Official C12 Clone - Build and Support Thread

[originalmusician]

Not much was said about the mic comparisons posted by TheJames on page 81 other than mic A is fuller down low, which I agree with. In addition, mic A appears to have more self noise, and I prefer the tonal quality and cleanliness of mic B for this particular application.

Since it appears no one else is going to weigh in, which is which or did I miss this somewhere? OK, don't be mad at me if I picked the wrong mic.  :'(

I also have stock capsule and a beesneez, so I'll do some of my own comparisons and see if I feel the same way.

OK, I have to go back on my word on this one. I kind of liked the Chinese capsule in the comparison when listening briefly to the online sound clips on my laptop computer. I thought it might sit better if it were put into a mix. But since I installed the Tim Campbell capsule in my Chunger C12, I got a chance to give it a proper workout and listen back on studio monitors.  In short, if I didn't need the Chinese capsule for testing new mic builds, I would throw it away.  The TK capsule is a super star in this mic build!

Sorry, I haven't gotten around to comparing it to the Beesneez yet.

 

[liquidfuzz]

Okay, first two questions regarding transformers.

I'm looking for output transformers. How about this one: LL1577 I don't really know the specs on the stock transformer so any insight is highly appreciated.

What's the specs on the power transformer?

 

[Banzai]

Stock is 12:1 ratio.

Power transformer you'll want something between 200/10 and 200/20V.

I'm looking for output transformers. How about this one: LL1577 I don't really know the specs on the stock transformer so any insight is highly appreciated.

 

[Matador]

For power transformer, stock specs are hard to come by.  But basically its:

Secondary: 200VAC @ 10mA (~2VA)
Secondary: 9.5VAC @ 500mA (~5VA)

 

[Matador]

Okay, so it's not me not being able to find the guide..? I couldn't find much info on the v1.4 board in the thread either, well it's mentioned on page 93. No mater if you chose to use a forum for build guide or not, I think it's a bit lame not to come up with an updated guide. Ah well, hopefully it's just yours and my lack of search skill.

Yeah, there isn't much difference with the new board.  It's probably easier to just ask and I'll try to answer your specific questions.

 

[liquidfuzz]

Stock is 12:1 ratio.

I was trying to figure out the impedance of the primary and secondary of the output tranformer. You don't happen to know this..?

 

[liquidfuzz]

Yeah, there isn't much difference with the new board.  It's probably easier to just ask and I'll try to answer your specific questions.

Okay, I can't find any good print of the akg c12 schematics, assuming v.1.4 is a blueprint of it, so I have some questions regarding connection/labelling on the board.

• PLATE - Plate?
• GRID - Should the grid connection just be soldered onto the leg of the socket? There is no lug.
• CATH - Is this the cathode connection, i.e. should it be wired to pin 3, or 8 depending on which triode I go for.
• FC - ?
• BP - Back Plate of capsule?
• RC - ?
• FC - ?

Cheers!

 

[Banzai]

Here's a decent print of the C12: http://danalexanderaudio.com/Micpics/AKG/c12.jpg

AKG used three different transformers. The last one was the Haufe T14/1, datasheet attached.

I was trying to figure out the impedance of the primary and secondary of the output tranformer. You don't happen to know this..?

 

[chunger]

• PLATE - Plate?
• GRID - Should the grid connection just be soldered onto the leg of the socket? There is no lug.
• CATH - Is this the cathode connection, i.e. should it be wired to pin 3, or 8 depending on which triode I go for.
• FC - ?
• BP - Back Plate of capsule?
• RC - ?
• FC - ?

Plate =  connect with wire from TP1 or TP2 pad on the tube PCB depending on which side of the tube you use

Grid = connect wire from "GRID" turret to the open pin on the tube socket correlating to the side of the tube you opt to use.

CATH = connect wire from "CATH" turret to TK1 or TK2 pad on the tube PCB depending on wich side of the tube you use.

FC = front capsule
RC = rear capsule
BP = front and rear backplates on capsule


The new revision power supply build is fully documented in this thread:

http://groupdiy.com/index.php?topic=58054.msg739085#msg739085

The microphone preamp build tracks almost the same as the old build documentation with the following slight deviations:

-Grid connection directly to tube socket
-capsule connections to directly to large turrets (same BP, FC, RC screen printing nomenclature)
-Plate connection simplified to its own turret

- (optional additional screw holes at bottom of the PCB can be drilled and tapped)

New build documentation for the V1.4 microphone board is still pending.

