.  This was discovered because B+ is too high.

Did this transformer come stock from Alctron?  In all of the many builds we have gone through here on this thread only 175VAC and 200VAC supplies were ever seen...

If Alctron has starting including 225VAC then indeed some of the values will need to change.

And at 200VAC those caps won't blow up...even after a while.  They are specified at full voltage rating at 105C (221F), and in reality they can operate at higher levels when down near ambient temp.  Of course, this is not universally true for all capacitor types, which is why I recommend not deviating from the Nichicon VZ line.

 

[Spack]

I don't know.  This was dropped on my desk to fix which I will do.  I was just trying to provide some help to you folks after doing several searches and not finding such a thread.

The transformer is stamped 200vac with a sticker with a bunch asian writing on it. 

No need to reply.  This was all just an observation which I figured had been made...  But I didn't see it.

 

[Matador]

No problem, this is useful information.

Just to make sure:  you measured 225VAC across a transformer labeled 200VAC?  That's a pretty hefty margin on secondary winding count.  I shouldn't give the winders as much benefit of doubt as I have.

 

[Category 5]

The transformer marked 200v actually outputs 225vac on a 120vac feed.  The one marked 175v outputs about 200vac.  I think they were rated on a "loose" 110vac service as some equipment still is.  The stock resistor values work for the 225vac part and the substitutions mentioned several times on the thread work for the smaller 200vac one. 

We have indeed only seen two parts thus far

One marked 200v that actually outputs about 225vac

One marked 175v that actually outputs about 200vac

 

[Spack]

yes marked 200vac.

Stock resistors 2x91k + 100k-variable + 470k yields an open circuit B+ voltage across the 470k from 198 to 229 (stop to stop on the pot).

I put an 80k in series with Vac transformer in order to knock that 318vdc across C1 back down to 282 vdc.

Adds another couple days to the B+ power on voltage ramp

 

[Matador]

yes marked 200vac.

Stock resistors 2x91k + 100k-variable + 470k yields an open circuit B+ voltage across the 470k from 198 to 229 (stop to stop on the pot).

I put an 80k in series with Vac transformer in order to knock that 318vdc across C1 back down to 282 vdc.

Adds another couple days to the B+ power on voltage ramp

There's another trick that doesn't impact the ramp time of the supply:  you can lower the value of the 470K bleeder resistor, which causes more "steady" current draw and increases drop across the series filter resistors in turn.  Halving the value doubles the current and doubles the drop.  I'm guessing a 330K would work well for high line voltages.

I *really* need to get the next prototype of my regulated supply done.

 

[chunger]

Hi,

I can get a new cap to you. . . please send email to confirm address.