Official C12 Clone - Build and Support Thread

[Matador]

Pops sound like caps leaking DC.  I would try to lift out one side of both C10 and C11 (both are filters so the mike will work without them, albeit at perhaps some higher hum) to see if it changes/goes away.

Bingo ! Pops and "windy" noises are now gone. S/N seems lower now, but I guess this is expected.
So, should I replace C10 and C11 ? If so, will 160V/4700pF styros work instead ?

Thanks a lot for your help

Yes should be no problem.

The styrene caps are notorious for this, as they tend to be sensitive to both a) isopropyl alcohol, and b) heat.  160V is sufficient for both caps.  You can even go +-10% on the value and it won't change the sound:  the filter between R11 and C10 for the tube bias and the filter between R16 and C11 for the polarization voltage are both at 1.1Hz.

 

[Matador]

HI Guys,

my C12 sounds great just wanted to adjust it a little as its a tad thin on the bottom end, or rather a little bright on the top.
where should i implement changes in the circuit to adjust this?
Im using a RK-12 from microphone parts as the capsule and a Sowter 9610 transformer.

regards

Spence.

You can get some more low end by increasing C12.  The stock 0.5uF value can be increased to 1uF or 2uF to extend the bass response (if you can get the caps to physically fit).  Metallized Polypropylene and Polyester Film caps can be found in these values and fit properly.  The Erse 1uF that Chunger sells is probably one of the highest quality caps you can find for that component (although a bit of filing is needed on the cutout).

Taming the high end has been discussed previous in the thread:  the C12 is known for the airy top-end, and it will never have that midrange Neumann focus.  You can tame the high end a bit with a 100pF to 470pF cap from plate to ground (ala ELA M251), and it can even be put on an internal switch should you want to flip it back and forth without getting out your soldering iron.  The cap will give you an apparent midrange boost but to be honest, a C12 is the wrong color crayon for a midrange focused sound.

 

[ArnoldLayne]

The styrene caps are notorious for this, as they tend to be sensitive to both a) isopropyl alcohol, and b) heat.  160V is sufficient for both caps.  You can even go +-10% on the value and it won't change the sound:  the filter between R11 and C10 for the tube bias and the filter between R16 and C11 for the polarization voltage are both at 1.1Hz.

OK, I probably scrubbed too roughly..
Now it looks like there is a problem with the rear capsule: in omni mode, the back sounds a bit thinner than the front; Cardio mode sounds fine; back of the figure 8 has way more bass and sounds muffled. Like it's trying to pick up the other side.
Aand back to checking the capsule connections..

 

[scott_humphrey]

The styrene caps are notorious for this, as they tend to be sensitive to both a) isopropyl alcohol, and b) heat.  160V is sufficient for both caps.  You can even go +-10% on the value and it won't change the sound:  the filter between R11 and C10 for the tube bias and the filter between R16 and C11 for the polarization voltage are both at 1.1Hz.

OK, I probably scrubbed too roughly..
Now it looks like there is a problem with the rear capsule: in omni mode, the back sounds a bit thinner than the front; Cardio mode sounds fine; back of the figure 8 has way more bass and sounds muffled. Like it's trying to pick up the other side.
Aand back to checking the capsule connections..

It is normal for the frequency response to change as you described when you adjust the polar pattern. Use it like an EQ!

 

[scott_humphrey]

Let me clarify: in omni mode the mic will have less bass, and in figure of 8 mode it will have a lot more bass. In cardioid mode it is in the middle. This is normal.

I say this because I can't tell if there is something wrong with your mic, but just wanted to be sure that you're away of this info. Someone who was unaware of this might mistakenly believe that the mic was faulty!

 

[Matador]

Fox Audio has a good page for this.

You can see the high end drops and midrange boosts between cardioid and figure-8.

If you had the patterns reversed, figure-8 would point both patterns "inwards", and the pickup pattern would become "all-directions-reject".

 

[ajemutt]

Hey all,

Has anyone used a 6201 tube for this build? I've been told that a good 6201 sounds just as nice as a good 6072, but that the 6201 might be a little more plentiful long term.

I'm curious to know what you folks think.


thx!


AJ

 

[Matador]

Hey all,

Has anyone used a 6201 tube for this build? I've been told that a good 6201 sounds just as nice as a good 6072, but that the 6201 might be a little more plentiful long term.

I'm curious to know what you folks think.


thx!