 

[Bowie]

  The output cap talk on the last page got me curious so I used one of my tested .47uf Sprague Vitamin Q 1950's PIO caps in there and made a comparison against the Erse.  Thought I might as well share my impressions in case it's of benefit to anyone.  Because a clinical A/B is not possible when working with one mic I did a few fingerstyle acoustic guitar takes (as identical as possible) with each cap so that I'd be able to listen for differences that remained consistent between the takes.  Understand that despite the detailed descriptions below, these differences were not large or game-changing in any way.  Actually quite subtle considering the big differences in materials in these two caps.  The Erse has a nice 'zing' in the upper registers that gives clarity up top.  The VitQ has equal HF extension but it's a touch more mellow in the lower highs, a little more 'airy' in the upper highs, and smoother.  Those who like the VitQ might feel that the Erse can sound a little 'metallic' up top.  Those who like the Erse might say it has a more exciting and clear top end.  Again though, it's a subtle difference and the better sound will depend on your tastes.

  The slight difference in uf rating didn't have any significant impact on the source though the Erse has a more swift low end response.  This is, again, a matter of taste and one is not better than the other here.  The Erse has more of a tight, "thump", while the VitQ has just a little more of a warmth and "bloom" to lower register notes.  This character extends up to the lower-mids and gives the VitQ a slightly bigger, relaxed feel, the Erse being tighter and more contained.  Again, "subtle difference" is the phrase of the day so don't let my descriptions lead you to believe that this is anything other than minutia.

  The VitQ tracks were heavier in harmonic overtones.  It even seems to be apparent in the spectral analyzer, which surprised me to the extent that I'm hesitant to even mention it.  Now, whether the VitQ is imparting overtones or just magnifying the overtones in the source (acoustic guitar) is the question.  I don't know enough about capacitor construction as of yet to say if a cap will impart harmonics to that degree.  Yet, the Sprague didn't sound dynamically compressed so the reason for it sounding more dense in overtones is undetermined.  Detail between the two caps was comparable, slightly favoring the VitQ in some areas though the Erse's top end gives the impression of clarity.

  All-in-all, both were satisfactory and I wouldn't recommend substituting the Erse unless there's a specific area you want to address, or if you just like to geek-out on this stuff like I do.  The positive is that it's not an expensive mod.  I just ordered a Mundorf Evo Oil and will likely compare that at some point as well.

 

[Phrazemaster]

Excellent details Chris - just the kind we builders need! Thanks!

BTW if you guys don't know, Bowie aka Chris Whitmore is a premiere supplier of awesome tubes for projects like this very one...since he's too humble to toot his horn - great service, fast, friendly, knowledgeable! PM him for any tube needs...

Thanks Chris!

Mike

 

[Bowie]

Excellent details Chris - just the kind we builders need! Thanks!
...since he's too humble to toot his horn - great service, fast, friendly, knowledgeable! PM him for any tube needs...
Mike

Thanks for the kind words, Mike.  Truly.  The community here has been great to me, both in terms of my tube biz and in helping me with my diy projects so I'm trying to give back by making time to contribute here more, be it through little reviews/advice or helping folks in troubleshooting their builds.  Everybody pitching in is what makes this such a great community that has come incredibly far.

 

[Matador]

Thanks for the detailed comparison Christian!  Did you happen to measure the actual capacitance of each cap?  It might also explain some of the differences (especially if you are outside of the nominal 20% tolerance).

One thing you might consider if you like to do these kinds of tests:  you can always record a take, then mike up a speaker at a measured distance (twice for the A/B comparison).  This keeps the performance identical, and you can get capsule positioning very close if you measure.  So long as you don't fiddle with the gain then it gives you about as fair a comparison point as you can get.

Another thing to note:  it would be interesting to compare two similar cap compositions with different voltage ratings (like a 160V versus a 650V).  A higher voltage rating cap (assuming the actual capacitance's are the same) will have more plate area and thicker dielectric:  might make for some sonic changes as well.

 

[Phrazemaster]

At least for electrolytics I've been advised to keep actual voltage going into the cap at about 2/3 the rating...something about too high a voltage causes the cap to actual have much lower capacitance...probably doesn't apply to film...

