[FEELER] C12 Clone Project

[kidvybes]

Quite a few companies advocate the ccda circuit that utilizes both halves of the tube like the stock HT-11A, but in this case, if the mics can sound fantastic with plate follower, I'm really keen on extending my tube life especially if dropping over $100/tube.

...just a quick thought on the differences I've observed when comparing tube mics with simple plate-follower circuits to ccda variations...IMHO, the plate-follower based designs offer more clarity, more detail, more natural/natural tonality with more "air"...they stack better when multi-tracking (minimal hash or mud buildup)...they also reveal more of a difference in tonality from tube to tube when swapping different tube options...implementing a design that allows for the swapping of triodes is brilliant, since as Chunger pointed out, the availability of low-microphonic NOS tubes is constantly diminishing...

...on the other hand, ccda mics tend to offer more "color" or "mojo"...they tend to be "character" mics rather than the more neutral/natural flavor that the plate-follower design offers...since the ccda utilizes both triodes of the tube, it becomes more critical to find a "balanced" tube option (both triodes offering matched performance characteristics), and while the tube doesn't seem to effect the mic's tonality as much as it does in a plate-follower, the overall performance will be effected if there is a substantial imbalance between the tube's 2 triodes...IMHO, ccda mics work best when single tracking a solo voice or instrument, unless of course you're going for a more distorted/driven, thicker character by doubling or stacking tracks...

...this is not to imply that capsule and transformer choices don't play a vastly important part in a mic's voicing, but I it would seem that when designing a microphone with a specific character/tonality in mind, implementing one or the other of these circuits would better compliment a particular capsule or tranny combo in achieving that ultimate voicing goal...

...if I were to liken the two circuit designs to classic preamps, I'd say the plate-follower is closer to the API (clean, detailed) and the ccda is more of a Neve (driven, thicker) sound...of course, those are very generalized comparisons but IMHO, they 2 designs tend to favor those tonal characteristics...

...both "flavors" have a place in a well-balanced mic locker, but I find myself reaching for the plate-follower based tube mics more often for vocal duties when tracking various vocal styles...since these are personal preferences, YMMV...

 

[Matador]

Hey Matador, quick un-related question.  Can this PSU be utilized in a G7 build?

Based on my eyeball of the schematic:  yes.  The G7 asks for a higher B+ (160V) but that is just a few resistor changes.

...both "flavors" have a place in a well-balanced mic locker, but I find myself reaching for the plate-follower based tube mics more often for vocal duties when tracking various vocal styles...since these are personal preferences, YMMV...

Such differences are born out of the circuit action as well:  the CDDA has a vastly lower output impedance, so the "RLC" action of the output impedance, the coupling cap, and the inductance of the transformer is completely different between the two. 

The CDDA can also get away with a far lower turns ratio transformer, which means you can get 6-9dB more output and make a much less expensive (as the transformer becomes cheaper) microphone...which is the real reason why I really think all of the clones use it.

 

[tonycamp]

KID VIBES "quote"
IMHO, ccda mics work best when used for a solo voice or instrument, unless of course you're going for a more distorted/driven, thicker character...

...if I were to liken the two circuit designs to classic preamps, I'd say the plate-follower is closer to the API (clean, detailed) and the ccda is more of a Neve (driven, thicker) sound...

Unless i am missing the point (as badly as a handful of gravel being thrown and missing the broad side of a barn, has been known to happen ), these two statements in context, stand in exact contradiction to one another???? ???

please correct me if I'm wrong
thanx
T

 

[kidvybes]

Unless i am missing the point (as badly as a handful of gravel being thrown and missing the broad side of a barn, has been known to happen ), these two statements in context, stand in exact contradiction to one another???? ???

please correct me if I'm wrong
thanx
T

...my point is that the ccda circuit IMHO, does not stack as cleanly as the plate-follower, resulting in undesireable muddyness or a lack of clarity/detail/sheen...in that same sense, I tend to use my Neve 1290 preamp for solo vocal duties or guitar cab, for instance where I want more density or "mojo" (coloration), and do not plan to stack multiple tracks for that particular voice or instrument...

...counterpoint, I prefer the plate-follower on multiple background vocals, or any stacked tracks where I want more clarity, detail and sheen, as a compliment to a more "colored" lead vocal...similarly, I also prefer API type preamps for duties where I also want the least amount of "mud" or "hashy" buildup, and a more neutral/natural overall vibe is preferred when multi-tracking...

