GroupDIY

Project Specific Discussions => Microphones => Topic started by: Matador on February 11, 2013, 03:30:36 PM

Title: Official C12 Clone - Build and Support Thread
Post by: Matador on February 11, 2013, 03:30:36 PM
This is the official build and support thread for the C12 Clone project.  All build related materials and pics will be posted first, and please feel free to post any technical, BOM, or assembly related questions.  I'll update this if there are any changes or discoveries which are of a general interest to all builders.

Previous schematic bundle:

C12 Schematic Bundle - Version 3 (http://musicalsparks.com/images/c12/c12_schematics_v3.pdf)

C12 BOM - Version 3 (http://www.musicalsparks.com/images/c12/c12_bom.pdf)

Latest schematic bundle:

C12 Schematic Bundle - Version 4 (http://musicalsparks.com/images/c12/c12_schematics_1v4.pdf)
Title: Re: Official C12 Clone - Build and Support Thread
Post by: chunger on February 11, 2013, 03:30:50 PM
The PCB set, donor bodies, electronic components and other parts for this C12 Clone project are available in the white market:

http://www.groupdiy.com/index.php?topic=50015.0 (http://www.groupdiy.com/index.php?topic=50015.0)

Or, directly from webstore here: 

http://store.studio939.com/ (http://store.studio939.com/)

Recommended capsules for this build are Tim Campbell's CT12 or Eric Heiserman HK12. Please contact Tim directly to order capsules.  The Eric Heiserman HK12's are stocked in the Studio 939 webstore.  Please be aware, currently, demand for Tim's capsules has far exceeded his production capacity.  Some persistence may be needed to obtain a capsule and lead times may be long.  Please plan accordingly for your build.  These are the backplate-correct CK12 type capsules that we have tested and recommend for the build.  Note: There are other chambered  variants being manufactured some of which may be available for DIY and may be suitable to your application, but we do not have 1st hand experience with them in studio.

http://www.timcampbell.dk/index2b.htm (http://www.timcampbell.dk/index2b.htm)

Cheaper edge-terminated capsules are a derivative of the K67 backplate which is much easier to manufacture consistently and can make a quite nice sounding capsule, but do not behave 100% like the original.

(http://studio939.zenfolio.com/img/s10/v17/p1421499798-4.jpg)

(http://studio939.zenfolio.com/img/s8/v80/p1456850396-4.jpg)

(http://studio939.zenfolio.com/img/s2/v70/p1456852208-4.jpg)

This project requires a donor microphone and is specifically designed to fit the Alctron HT-11A.  This is a popular microphone platform and several other companies re-brand and distribute it.  The Apex 460 is a very common version.

(http://studio939.zenfolio.com/img/s4/v68/p1163676630-4.jpg)
Title: Re: Official C12 Clone - Build and Support Thread
Post by: chunger on February 11, 2013, 03:31:09 PM
IMPORTANT NOTE: This DIY project involves working with circuits that carry LETHAL voltages.  The processes and build procedures demonstrated in this thread are for educational purposes only.  All work should only be performed by qualified technicians.  While the parts count in this project is low and build procedures outlined in this project straight-forward, a high voltage tube microphone and power supply is not a recommended beginner DIY project.  Schematics provided in the first post by Matador should be studied and thorough knowledge of all connections and components clarified prior to attempting this build.

Before beginning this project, a few strong recommendations:

1.  If you are new to DIY electronics and do not have confidence and technical knowledge to trouble-shoot the circuit when problems arise, make sure you have a solid fall-back plan.  Before purchasing expensive parts, find someone (friend or professional) local to you who can assist in person if you get stuck!  I will re-iterate that this is not a recommended project for complete beginners.  Please consider starting out with an easier low-voltage project like the VP26 microphone preamp kit from Classic Audio Products.

2.  A digital multimeter that you understand how to use.

3.  A temperature controlled soldering iron.  Delicate electronic components can easily become damaged with even low-wattage non-regulated soldering irons.  Weller, Hakko, and other name-brand tools are good, but I have been using a budget Chinese regulated 75 watt iron for ~20 projects and it has worked smoothly and heats up to operating temperature in under 5 seconds.

http://www.amazon.com/Aoyue-2930-Programmable-Soldering-Station/dp/B00BTQ0CW0/ref=sr_1_1?ie=UTF8&qid=1380515211&sr=8-1&keywords=aoyue+2930 (http://www.amazon.com/Aoyue-2930-Programmable-Soldering-Station/dp/B00BTQ0CW0/ref=sr_1_1?ie=UTF8&qid=1380515211&sr=8-1&keywords=aoyue+2930)

Or, a cheaper 45 watt regulated alternative.

http://www.amazon.com/Aoyue-937-Digital-Soldering-Station/dp/B000I30QBW/ref=sr_1_1?ie=UTF8&qid=1380515363&sr=8-1&keywords=aoyue+937%2B (http://www.amazon.com/Aoyue-937-Digital-Soldering-Station/dp/B000I30QBW/ref=sr_1_1?ie=UTF8&qid=1380515363&sr=8-1&keywords=aoyue+937%2B)

4.  Hakko 808 de-soldering tool.  This expensive tool can save you from hours of frustration and damaging the traces on your PCB if you need to remove components after they have been soldered in.


OK with a full understanding of the inherent risks involved in working with DIY electronics, the first step in this project is stripping the stock Alctron HT-11A 9 pattern power supply.  We will be reusing most of the original A/C components and wiring in order to save time and cost.

(http://studio939.zenfolio.com/img/s8/v75/p1430017320-4.jpg)

4 screws secure the PSU cover.

(http://studio939.zenfolio.com/img/s8/v75/p1430017448-4.jpg)

And 3 screws secure the stock PCB.

(http://studio939.zenfolio.com/img/s2/v73/p1430017646-4.jpg)

With the PCB loose, we can begin de-soldering the required wires.

(http://studio939.zenfolio.com/img/s8/v77/p1430017796-4.jpg)

I have grown quite fond of the Hakko 808 desoldering tool. . . while not necessary in this operation, I typically bring it out when doing disassembly work.

(http://studio939.zenfolio.com/img/s2/v73/p1430017974-4.jpg)

Disconnect all wires that are connected to the main PCB.  Be sure to note the mains from the IEC and the 9V and 200V A/C wires.

(http://studio939.zenfolio.com/img/s8/v85/p1430018128-4.jpg)

With the PCB removed, we can decide which wires to re-use.

(http://studio939.zenfolio.com/img/s8/v74/p1430018264-4.jpg)

I opt to desolder the 3 pin and 7 pin XLR connectors.  The wires that I removed were well soldered and insulated with heat shrink tubing, so it is a viable option to re-use some of these wires, but I like to use new silver teflon wiring throughout.

(http://studio939.zenfolio.com/img/s8/v81/p1430018336-4.jpg)

One note here. . . the 7 pin xlr connector in the stock PSU is wired with pin 7, pin 4, and the chassis bridged together and connected to ground.  In our new power supply, we will need pin 4 to send our bias voltage to the microphone, so you will need to cut the ground bridge to pin 4 and solder a new wire if reusing the stock wires on the 7 pin XLR.

Now, we must decide if we reuse the stock 9 position pattern switch or if we replace it.  The parts kit includes a sealed Lorin switch, so in this build, we will opt to remove the stock switch and use the kit supplied replacement.  There is a lot less desoldering involved and if you do not own a Hakko 808, I would strongly recommend using the new switch.  If you have good desoldering capabilities, it is a tossup.  Both of the previous prototype builds used the stock switch without any issues whatsoever.  Mechanically, it is a bit stronger than the plastic-bodied Lorin switch, but the contacts are not sealed and are probably not as solid.

To remove the stock knob, first pry off the top cover to reveal the tensioning nut.

(http://studio939.zenfolio.com/img/s8/v80/p1430018504-4.jpg)

A special keyed tool is needed to remove this knob, so in the interest of time, I bring out my own special tool.  . . a dremel cut-off wheel.

(http://studio939.zenfolio.com/img/s8/v85/p1430018690-4.jpg)

The smell of melting plastic is a wonderful thing. . . it only takes seconds to cut around the perimeter of the plastic knob to access the knob-setting screw.  Once the plastic is clear, normal tools can be used to easily remove the knob.

(http://studio939.zenfolio.com/img/s3/v39/p1430019256-4.jpg)

(http://studio939.zenfolio.com/img/s8/v81/p1430019416-4.jpg)

The stock switch comes out.

(http://studio939.zenfolio.com/img/s2/v71/p1430019528-4.jpg)

The Lorin switch can be found in this baggie.

(http://studio939.zenfolio.com/img/s8/v77/p1430019648-4.jpg)

(http://studio939.zenfolio.com/img/s8/v74/p1430019768-4.jpg)

Remove the nut and lock washer to access the stop ring.  We will place the stop ring's pin into this slot for our 9 position configuration.

(http://studio939.zenfolio.com/img/s8/v75/p1430020014-4.jpg)

(http://studio939.zenfolio.com/img/s8/v85/p1430019922-4.jpg)

Next, pull the 8 402K switch resistors.  They can be found in this baggie.

(http://studio939.zenfolio.com/img/s8/v81/p1430020122-4.jpg)

Use a small screwdriver to bend the leads on the resistors.

(http://studio939.zenfolio.com/img/s2/v73/p1430020304-4.jpg)

Place a wire into the pin 1 slot and position the first resistor between pin 1 and pin 2. . . and another resistor between pin 2 and pin 3.  We will go around the switch in this fashion.

(http://studio939.zenfolio.com/img/s8/v82/p1430021380-4.jpg)

.  . . and go around until we get to pin 9 where we will add another wire.  In this case, I use red.  I also add a grey wire to the center switch terminal.

(http://studio939.zenfolio.com/img/s8/v75/p1430021510-4.jpg)

I attache another wire to the center pin and test the switch for function.  We should have 3.2M ohm between the red and white wires. . . and between the white or red wires and the center terminal, we should have nice 400K steps all the way around.

(http://studio939.zenfolio.com/img/s8/v80/p1430021738-4.jpg)

If you opt to reuse the stock switch, I found that it is possible to desolder all of the stock resistors and replace them with the kit resistors and new wires without removing the switch. . . this way, the stock knob can be retained without destroying it upon removal.  As mentioned above, without good desoldering tools, this could be a very difficult operation as the plastic parts in the stock switch melt quite easily.  The stock switch with resistors and wires replaced would look like this.

(http://studio939.zenfolio.com/img/s4/v66/p1322904750-4.jpg)

Next, I cut the power supply pcb loose from the PCB set with a cutoff wheel.

(http://studio939.zenfolio.com/img/s4/v68/p1430021872-4.jpg)

A file can be used to quickly touch up the protruding tabs.

(http://studio939.zenfolio.com/img/s2/v71/p1430022104-4.jpg)

And we can now test fit the new pcb into the case.

(http://studio939.zenfolio.com/img/s4/v62/p1430022234-4.jpg)

Because I decided to desolder the stock XLR connectors, I use 22 gauge silver teflon wire to rewire the jack.  The colors chosen have no particular significance.  They are just what I had on hand and selected so I can differentiate easily between the various pins when wiring up the psu.

(http://studio939.zenfolio.com/img/s8/v80/p1430022426-4.jpg)
Title: Re: Official C12 Clone - Build and Support Thread
Post by: chunger on February 11, 2013, 03:31:23 PM
It never hurts to keep builds clean.  Since building microphones, I've been extra obsessive about it.  Most local drugstores would have 90% isopropyl alcohol, and along with a toothbrush, this seems to work quite well cleaning flux off of my solder joints.  It dries quickly and does not leave residue.

(http://studio939.zenfolio.com/img/s4/v63/p1432252828-4.jpg)

So, I start by giving the bare pcb a good dunk and scrub.

(http://studio939.zenfolio.com/img/s2/v70/p1432253104-4.jpg)

Since we already have the resistors out, I start by populating the metal film resistors on the PCB.  All parts are clearly marked on the PCB.  Note:  The current revision PCB's do not have values listed on the components.  Please refer to the BOM and schematic to verify the value of each component indicated on the PCB.

IMPORTANT NOTE:  Around 12/20/2014, we have transitioned to a new BOM for the C12 kit.  Please note the following component changes from the original project BOM

R1, R2 = 68.1K
R9, R10 = 221R
R6 = 499K
C1, C2 = 47uF 350V

All other components are the same as 1st revision.

C12 Schematic Bundle - Version 3 (http://musicalsparks.com/images/c12/c12_schematics_v3.pdf)

C12 BOM - Version 3 (http://www.musicalsparks.com/images/c12/c12_bom.pdf)

For builders who wish to use the 12AT7 tube in their build instead of the original 6072A tube, 33K resistors should be substituted in the R1 and R2 positions.

Part Number RN60D3302FB14 (http://www.mouser.com/ProductDetail/Vishay-Dale/RN60D3302FB14/?qs=sGAEpiMZZMu61qfTUdNhG6Cm1yz0MwZFluZkz52pP%252bs%3d)

(http://studio939.zenfolio.com/img/s8/v79/p1432253462-4.jpg)

After placing all the resistors, bend the leads out to keep them in place, flip the board over, and solder.

(http://studio939.zenfolio.com/img/s4/v66/p1432253800-4.jpg)

(http://studio939.zenfolio.com/img/s2/v59/p1432253932-4.jpg)

Next, pull the 10 1N4007's from this baggie:

(http://studio939.zenfolio.com/img/s8/v77/p1432254082-4.jpg)

And populate them making sure to heed the polarity indicated on the silk screen.

(http://studio939.zenfolio.com/img/s4/v62/p1432254470-4.jpg)

(http://studio939.zenfolio.com/img/s2/v59/p1432254760-4.jpg)

(http://studio939.zenfolio.com/img/s2/v72/p1432254892-4.jpg)

And, another trip to the cleaning dish to clear the flux from the solder joints.

(http://studio939.zenfolio.com/img/s4/v66/p1432255098-4.jpg)

It's not a bad idea to triple check to make sure everything is in the correct polarity.

(http://studio939.zenfolio.com/img/s8/v74/p1432255412-4.jpg)

Next, place the wirewound resistors.

(http://studio939.zenfolio.com/img/s8/v80/p1432255628-4.jpg)

And pull the terminal blocks from this bag:

(http://studio939.zenfolio.com/img/s4/v66/p1432255972-4.jpg)

And populate the terminal blocks.  I find it easiest to solder one lug and then check to confirm the block is seated flush to the PCB.  If not, pressure can be applied to the block while re-heating the single solder joint to position the block.

(http://studio939.zenfolio.com/img/s8/v84/p1432256272-4.jpg)

And terminal blocks are in place.

(http://studio939.zenfolio.com/img/s2/v53/p1432256562-4.jpg)

Next, pull the trimmer pots.  Note: all 3 of these trimmer pots are different values.  Please refer to the BOM, schematic, and the silk-screen print on the PCB and make sure the trimmers are placed in the correct positions.  Switching these up is a very common build error.

(http://studio939.zenfolio.com/img/s8/v83/p1432256718-4.jpg)

And install in the same manner as the terminal blocks.  Values can be checked with a DMM by probing the outer 2 legs of the pots.

(http://studio939.zenfolio.com/img/s2/v70/p1432256764-4.jpg)

(http://studio939.zenfolio.com/img/s4/v66/p1432256956-4.jpg)
Title: Re: Official C12 Clone - Build and Support Thread
Post by: chunger on February 11, 2013, 03:31:35 PM
Next, pull hardware for mounting the heatsink and LM317 regulator.

(http://studio939.zenfolio.com/img/s8/v81/p1433747250-4.jpg)

(http://studio939.zenfolio.com/img/s8/v80/p1433747368-4.jpg)

Position the insulating pad on the heatsink.

(http://studio939.zenfolio.com/img/s2/v70/p1433747578-4.jpg)

Place the plastic shoulder washer in the LM317.

(http://studio939.zenfolio.com/img/s2/v72/p1433747854-4.jpg)

Put the 4-40 screw through the shoulder washer.

(http://studio939.zenfolio.com/img/s3/v7/p1433748028-4.jpg)

And place the assembly on the heatsink.

(http://studio939.zenfolio.com/img/s8/v75/p1433748230-4.jpg)

On the back side, the flat washer goes first.

(http://studio939.zenfolio.com/img/s2/v52/p1433748808-4.jpg)

Then the lock washer.

(http://studio939.zenfolio.com/img/s8/v74/p1433749292-4.jpg)

And finally the nut.  Fit everything together loosely right now.

(http://studio939.zenfolio.com/img/s8/v77/p1433749750-4.jpg)

Next, with the LM317 free to wiggle still, place the entire assembly on the pcb.