 

[Bowie]

Thanks for the detailed comparison Christian!  Did you happen to measure the actual capacitance of each cap?  It might also explain some of the differences (especially if you are outside of the nominal 20% tolerance).

One thing you might consider if you like to do these kinds of tests:  you can always record a take, then mike up a speaker at a measured distance (twice for the A/B comparison).  This keeps the performance identical, and you can get capsule positioning very close if you measure.  So long as you don't fiddle with the gain then it gives you about as fair a comparison point as you can get.

Another thing to note:  it would be interesting to compare two similar cap compositions with different voltage ratings (like a 160V versus a 650V).  A higher voltage rating cap (assuming the actual capacitance's are the same) will have more plate area and thicker dielectric:  might make for some sonic changes as well.

Happy to contribute. 

  Yes, they both measured within spec, though the values are 47uf and 56uf respectively.  It didn't seem to have much bearing on this test due to the source (acoustic git), and I didn't see any real difference in low end response in the spectral analyzer, even in the lower regions.  I'm sure it would be more noticeable on kick or bass though.

  I sometimes do exactly as you describe, using a speaker, but it's never quite as satisfying as a live instrument with raw transients, bandwidth, etc and that's what I was looking for here.  I do agree with you that a speaker is more consistent though and if these were products I was dealing in I would certainly make every effort for consistency.  If time allows, I'll do a comparison between the Sprague and a Mundorf, in front of a speaker for the folks on here.  Will be interesting to compare 1950s PIO with 2010s FIO.

  That's a great idea about testing caps of different voltage ratings.  I don't expect it to be big, but it would be nice to know if there is a difference.  Finding high-end caps that even fit in that spot was a bit of a challenge to begin with but I'm sure there's plenty out there.

At least for electrolytics I've been advised to keep actual voltage going into the cap at about 2/3 the rating...something about too high a voltage causes the cap to actual have much lower capacitance...probably doesn't apply to film...

I've heard of this, not going too big w/ electrolytics, though it's never been qualified in any of the mentions I've seen so I never knew what to think.  Maybe someone will chime in.
  I'm pretty sure you're right about film not having this issue or people would run into trouble using 600v orange drops in all the signal sections of various gear.  Still, I wonder if voltage ratings have an affect.  The guys on the hi-fi forums often think so (not that I put any faith in anything I read on a hi-fi forum).

 

[Phrazemaster]

Nice comments Chris.

I used a V-Cap OIMP as the output cap...just b a r e l y fit!

Still waiting on. TC12 to test it with.

 

[patterson]

Hi.  I'm having some trouble with my heater on the power supply.  it reads 11.3 and it doesn't seem that anything I do to the 2k trim pot affects it.  I'd be grateful for any  suggestions.

 

[JessJackson]

I used matador c12 on this joint.

https://www.youtube.com/watch?v=KJ-mfwEHAvI

Sounds very nice Jess.  Was this Tim's capsule?  Any other details on what amp/processing you used?  This mic suits the vocalist well.

Did you use Matador's PSU or one of your originals?  i remember a while back you had mentioned there were some audible differences.

Thanks, yeah Tims capsules w single mesh on basket... LOADS of ITB processing haha. thats kinda my thing. Avalon 737 into TubeTech CL1b into SSL - G+ into Apogee AD16x on the way in. I can't remember if this was recorded before or after i did the elam251 mod to the mic. :/


Yeah it suites her well but makes her sound a lil older. u87ai just with avalon was used on here here.. and on Tyga u87ai Neve 1081 > LA2A > HD Omni :  https://www.youtube.com/watch?v=MzVdDHpSuNc





PSU was matadors psu with regulated heater.

 

[Reverend]

Guys, I built two Matador/Chunger C12 Clones. On the second, I wired it to use the right side of the tube. However, somehow, the microphones are out of phase. Can someone give me an idea on the best way to re-wire/re-solder one so they are both in phase with each other? Thanks.

 

[Category 5]

Guys, I built two Matador/Chunger C12 Clones. On the second, I wired it to use the right side of the tube. However, somehow, the microphones are out of phase. Can someone give me an idea on the best way to re-wire/re-solder one so they are both in phase with each other? Thanks.

Just swap the wires on either side of the output transformer (one side only), or swap pin 2/3 on the output of the inverted mic'a PSU.