...as an overview, when I  do employ the ccda (Neve) for a lead vocal, I tend to reach for the plate-follower (API) for any additional stacked background vocals...I would rarely use the plate-follower for the lead vocal and employ the ccda for stacked background vocal duties, unless I was going for a more low-fi, character vibe...

Neve (ccda) is like tinted glass = thicker, more colored "mojo" vibe
API (plate-follower) is like clear glass = cleaner, more detailed, more neutral/natural vibe

...any clearer?

 

[Biasrocks]

First, let me say that the progress on this project is great. I suspect that we're
all going to be treated to a great sounding piece of kit that will find many uses in our
studios. Great work guys!

Neve (ccda) is like tinted glass = thicker, more colored "mojo" vibe
API (plate-follower) is like clear glass = cleaner, more detailed, more neutral/natural vibe

Comparing microphones to pre-amps is like comparing red heads to brunettes. I have
never chosen a microphone based on it's electronic design, only on how it sounds in a
given situation.

I understand you're trying to make it clear for the punters, but we're all big boy grown ups
here at GDIY, generally trying to learn and gain knowledge through this process.

Here's an excellent summary of the various types of tube circuits, with the advantages and
disadvantages of each type clearly laid out.

Read, learn, build, listen, draw your own conclusions.

http://www.tubecad.com/october99/index.html

Regards,
Mark

 

[kidvybes]

Comparing microphones to pre-amps is like comparing red heads to brunettes. I have
never chosen a microphone based on it's electronic design, only on how it sounds in a
given situation.

...the overview I stated wasn't meant to be a directive on how to choose/use the gear, as much as a reflection upon, after using the gear purely based on it's performance, and later learning about the design, discovering that my preferences seem to follow suit based on those designs...

...again, generalizing, isn't the Neve 1073/1290 based on a 2-stage circuit (like the ccda)?...and the classic API, a single-stage circuit (like the plate-follower)?...

...yes, I understand the structural integrity/differences...my evaluation is simplified and meant to reflect impressions based on actual usage of the gear in a modest recording environment...as stated, YMMV...

BTW, what's wrong wih comparing redheads to brunettes?...

 

[tonycamp]

Hey there Kidvibes, i'm not doubting your experience or your intention as i believe they are from a contributive origin . Go back and read that post, you say exactly 2 opposing things about cathode and plate follower in that post. just reads confusing and i'm pointing it out to you so you can clarify that post.

T

 

[kidvybes]

Hey there Kidvibes, i'm not doubting your experience or your intention as i believe they are from a contributive origin . Go back and read that post, you say exactly 2 opposing things about cathode and plate follower in that post. just reads confusing and i'm pointing it out to you so you can clarify that post.

T

...yes Tony...no problem, bro...I've re-read and clarified in my follow-up post, but I don't see the contradiction...IMHO, plate-follower/API (clean, clear & neutral) particularly great when stacking multiple tracks...ccda/Neve (mojo & color) better for solo tracking when adding character...

...and these are just general observations, and are not meant as a substitute for actually using the gear and making your own judgements...

 

[tonycamp]

...on the other hand, ccda mics tend to offer more "color" or "mojo"...they tend to be "character" mics rather than the more neutral/natural flavor that the plate-follower

IMHO, ccda mics work best when used for a solo voice or instrument, unless of course you're going for a more distorted/driven, thicker character...


...if I were to liken the two circuit designs to classic preamps, I'd say the plate-follower is closer to the API (clean, detailed)


Seriously, this is all over the place, nuetral/natural is not distorted/driven and thicker unless i'm reading wrong, you are saying 2 different things at the same time very confusing???

My suggestion to your appreciated attempt at explaining the sound differences of these mics, is be short, to the point and parse your adjectives carefully

 

[kidvybes]

"IMHO, ccda mics work best when used for a solo voice or instrument, unless of course you're going for a more distorted/driven, thicker character..."

Seriously, this is all over the place, nuetral/natural is not distorted/driven and thicker unless i'm reading wrong, you are saying 2 different things at the same time very confusing???

...Tony, the issue seems to be in the phrase above...I went back and clarified as follows:
"..IMHO, ccda mics work best when single tracking a solo voice or instrument, unless of course you're going for a more distorted/driven, thicker character by doubling or stacking tracks..."