(http://studio939.zenfolio.com/img/s2/v72/p1433750216-4.jpg)

Set your soldering iron to the nuclear setting if you have that. .. the heat sink is very efficient at, well, dissipating heat, a bit more juice than normal might be needed to get a nice joint.  Solder one leg while simultaneously pressing down firmly on the heat sink to seat it flush to the pcb.

(http://studio939.zenfolio.com/img/s8/v81/p1433771748-4.jpg)

After verifying the heatsink is sitting where it should, solder the remaining leg into place and tighten the LM317 to final torque.  It should press firmly against the heatsink.

(http://studio939.zenfolio.com/img/s8/v83/p1433771942-4.jpg)

Next, verify with a multimeter that the heatsink is in fact electrically isolated from the metal face of the LM317.

(http://studio939.zenfolio.com/img/s8/v77/p1433772254-4.jpg)

And solder the LM317 into the pcb.

(http://studio939.zenfolio.com/img/s8/v84/p1433772604-4.jpg)

And, because I'm obsessive compulsive, I take the opportunity to scrub the pcb again with denatured alcohol to remove flux.

(http://studio939.zenfolio.com/img/s8/v80/p1433772708-4.jpg)

Next, pull the electrolytic capacitors and populate them on the pcb.

(http://studio939.zenfolio.com/img/s8/v74/p1433773088-4.jpg)

Special Note:  Pay particular attention to the values of the small electrolytic capacitors.  Even though they are the same size, the values are different.  Please heed and double check the small value markings on each capacitor carefully before installing.  If accidentally switched on the PCB, can result in smoke, lack of B+ voltage, overheated transformer, and other unpleasantness.  We have had 2 instances of this particular build error reported.

The small one near the heatsink seems like it would be most difficult to install if other tall parts surround it, so install that one first.  Polarity matters on these capacitors so make sure the long leg goes into the "+" side and the side indicated by the white stripe goes on the "-" side.

(http://studio939.zenfolio.com/img/s8/v75/p1433773694-4.jpg)

The silkscreen clearly indicates a "+" symbol as a guide.  Also, all of the capacitors orient the same direction on the pcb, so all of the white stripes should end up facing one direction.

(http://studio939.zenfolio.com/img/s8/v83/p1433774066-4.jpg)

Place all of the capacitors in position.

(http://studio939.zenfolio.com/img/s8/v76/p1433774236-4.jpg)

and solder in place.

(http://studio939.zenfolio.com/img/s8/v81/p1433774596-4.jpg)

And, I take another cleaning break.

(http://studio939.zenfolio.com/img/s8/v76/p1433779290-4.jpg)

Next, pull the fuse holder and the 2-56 screw, nut, and lock washer.

(http://studio939.zenfolio.com/img/s2/v73/p1433779856-4.jpg)

The lock washer and nut install on the back side of the pcb.

(http://studio939.zenfolio.com/img/s2/v72/p1433779988-4.jpg)

And once the fuse holder is aligned with the silkscreen, tighten to final torque.

(http://studio939.zenfolio.com/img/s8/v78/p1433780244-4.jpg)

And, the power supply pcb is now fully populated.

(http://studio939.zenfolio.com/img/s8/v80/p1433780512-4.jpg)

(http://studio939.zenfolio.com/img/s4/v66/p1433780912-4.jpg)
Title: Re: Official C12 Clone - Build and Support Thread
Post by: chunger on February 11, 2013, 03:31:50 PM
Next, begin installing components back into the chassis.  Start with the 7 pin and 3 pin XLR jacks.

(http://studio939.zenfolio.com/img/s8/v79/p1433781386-4.jpg)

A quick test fit of the populated pcb informs the wire path.

(http://studio939.zenfolio.com/img/s8/v78/p1433781900-4.jpg)

(http://studio939.zenfolio.com/img/s2/v71/p1433782500-4.jpg)

Next, because I foolishly disconnect the stock wiring, I need to re-solder the 3 pin xlr. 

Pin 5 is audio -
Pin 6 is audio +
pin 7 is ground

(http://studio939.zenfolio.com/img/s8/v74/p1433782978-4.jpg)

At this time, the pcb can be fitted for final installation.

(http://studio939.zenfolio.com/img/s2/v72/p1433784952-4.jpg)

(http://studio939.zenfolio.com/img/s8/v81/p1433785528-4.jpg)

And the wire leads on the 7 pin XLR trimmed to length, stripped, tinned, and installed.

Pin 1 = B+
Pin 2 = heater
Pin 3 = pattern
pin 4 = bias
pin 5 = audio -
pin 6 = audio +
pin 7 = ground

(http://studio939.zenfolio.com/img/s8/v78/p1433786024-4.jpg)

Next, install the pattern switch.  I opt to cut the position pin from the switch chassis.  I considered drilling a hole in the case to use the stop pin, but the hole would not have been completely hidden behind the knob I chose to use, so I decided to simply cut the pin and trust the lock washer to secure the switch from rotating after installation.

(http://studio939.zenfolio.com/img/s8/v82/p1433786734-4.jpg)

(http://studio939.zenfolio.com/img/s2/v73/p1433787036-4.jpg)

The Lorin switch is a little bit long for the knob, so I use a cutoff wheel to shorten it a bit.

(http://studio939.zenfolio.com/img/s8/v77/p1433787752-4.jpg)

(http://studio939.zenfolio.com/img/s4/v66/p1433788240-4.jpg)

And, the knob is installed.

(http://studio939.zenfolio.com/img/s8/v82/p1433789008-4.jpg)

Trim the switch leads to length and tin the tips.

(http://studio939.zenfolio.com/img/s8/v84/p1433789800-4.jpg)

And install the wires into the terminal block.

1 = red
2 = grey (original switch green)
3 = white

(http://studio939.zenfolio.com/img/s8/v82/p1433790332-4.jpg)

And the DC side of the psu is now all wired up.

(http://studio939.zenfolio.com/img/s8/v76/p1433793344-4.jpg)

Next, install the 9.5V and 200V A/C leads from the power transformer in the corresponding terminal blocks.

(http://studio939.zenfolio.com/img/s8/v78/p1433793912-4.jpg)

And solder the fuse holder terminals to the power switch.

(http://studio939.zenfolio.com/img/s2/v70/p1433794644-4.jpg)

Install the slow blow fuse.

(http://studio939.zenfolio.com/img/s8/v76/p1433795386-4.jpg)

And the power supply is now complete.

(http://studio939.zenfolio.com/img/s8/v75/p1433796128-4.jpg)

(http://studio939.zenfolio.com/img/s8/v79/p1433796948-4.jpg)

OK. . . time to power it up and see if anything smokes or explodes.

(http://studio939.zenfolio.com/img/s4/v67/p1434207926-4.jpg)

No smoke.  No exploding capacitors.  These are very good signs.

With no load, B+ is at 195V out of the gate.

(http://studio939.zenfolio.com/img/s8/v85/p1434208124-4.jpg)

Heater is sitting at 7.7V.

(http://studio939.zenfolio.com/img/s8/v79/p1434208524-4.jpg)

And our bias is sitting at -1.03V.

(http://studio939.zenfolio.com/img/s8/v78/p1434209016-4.jpg)

Since I know the heater in this power supply is regulated, I adjust that without load to 6.3V with a few turns of the trim pot.

(http://studio939.zenfolio.com/img/s8/v76/p1434209546-4.jpg)

Matador recommends strapping a 180K resistor across B+ and Ground to calibrate B+ and the bias voltage within a reasonable approximation.

I plan to fire up the microphone with the stock Alctron capsule connected, and the original power supply has a B+ specification of 200V.  Because the B+ section of our new power supply is completely passive and sitting at 195V unloaded, I know for certain when connected to a load, it will settle at something lower than 195V which should be within the operating range of the stock capsule.  Note here, for the final installation of Tim Campbell's CT12 capsule, the B+ voltage should never exceed 120V.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: chunger on February 11, 2013, 03:32:08 PM
Next, pull the pcb and electronic parts for the microphone preamp.  There are really not that many parts in this part of the build, so sorting and locating parts should be pretty straight forward.

(http://studio939.zenfolio.com/img/s8/v83/p1449628680-4.jpg)

(http://studio939.zenfolio.com/img/s2/v70/p1449629318-4.jpg)

Special Note:  For kit builders using the 1uF capacitor option.  The kit supplied .56uF original value capacitor does not need any modification to fit.   Erse changed the specs on this particular 1uF capacitor that is supplied in kits ordered after 9/6/2013.  To accommodate the larger diameter capacitor, file the relief slot in the microphone pcb at a 45 degree angle to allow the capacitor to sit slightly lower towards the center of the microphone.

(http://studio939.zenfolio.com/img/s10/v103/p1974644490-4.jpg)

The relief cut looks like this when finished.

(http://studio939.zenfolio.com/img/s9/v96/p2049594378-4.jpg)

The final fit for the capacitor does not leave much wiggle room, but this maximum dimension capacitor fits.  Be careful soldering around the R17 turrets and they are very close to the capacitor.

(http://studio939.zenfolio.com/img/s10/v101/p2022936913-4.jpg)

Pull the turrets first to prep the board for mounting the components.

(http://studio939.zenfolio.com/img/s8/v77/p1449629916-4.jpg)

4 turrets are mounted on the back side of the pcb to accomodate capacitors.

(http://studio939.zenfolio.com/img/s8/v79/p1449630440-4.jpg)

I use a piece of cardboard to hold the turrets in place and flip the whole assembly to solder from the back side.

(http://studio939.zenfolio.com/img/s8/v83/p1449630918-4.jpg)

(http://studio939.zenfolio.com/img/s8/v78/p1449631340-4.jpg)

Press firmly down on the pcb while soldering the turrets to make sure they stand up straight and seat flush to the pcb.

(http://studio939.zenfolio.com/img/s8/v75/p1449631980-4.jpg)

And here are the 4 turrets that mount on the back side of the pcb soldered in.

(http://studio939.zenfolio.com/img/s8/v78/p1449633354-4.jpg)

Next, begin installing the front side turrets in the same manner.

(http://studio939.zenfolio.com/img/s2/v72/p1449633666-4.jpg)

(http://studio939.zenfolio.com/img/s8/v78/p1449634050-4.jpg)

Because the tube mounts to the back side of the pcb, to improve clearance, modify this turret for the C12 capacitor before installing.

(http://studio939.zenfolio.com/img/s8/v74/p1449634496-4.jpg)

Using a cutoff wheel on the dremel, cut a notch into the bottom of the turret.

(http://studio939.zenfolio.com/img/s8/v77/p1449634980-3.jpg)

A wire will fit into this notch and allow the tube to have a little bit more clearance over the top of this turret.

(http://studio939.zenfolio.com/img/s8/v78/p1449635048-4.jpg)

(http://studio939.zenfolio.com/img/s2/v71/p1449635160-4.jpg)

(http://studio939.zenfolio.com/img/s8/v79/p1449635296-4.jpg)

Next, install the 4 capsule connection pins to the pcb.  In this build, we solder these in from the back side.

(http://studio939.zenfolio.com/img/s2/v72/p1449635434-4.jpg)

(http://studio939.zenfolio.com/img/s2/v70/p1449635672-4.jpg)

Connect a length of wire to the bottom of the turret labeled "grid".  I select a gray wire.

(http://studio939.zenfolio.com/img/s2/v72/p1449636804-4.jpg)

At this stage, it is a perfect time to scrub the board down with some 90% isopropyl alcohol to clean off flux residue.  If there is a part that is most important to clean, it is at the base of these turret connections and around the tube pcb that we will install next.  This is a non-optional step.  Unlike the power supply, the high impedance sections of the microphone pcb need to be kept impeccably clean in order to avoid any leaks that could lead to noise and other problems.  Liberally dunk the assembly into the alcohol and use a brush to mechanically loosen and dissolve all of the solder flux.

(http://studio939.zenfolio.com/img/s8/v76/p1449637086-4.jpg)

(http://studio939.zenfolio.com/img/s8/v82/p1449637704-4.jpg)

(http://studio939.zenfolio.com/img/s2/v72/p1449638156-4.jpg)

Next, pull the tube-mounting pcb. 

Important note:  The plate follower topology of this microphone circuit only uses one half of the tube.  We can choose to use either the left side "TK1, TG1, TP1" or the right side "TK2, TG2, TP2".  If using expensive and increasingly rare NOS tubes and building more than one microphone, I strongly recommend wiring the microphones to utilize opposite sides of the tube.  This way, the tubes can be switched between the microphones and the service life of the tubes doubled or at least significantly increased.

(http://studio939.zenfolio.com/img/s2/v70/p1449638424-4.jpg)

We will need to mount a SMD zero ohm resistor to connect the heater voltage to whichever side of the tube you choose to utilize.  I will use the left side "TK1, TG1, TP1" for this build.  To mount the SMD zero ohm resistor, first apply some flux to the pads.  These come in different forms.  I use a paste because that is what i have in my toolbox.

(http://studio939.zenfolio.com/img/s8/v85/p1449638622-4.jpg)

Apply a small amount of solder to one of the pads.

(http://studio939.zenfolio.com/img/s8/v79/p1449638958-4.jpg)

Next, re-apply flux to the pad and use tweezers or in my case some small needle nose pliers to position the resistor while re-melting the solder that was previously pre-applied to the board.

(http://studio939.zenfolio.com/img/s8/v85/p1449639024-4.jpg)

Once satisfied with the position of the component, solder the opposite side as normal.

(http://studio939.zenfolio.com/img/s2/v71/p1449639146-4.jpg)

Don't tell anyone, but that was my very first SMD component. . . not as difficult as some make it out to be.

Next, install the tube socket.  We will need a tube we do not care about at all to loosen up the sockets because they are very stiff when new.  A good candidate is the stock tube inside the HT-11A donor microphone.  The bottom portion of the spring-loaded tube shock support easily compresses and kicks out the side of the microphone frame.

(http://studio939.zenfolio.com/img/s8/v78/p1449639298-4.jpg)

Once the lower support is out of the way, the tube can be easily removed.

(http://studio939.zenfolio.com/img/s8/v77/p1449641212-4.jpg)

(http://studio939.zenfolio.com/img/s8/v83/p1449641734-4.jpg)

I use a pen to gently loosen up the tube sockets because I could not insert the tube into the socket otherwise without risking bending the solder leads.  Do not loosen them too much.  Just enough to allow insertion and removal of the tube but retain a solid grip and contact.

(http://studio939.zenfolio.com/img/s8/v77/p1449642600-4.jpg)

And test fit the beater tube to the socket.

(http://studio939.zenfolio.com/img/s8/v77/p1449642164-4.jpg)

Next, I dunk and scrub the pcb in alcohol.

(http://studio939.zenfolio.com/img/s8/v77/p1449642770-4.jpg)

If you pen leaked all over the tube socket like mine did, it wouldn't be a bad idea to clean that also in alcohol before fitting to the pcb.

(http://studio939.zenfolio.com/img/s8/v80/p1449643258-4.jpg)

Next, solder the tube socket into position.

(http://studio939.zenfolio.com/img/s2/v73/p1449643638-4.jpg)

And clean the flux off.  These connections are very important to keep clean.

(http://studio939.zenfolio.com/img/s8/v79/p1449643754-4.jpg)

Align the 2 pcb's and solder one tab.

(http://studio939.zenfolio.com/img/s2/v70/p1449644472-4.jpg)

Using a straight edge as a guide, re-heat the pad and align the 2 pcb's to perfectly perpendicular.

(http://studio939.zenfolio.com/img/s8/v85/p1449644748-4.jpg)

Once satisfied with the alignment, solder the remaining accessible tabs.

(http://studio939.zenfolio.com/img/s8/v77/p1449653672-4.jpg)

At this point, attach the previously attached red wire to the plate pad on the pcb marked TP1  (or alternately if building the left-side of the tube TP2).

(http://studio939.zenfolio.com/img/s8/v74/p1449654018-4.jpg)

And connect the gray grid wire to the "TG1" pad and install a new wire from the turret indicated for cathode to "TK1"

IMPORTANT NOTE: Version 1.2A PCB's have a screen printing difference from version 1.1A.  The screen printing indicating "CATH" (the cathode wire connection point), has moved from the C10 turret to the C11 turret.  As this a ground point, either location will work for connecting the blue wire.  Following this build thread exactly as pictured works without problems.  Changing the ground point to the C11 junction also works 100%

(http://studio939.zenfolio.com/img/s8/v76/p1449654180-4.jpg)

Next, clean the pcb of solder flux.

(http://studio939.zenfolio.com/img/s2/v70/p1449654466-4.jpg)

The pcb has provisions for triangulating support braces for the tube pcb.  Wire lead cutoffs from the large psu capacitors can be used to create these supports.