AJ

I'll have some updates on this topic (e.g. 6201) in a week or so.  The fast answer is:  probably not a good tube, at least for this application...

Probably better to focus on high quality / low-noise true 12AT7 tubes.

 

[ArnoldLayne]

@scott-humphrey: thanks for pointing this out. I know polar patterns influence the frequency response, but in this case it is definitely an issue.. It probably appeared after I resoldered the teflon standoffs on the top side of the PCB (they were on the bottom).

@matador: I started to read this page a couple of days ago but didn't finish it. Now I will  It's a great ressource,especially for noobies like me ;D

 

[ArnoldLayne]

Looking at the schematics, couldn't C13 be a possible culprit ?  ???
I'm going to replace it anyway, along with C10 & C11.

 

[scott_humphrey]

Also, try flipping the polarity switch on your mic preamp when you talk into the backside of the capsule in figure of 8 mode. If this fixes the problem, it is simply that the backside of the capsule is out of phase with your headphones. You can see why this might happen from the Fox Audio page that Matador pointed out.

 

[ArnoldLayne]

Thanks for the tip, but it didn't fix the problem. My voltages are somewhat normal:
Omni= 0V
Cardio= 50V
Figure 8= 115V when I probe, then down to 107V..

 

[Matador]

Thanks for the tip, but it didn't fix the problem. My voltages are somewhat normal:
Omni= 0V
Cardio= 50V
Figure 8= 115V when I probe, then down to 107V..

What problem are we talking about now? The popping/wind noises?

 

[melodeath]

Thanks for the tip, but it didn't fix the problem. My voltages are somewhat normal:
Omni= 0V
Cardio= 50V
Figure 8= 115V when I probe, then down to 107V..

What problem are we talking about now? The popping/wind noises?

I think he is talking about his polar pattern/rear diaphragm issue

 

[ArnoldLayne]

Yes (see post # 762).
Since C10 and C11 have been damaged, it's possible that C13 has been too..

 

[OPR]

MBHO, Korby, Beyerdynamic, Lawson, Telefunken, Beesneez, Tskguy and even AKG manufacture versions of this capsule that are readily available for sale and can be used in this build.

Can anyone provide Links to where these can be purchased? I know where the Beez neez can be found But I contacted MBHO about a Ck12 style capsule as their web sit doesn't list anything as being a Ck12 style capsule...It would be good to clarify availability.

 

[chunger]

MBHO, Korby, Beyerdynamic, Lawson, Telefunken, Beesneez, Tskguy and even AKG manufacture versions of this capsule that are readily available for sale and can be used in this build.

Can anyone provide Links to where these can be purchased? I know where the Beez neez can be found But I contacted MBHO about a Ck12 style capsule as their web sit doesn't list anything as being a Ck12 style capsule...It would be good to clarify availability.

I'm curious about this too. . . I'm sure that industry insiders may be able to negotiate and maneuver their channels for parts, but I think it may be a rare thing for a company to offer premium capsules for sale to the general DIY public upon request at small quantity (at non-absurd prices).  Thiersch, Beesneez, and Tim (current backlog aside) being notable exceptions. . . their efforts well appreciated in these parts of the web.

This is one of the primary reasons I went with the Campbell capsule in the beginning.  He has perpetually made his capsules available to the DIY market since well before I got into DIY. . . and still does to the limits of his production capacity. . . it will just take him some time to catch up with the current backlog.  Currently, I am optimistic about tskguy's capsule development because I know it is dimensionally backplate correct, is machined to exceedingly high tolerance standards, and production methods should be tailored to handle the quantities we are concerned with.

 

[Matador]

Yes (see post # 762).
Since C10 and C11 have been damaged, it's possible that C13 has been too..

You are probably just hearing the regular pattern differences.

You say omni sounds ok:  if you polarization on the rear capsule were messed up omni would not work.

Can you post some sound samples of what you are hearing?

 

[Spencerleehorton]

Hi Matador,


thats great stuff, i have a 1.0uf in there at the moment so to open up the bottom end i will try a 2.2uf vishay.
It has a cheap transformer in there and not a Sowter so i will change this first and see if it cures it.
Thanks for your help.

regards

Spence

 

[ArnoldLayne]

You say omni sounds ok:  if you polarization on the rear capsule were messed up omni would not work.

Actually, omni sounds edxactly like cardio.