...other than that clarification, my use of adjectives in reference to the 2 different circuits is consistant throughout my posts...I hope that clears things up...

 

[alexc]

I'm glad to hear an experienced opinion on the merits of the ccda and plate follower configs.

Especially as I will keep my ccda modded apex style as well as making one of these wonderful offerings!

Basically eveyone needs brunettes and redheads right? And what of blondes, I ask?

Cheers and thanks kindly to all the contributors of this fine project.

Alex

 

[chunger]

I think real blondes are harder to find these days just like mic grade GE6072a tubes

 

[Matador]

A few more pics:

Here's the completely stuffed board.  The 1000pF and 5000pF caps are 630V polystyrene, and the big yellow output cap is 630V polypropylene:

The board doesn't have to be in the frame to mount all of the components.  I installed the sample 12AX7 tube for testing purposes:

So a short note on the output jack:  there is a small setscrew that holds it in:  but it must be tightened (e.g. turned clockwise) in order to loosen the output jack for removal.  The wiring at the jack was sub-par in my opinion, so I'll redo it with new wire (there were many whiskers of wire around).

 

[Matador]

A few final pics before the next solder-fume sniffing session (probably Tuesday if all goes well).

First off:  the loose screw thing was bugging the hell out of me.  So I re-tapped all of the screws to 2-56 threads.  I think the factory screws must be 2mm, as the tap had just enough to bite into to rethread the hole.  Very nice to not need a drill bit!

There are a total of 16 screws:  4 hold the base plate to the rails, another 4 go into the transformer housing, there are 4 that hold the PCB in place, 2 to hold the top of the side rails, and 2 to hold the capsule suspension mount to the top plate.  After tapping and switching to good zinc plated steel screws, I'l happy to say that everything locks tight and feel must more solid and stable.

So, back to the 7-pin XLR jack.  New wires are cut for the various signals:

I matched the same assignments that I used in the PSU so I could keep it consistent.

After the new wires get heat shrink tubing, the jack is reinstalled and the transformer can then go it.  The two secondaries wire right to pins 5 and 6 of the jack, get heat shrunk, then the transformer can find it's permanent home (as much as anything is permanent in a prototype).  I am using a Cinemag CM-2480 for this prototype:

The wires feed up through pre-drilled holes in the top of the housing:

After this, the transformer housing can be buttoned up to the side rails (with the new screws!):

Now the PCB can be wired to the new wires coming from the XLR jack.  Just follow the silkscreen on the PCB (which I'll make clearer on the final version):

The primary is left unconnected until I can check that the circuit is working properly.

Now I can wire up the tube board:  there are three connections on the bottom of the turrets.  One for plate, grid, and cathode.  Those wires go to the back of the tube adapter PCB:

I am wiring to the second half of the tube, which is denoted on the silkscreen on the adapter.  I also must activate the second half's heater, which is done by bridging from the heater supply to pin 5 of the tube.  I used a small section of soldering braid to do this, but a more elegant way would be to buy a zero ohm 1210 sized SMD resistor, as that's what I used on the layout.

Until next time!

 

[manulaudic]

whenever the pcb is ready for sale count me in for one

Its looking fantastic !!

M

 

[Melodeath00]

So just to be clear, this C12 project is authentic to the original C12, EXCEPT that it is cdda instead of plate follower?

 

[tonycamp]

So just to be clear, this C12 project is authentic to the original C12, EXCEPT that it is cdda instead of plate follower?

I'm pretty sure its a plate follower. Let me say this, its an exact copy of the original c12 circuit surely. If not, then  on me!

 

[chunger]

This is a plate follower circuit. . . same as original.  The discussion above was instigated by my suggestion to run opposite halves of the tube on stereo pair builds as an "advantage" of the plate follower circuit because it can extend the service life of rare NOS tubes.

If you want the CCDA type circuit, by all means, straight mods/optimizations to the stock Alctron HT-11A or Apex 460 PCB are well documented.

 

[earl]

hopefully this is going to be offered as a complete kit everything included now i will go back and read the rest of the thread

 

[0dbfs]

Matador & Chunger, this is looking very nice. I am interested in a pair of these depending on price and what the options end up being. Very interested in the c12 style head baskets too if those are part of this feeler.

Cheers,
JB