(http://studio939.zenfolio.com/img/s8/v76/p1449655062-4.jpg)

And all turrets are installed at this point and we are ready to populate the pcb with electronic components.

(http://studio939.zenfolio.com/img/s2/v72/p1449655670-4.jpg)

There are many ways to attach components to turrets.  I choose to wrap the components around the side of the turret.  They can also be inserted directly into the top holes.  If wrapping around, mil-spec is to use half of a turn at each connection.  Populate the resistors first.

For builders who wish to use the 12AT7 tube in their build instead of the original 6072A tube, a 47K resistor should be substituted in the R17 position.

Part Number RN60D4702FB14 (http://www.mouser.com/ProductDetail/Vishay/RN60D4702FB14/?qs=%2fha2pyFadujO22lygKx5oKO4fUupTzt9QlPPnAc4FeUDRI8J3qDPMg%3d%3d)

(http://studio939.zenfolio.com/img/s8/v79/p1432253462-4.jpg)

(http://studio939.zenfolio.com/img/s2/v72/p1449655670-4.jpg)

(http://studio939.zenfolio.com/img/s8/v74/p1449655992-4.jpg)

Be careful with the temperature setting on the iron and the length of time heat is applied to the turret.  If left on too long, the turrets can come pull away from the pcb and it is a drag re-setting them into the pcb.

(http://studio939.zenfolio.com/img/s8/v81/p1449656258-4.jpg)

And resistors are in place.

(http://studio939.zenfolio.com/img/s8/v82/p1449656410-4.jpg)

While it is not completely necessary to clean these connections, this is the last chance to really dunk and scrub the board because the capacitors do not like exposure to isopropyl alcohol.

(http://studio939.zenfolio.com/img/s2/v70/p1449657566-4.jpg)

Next, I install the output capacitor.  Note the configuration of the wire leads.  I wanted to make a 100% solid connection while retaining the ability to swap this capacitor easily if I decide to move up from the original .5uF specification to a 1uF cap.  I leave enough lead to pull on with needle nose pliers.

(http://studio939.zenfolio.com/img/s8/v76/p1449658048-4.jpg)

Next, the 5000pf caps are installed on the back side of the pcb.

(http://studio939.zenfolio.com/img/s8/v80/p1449658344-4.jpg)

And the 1000pf capacitor on the front side.  The mic preamp board is now fully populated.

(http://studio939.zenfolio.com/img/s8/v78/p1449658688-5.jpg)

(http://studio939.zenfolio.com/img/s8/v74/p1449658516-4.jpg)

(http://studio939.zenfolio.com/img/s8/v76/p1449658880-5.jpg)

(http://studio939.zenfolio.com/img/s8/v77/p1449659324-4.jpg)

(http://studio939.zenfolio.com/img/s8/v80/p1449659870-4.jpg)
Title: Re: Official C12 Clone - Build and Support Thread
Post by: chunger on February 11, 2013, 03:32:36 PM
Next, with the preamp pcb assembled, strip the stock HT-11A microphone to prep for installation.

First unscrew the stock pcb's.

(http://studio939.zenfolio.com/img/s8/v80/p1456800220-4.jpg)

Remove the screws holding the base plate and transformer housing. . . the metal plates that secure the wires are easily pried off with a screwdriver.

(http://studio939.zenfolio.com/img/s8/v81/p1456800344-4.jpg)

Gently lifting the pcb gives access to the capsule wire solder points.  Remove those by unsoldering or cutting year the joint to retain as much of the wire as possible.

(http://studio939.zenfolio.com/img/s8/v79/p1456800476-4.jpg)

(http://studio939.zenfolio.com/img/s8/v74/p1456800652-4.jpg)

Next, pull the bell-housing clear of the output transformer.  The stock ~5:1 ratio transformer is designed for use in CCDA type cathode follower circuit and is unsuitable for use in the plate follower C12 circuit.

(http://studio939.zenfolio.com/img/s8/v85/p1456800790-4.jpg)

The set screw for the 7 pin XLR connector is located here.  It is a reverse direction mechanism, so to loosen the connector, tighten this screw in all the way.

(http://studio939.zenfolio.com/img/s8/v80/p1456800930-4.jpg)

And I opt again to de-solder the XLR connector completely and install new wiring in my microphone.  In this instance, the factory original solder joints looked a little bit suspect, so it is not as much of a toss-up as the power supply connector.

(http://studio939.zenfolio.com/img/s8/v75/p1456801020-4.jpg)

And new silver teflon wires are attached observing the same color to pin orientation as inside the power supply.  We leave pin 5 and pin 6 open at this time because these connect to the output transformer leads.  Remember to use shrink tubing at the terminals as these wires can get pushed around quite a bit during installation.

(http://studio939.zenfolio.com/img/s8/v74/p1456807856-4.jpg)

At this point, re-install the newly wired connector back into the microphone base.

(http://studio939.zenfolio.com/img/s8/v75/p1456807916-4.jpg)

Again, the set screw must be "loosened" all the way to secure the XLR connector into the base.  The screw pushes outward against the base making solid contact with the microphone body securing the connector as well as grounding the connector's ground lug to the mic body.

(http://studio939.zenfolio.com/img/s2/v73/p1456808004-4.jpg)

Install the preamp pcb into the microphone body.

(http://studio939.zenfolio.com/img/s8/v74/p1456808122-4.jpg)

(http://studio939.zenfolio.com/img/s8/v83/p1456808268-4.jpg)

One of the pcb screws will need to be switched to a 12mm long M2 screw which is included in the kit as the frame rail has a through hole in that location to accomodate the stock tube socket.

(http://studio939.zenfolio.com/img/s8/v77/p1456808396-4.jpg)

Next, re-attache the microphone base and bring out the output transformer of your choice.  In this build, we will be using AMI's T14 transformer.  Alternately, the Cinemag 2480 will work well in this microphone.  These are both premium quality transformers with the Cinemag being significantly less expensive.  I would venture to say the build quality on both are on par with each other.  They are just wound and spec'd slightly differently.

(http://studio939.zenfolio.com/img/s8/v74/p1456800132-4.jpg)

(http://studio939.zenfolio.com/img/s2/v71/p1456808448-4.jpg)

It is completely possible and a clean build option to re-use the original metal bell-housing to encase the new output transformer and there may actually be some benefits in terms of isolation to be had in that scenario, but I opt to mount the transformer simply with 3 zip ties because I prefer not to leave slack an then blindly stuff all of the wires into the bell housing and press them against the 7 pin XLR connector.  I'm sure it would work great, but the wires connected to the T14 transformer look to be a bit fragile, so I choose to have all the wiring visible for inspection and trouble-shooting if necessary.  Plus, I might very well forget which microphone this is and need a visual confirmation of what transformer I actually put in there in the future!

Before installing the transformer, do a quick test to verify which side is the capsule side and which side connects to the pcb and which side connects to the output XLR connector on pin 5 (-) and pin 6 (+).

The red wires in this instance read 20.4R on my multimeter and are my output side which will connect to the XLR.

(http://studio939.zenfolio.com/img/s8/v81/p1456808552-4.jpg)

The blue wires read 930R and will connect to the pcb to the terminals labelled  XP1 (+) and XP2 (-).

(http://studio939.zenfolio.com/img/s2/v72/p1456808670-4.jpg)

I determine which set of wires I will select as + and - for audio, trim the red wires to length and solder them to the XLR connector.

(http://studio939.zenfolio.com/img/s8/v85/p1456808782-4.jpg)

Next, i secure the transformer to the frame rails with one large zip tie and 2 small zip ties.

(http://studio939.zenfolio.com/img/s8/v74/p1456822834-4.jpg)

(http://studio939.zenfolio.com/img/s4/v66/p1458215836-4.jpg)

Determine a clean wiring path, cut, strip, and solder the rest of the wire leads from the 7 pin XLR to the microphone preamp pcb.  The pin labels are identical to the ones inside the pcb.  Because I used the same color code wires inside the microphone as inside the power supply, I can double check that my connections are correct.

(http://studio939.zenfolio.com/img/s8/v75/p1456823124-4.jpg)

(http://studio939.zenfolio.com/img/s2/v70/p1456823356-4.jpg)

And here is the base of the microphone with all of the wires installed.

(http://studio939.zenfolio.com/img/s8/v80/p1456823558-4.jpg)

(http://studio939.zenfolio.com/img/s8/v77/p1456823714-4.jpg)

(http://studio939.zenfolio.com/img/s8/v81/p1456823826-4.jpg)

Carefully clean the solder flux off of the newly made connections on the pcb.  Be careful around capacitors and the delicate output transformer wires.

(http://studio939.zenfolio.com/img/s2/v71/p1456831562-4.jpg)

(http://studio939.zenfolio.com/img/s8/v74/p1456831814-4.jpg)

It may be redundant to do this, but I connect an extra wire to the backplate terminal on the stock Alctron capsule to install for testing.

(http://studio939.zenfolio.com/img/s8/v74/p1456823942-4.jpg)

(http://studio939.zenfolio.com/img/s2/v70/p1456823986-4.jpg)

And, the stock capsule is wired in for testing. . . I did not place much emphasis on neatness here as this is just for function testing purposes.

(http://studio939.zenfolio.com/img/s4/v68/p1458207348-4.jpg)

Next, install a tested/functional tube that you do not care much about or is relatively inexpensive to replace.  Here I am using an Electro-Harmonix tube. . . this particular sample should probably be more aptly named "Electro Microphonix".  The important thing is you have a capsule and a tube installed in the microphone at this time that you can afford to blow up without crying too much.

Note:  It is imperative if you are following this "unscientific" initial verification process to make sure the tube and capsule that are being used for calibration and function verification are 100% stable, broken in, and functional.  Otherwise, all manner of problems that are difficult to trace can surface.  The 12AX7 tube that originally shipped with my HT-11A was a hissy, intermittent, crackling mess and totally unsuitable for even function testing.  The Electro Harmonix 6072A tube used for function testing was fired up in a guitar amp for about a week and tested in studio to be completely stable in another microphone.  If purchasing a nice NOS tube from Christian Whitmore for this project and you do not have a known, stable tester tube on hand, please consider sourcing a stable but cheap tube from him for testing purposes.  . . perhaps a tube that is more microphonic than acceptable for microphone use, but is stable and good enough for setting up voltages and function checking.

(http://studio939.zenfolio.com/img/s8/v78/p1456824188-4.jpg)

(http://studio939.zenfolio.com/img/s8/v75/p1456824390-4.jpg)

First I adjust my heater voltage with the trimmer pot inside the power supply measuring from the microphone because there will be some loss along the cable.  Set this to 6.3 volts.  Measuring from inside the power supply, set B+ voltage to 120V and the bias voltage to -1V.

(http://studio939.zenfolio.com/img/s8/v81/p1456831260-4.jpg)

With the tube DC conditions properly set, and the capsule's AC conditions set, assemble the microphone and test for audio and patterning.  "Check 1, 2. . . Check 1, 2. . . "  For this build, the microphone fired up right away without any problems whatsoever.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: chunger on February 11, 2013, 03:32:49 PM
With the circuit tested on our cheap/free donor microphone capsule and expendable tube, it's time to install our premium components to bring this microphone to life.

For this build, we will be using our custom headbasket designed and produced specifically for this project.

(http://studio939.zenfolio.com/img/s8/v74/p1456832522-4.jpg)

(http://studio939.zenfolio.com/img/s8/v83/p1456896492-4.jpg)

And Tim Campbell's outstanding CT12 capsule which is an authentic reproduction of the original C12 capsule and uses the actual old stock membrane material used in the original capsules.  Tims handmade capsule to my knowledge, is the only readily available capsule that utilizes the original capsule's backplate and resonating chamber design.  I do not know about specifics, but it is not a trivial task assembling and calibrating the internal components of this complex assembly.  Most other edge terminated capsules currently available are based on a completely different K67-based backplate configuration.  That is not to say the other capsules cannot be made to work in the circuit and sound amazing.  Certainly the newer designs are easier to manufacture consistently.  It's just that there are few options if "original vibe" is the target.  Tims capsules take a long time to build and the lead time can be long at times, but he does not take your money until your particular capsule is being made and has been of great support and resource to the DIY community.  Also, in my experience, his projections of actual lead time at the time a reservation is placed are for the most part accurate, so it is not an open-ended time-frame.

(http://studio939.zenfolio.com/img/s8/v75/p1456848224-4.jpg)

The CT12 capsule has isolated backplates which we will bridge together at the solder terminals on the capsule.  With this capsule being scavenged from a previous prototype, Matador already soldered in wires for the front diaphragm, rear diaphragm, front/rear backplates, as well as bridge the front and rear backplates together.

The capsule originally came with plastic cover plates to protect the delicate diaphragm membranes from solder splash.  I replace these protectors at this time as I transfer the capsule from the older prototype to the new microphone depicted here.

(http://studio939.zenfolio.com/img/s8/v77/p1456848364-4.jpg)

(http://studio939.zenfolio.com/img/s8/v75/p1456848620-4.jpg)

And, just because it's expensive and I cannot afford to much this up, I put a plastic bag over the entire assembly before de-soldering the capsule from the previous prototype.

(http://studio939.zenfolio.com/img/s8/v80/p1456848786-4.jpg)

Next, remove the stock headbasket and de-solder the stock test capsule.  Remove the capsule and the saddle.

(http://studio939.zenfolio.com/img/s8/v76/p1456849078-4.jpg)

And install the brass mount provided with the Tim Campbell CT12 capsule.

(http://studio939.zenfolio.com/img/s8/v80/p1456849836-4.jpg)

Carefully install the capsule and solder the four connections to the proper lugs on the microphone pcb.

(http://studio939.zenfolio.com/img/s2/v73/p1456849976-4.jpg)

For this build we will be using a NOS vintage GE five star 6072A tube.  Microphone-grade copies of this tube are becoming more and more rare.  I source my tube from Christian Whitmore who tests his tubes for microphonics, noise, and audio quality.  He also burns the tube in for 72 hours to ensure stability.  The selection process is VERY stringent and the best, modern measuring equipment is used to ensure the tube is up to the highest standards for microphone use.  These days, less than 1 out of 10 samples will measure up.

(http://studio939.zenfolio.com/img/s1/v55/p1286669790-4.jpg)

(http://studio939.zenfolio.com/img/s8/v74/p1456850114-4.jpg)

At this point, our C12 clone is electronically completely assembled.

(http://studio939.zenfolio.com/img/s8/v80/p1456850396-4.jpg)

(http://studio939.zenfolio.com/img/s8/v76/p1456851426-4.jpg)

(http://studio939.zenfolio.com/img/s8/v76/p1456851572-5.jpg)

(http://studio939.zenfolio.com/img/s8/v76/p1456851732-5.jpg)

(http://studio939.zenfolio.com/img/s8/v74/p1456851896-5.jpg)

Install the new headbasket.

(http://studio939.zenfolio.com/img/s8/v80/p1458228424-5.jpg)

And confirm or adjust the heater voltage again for the final tube.

(http://studio939.zenfolio.com/img/s8/v74/p1456899038-4.jpg)

The rest of the calibrations can be made with the microphone assembled, so power down and assemble the body.

(http://studio939.zenfolio.com/img/s2/v70/p1456852208-5.jpg)

(http://studio939.zenfolio.com/img/s8/v81/p1456852416-5.jpg)

(http://studio939.zenfolio.com/img/s8/v80/p1456896306-4.jpg)

Our B+ voltage has shifted downward to 108.4 volts upon installation of the Tim Campbell capsule.

(http://studio939.zenfolio.com/img/s8/v83/p1456897550-4.jpg)

A few turns on the trim pot bring us back to our nominal 120 volts. 

(http://studio939.zenfolio.com/img/s8/v80/p1456897976-4.jpg)

Re-adjust the bias voltage to -1.0 volts.

(http://studio939.zenfolio.com/img/s8/v83/p1456898288-4.jpg)

And at this point, all calibrations are completed for this microphone.  Re-install the cover plate on the power supply.

(http://studio939.zenfolio.com/img/s8/v75/p1456899992-4.jpg)

And the C12 clone is complete!  Humans win.

(http://studio939.zenfolio.com/img/s8/v79/p1456900618-4.jpg)
Title: Re: Official C12 Clone - Build and Support Thread
Post by: chunger on February 11, 2013, 03:33:06 PM
reserved
Title: Re: Official C12 Clone - Build and Support Thread
Post by: 3nity on February 18, 2013, 06:35:24 PM
Why do you want to wreck that knob? its pretty easy to take out with some long nose pliers.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: chunger on February 18, 2013, 10:29:05 PM
Why do you want to wreck that knob? its pretty easy to take out with some long nose pliers.

