[FEELER] C12 Clone Project

[Matador]

Hi Guys,

how do i get hold of a couple of pcbs for this?
Has anyone done a link to mouser yet for the BOM?

really interested in this.

regards

Spence.

We are still prototyping a few BOM / capsule / transformer / layout combinations.  I expect we should be ready for prime time very soon.

Of course, we still have 15 color combinations to try next! 

 

[JessJackson]

I will definitely be building a few of these, I laid out some different types of coupling caps I sourced for size comparisons and have box's of the russian mgm 0.5's mainly reading around 0.6 - 0.7 if anyone wants to trade some for other parts attaining to this circuit.

I think that a cutout would be necessary for those of us wanting to use larger PIO types.

Cheers,

J

 

[chunger]

At this point in this configuration, it looks like .632" is going to be the theoretical absolute maximum diameter for output capacitor.  This is a skinny body and there are certainly many more capacitor options available than the stock HT-11A configuration, but we were not able to flip the tube over and still have the tube easily removable because of the frame rails, so we were not able to buy more diameter clearance.

 

[JessJackson]

This is why I feel a cut out could easily be implemented in the PCB.

0.6" will most likely not be enough clearance for the stock PIO MP Bosch caps not to mention slightly larger 1uf types. The is most likely the reason AKG implemented the cap suspended in the center of the body connecting directly between the bottom of the tube socket and o/p transformer.

 

[chunger]

.632" limit is with the cutout.  Updated iteration of the pcb incorporates an 11mm cutout which should allow enough recess for the 16mm cap to clear.  It will probably contact the tube on the opposite side of the pcb and there might be a little more wiggle room depending on how the tube is seated but I suspect not much more.  Original C12 has tube occupying upper portion of the pcb leaving room at the bottom for their large cap.  We cant do this but have a slightly larger diameter body tube.

 

[funkymonksf]

It's always  compromise, however, we should be able to get the essential flavor out of the circuit and pcb utilized. And in regard to the 1000 and 5000 pf caps, from research, learned that polystyrene are originally used. So why not use them? I know the coupling capacitor is highly important, but if we stay true to the circuit, any .47-.5uf will be perfect and I'm certain even a quality 1.5uf polypropylene cap will work if at a 250v rating, which is still acceptable. I am thrilling to know I will be able to build this amazing mic once all the details are figured out. Heres to matador and chunger! Hear hear!!

 

[chunger]

I guess my 1000pf 200V k40y-9 cap came from Ohio instead of mother russia, so it arrived early.  A little creative lead bending confirms that it will fit.

A few more parts and it'll be ready for some of this:

http://youtu.be/2uloWqjazb8

 

[Matador]

Quick update:  I submitted the panel for a few more copies of version 2 of the boards.  Just waiting to hear back on the cost and the schedule for getting them back.

After much deliberation and pouring over PM's, we settled on:  Bright Neon "Pepto" Pink for the boards, with Mint "Mylanta" Green solder mask.

(Can anyone tell it was Thanksgiving around these parts???) 

;D

 

[Volume11]

Quick update:  I submitted the panel for a few more copies of version 2 of the boards.  Just waiting to hear back on the cost and the schedule for getting them back.

After much deliberation and pouring over PM's, we settled on:  Bright Neon "Pepto" Pink for the boards, with Mint "Mylanta" Green solder mask.

(Can anyone tell it was Thanksgiving around these parts???) 

;D

What the hell? Does each board come with a hit of acid  ? Just kidding, I could care less about the color of the pcb, although it does make gutshot pics a little more intriguing. Looking forward to this project  ;D

 

[chunger]

A few more items are trickling in. . . Oliver from AMI sent a T14 sample.

We also have a couple of rough samples from v1.0 prototype (Tim Campbell stock CT12 capsule, styrene input caps, polypropylene output cap, Cinemag 2480 transformer).  This is mono drum overhead.  Preamp is jsteiger 's Classic Audio Products VP26 w/ GAR2520 opamp.  Console is MCI JH600.  Apogee Rosetta converter RME interface Logic Studio.


Direct to digital.


Tracked to 2" tape

 

[Enchilada]

You must have a nice room to record in!

 

[chunger]

You must have a nice room to record in!

We try, but it is less than ideal. . . ceiling height is low and the room treatments are incomplete.  This photo was taken while acquiring audio data for bass guitar development.  Hopefully, we will be able to iterate on this microphone in a similar manner when we get more prototypes built up.

In particular, we are contending with 2 issues inside the room that inhibit the use of the C12 as the best overhead mic (for this room).

1.  proximity of the side walls.  From what I read, the unique internal chamber design of the C12 capsule lends itself to greater off-axis sensitivity in the treble registers than other designs.  Because of this, we fight phasing or wavering from the cymbals more than with other mics.  Very specific placement in this case minimized the effect.

2.  mid-bass buildup in the room centered around 500hz.  When a high SPL source is driving the room (like drums) these frequencies often muddy up, but this effects all mics.  I need to build and install the slat resonators originally spec'd for the room that were never installed.

We were unprepared for how much clarity and detail comes into this mic in all registers and had a bit of problems making it play nice with the other mics.  For drum overheads, the feel is very different than other mics we've tried and we will have to adjust and experiment.  The room at my house has much higher ceilings (10.5ft. - 14ft.)  That may be a more suitable environment to attempt real-world use of the C12 as a drum overhead again.  Also, we need to build the 2nd microphone to put up a L/R pair for overheads.  I am eagerly waiting for microphones to arrive by boat from China so I can complete the 2nd prototype.

 

[Matador]

I will be sacrificing my Apex460 to this effort for round two.

I placed the order for the second round of prototype boards:  hopefully these will be the final versions.  I also have an order in to Mouser and JustRadio's for BOM parts and styrene caps.  I will stick with the 0.5uF film cap to match the first one.  The EH6072A from my Apex 460 will be reused.

I do not however have a second Tim Campbell CT12 to put it in:  I might leave my Dave Thomas C12-style in there for now until there is something else to test.

 

[morbleu]

I'm in for a pair as well!
Andreas

 

[chunger]

Hey Matador,

I have a 2nd CT12 we can use as well as the T14 and a matching 6072a to prototype 1.  This'll probably give us the closest comparison.

I also have a 2nd psu that I've already swapped resistors on for the pattern switch. . . power to the hakko 808 de-soldering tool!  This way,  you don't have to hack up the psu from your working 460 and will be able to restore it back to original configuration when the large shipment of HT-11A's arrives.

 

[chunger]

mic was placed above and slightly behind the drummer's head approx. ~6.5-7ft. distance from the floor.  It was not placed particularly close.

 

[chunger]

To clarify.

When I said close, I wasn't refering to spot mic close.

I would refer to 5-6ft as close placement for an overhead.

The mic sounds great in that position aside from the cymbal decay flopping in and out of the picture. I would attribute that more to the kits interaction with the room than anything else.

Regards,
Mark

When your room has only a 7.5ft. ceiling, the options are a bit limited in this regard   Work with what you have, right?  FWIW, ceiling is an aborbed false ceiling (4 inches of Owens Corning 703 w/ cloth overlay).  I do believe the cymbal flop is due to room interaction.

 

[desol]

Wow...the digital to tape difference is pretty huge. But i don't wanna get into that...

Like Mark said, it sounds good...apart from the cymbal phasing. Let us know when you have a vocal test chunger!

 

[Matador]

I received confirmation the second round of boards is in process.  I should have them in my grubby hands by end of next week!

 

[Lowfreq]

This is a great looking project so far. Do I need to get my name on a list for one? I'm keen!!