I certainly didn't want to wreck the knob, but I'm assuming the torque applied to the knob tensioning nut varies from copy to copy.  Mine did not come out by conventional means and I didn't feel like making a special tool to remove it.

I'll try pliers on a few samples I have laying around though and see if I have success removing the knob.  In either case, the kit includes a knob.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: tonycamp on February 18, 2013, 11:59:48 PM
looks great Matachung!
Title: Re: Official C12 Clone - Build and Support Thread
Post by: peterc on February 19, 2013, 12:44:27 AM
This is quite inspiring, well done.

If I can make one comment, heatsink compound on both sides of the regulator insulating washer will increase heat dissipation by a factor of 2 or more.

Peter
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Matador on February 19, 2013, 10:29:59 AM
Why do you want to wreck that knob? its pretty easy to take out with some long nose pliers.

I tried on two prototype supplies:  the plastic is brittle and tends to crack when you try to get needle-nose pliers in to loosen the top of the slitted nut.  It was obviously intended to be removed only with the proper tool.  ;)  Perhaps if you have pliers that are thin enough then it wouldn't be a problem.

In any case, I highly recommend using the alternate Lorlin switch:  the stock switch can only be rebuilt if you have the proper soldering tools, as the plastic carrier melts quite easily.  If it melts enough, then the switch no longer makes contact at that position, and then the polar patterns start to jump around as you move the switch.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: 3nity on February 19, 2013, 10:53:17 AM
Its all cool i understand chinesse stuff tends to vary from unit to unit.

I performed some mods long ago on my psu and switch never melted down.
i was using a 25watts iron maybe not too hot to melt it!

Looks good though!
Title: Re: Official C12 Clone - Build and Support Thread
Post by: spudstyle on February 25, 2013, 10:23:30 AM
Waow !!! This is "lego mode" for newbies like me :)
Thank you chunger !!!
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Winetree on February 25, 2013, 02:25:27 PM
Your photo color books have have made many mics possible.
Thanks.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Matador on February 25, 2013, 03:10:23 PM
First post updated with latest schematics.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: poctop on February 25, 2013, 06:11:26 PM
Super nice Job Guys ,  i wish i could do a build guide like this , you guys rocks and i am sure many folks appreciate the extreme amount of work you have been putting into this ,

Best, :)
Dan,
Title: Re: Official C12 Clone - Build and Support Thread
Post by: tonycamp on February 25, 2013, 06:51:05 PM
Hey Chung,

when are the pcbs and component kits going to be available? (sorry if i missed it somewhere)
I'm going to the metal supply house on monday next week to try to hunt down some appropriate tubing, I pretty much have a simple method worked out for offset and extending rails as well, I'll let you know how I make out next week.

T
Title: Re: Official C12 Clone - Build and Support Thread
Post by: chunger on February 28, 2013, 08:11:37 AM
I just confirmed general function and calibration on final revision PCB's and parts kits.

pcb's, parts kits, and AMI transformers are now officially available on the webstore http://store.studio939.com (http://store.studio939.com)

Title: Re: Official C12 Clone - Build and Support Thread
Post by: Tommy Radonicus on February 28, 2013, 09:10:12 AM
I'm going to the metal supply house on monday next week to try to hunt down some appropriate tubing, I pretty much have a simple method worked out for offset and extending rails as well

I've been researching this myself locally (In Australia) as well .. Curious to see how this goes.   8)
Title: Re: Official C12 Clone - Build and Support Thread
Post by: chunger on March 02, 2013, 01:45:37 PM
Just finished up posting the complete build procedure.

A package has been sent to Tim Campbell yesterday for evaluation.

I wish I had a new capsule to show the assembly procedure, but unfortunately, I had to scavenge a capsule from a previous prototype so the picture sequence does not perfectly represent a new build.  I may go back in and re-visit various sections of the build later to clean things up when I have a chance, but in general, I think I've covered everything with enough detail that most people should be able to get through the build.  I also think the new headbasket looks stunning and am very pleased with the proportions of the new mic even though it's too tall now to fit in the original donor mic's pleather baggie.  It still fits in the hard case with room to spare though.

I received a lot of orders for pcb's and parts kits.  I am just finishing up bagging up the kits.  Orders may experience a bit of delay due to volume right now.  Thanks for all your support!

We are running a bit low on HT-11A microphones at this time, but a new order is being worked on to replenish stock and this time I will be ordering significantly more units so we will be able to stay in stock for a while when that arrives.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Matador on March 02, 2013, 02:10:41 PM
Wow I almost ran out of popcorn for this build. ;) That final version looks stunning, and the build pics are gorgeous.

Many thanks to Chunger for doing all of the really hard work for this project:  sourcing bodies and parts from China, getting custom head-baskets made, arranging component kits, talking to Tim and Oliver, driving prototypes and parts all over Northern California, making detailed CAD renderings of all of the internal mike dimensions, etc, etc, etc.  The very first prototype literraly dropped right in and every screw hole lined up perfectly on the first try due to the attention to detail.  In my 20 years in the electronics industry, this has never happened to me before.  I can guarantee to everyone here that designing the PCB's was the easiest part of this entire project. ;)

I hope every gets a chance to build one of these mikes and hear it in their studio, and will be impressed as we were.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: EvLoutonian on March 03, 2013, 05:05:57 AM
That's a good wrap!
I have to admit, it gets my interest piqued!
Title: Re: Official C12 Clone - Build and Support Thread
Post by: chrispsound on March 04, 2013, 05:20:13 AM
Could I just jumper RB and FB at the board or does there need to be another wire attached to the capsule backplate and connected to the PCB?  I am asking this because I already have a Apex 460 with a microphone parts rk12 in it that I would like to use with your PCB and I am pretty sure the two backplates are not isolated.  Thanks, Chris
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Matador on March 04, 2013, 10:13:22 AM
Could I just jumper RB and FB at the board or does there need to be another wire attached to the capsule backplate and connected to the PCB?  I am asking this because I already have a Apex 460 with a microphone parts rk12 in it that I would like to use with your PCB and I am pretty sure the two backplates are not isolated.  Thanks, Chris

Yes.  Electrically, they are the same net.  The isolated backplate feature is really only used on the ELA M25x that has the on-body polar pattern switching.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: tonycamp on March 04, 2013, 07:53:12 PM
Just checked out the final build! :o MataChung! You guys just killed this! Absolutely awesome! Imagine how insane it would have been if the pcb was black :-\....... ;D  I got my shipped notice today, cant wait to build my "Sweetbaby". Thats gonna be her name, my Mk47 is named "Badboy"! Corny yet appropriate?

thanx fella's, again awesome job!
T
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Winetree on March 07, 2013, 08:31:23 PM
Got Power Supply built. On voltage adjust the Bias will go down to -2.6 VDC
but I can only got it up to 0VDC and I run out of turns. Small range. It says you can adjust unconnected to mic.
I have the 502 (5K) Bias trimmer placed correctly. Regulator feels cold. Does it regulate bias?
Other voltages in ballpark.
Any suggestions.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: JessJackson on March 07, 2013, 08:35:25 PM
It should be -1vdc (negative one)

Got Power Supply built. On voltage adjust the Bias will go down to -2.6 VDC
but I can only got it up to 0VDC and I run out of turns. Small range.
I have the 502 (5K) Bias trimmer placed correctly.  Everything else OK.
Any suggestions.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Winetree on March 07, 2013, 08:42:31 PM
Thanks, Human error Misread read Build Guide
Heater can now be adjusted to 6.3 VDC.
On to Mic Build.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Matador on March 07, 2013, 11:59:32 PM
There needs to be a return current to establish the bias.  If you don't want to use a mike, a 180K resistor is perfect, because the tube is meant to be biased to 0.7mA with -1V on the grid (and a 120V plate supply).  The 180K resistor goes between the B+/120V node and ground.

Otherwise, the only return current is through the 470K bleeder resistor, so the bias will jump after a tube is installed.  Keep in mind that the B+ and bias voltage are not regulated:  they require a current in order to establish themselves.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: JessJackson on March 09, 2013, 08:10:41 PM
Matador, Speaking on this... does anyone think it could be worth building a rectified, choked PS like erics here:

http://www.groupdiy.com/index.php?topic=50834.40

My problem is that different studio locations have different fluctuating voltages and with a passive PS the heater can be anywhere from 5.7-6.9.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: tonycamp on March 10, 2013, 10:37:19 PM
Hi fella's,

I built my Matachung C12 clone this weekend! Was really fun and looks great! The quality of all the parts is outstanding. I will be waiting on a couple of Tim Campbells little darling's now. In the meantime, i THINK i found one discrepancy in Chungers build thread regarding audio pins 5 and 6. They are referred to as pin 5+ pin 6- in one post, and pin 5- pin 6+ in another post?(attached)
I just wanted to point this out so there are no wiring out of phase issues for anyone. I will double check this tmrw, to see if i'm confused about it, i just wanted to make sure it was noted.

I BELIEVE IN STOCK WIRING CONFIG, pin 6 IS + I am a dimwit though, so double check me ;)

T
Title: Re: Official C12 Clone - Build and Support Thread
Post by: tonycamp on March 10, 2013, 10:38:16 PM
2nd post
Title: Re: Official C12 Clone - Build and Support Thread
Post by: chunger on March 10, 2013, 10:49:42 PM
Good catch. . . I've corrected the discrepancy.

Pin 5 -
Pin 6 +

 :o
Title: Re: Official C12 Clone - Build and Support Thread
Post by: tonycamp on March 11, 2013, 12:40:37 AM
Hey Chung,

unplugged mic, B+ wont go below 175V!? my bias doesn't move from 0 when turning down? Do you know of a simple reason for this? or did i get the B+ and bias trimmers backward? The Heater is at 6.30v perfect.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Matador on March 11, 2013, 01:35:17 AM
The heater supply in this design is regulated to the adjusted voltage.

The stock transformer has a 9.5V secondary.  That's about 12.7V after the rectifier diode.  At 600mA heater current, another 2.82V is lost across the 4.7 ohm filter resistor, bringing us down to 9.88V at the regulator input.  The regulator must maintain about 1.5V forward bias so that means the voltage feeding the rectifier cannot drop below 6.3V + 1.5V = 7.8V. 

That gives us about 2V of margin, or about 20% of the secondary voltage ratio:  that means the incoming 120V line voltage would have to be grossly out of spec before the heater voltage started to lower (and this is completely ignoring the fact that the heater has 10-15% tolerance all by itself).

As far as the plate voltage goes:  the tube will operate correctly with anything within 20V or so of the trimmed voltage:  the bias supply might suffer a bit, reducing capsule sensitivity if the voltage were to loose, but again the mains voltage would need to be way out of whack.  If it was good enough for AKG...;)

I'm not sure there would be much benefit to a choke in the B+ line:  this circuit doesn't pull a lot of current, and the single tube current range is pretty small (from about 0.1mA to about 2mA).  The PSU caps are more than capable of supplying this between charging cycles.  This is unlike a guitar amp that might have 50-100W output power swings, this design is essentially operated as a high-impedance "constant current source".
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Matador on March 11, 2013, 01:36:31 AM
Hey Chung,

unplugged mic, B+ wont go below 175V!? my bias doesn't move from 0 when turning down? Do you know of a simple reason for this? or did i get the B+ and bias trimmers backward? The Heater is at 6.30v perfect.

You really need a test load to set B+ and bias:  put a 180K resistor between B+ and ground right at the 7-pin cable jack on the PSU.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: tonycamp on March 11, 2013, 01:56:18 AM
Hi Matador,

I'm using the mic as a test load, plugged in, I'm getting 130vdc with the trimmer backed out all the way? The heater is perfect, and the bias is at .032 measured at xp1 pin on the mic, bias trimmer is also backed out all the way?
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Matador on March 11, 2013, 02:44:44 AM
Hi Matador,

I'm using the mic as a test load, plugged in, I'm getting 130vdc with the trimmer backed out all the way? The heater is perfect, and the bias is at .032 measured at xp1 pin on the mic, bias trimmer is also backed out all the way?

XP1?  That is the primary of the output transformer...this should be sitting at DC ground (32mV is pretty close).

Bias is measured at the PSU "P4" node (or the middle node of the 5-pin header).  With nothing connected, you should get between 0V at one end of R3's travel, and about -1.75V at the other end.  This is because R6 establishes a bleeder current which should drop across R3.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Winetree on March 11, 2013, 12:45:43 PM
Finished build and ready to test.
Question; Does it matter which red wire from transformer goes to pin 5 or 6 on Xlr.
Same with blues wires to txp 1 or 2. They're  labeled + and -
If so how do you tell?
Title: Re: Official C12 Clone - Build and Support Thread
Post by: tonycamp on March 11, 2013, 01:33:05 PM
Finished build and ready to test.
Question; Does it matter which red wire from transformer goes to pin 5 or 6 on Xlr.
Same with blues wires to txp 1 or 2. They're  labeled + and -
If so how do you tell?


I believe you just have to designate one side or the other to + or -, then commit to it, the blue wire follows the polarity of the red wire right next to it, but then again, listening to my advise could be a fail ???, as i'm having some voltage adjustment issues? i intend on resolving these tonight...i hope :o
Title: Re: Official C12 Clone - Build and Support Thread
Post by: tonycamp on March 11, 2013, 01:38:52 PM

You really need a test load to set B+ and bias:  put a 180K resistor between B+ and ground right at the 7-pin cable jack on the PSU.

Thanx Matador,

Ok, i put a 182k(closest i had) resistor across  B+ to ground, i adjusted B+ to 120v, and the heater is good at 6.3v, but i get 0 action out of the bias trimmer?? Any ideas?

T
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Matador on March 11, 2013, 02:34:42 PM
Finished build and ready to test.
Question; Does it matter which red wire from transformer goes to pin 5 or 6 on Xlr.
Same with blues wires to txp 1 or 2. They're  labeled + and -
If so how do you tell?

It's really doesn't matter:  just make sure you have primary vs. secondary sorted out and you'll be fine. ;)
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Matador on March 11, 2013, 02:52:13 PM

You really need a test load to set B+ and bias:  put a 180K resistor between B+ and ground right at the 7-pin cable jack on the PSU.

Thanx Matador,

Ok, i put a 182k(closest i had) resistor across  B+ to ground, i adjusted B+ to 120v, and the heater is good at 6.3v, but i get 0 action out of the bias trimmer?? Any ideas?

T

Well, that's not good. ;)  The obvious place to look is at the bias trimmer pot:  it may be that you've dialed it all the way in so that it looks like a short.  Sometimes the pots can take 4 or 5 turns to "go back" the other direction.

I would start by reflowing the pot connections, then if that doesn't help I would take it out and make sure you can read 5K between the two outside pins, and that you can read a variable resistance between any outer pin and the middle pin.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: tonycamp on March 11, 2013, 06:46:09 PM
I reflowed everything, i very carefully checked all product placement, it all looks A OK.
So here's what i've got now, i replaced the 5k bias trimmer for the heck of it, and as i was doing it i realized the stock wiring has pin 4(bias pin) jumped to ground at both mic and psu 7 pin xlr's(I believe that's for the stock cathode config??). I clipped those and now i have a properly adjusted -1.0v bias, 6.3v heater, but I still cannot get 120v out of the B+, its 130V B+ and the trimmer is backed off 100%? 

any ideas how i'm screwin up this time?

thanks
T

Title: Re: Official C12 Clone - Build and Support Thread
Post by: chunger on March 11, 2013, 07:34:12 PM
I reflowed everything, i very carefully checked all product placement, it all looks A OK.
So here's what i've got now, i replaced the 5k bias trimmer for the heck of it, and as i was doing it i realized the stock wiring has pin 4(bias pin) jumped to ground at both mic and psu 7 pin xlr's(I believe that's for the stock cathode config??). I clipped those and now i have a properly adjusted -1.0v bias, 6.3v heater, but I still cannot get 120v out of the B+, its 130V B+ and the trimmer is backed off 100%? 

any ideas how i'm screwin up this time?

thanks
T

You MUST disconnect the jumper from pin 4 to ground at both the microphone 7 pin jack and the power supply jack when constructing this kit.  We utilize pin 4 for the bias voltage while the original microphone did not.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: tonycamp on March 11, 2013, 07:44:40 PM
Yes Chung, i over looked it, it kinda hides in there, it didn't help that i just left stock wiring alone. You have any idea about the 130v thing i mentioned?

thanx
T
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Matador on March 11, 2013, 07:47:28 PM
I reflowed everything, i very carefully checked all product placement, it all looks A OK.
So here's what i've got now, i replaced the 5k bias trimmer for the heck of it, and as i was doing it i realized the stock wiring has pin 4(bias pin) jumped to ground at both mic and psu 7 pin xlr's(I believe that's for the stock cathode config??). I clipped those and now i have a properly adjusted -1.0v bias, 6.3v heater, but I still cannot get 120v out of the B+, its 130V B+ and the trimmer is backed off 100%? 

any ideas how i'm screwin up this time?

thanks
T

You can get 120V with the test load:  pop the tube off of the mike body, and with it warmed up, measure the grid, cathode, and plate voltages right at the tube socket.  You can probe the TK, TG, and TP nodes on whatever side you chose to "activate".

It looks like your tube isn't pulling much current for some reason...
Title: Re: Official C12 Clone - Build and Support Thread
Post by: 3nity on March 11, 2013, 10:00:04 PM
Chunger & Matador
Hope this is not an issue ..
High impedance isolation teflon pins being soldered straight to pcb!!
well this is supposed to isolate high impedance from pcb isnt?
(http://studio939.zenfolio.com/img/s2/v70/p1449635672-4.jpg)
Title: Re: Official C12 Clone - Build and Support Thread
Post by: tonycamp on March 11, 2013, 11:41:48 PM
Ok, I know i'm a newb and all, but i tried everything i could think of and have been told to try, Matadors instruction to put a 180k resistor as a dummy load allowed me to get the proper B+ voltage. But then with the mic plugged in, and using 2 different tubes, i have not been able to achieve the proper b+ of 120v. I started to trouble shoot the mic next, and what i found seems impossible. R15 and R14 250m resistors read DEAD! Nothing, nada, zero, no continuity what so ever, open! I just got a new fluke 87v, and i thought i was doing something wrong, till i broke out the old MM and the same thing, no reading? Would r15 and r14 being dead, and a break in this circuit cause the voltage to stay up around 130v with the B+ trimmer turned all the way counter clockwise? Other 200m to 500m resistors test fine? I've been spending way to much time on this, so i ask, am i crazy or missing something?

thanx
T
Title: Re: Official C12 Clone - Build and Support Thread
Post by: chunger on March 12, 2013, 04:08:22 AM
Chunger & Matador
Hope this is not an issue ..
High impedance isolation teflon pins being soldered straight to pcb!!
well this is supposed to isolate high impedance from pcb isnt?
(http://studio939.zenfolio.com/img/s2/v70/p1449635672-4.jpg)

I inquired about this point with Matador in the prototype stages of the build. . . in this situation, we are pretty much using the part simply as another turret to facilitate easier soldering of the capsule leads.  I am not the technical lead on the project (I just take pretty pictures), but Matador explained to me that in this application, provided the pcb is throughly cleaned with isopropyl alcohol, the FR4 material is a good enough isolator for our purposes.  In use, the prototypes have not exhibited noise or other anomalies associated with leaks  attributed to the physical layout so I questioned it no further.  But, it's worth re-iterating especially in this section of the build that it is important to clean the board thoroughly when assembling the kit.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: 3nity on March 12, 2013, 09:42:43 AM
From what i see proper use of those isolation pins include different design.
Capsule leads and parts lead would solder to the pins instead of traces doing that.

Good to know anyways!

Title: Re: Official C12 Clone - Build and Support Thread
Post by: Matador on March 12, 2013, 10:50:37 AM
What is seen most often is that the connection of the bottom of the isolation pin is a floating via.  Then the other connections are made "on top".

I experimented with this in the first prototype:  isolating the bottoms of the standoffs means there are 4 extra wires connections that have to be made, two of which are critical ground junctions.

In order to combat noise, the soldermask extends right up to the plated turret hole.  This formulation of soldermask has a surface resistance of about 8Gohm per centimeter, which means that if the area around the turret is clean there will be no leakage paths to ground that are anywhere near the impedance of the actual circuit.  The layout in this area is controlled so that there is at least 1cm of solder mask between all of the high impedance nodes (notwithstanding the turrets).

So in short, we want to balance noise benefits with wiring complexity.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Matador on March 12, 2013, 11:03:19 AM
Ok, I know i'm a newb and all, but i tried everything i could think of and have been told to try, Matadors instruction to put a 180k resistor as a dummy load allowed me to get the proper B+ voltage. But then with the mic plugged in, and using 2 different tubes, i have not been able to achieve the proper b+ of 120v. I started to trouble shoot the mic next, and what i found seems impossible. R15 and R14 250m resistors read DEAD! Nothing, nada, zero, no continuity what so ever, open! I just got a new fluke 87v, and i thought i was doing something wrong, till i broke out the old MM and the same thing, no reading? Would r15 and r14 being dead, and a break in this circuit cause the voltage to stay up around 130v with the B+ trimmer turned all the way counter clockwise? Other 200m to 500m resistors test fine? I've been spending way to much time on this, so i ask, am i crazy or missing something?

thanx
T

I would be shocked if any common DVM/meter would be able to read this range of resistance.  The Fluke 87V tops out at 50M, which is pretty typical.

Again, please post the actual tube operating points (the grid, cathode, and plate voltages, or TG, TK, and TP respectively) and we can help you figure it out from there.  What you should see is:  TG at somewhere near the -1V bias level (the meter impedance will foul up reality in this case), TP sitting near half the B+ voltage (perhaps 75V or so), and the cathode TK sitting at ground.

It might also help if you can post some pictures of the interior and the tube wiring so we can confirm everything looks ok.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: tonycamp on March 12, 2013, 03:07:42 PM
Thanx Matador,

Ok here are the readings

Tg1 grid bias =.032
Tk1 cathode=Grnded
Tp1 plate voltage=148v
Title: Re: Official C12 Clone - Build and Support Thread
Post by: tonycamp on March 12, 2013, 03:09:17 PM
2nd shot
Title: Re: Official C12 Clone - Build and Support Thread
Post by: tonycamp on March 12, 2013, 03:10:06 PM
3rd shot

thanx
T
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Matador on March 12, 2013, 04:18:35 PM
If your plate voltage is that high (and I'll assume that the B+ isn't trimmed back to 130V, since you have 148V on the plate), then there isn't any plate current flowing.  This explains why you cannot trim the B+ low enough.  Since this supply is not regulated (nor is the original) it requires a plate current to flow before it can be trimmed.

First off, the grid voltage doesn't look correct.  Did you remove the short between the bias voltage wire and ground in the stock XLR wire mount inside the mike?  Just like in the PSU, Alctron has a wire whisker bridge from the ground wire over to the pin we use for the P4 right on the XLR jack in the bottom of the microphone itself.  I highly recommend that anyone contemplating building this mike remove all of the stock wiring from the XLR jacks in both the PSU and the mike:  the soldering was suspect from the factory IMHO, and it's better if you put a new wire there yourself with a fresh piece of heat shrink tubing for each (mainly to make sure there are no shorts anywhere) just like Chunger did in the build pics.

Even if the bias is shorted in the mike:  it doesn't explain the lack of plate current:  even if the grid is grounded, we should be flowing plate->cathode current:  nearly 1mA if the tube datasheet is to be trusted.  Are you sure that the heater is activated?  From your picture, it looks like you are using the "first" side of the tube (connected to TP1, TK1, and TG1).  What is pin4 sitting at (referenced from pin9)?  Is the tube glowing on the inside (may need to be in a dark room to see it)?

The only other explanation is that we have a ground reference problem.  With the mike powered down, set your meter to "low resistance" measuring mode (unless your DVM is auto-ranging), and plug the negative side of your DVM to the ground node in the PSU (labeled P6), or your green wire in the bottom picture.  Connect the 7-pin cable, and put the other side of your DVM on the P6 node in the mike (right above XP2).  You should be reading less than an ohm between these two points.  Then move the DVM over to pin9 on the tube socket, and you again should be reading less than 1 ohm.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: poctop on March 12, 2013, 04:21:09 PM
One piece of advise for everyone 

Speaking of High Impedance Isolation , I would strongly advice everyone going forward to have a special attention to this section in the red rectangle on the board ,
Comments from Matador will only apply if this section of the boards is impecably clean , attention to small details like this one will make this project works like a charm or transformer in a popping-windying Nightmare.

as the first depicted picture in this build thread shows.
Hope this helps everyone.
Best
Dan,

(https://io.groupdiy.com/file/gdiy-2017/u/39511/58d0281993bbb.jpg)

Title: Re: Official C12 Clone - Build and Support Thread
Post by: chunger on March 12, 2013, 04:45:50 PM
the reason I avoided re-using the stock bell housing setup in my sample build was to avoid shorts and other hookup problems at the base of the microphone that can result from sloppy soldering and faults in heat shrink tubing installation.  It is impossible to visually inspect for solid wiring once everything is jammed into the bell-housing.

I hope that I placed a strong enough emphasis in the build documentation about keeping the microphone pcb impeccably clean in this build.  Please take the time to scrub the board properly with 90% isopropyl alcohol and make sure all solder flux residue has been cleaned especially in the sections that poctop highlighted.  This is not merely for aesthetics.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: tonycamp on March 12, 2013, 05:10:51 PM
Ok guys thanx, I new someone was going to flame me for that! ;D i want to say that i have 91% alcohol right in front of me the whole time, and i use it frequently. I noticed the picture showed that flux scale, really hard to see before the pic? it is a testament to how important it is to be clean, and i will have to clean it better for sure, also, i shrink wrapped and very carefully place the wires in the bell housing.

Matador, thanx for the reply, I did have a tube glowing in there nicely(maybe to nicely?), the B+ trimmer is counter clockwise 100% and the 148v reads at psu w/without mic plugged in? I clipped the p4 jumper at all connectors. My next move is to completely strip all the wiring off and start over on it, including the 7 pin mic cable, i will be very slow and deliberate to see if i can catch THE problem

I'll report back when i'm done

thanx a ton for the support fella's! BTW, not too long ago, i would read these threads and think "what the heck is B+ plate v, and grid bias?" now i almost know! lol!;D
T

Title: Re: Official C12 Clone - Build and Support Thread
Post by: Matador on March 12, 2013, 05:25:12 PM
Before you do all of that, let me be more specific:

1) Plug in mike, fire everything up
2) Set DVM to voltage mode
3) Clip the negative/ground lead to the PSU P4 node (in the PSU itself).
4) Measure TP1, TG1, TK1, and heater with the other probe lead - measure right at the tube pins (1, 2, 3, and 4)

Everything must be connected while this is done.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: tonycamp on March 12, 2013, 08:29:15 PM
Thanx again for the help Matador,

Ok then, Mic plugged in, pin 4 jumper to ground cut everywhere, no tube inserted, power supply on.

Measurements on the tube socket, MM set to dcv
Tp1, tube socket pin1 (B+ plate voltage)=148
Tg1, tube socket pin2 (grid bias)=.032
Tk1, tube socket pin3 (cathode grnd)=grounded
       tube socket pin4 (heater)=6.3volts

This is what i reported early, minus the heater voltage

thanx
T

Title: Re: Official C12 Clone - Build and Support Thread
Post by: Matador on March 12, 2013, 10:19:19 PM
Thanx again for the help Matador,

Ok then, Mic plugged in, pin 4 jumper to ground cut everywhere, no tube inserted, power supply on.

Measurements on the tube socket, MM set to dcv
Tp1, tube socket pin1 (B+ plate voltage)=148
Tg1, tube socket pin2 (grid bias)=.032
Tk1, tube socket pin3 (cathode grnd)=grounded
       tube socket pin4 (heater)=6.3volts

This is what i reported early, minus the heater voltage

thanx
T

Just to be clear:  this is all with no tube installed?

What is the grid bias at the PSU (node P4)...is it 0.032V as well (it should be).  Adjusting the 5K resistor R3 does nothing?

If you remove the cable from the PSU, and re-install the 180K resistor between B+ and GND at the XLR output jack, does the bias recover?  Is it then adjustable.

Can you re-install the tube and post the pin 1-4 data again (I assumed all this stuff was with tube installed:  no tube, no plate current).
Title: Re: Official C12 Clone - Build and Support Thread
Post by: tonycamp on March 12, 2013, 11:21:01 PM
Thanx again for the help Matador,

Ok then, Mic plugged in, pin 4 jumper to ground cut everywhere, no tube inserted, power supply on.

Measurements on the tube socket, MM set to dcv
Tp1, tube socket pin1 (B+ plate voltage)=148
Tg1, tube socket pin2 (grid bias)=.032
Tk1, tube socket pin3 (cathode grnd)=grounded
       tube socket pin4 (heater)=6.3volts

This is what i reported early, minus the heater voltage

thanx
T

Just to be clear:  this is all with no tube installed?

What is the grid bias at the PSU (node P4)...is it 0.032V as well (it should be).  Adjusting the 5K resistor R3 does nothing?

If you remove the cable from the PSU, and re-install the 180K resistor between B+ and GND at the XLR output jack, does the bias recover?  Is it then adjustable.

Can you re-install the tube and post the pin 1-4 data again (I assumed all this stuff was with tube installed:  no tube, no plate current).

Yes, all the measurements were taken with NO tube installed, the grid bias trimmer seems to work fine, at p4 on the power supply and at the bottom of the mic pcb wire hookup p4 position, I measure -1v(i adjusted it with the 5k R3 trimmer), but at the tube socket pin 2(grid bias)measures 0.032? this seems wrong to me?

I will put the 182kR across plate to ground, and then I'll put the tube in and report all the measurements at all 4 socket pins, for both.

Title: Re: Official C12 Clone - Build and Support Thread
Post by: Matador on March 12, 2013, 11:45:02 PM
If the p4 node at the bottom of the mike is ok, then it's fine.  You really cannot read the grid directly as the impedance of the meter will demolish the voltage.

Install the tube and report pin 1-4.  I suspect the PSU is fine, and it's something simple.

You are very close!
Title: Re: Official C12 Clone - Build and Support Thread
Post by: tonycamp on March 13, 2013, 12:07:17 AM
Ok Matador, here we go

At the PSU with a 182k resistor accross pin 1 to grnd 7

P5 B+ reads=                  92v (trimmer is all the way counter clockwise)
P8 heater reads=              6.5v
P4 bias reads=               -1.46v

With the tube in it and glowing

tube socket pin 1(B+) reads=120v                          psu reads=133v(trimmer is 100% counter clockwise)
tube socket pin 2(grid bias) reads=-.653                  psu reads=-1.1
tube socket pin 3(cathode grnd) reads=grnd             psu reads=grnd
tube socket pin 4(heater) reads=6.28                       psu reads=6.51

I did reflow every point on the mic and psu pcb's(after i cleaned them :P), the fact that the resistor load got the B+ down to 92v has to mean the problem is in the mic?

Thanx
T

Title: Re: Official C12 Clone - Build and Support Thread
Post by: Matador on March 13, 2013, 11:16:37 AM
So for some reason, the tube flows only 0.1mA plate current when it should be flowing over 4mA (without considering the dropping across the PSU filters).

Let's eliminate the tube and its biasing from consideration.  Remove the tube, and we'll substitute a fixed "plate resistance" to simulate the tube.  Under normal conditions, we should see about 0.5mA of current with the plate sitting at about 60V, which is a plate resistance of about 120K.

Remove the tube, and solder our virtual plate resistance between pins 1 and 3 of the tube socket.  You can tack it right to the bottom where the solder lugs stick out.  This should simulate the DC conditions of the tube, and you should be able to see pin 1 of the socket sitting at around 50-60V and the B+ at about 92V (with the B+ adjust trimmer 100% fully clockwise).

What tube are you using by the way?
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Matador on March 13, 2013, 12:46:50 PM
In case it is useful, here is a plot for the DC biasing conditions of a 12AY7/6072A tube in the C12 circuit with a 100K plate load resistor:

(http://www.musicalsparks.com/images/c12/12ay7_c12_bias.jpg)

So you can see with -1V grid bias, we follow the -1V curve down until it intersects the load line, and we have a plate voltage of about 50V at about 0.5mA - 0.6mA plate current (or about 82K to 100K of plate resistance).

You can also see the gain from the curve:  if the grid voltage goes from -1V to -2V (a 1V change), then plate voltage swings from 50V to about 80V, or 30V, for a gain of 30 (or 29.5dB).

Like I stated above to tonycamp, we can use a plate resistor to test the circuit prior to putting in a real tube by inserting a resistance from plate (pin 1) to cathode (pin 3) of 82K to 100K which should simulate the above idling point.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: micaddict on March 13, 2013, 01:05:05 PM
Gotta love this forum.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: tonycamp on March 13, 2013, 01:14:13 PM
So for some reason, the tube flows only 0.1mA plate current when it should be flowing over 4mA (without considering the dropping across the PSU filters).

Let's eliminate the tube and its biasing from consideration.  Remove the tube, and we'll substitute a fixed "plate resistance" to simulate the tube.  Under normal conditions, we should see about 0.5mA of current with the plate sitting at about 60V, which is a plate resistance of about 120K.

Remove the tube, and solder our virtual plate resistance between pins 1 and 3 of the tube socket.  You can tack it right to the bottom where the solder lugs stick out.  This should simulate the DC conditions of the tube, and you should be able to see pin 1 of the socket sitting at around 50-60V and the B+ at about 92V (with the B+ adjust trimmer 100% fully clockwise).

What tube are you using by the way?

Good morning Matador, Great graph! This is like doing a science project in school, except in this case, you actually give a poo! ;D

I've been using the chinese donor Alctron tube, i swapped in a 12ax from my ampeg, to make sure it wasn't a tube issue, but the Alctron tube glows nicely and seems fine for testing purposes(he says with 0 confidence :-\).

To be clear, you want me to pull tube, strap a 128k resistor across tube socket pin 1 to 3?, then measure pin 1 B+v at mic(should be 50-60v), and B+v at PSU should be 92v?

I've been staring at the schemo, trying to understand better? still too much of a newb, but getting better slowly and carefully. I hope all these posts help others, and i'm not just cluttering up the airwaves.

thanx again for your help Matador
T
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Matador on March 13, 2013, 01:44:02 PM
Yes.  You can also try just inserting the resistor
into the socket itself (if the socket is tight enough to hold the resistor leads).

Before that, another easy experiment:  hard short the grid (pin 2).  From the curve above, this should flow 1mA (limited by B+).  If the current shoots up (and B+ drops down from 130) then the problem lies in the grid biasing.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: tonycamp on March 13, 2013, 01:46:32 PM
Ok done,

B+ trimmer fully counter clockwise, 127k resistor across tube socket pin 1 to 3,
socket pin 1 reads=53v

at the PSU, pin P5 B+ reads=95v

Exactly as you said! what now said the zombie woof?lmao!!! ;D

I picked up a 6072 tube from Christian for this mic, but I dare not put that sucker in till i'm sure i wont fry a c note :o
Title: Re: Official C12 Clone - Build and Support Thread
Post by: chunger on March 13, 2013, 02:01:16 PM
Just a thought, tonycamp,

I highly distrust the tubes that come stock on the HT-11A and the 12AX7 is wrong type for the circuit.  I recommend sourcing a known-working, stable, and broken in 6072A or 12AT7 for this build.  If you're already ordering from Christian Whitmore, he  can supply you with a tube at low cost that spec's out for testing, but perhaps is microphonic or otherwise not "mic-grade" but will allow you to test for function and calibrate voltages.



Title: Re: Official C12 Clone - Build and Support Thread
Post by: tonycamp on March 13, 2013, 02:11:16 PM
Just a thought, tonycamp,

I highly distrust the tubes that come stock on the HT-11A and the 12AX7 is wrong type for the circuit.  I recommend sourcing a known-working, stable, and broken in 6072A or 12AT7 for this build.  If you're already ordering from Christian Whitmore, he  can supply you with a tube at low cost that spec's out for testing, but perhaps is microphonic or otherwise not "mic-grade" but will allow you to test for function and calibrate voltages.

I was just thinking where can i get another 6072, Christians select 6072 arrived yesterday, i'll have to hit em up for a tester if i cant find one here. I tried to desolder the one out of my mk47 donor i got from you, but petted the bunny on that one George :D
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Matador on March 13, 2013, 02:28:50 PM
Agreed with Chunger:  for some reason this tube is highly suspect.

And don't worry about the questions:  that's what this thread is all about.  All of this troubleshooting applies equally well to any tube circuit:  the tube doesn't know what circuit it's installed in!  I'm sure others will benefit from this:  I had it in the back of mind to make a checklist of tests that people could use in order to make sure everything was working correctly prior to installing the tube.

I would quickly try removing the test resistor, re-installing the tube, and shorting the grid.  You should see a similar collapse of the B+ voltage like the test resistor.  If not, then the tube is highly suspect, as everything else appears as it should be.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: tonycamp on March 13, 2013, 02:57:13 PM
Agreed with Chunger:  for some reason this tube is highly suspect.

And don't worry about the questions:  that's what this thread is all about.  All of this troubleshooting applies equally well to any tube circuit:  the tube doesn't know what circuit it's installed in!  I'm sure others will benefit from this:  I had it in the back of mind to make a checklist of tests that people could use in order to make sure everything was working correctly prior to installing the tube.

I would quickly try removing the test resistor, re-installing the tube, and shorting the grid.  You should see a similar collapse of the B+ voltage like the test resistor.  If not, then the tube is highly suspect, as everything else appears as it should be.

Ok, Alctron tube back in,
i jumped grid tube socket pin 2 to ground, and got 54v B+ at pin1 on the tube socket and 94v B+ at p5 on the PSU

removed the grid jumper, i get 120v B+ at pin1 tube socket and 130v B+ at p5 on the PSU!......=I'm absolutely positively sure, that all this says bad tube.....maybe i think? ;D

T
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Matador on March 13, 2013, 03:56:55 PM
Interesting.  That actually looks correct.

Let's debug the bias supply next:  try the following in sequence:

1) Instead of shorting the grid, short the turret where R11, R15, and C10 connect.  This is the node at the turret right "above" the upside-down turret called "CATH".  In your second picture, it is the next turret to the right along the top (you can see that the second, third, and fifth turrets have a link together).

You should observe similar behavior as directly shorting the grid.

2) Lift up C10 on the underside where it connects along the top (next to your purple wire), and remove the short from step 1 above.  See what happens to B+ and plate voltage (pin 1).

Something is odd with one of the three components above (R11, R15, or C10).
Title: Re: Official C12 Clone - Build and Support Thread
Post by: tonycamp on March 13, 2013, 06:44:15 PM
Ok, sorry for the delay, i had to do a little of this pita thing i call work! ;D I will get on it and report my findings
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Matador on March 14, 2013, 01:19:53 AM
How much soldering did you do to the styrene caps?  How long did you leave the iron on the turrets when installing them?
Title: Re: Official C12 Clone - Build and Support Thread
Post by: tonycamp on March 14, 2013, 03:40:27 AM
very quickly, i have solid soldering skills and i even use an alligator heat clip on the leads of sensitive caps. do you think a cap went bad?
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Matador on March 14, 2013, 10:37:54 AM
This was the node that should be grounded:

(http://www.musicalsparks.com/images/c12/debug/mic2.jpg)

You can leave C10 pulled out if you haven't put it back in.

Grounding this node should mimic grounding the grid directly if everything is working properly.

You can also lift the side of C13 that is connected to the turret labeled "grid" and test that config as well.

It looks like there is DC current flowing through the 250M resistor and is messing up the biasing.  Due to the high impedance, even a tiny current can blow up to a significant voltage.  This could be caused by:

1) Leaking C13 which leaks polarization voltage onto the grid
2) Leaking C10 which leaks bias current and causes a drop across R11 which will cut off the tube
3) Bad tube which is leaking grid current, which forms a drop across R15

If you are careful with soldering I am leaning towards #3.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: tonycamp on March 14, 2013, 12:08:48 PM
Ok, here's the measurement from the turret in your pic,(previously i shorted the one below it ::))

Shorted to ground, My measurements read as follows with tube inserted

at mic tube socket pin 1, plate B+=97v and at the psu 119v
at mic tube socket pin 2 grid bias -0.5v and at the psi -1.131(i noticed the bar meter on my fluke was pulsing a bit?)
at mic tube socket pin 3 grnd grnd
at mic tube socket pin 4 heater 6.3 and 6.5

I hope i did that correctly this time, should i just order those 3 styrenes and replace them? A tester tube is on the way from Christian. I once overed my wiring, looks good, shows good continuity and no shorts between wires on PSU and mic.

thanx again
T
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Matador on March 14, 2013, 01:19:51 PM
This was with C10 removed?

This action is correct:  that means the 250M R15 resistor is probably ok. 

Leave C10 out, then ground the node P4 right as it enters the bottom of the mike.  It should behave the same as above.  This should confirm that R11 is ok (I'm guessing it is...these resistors are tough).

Title: Re: Official C12 Clone - Build and Support Thread
Post by: Matador on March 14, 2013, 01:36:45 PM
And while everything is apart please confirm the correct orientation of C5 in the PSU (4.7uF electrolytic cap).
Title: Re: Official C12 Clone - Build and Support Thread
Post by: tonycamp on March 14, 2013, 01:58:39 PM
This was with C10 removed?

This action is correct:  that means the 250M R15 resistor is probably ok. 

Leave C10 out, then ground the node P4 right as it enters the bottom of the mike.  It should behave the same as above.  This should confirm that R11 is ok (I'm guessing it is...these resistors are tough).

c10 was re installed with a heat dissipator

C5 is correctly oriented in PSU

I will pull c10 and do that test later, unfortunately i'm going to have to work my job till the end of the day, so i'll report it later tonight

thanx M
Title: Re: Official C12 Clone - Build and Support Thread
Post by: tonycamp on March 14, 2013, 10:29:42 PM
This was with C10 removed?

This action is correct:  that means the 250M R15 resistor is probably ok. 

Leave C10 out, then ground the node P4 right as it enters the bottom of the mike.  It should behave the same as above.  This should confirm that R11 is ok (I'm guessing it is...these resistors are tough).

Ok Matador,

with c10 cap removed, the reading is -1.1v at p4 entering the mic? What do you suggest from here?

thanx
T
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Matador on March 14, 2013, 11:40:21 PM
This was with C10 removed?

This action is correct:  that means the 250M R15 resistor is probably ok. 

Leave C10 out, then ground the node P4 right as it enters the bottom of the mike.  It should behave the same as above.  This should confirm that R11 is ok (I'm guessing it is...these resistors are tough).

Ok Matador,

with c10 cap removed, the reading is -1.1v at p4 entering the mic? What do you suggest from here?

thanx
T

First off, measure pins 1-4 with C10 out.

Then measure pins 1-4 again with the P4 node shorted right where it enters the mike.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Matador on March 14, 2013, 11:46:41 PM
Just to ask:  has anyone else got this working successfully?  ;)
Title: Re: Official C12 Clone - Build and Support Thread
Post by: tonycamp on March 15, 2013, 03:08:36 AM
This was with C10 removed?

This action is correct:  that means the 250M R15 resistor is probably ok. 

Leave C10 out, then ground the node P4 right as it enters the bottom of the mike.  It should behave the same as above.  This should confirm that R11 is ok (I'm guessing it is...these resistors are tough).

Ok Matador,

with c10 cap removed, the reading is -1.1v at p4 entering the mic? What do you suggest from here?

thanx
T

First off, measure pins 1-4 with C10 out.

Then measure pins 1-4 again with the P4 node shorted right where it enters the mike.

Matador, i was wondering the same thing, am i the only one who's attempted to put this together so far?, or is it so easy that i'm the only jackass who cant get it done? ;D

Both sets are measurements with no C10

tube socket pin 1= 117v at psu 131v
"        "        pin 2= -0.55 at psu 1.1v
"        "        pin 3=grnd grnd
"        "        pin 4=6.3 at psu6.5

with the p4 at the entry of the mic shorted to ground

tube socket pin 1=113v at psu 125v
"       "         pin 2=0.56 at psu .040
"       "         pin 3 grnd grnd
"       "         pin 4=6.3 at psu 6.5

thanx
T
Title: Re: Official C12 Clone - Build and Support Thread
Post by: chunger on March 15, 2013, 03:12:04 AM
Just to ask:  has anyone else got this working successfully?  ;)

I got 1 to work. . . it was a smooth build  8)

Several kits went out to early adopters who have parts in hand, so I'm hoping those folks don't have too long of a build queue, but that's probably wishful thinking.  This is DIY-world after all.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: tonycamp on March 15, 2013, 03:16:31 AM
Just to ask:  has anyone else got this working successfully?  ;)

I got 1 to work. . . it was a smooth build  8)

Hey!, no fair, thats kinda like Thomas Edison saying he has working lights in his house!
Title: Re: Official C12 Clone - Build and Support Thread
Post by: chunger on March 15, 2013, 03:24:23 AM
You would be shocked at my lack of technical knowledge and the general incompetence displayed behind the scenes at the Chinese Labor Camp.  But, I do think things through quite thoroughly before ever pickup up a soldering iron and make sure:

1.  I won't hurt myself or blow something up
2.  I'm certain each step is correct

With such a severe deficiency in trouble-shooting capability, I need to make EVERY effort to not make a mistake.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: tonycamp on March 15, 2013, 03:34:22 AM
Hey Chung, right there with you! I'm very careful, and I've been pretty successful with my projects so far, this one is very well put together and should be a piece of cake considering the work you guys put in, it's gonna be something silly in the end, and probably my fault. Thank goodness for matadors cognitive capacity!, otherwise  i'd be adrift, paddle free!

Cant wait to get this girl rollin, thanx again for the project fella's!

T
Title: Re: Official C12 Clone - Build and Support Thread
Post by: kidvybes on March 15, 2013, 08:50:40 AM
Just to ask:  has anyone else got this working successfully?  ;)

...triplets here:
http://www.groupdiy.com/index.php?topic=51766.0

Title: Re: Official C12 Clone - Build and Support Thread
Post by: micaddict on March 15, 2013, 10:54:09 AM
Quote
...triplets here

Might as well go quadrophonic then.  8)
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Tim Campbell on March 15, 2013, 11:10:37 AM
pics might help.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Winetree on March 15, 2013, 11:46:35 AM
The Triplets are fine and are resting
waiting for new capsules.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: tonycamp on March 15, 2013, 12:15:58 PM
good to see these successes! I'll be joinin ya"ll shortly ;)
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Matador on March 15, 2013, 01:11:02 PM
Both sets are measurements with no C10

tube socket pin 1= 117v at psu 131v
"        "        pin 2= -0.55 at psu 1.1v
"        "        pin 3=grnd grnd
"        "        pin 4=6.3 at psu6.5

with the p4 at the entry of the mic shorted to ground

tube socket pin 1=113v at psu 125v
"       "         pin 2=0.56 at psu .040
"       "         pin 3 grnd grnd
"       "         pin 4=6.3 at psu 6.5

thanx
T

So let's summarize so far:

1) Shorting the grid at pin 2 causes the current to shoot up:  correct
2) Shorting the turret where C10, R11, and R15 join causes the current to shoot up:  correct
3) Removing C10:  current changes: incorrect
4) Removing C10, shorting right at P4 where it enters the mike:  not much current change:  incorrect

DC bias current should not change when C10 is removed:  it is a filter only.  C10 is suspect.

So let's narrow down the rest of the components at these nodes (which are R11 and C13).

Pull C13.  Leaving C10 out, short the same node as step 2 above and make sure the current still increases (meaning pin 1 drops).  Then short P4 as it enters the mike:  if R11 is ok, you should see the current increase the same way as it did shorting the turret as in step 2.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: tonycamp on March 16, 2013, 02:14:23 PM
Both sets are measurements with no C10

tube socket pin 1= 117v at psu 131v
"        "        pin 2= -0.55 at psu 1.1v
"        "        pin 3=grnd grnd
"        "        pin 4=6.3 at psu6.5

with the p4 at the entry of the mic shorted to ground

tube socket pin 1=113v at psu 125v
"       "         pin 2=0.56 at psu .040
"       "         pin 3 grnd grnd
"       "         pin 4=6.3 at psu 6.5

thanx
T

So let's summarize so far:

1) Shorting the grid at pin 2 causes the current to shoot up:  correct
2) Shorting the turret where C10, R11, and R15 join causes the current to shoot up:  correct
3) Removing C10:  current changes: incorrect
4) Removing C10, shorting right at P4 where it enters the mike:  not much current change:  incorrect

DC bias current should not change when C10 is removed:  it is a filter only.  C10 is suspect.

So let's narrow down the rest of the components at these nodes (which are R11 and C13).

Pull C13.  Leaving C10 out, short the same node as step 2 above and make sure the current still increases (meaning pin 1 drops).  Then short P4 as it enters the mike:  if R11 is ok, you should see the current increase the same way as it did shorting the turret as in step 2.

Hello Matador,

Ok, pulled C13 and jumped left turret at r15 to ground, C10 still out

tube socket pin 1=97v at psu=119v
"      "        pin 2=-0.50 at psu=-1.15
"      "        pin 3=grn
"      "        pin 4=6.3 at psu=6.5

Removed jumper at R15 and jumped p4 to grnd entering the mic

tube socket pin 1=97v at psu 119v
"      "        pin 2=0.544 at psu 0.039
"      "        pin 3 grnd
"      "        pin 4 6.3 at psu 6.5

?

thanx
T

Title: Re: Official C12 Clone - Build and Support Thread
Post by: Matador on March 16, 2013, 02:39:06 PM
Ahh...that is now correct.  Either C10 or C13 is suspect.  C13 could be leaking polarization voltage on to the grid, or C10 is leaking to ground and causing a bias across R15.  If C10 was leaking, this should try to pull the grid higher which would make the current higher, which isn't what you are seeing.  If C13 was leaking, then it would drop across R15 which would make the polarization voltage lower which would cause the current to drop (which you are seeing).  So I'm leaning towards C13 but you should check both.

Do you have any non-styrene 1nF and 5nF caps you can try in these positions? 

In order to isolate between the two, you can try:

1) Leave P4 grounded and both caps out.  You should see pin1 at ~97V just like you already have.
2) Insert C10 back in.  You shouldn't see pin1 change from 97V, as the cap should not effect the DC bias level.
3) If on inserting C10 you see pin1 jump back up to 120V, then C13 is suspect and should be replaced.
4) Assuming #2 is successful (pin1 stays at 97V after C10 goes back in), re-insert C13.  If you see pin1 shoot back up to 120V then C10 needs to be replaced.

If either of those two caps are leaking DC current then it will cause foul-ups of the bias (due to the astronomically high impedances of the bias resistors).
Title: Re: Official C12 Clone - Build and Support Thread
Post by: tonycamp on March 16, 2013, 02:55:04 PM
Cool Matador,

and then there were 2!, i do not have any caps to use as substitutes, I am going to frys right now tho get some new soldering tips, i'll look for a couple of the caps while i'm there(prob wont have), i will follow your instruction when i return. Do you by chance know the manufacturer of the styrenes in the kit, or part #'s, so i can order new ones?

again, thanx a lot for guiding me through this buddy
T
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Matador on March 16, 2013, 05:15:36 PM
I got the original styrene parts from www.justradios.com:  I think Chunger may have as well.  Go to their cap page, and look for the section titled 'Polystyrene Film "Tubular axials"'.

You should be able to find 1000pF and 5000pF (or 1nF and 5nF, or maybe even 0.001uF or 0.005uF) ceramic caps at Frys for testing.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: tonycamp on March 16, 2013, 07:25:19 PM
Ahh...that is now correct.  Either C10 or C13 is suspect.  C13 could be leaking polarization voltage on to the grid, or C10 is leaking to ground and causing a bias across R15.  If C10 was leaking, this should try to pull the grid higher which would make the current higher, which isn't what you are seeing.  If C13 was leaking, then it would drop across R15 which would make the polarization voltage lower which would cause the current to drop (which you are seeing).  So I'm leaning towards C13 but you should check both.

Do you have any non-styrene 1nF and 5nF caps you can try in these positions? 

In order to isolate between the two, you can try:

1) Leave P4 grounded and both caps out.  You should see pin1 at ~97V just like you already have.
2) Insert C10 back in.  You shouldn't see pin1 change from 97V, as the cap should not effect the DC bias level.
3) If on inserting C10 you see pin1 jump back up to 120V, then C13 is suspect and should be replaced.
4) Assuming #2 is successful (pin1 stays at 97V after C10 goes back in), re-insert C13.  If you see pin1 shoot back up to 120V then C10 needs to be replaced.

If either of those two caps are leaking DC current then it will cause foul-ups of the bias (due to the astronomically high impedances of the bias resistors).

C10 back in, tube socket pin 4 holds at 97v
C13 back in, tube socket pin 4 jumps to 120v to 130v! acted very erratic!

DAG NABBIT!!! C10 IS THE VARMINT!!!

Is it normal to want to smash it with a hammer now? >:(

You know, i'm thinking i should just replace all 3 styrenes now that i've ironed them a bunch of times(i did heat sink clip them every time)? Also as i've been thinking about it, pre tinning the outside of turrets and wrapping around would allow an ultra quick contact with the iron, vs filling the turret which gives more mass for the heat to hang onto longer, maybe i did toast it? we'll never know ???

Thanx again for all your help Matador, if i can return the favor someday(obviously outside the realm of electronics), it would make me happy

T
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Matador on March 16, 2013, 07:41:42 PM
C10 back in, tube socket pin 4 holds at 97v
C13 back in, tube socket pin 4 jumps to 120v to 130v! acted very erratic!

DAG NABBIT!!! C10 IS THE VARMINT!!!

Just to make sure:  if it goes wonky with C13 back in, then C13 is the culprit...not C10. 

Was that just a typo?
Title: Re: Official C12 Clone - Build and Support Thread
Post by: tonycamp on March 16, 2013, 07:49:09 PM
C10 back in, tube socket pin 4 holds at 97v
C13 back in, tube socket pin 4 jumps to 120v to 130v! acted very erratic!

DAG NABBIT!!! C10 IS THE VARMINT!!!

Just to make sure:  if it goes wonky with C13 back in, then C13 is the culprit...not C10. 

Was that just a typo?

Ok, i'm replacing all three just to be safe, you did say c10 on number 4. above though

T
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Matador on March 16, 2013, 07:49:49 PM
Also, if you are going to order new ones from JustRadios, buy a couple of all of these following types (since you only need two values, 1000pF and 5000pF, and they are all less than $1):

1) 500V 5% Dipped Silver Mica Capacitor
2) 630V Metal-Foil Polypropylene "Orange Dip" Capacitors
3) 630V Metalized Polypropylene Film "Tubular axials"
4) 630V Polystyrene Film "Tubular axials"

For C11 and C10 it's not as critical, as they are just filters that dump noise to ground.  However audio does pass through C13 and you might find slightly different "mojo" with the above types.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Matador on March 16, 2013, 07:51:04 PM
Ok, i'm replacing all three just to be safe

T

Understood:  when you get them, I highly suggest putting them in one at a time in a process like you just did, and you can test each one in turn and make sure they are ok.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: tonycamp on March 16, 2013, 07:54:12 PM
will do all of the above Matador, thanx a million

Edit 8 months later; I just noticed i never resolved on this thread, even though i've had this mic working for 8 months now, somehow i must have burned a polystyrene cap..C10(i think it was), i replaced all three, put in the Tim Campbell capsule, and  :o amazing mic!

thanx Matador and Chung
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Matador on March 20, 2013, 10:46:37 AM
Got one working today. It seems that the meter drags down the readings on the B+/Bias circuit. So the only way I was able to get it adjusted is by taking quick readings followed by an adjustment, repeated until I got it into the correct range. I'm assuming this is normal.

Yes.  If you use a DVM with 1M input impedance, it will draw 120uA of current from B+.  This will drop an additional 20V or so from the B+ supply.

If you have a DVM with 10M input impedance, or a scope with a 10x mode, this is preferred.  Otherwise, you can not stuff the 470K bleeder resistor until after you have made the circuit adjustments, and then place it back in after the mike is set up.  The bleeder will substitute for the meter, so the voltage will by definition not be higher due to the effect of the meter.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Ericbazaar on March 21, 2013, 07:43:26 AM
Hi at all,

first to my Person, i am absolutely new in Mic Building and I'm from the area Ribbon Mic. I am from Germany and please excuse my bad English.
I saw a few weeks ago the studio page 939 and I knew I will build this microphone. I ordered everything.
I build the Mic in last 2 Days.
I have some questions. Is it even possible to make a test with the stock Tube and the stock Capsule? I still waiting for the right Tube and Capsule. The shipping takes a long time from the USA, unfortunately. The values ​​of the PSU are normal.
Unloaded B+ = 195V
Heater          = 6.5V
Bias              = -1,0V
Is it possible to test the microphone without a right tube and a right Capsule? Unfortunately I have ever started a recording and this micro does not sound good, extremely quiet level, it hums, it has no bass, sounds harsh.
Please do not scold me, I should not have to make, I know...
I only have the stock tube, so can I measure values​​ with it? I have ordered a 6072A gold by Electro Harmonix. Should I rather wait for the tube?
How are the values ​​at the micro body and how can I measure, without tube?

Many Thanks

Eric

 
Title: Re: Official C12 Clone - Build and Support Thread
Post by: HellfireStudios on March 21, 2013, 09:45:12 AM
I would not do any calibration without the intended capsule and tube, but a functionality test (make sure it outputs sound) could be done with the the original capsule and tube.

-James-
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Ericbazaar on March 21, 2013, 10:17:16 AM
Hi again,

here are a few pictures. The SMD is unfortunately not in the middle of the contacts, are there problems? Have I done everything right?
https://www.dropbox.com/s/pjuybi39d2v5s4n/IMG_9591_DxO.jpg
https://www.dropbox.com/s/16lcztrhe1d5nzt/IMG_9593_DxO.jpg 
https://www.dropbox.com/s/oh81wvr3lrqgmok/IMG_9594_DxO.jpg
https://www.dropbox.com/s/l798dj43an0tped/IMG_9595_DxO.jpg
https://www.dropbox.com/s/8yw2yav3pxgwy9z/IMG_9596_DxO.jpg
https://www.dropbox.com/s/zybzkoq6upfteqm/IMG_9597_DxO.jpg
https://www.dropbox.com/s/4jthrjxmvjfv61o/IMG_9598_DxO.jpg
https://www.dropbox.com/s/ar7tbit50kjgjqi/IMG_9599_DxO.jpg
https://www.dropbox.com/s/ty6cflqsv0t9dlg/IMG_9600_DxO.jpg
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Matador on March 21, 2013, 10:53:44 AM
Hi at all,

first to my Person, i am absolutely new in Mic Building and I'm from the area Ribbon Mic. I am from Germany and please excuse my bad English.
I saw a few weeks ago the studio page 939 and I knew I will build this microphone. I ordered everything.
I build the Mic in last 2 Days.
I have some questions. Is it even possible to make a test with the stock Tube and the stock Capsule? I still waiting for the right Tube and Capsule. The shipping takes a long time from the USA, unfortunately. The values ​​of the PSU are normal.
Unloaded B+ = 195V
Heater          = 6.5V
Bias              = -1,0V
Is it possible to test the microphone without a right tube and a right Capsule? Unfortunately I have ever started a recording and this micro does not sound good, extremely quiet level, it hums, it has no bass, sounds harsh.
Please do not scold me, I should not have to make, I know...
I only have the stock tube, so can I measure values​​ with it? I have ordered a 6072A gold by Electro Harmonix. Should I rather wait for the tube?
How are the values ​​at the micro body and how can I measure, without tube?

Many Thanks

Eric

Kein Problem...your English is far better than my German. ;)

You can test with stock tube and capsule:  however you'll have to re-do the calibration with your new tube.

As before, with tube installed, take voltage readings on pins 1, 2, 3, and 4 right at the tube socket with tube installed.  The stock tube is a 12AX7, which has too much gain for this circuit, so that may explain some of the harshness.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Ericbazaar on March 21, 2013, 11:19:46 AM
Hi at all,

first to my Person, i am absolutely new in Mic Building and I'm from the area Ribbon Mic. I am from Germany and please excuse my bad English.
I saw a few weeks ago the studio page 939 and I knew I will build this microphone. I ordered everything.
I build the Mic in last 2 Days.
I have some questions. Is it even possible to make a test with the stock Tube and the stock Capsule? I still waiting for the right Tube and Capsule. The shipping takes a long time from the USA, unfortunately. The values ​​of the PSU are normal.
Unloaded B+ = 195V
Heater          = 6.5V
Bias              = -1,0V
Is it possible to test the microphone without a right tube and a right Capsule? Unfortunately I have ever started a recording and this micro does not sound good, extremely quiet level, it hums, it has no bass, sounds harsh.
Please do not scold me, I should not have to make, I know...
I only have the stock tube, so can I measure values​​ with it? I have ordered a 6072A gold by Electro Harmonix. Should I rather wait for the tube?
How are the values ​​at the micro body and how can I measure, without tube?

Many Thanks

Eric

Kein Problem...your English is far better than my German. ;)

You can test with stock tube and capsule:  however you'll have to re-do the calibration with your new tube.

As before, with tube installed, take voltage readings on pins 1, 2, 3, and 4 right at the tube socket with tube installed.  The stock tube is a 12AX7, which has too much gain for this circuit, so that may explain some of the harshness.

Hi Matador,

ok…Fair I between PSU/P6 and Mic Tube Socket Pin 1 so I have B + of 130V with a bias value of -1 volt. I change the bias to 0.0 volts B + drops to 90Volt on Tube SOCKT Pin 1, is this a correct response?
The Measurements are: PSU/P6         Tube Pin 1 = about 130V 
                                                       Tube Pin 2 = about -0,45V or ca 460mV
                                                       Tube Pin 3 = about 41,3mV
                                                       Tube Pin 4 = about 6,3V

                                                       Polar at Omni = 78V
                                                       Polar at Cardioid = 30V
                                                       Polar at Figure 8 = 0,0V
All with Stock-12ax7-Tube.

Thanks Eric
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Winetree on March 22, 2013, 05:11:25 PM
I got 118.5 VDC with the stock capsules with all three C-12s.
Thought that would change with Tim's capsules
Looks like it doesn't. Does it 1.5 vdc really matter?
Title: Re: Official C12 Clone - Build and Support Thread
Post by: canidoit on March 23, 2013, 03:14:45 AM
Are there any instructions for those that use 240 volts for the power supply for the C12 clone?

Thanks

Title: Re: Official C12 Clone - Build and Support Thread
Post by: chunger on March 23, 2013, 04:04:46 AM
Are there any instructions for those that use 240 volts for the power supply for the C12 clone?

Thanks

Yes. . . there's a little red switch at the back of the PSU box.  Set it to 220V.   ;D  You should be good to go!

That's the beauty of re-using the stock power transformer and mains wiring.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: canidoit on March 23, 2013, 06:05:04 AM
Thanks Chunger.

Just curious, how does it compare sonically to an original C12??

Also how would you describe the sound and what records best on it.

Have you tried different tubes on it yet?

When do you think you will have all the stock to build a complete C12. I can see you are sold out on the body.

Thanks
Title: Re: Official C12 Clone - Build and Support Thread
Post by: chunger on March 23, 2013, 07:07:54 AM
Thanks Chunger.

Just curious, how does it compare sonically to an original C12??

Also how would you describe the sound and what records best on it.

Have you tried different tubes on it yet?

When do you think you will have all the stock to build a complete C12. I can see you are sold out on the body.

Thanks

I guess much would depend on which original C12 as there were many iterations and variances between individual microphones.  Tim explained to me that he has many original capsules, and they all sound different.  I do not own an original C12, so I have not had the opportunity to do head to head tests.  I have, however, located a pristine original C12 local to me and am trying to arrange a rental so I can test.  I am, however waiting a little while for the prototypes we have running in the studio to break in and loosen up a little bit before spending money on the rental for a test session.

This microphone in it's recommended configuration with the original GE tube, Tim's reproduction capsule, proper headbasket mesh specification (albeit with a larger diameter tube than original), and original spec transformer must land  at least in the general ball-park of the microphone it seeks to emulate.

Many kits have shipped now and I hope someone who also owns an original C12 might be able to chime in.

I have not yet tried different tubes in the circuit.  Only the Electro Harmonix 6072a and the NOS GE 6072A.

So far, the mic has worked well on drum overheads, female vocals, and acoustic guitars.  It has a good dose of air and top end, a bit of scoop in the mids. . . we find it not particularly forgiving of "artifacts" in vocal application.  It would work very well on smoother, polished voices, but can accentuate problems if the voice is a bit grittier.  The top can be a bit forward.  The microphone also does not seem to be as forgiving of a problematic room as some of the other microphones we use.  Off-axis, it seems to pick up a lot.  I hope to hear the microphone on piano and cello soon and report back.

This is a very different animal than the Neumann microphones we have used in our little home studio up until now.  I cannot say we have "figured it out" quite yet, but time and incremental optimizations will get us where we need to go with this mic.

I am actively working on another very large import batch of microphones from China.  I was hoping stock would hold out longer because I am doing development on all of the 3 models I carry to improve the features, improve quality, and lower prices.  Extensive development work particularly on 2 of the models is holding up the process a bit right now, but in the long run, I will be able to offer a much better product for DIY at a better price.  I am ordering a large number of HT-11A microphones to replenish stock. . . 100 units in the next shipment and that should last a while.  Stay tuned to this thread for updates as they come in.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: micaddict on March 23, 2013, 07:40:13 AM
Thanks for the update.

Quote
I have not yet tried different tubes in the circuit.  Only the Electro Harmonix 6072a and the NOS GE 6072A.
Same type, but different at the same time. Despite the breaking in period, is there anything you could say about the experienced difference in tone between those two? If you did already, please forgive.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Matador on March 23, 2013, 11:47:04 AM
I got 118.5 VDC with the stock capsules with all three C-12s.
Thought that would change with Tim's capsules
Looks like it doesn't. Does it 1.5 vdc really matter?

The capsule has no effect on the B+, bias, or polarization voltages.


The tube itself sets it's own idling point:  there is a negative feedback that happens when fiddling with R4 (the B+ adjust resistor).  Decreasing the resistance causes the voltage to increase, which causes current through the tube to increase, which causes more drop across R1, R2, R4, which lowers B+ back.  This is not a regulated circuit which would tend to keep the voltage constant regardless of the current (all other things being equal).

One can lower the values of R1 and R2 to around 82K to bias the adjustment range to higher voltages.  The same works in reverse as well.

Title: Re: Official C12 Clone - Build and Support Thread
Post by: Matador on March 23, 2013, 12:17:16 PM
I agree with Chunger's assessment of the tone:  the sound is very "high-forward".  The C12 circuit has bandwidth well in excess of the range of hearing, so the high-end emphasis of the capsule (above 8K, with a peak in the 10K range) brings forward little details like mouth smacks, lip noises, string squeaks, etc.  You have to have your recording environment in order or else everything comes through loud and clear!

This is as good a time as any to bring up the ELA M251 tweaks:  if we take the 50V/0.6mA idling point as constant, this means the plate looks like about 83K resistance.  The plate resistor R17 (100K) sits at AC ground, which means that the output impedance of the tube stage looks like about 45K (100K || 83K).

We can form a low-pass filter from the output impedance by putting a cap from the plate to ground.  A 1,000pF cap from a 45K source impedance gives a -3dB point of about 4kHz, which means that the circuit response is down -9dB at 8kHz.  This is essentially an inverse of the high-frequency peak of the C12 type capsule.

It is very easy to add this cap to the C12 circuit: 

(http://musicalsparks.com/images/c12/c12_to_elam251.jpg)

It sits "next" to the output coupling cap, and attaches down at the other end of the 500K resistor R13 (the bottom node is ground).  Lower cap values will move the filter up in frequency, so a 470pF will be -3dB down at about 8kHz.

My opinion on this:  without much of a Neumann-esque midrange focus, and taking the high-end out with a cap filter, then nothing is left to really "shine" through.  However if you doing a lot of acoustic instruments in sparse mixes (like perhaps a female singer and a guitar player), it might just be the ticket to getting a natural sound without having to do any additional processing after-the-fact.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: HellfireStudios on March 23, 2013, 01:29:31 PM
I brought this idea up before in another thread, but maybe it can be answered now. Could the ELA M251 smoothing cap be implemented on a switch? I guess what I'm asking is would it hurt the mic to switch a smoothing cap in and out of the circuit while it is turned on? Thanks.

-James-
Title: Re: Official C12 Clone - Build and Support Thread
Post by: micaddict on March 23, 2013, 02:57:19 PM
Quote
My opinion on this:  without much of a Neumann-esque midrange focus, and taking the high-end out with a cap filter, then nothing is left to really "shine" through.

Good point. Don't throw away the strong points in an attempt to average everything out. Do I read you right there?
And yes, U47 and C12 are very complementary or yin and yang.
Still, the Ela M251 is very highly regarded indeed, perhaps even more so than the C12. Well, for vocals that is.

Anyway, interesting stuff. Keep it coming, please.

Title: Re: Official C12 Clone - Build and Support Thread
Post by: JessJackson on March 25, 2013, 04:53:55 AM
Great points,

Another option is to discus the component materials used.

Replacing the output coupling cap with a PIO (paper in oil) cap such as the original bosch caps used in this circuit. I have found to smoothen out the top end and take away some of the "brittle" sibilance.

Also I read a somewhere on klaus forum a while back that metal oxide resistors in the high impedance sections of the mic dont sound good and add to the "brittle" sterile top end. and carbon wirewound resistors used in the original design definitely contribute to the original sound of this mic.

These are not sourced with ease though and i've been through boxes and boxes of high ohmage resistors looking for the odd few. only to come across one or two of the correct values.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Matador on March 25, 2013, 12:08:03 PM
I mis-stated something about the 251 circuit above:  the stock plate cap is 100pF, not 1,000pF.  The 1,000pF value is my change, not Telefunken's.  The stock roll-off (with 100pF) happens above about 20kHz.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: JessJackson on March 25, 2013, 02:24:05 PM
correct, but i think the frequency was slightly lower. The 251 (modded c12) was created with the sole purpose of broadcast use (de-emphisis) added as to not effect the pilot tone (19khz) and subcarrier frequency needed for stereo transmission.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Matador on March 25, 2013, 03:17:01 PM
Oh no! Is the silkscreen incorrect?
Title: Re: Official C12 Clone - Build and Support Thread
Post by: dandeurloo on March 25, 2013, 04:43:13 PM
A pair of these are in my future!
Title: Re: Official C12 Clone - Build and Support Thread
Post by: drumminkiger on March 25, 2013, 06:40:04 PM
I'm really curious about any option to switch between the C12 and 251 frequency response. It would be awesome if there was an option for a daughter board or something that would allow this. I dunno if im savy enough to create something like that myself though..
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Melodeath00 on March 25, 2013, 08:25:46 PM
I think there is a tiny bit more of a difference in the circuit of a C12 and 251 than just a capacitor. I'm not expert, but it's what I've been told.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Matador on March 25, 2013, 08:45:50 PM
I cannot speak to the differences between the capsule construction, and the electro-mechanical headbasket/mounting considerations, but just comparing schematic to schematic:

1) The 25x variants have the plate->ground 100pF cap, the C12 does not
2) The 25x variants use the capsule itself as the grid coupling element.  This means there is no coupling capacitor like in the C12
3) The polar-pattern switching is accomplished on the 25x in a similar fashion as a U87:  with isolated backplates and using 0V to 60V in different connections to the four capsule elements.  I'm not convinced the polarization design accounts for any of the possible sound differences.
4) The 25X contains a cathode bias bypass cap that is much higher in value than the C12 equivalent.  Many claim that the C12 is fixed bias but it isn't.  The 25x probably has higher gain over some portion of the passband due to this.

#1 and #4 are easily accommodated with a few BOM changes, and placing a few components directly on the tube board.  #2 is much more tricky, as we wouldn't be able to make use of the PSU polar pattern switch.   On the C12, one diaphragm sits at ground, the backplate sits at half the supply voltage (60V), and the other diaphragm goes from 0V to 120V (to go between omni and figure 8).   It may be possible to make the mike switchable between omni and cardioid and eliminate the grid cap but I'll have to give it some thought.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: HellfireStudios on March 25, 2013, 09:56:58 PM
I cannot speak to the differences between the capsule construction, and the electro-mechanical headbasket/mounting considerations, but just comparing schematic to schematic:

1) The 25x variants have the plate->ground 100pF cap, the C12 does not
2) The 25x variants use the capsule itself as the grid coupling element.  This means there is no coupling capacitor like in the C12
3) The polar-pattern switching is accomplished on the 25x in a similar fashion as a U87:  with isolated backplates and using 0V to 60V in different connections to the four capsule elements.  I'm not convinced the polarization design accounts for any of the possible sound differences.
4) The 25X contains a cathode bias bypass cap that is much higher in value than the C12 equivalent.  Many claim that the C12 is fixed bias but it isn't.  The 25x probably has higher gain over some portion of the passband due to this.

#1 and #4 are easily accommodated with a few BOM changes, and placing a few components directly on the tube board.  #2 is much more tricky, as we wouldn't be able to make use of the PSU polar pattern switch.   On the C12, one diaphragm sits at ground, the backplate sits at half the supply voltage (60V), and the other diaphragm goes from 0V to 120V (to go between omni and figure 8).   It may be possible to make the mike switchable between omni and cardioid and eliminate the grid cap but I'll have to give it some thought.

Could an internal switch be used to select the 251/C12 plate-to-ground cap? A simple SPDT on-off-on switch could be used to accomodate three different flavors of high end. I like the idea of using a 100pF for the 251-ish sound, nothing for the C12 top, and a 500-1000pF for an even warmer/darker sound.

Would the switch have to handle a higher voltage and current than a normal mic switch (switching that 120V plate voltage is what concerns me)? Also, can they be switched while the mic is turned on without harm coming to it?

-James-
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Matador on March 26, 2013, 01:05:23 PM
I don't see a problem with it:  most switches can be found in 120V flavors.  If its inside the body, one would have to unplug the mike to get at it in any case.

It's odd to think of a mike with a "high cut" switch, but with a C12 it might be just the ticket to a new sonic crayon. ;)
Title: Re: Official C12 Clone - Build and Support Thread
Post by: HellfireStudios on March 26, 2013, 01:53:47 PM
I don't see a problem with it:  most switches can be found in 120V flavors.  If its inside the body, one would have to unplug the mike to get at it in any case.

It's odd to think of a mike with a "high cut" switch, but with a C12 it might be just the ticket to a new sonic crayon. ;)

My original intent was to apply this capsule switching design into a full DIY mic that has a 251 variant as its circuit (no smoothing cap). Implementing the switch in the apex 460 type of mic of mic might require the models with a pad and low cut switch.

-James-
Title: Re: Official C12 Clone - Build and Support Thread
Post by: JessJackson on March 27, 2013, 06:10:24 PM
I don't see a problem with it:  most switches can be found in 120V flavors.  If its inside the body, one would have to unplug the mike to get at it in any case.

It's odd to think of a mike with a "high cut" switch, but with a C12 it might be just the ticket to a new sonic crayon. ;)

My original intent was to apply this capsule switching design into a full DIY mic that has a 251 variant as its circuit (no smoothing cap). Implementing the switch in the apex 460 type of mic of mic might require the models with a pad and low cut switch.

-James-

Best idea
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Winetree on March 27, 2013, 07:39:38 PM
There's a real Elam 251 on ebay for $14,200 with 15 hrs. to go.
Thank heavens for DIY.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Ericbazaar on March 27, 2013, 07:55:43 PM
Hello Again,

I'm really desperate. I built this micro-and it does not work. Unfortunately I have not the new capsule, I ordered a capsule of Microphone Parts. I live in Germany and the shipping takes a long time! All values ​​are good, B + on PSU = 120v, B + on Tube Pin 1 = 80V, 6.3 V Heater on Tube and on PSU bias - 1V. Tested with a Electro Harmonix 6072a Gold. The microphone is in an audio test totally quiet and thin. Can this be the stock capsule? Perhaps the T14 Transformer is broken? The red cable show 22Ohm, the blue cables show nothing (but should show about 900ohm, right?). What should I do to find the error? I would like this micro works, please! I'm really not an expert!
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Matador on March 27, 2013, 08:46:29 PM
Primary should read 900, secondary 20-ish.  If the primary is open it's kaput.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Ericbazaar on March 27, 2013, 09:06:32 PM
The T14 can go wrong so quickly? $ 95 for nothing, really great): I have treated this thing really careful, I can fix it? I have checked through the blue wire, no pass! $ 95 again? I'm really tired.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: chunger on March 28, 2013, 12:43:49 AM
The T14 can go wrong so quickly? $ 95 for nothing, really great): I have treated this thing really careful, I can fix it? I have checked through the blue wire, no pass! $ 95 again? I'm really tired.

Hi Eric,

Send your contact info to me and I'll get another T14 out to you ASAP!  I'll take the issue up with Oliver and sort it out.  This is assuming you purchased the T14 through me.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Volume11 on March 28, 2013, 04:30:28 PM
hey guys, when I test the wire wound resistors with my fluke 175, I get a reading of 9.3ohms on both of them, instead of 4.7ohms. Is there a specific reason for this that I am unaware of? They are testing at twice the resistance. Would it have anything to do with the wattage? I am new to this DMM, so maybe it has something to do with it?

Also Chunger, can you tell me what gauge of the silver teflon wire you use is, and maybe a good source?

Thanks
Title: Re: Official C12 Clone - Build and Support Thread
Post by: HellfireStudios on March 28, 2013, 05:53:51 PM
You have to pull one leg of the resisitor off the pcb (or pull it completely out of the circuit) before you can test its resistance accurately.

-James-
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Matador on March 28, 2013, 05:56:07 PM
Here is a short spoken-word (mine) test of a C12 I built for kidvybes.  He is using a GT-12 capsule, a GE 6072A, and an AMI T14 for his build.

C12 Test Mp3 (http://www.musicalsparks.com/images/c12/mp3/c12_test.mp3)

It's not a great recording environment but it will give you an idea of what to expect.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: micaddict on March 28, 2013, 06:00:20 PM
Mark and Matador, thanks for the samples.

Keep them coming, folks!



Henk
Title: Re: Official C12 Clone - Build and Support Thread
Post by: kidvybes on March 28, 2013, 06:17:13 PM
Here is a short spoken-word (mine) test of a C12 I built for kidvybes.  He is using a GT-12 capsule, a GE 6072A, and an AMI T14 for his build.

C12 Test Mp3 (http://www.musicalsparks.com/images/c12/mp3/c12_test.mp3)

It's not a great recording environment but it will give you an idea of what to expect.

...I am eagerly awaiting the arrival of this mic for a project I am midway thru, with a very talented female vocalist (with a very dynamic voice)...I hope to provide additional samples once I have the opportunity to run some sessions with her...

BTW, the capsule I provided Matador for this build is the ADK Custom Shop (3-Zigma) GK12d (which appears to use a K67 drill pattern combined with an edge-terminated diaphragm):
http://www.adkmic.com/catalog/customshop/ModsAndParts.php

...I am interested in hearing how the voicing of this capsule compares with Tim Campbell's historically accurate C12 capsule in this C12 clone...based on Matador's short clip, it sounds nicely balanced...

...this is probably one of the finest quality capsules available from the Asian based microphone manufacturers...Larry Vilella at ADK maintains very high QC on these capsules and uses them in his new Z-MOD Series mics:
http://www.adkmic.com/catalog/customshop/Z-Mods.php
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Volume11 on March 28, 2013, 07:23:27 PM
You have to pull one leg of the resisitor off the pcb (or pull it completely out of the circuit) before you can test its resistance accurately.

-James-
Thanks for the response... I actually tested both of them completely out of the circuit. Weird, right?
Title: Re: Official C12 Clone - Build and Support Thread
Post by: gary o on March 28, 2013, 07:54:08 PM
Reading from the link to the ADK web site telling us they used a $6 resistor in their mics I guess thats the grid resistor........ will the $6 res make a difference than a cheaper res this or any mic build ?

I have a ADK Vienna its good for the money
Title: Re: Official C12 Clone - Build and Support Thread
Post by: chunger on March 28, 2013, 08:59:53 PM
hey guys, when I test the wire wound resistors with my fluke 175, I get a reading of 9.3ohms on both of them, instead of 4.7ohms. Is there a specific reason for this that I am unaware of? They are testing at twice the resistance. Would it have anything to do with the wattage? I am new to this DMM, so maybe it has something to do with it?

Also Chunger, can you tell me what gauge of the silver teflon wire you use is, and maybe a good source?

Thanks

Hi Volume 11,

I recall vaguely during my build that the 4.7ohm resistors measured a bit off (perhaps a wide tolerance part, but it shouldn't be almost 100% off).  I'll wait for Matador to chime in and see if that variance is still ok in the circuit.  I may seek a tighter tolerance resistor for future kits in that position.

For PTFE silver teflon wire, I am generally using 20 and 22 gauge stranded. . . and 28 gauge stranded for capsule connections.  I now have kits in hand with all of the original wire colors in the stock psu for $5.  Alternately, you can find various sources on Ebay and such for small quantities in various colors.  I need to clean a bit of my mess before I can take pictures and post to the webstore, but email me and I can send out a wire kit if you like.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Matador on March 28, 2013, 09:41:42 PM
It would be odd for both to be in error that much.  Are you using a high-impedance probe?

The tube draws about 300mA of heater current, and the voltage before filtering is about 12.7V.  10 ohms drops three volts a piece, which leaves nothing for the regulator to work on.

We need 6.3V, which means pre-regulator we need about 8.3V.  12.7 - 8.3 = 4.4V of drop at 300mA, which means total resistance (R7+R8) cannot be higher than about 14 ohms worst case.  I picked about 10 ohms to be safe.

I would install them, then measure the regulator output (or heater voltage).  If those really are 10 ohms a piece, you won't be able to dial the heater voltage up to the required 6.3V.  If you can dial it in, then somethings odd with the meter reading(s).

The 5W resistors are overkill:  dissipation in R7 and R8 is 0.3*0.3*4.7 = 0.423W each.  A half watt part would work, or a 1W to be conservative.  Should be easy to find 1% resistors in that value.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Volume11 on March 29, 2013, 05:42:07 AM

Hi Volume 11,

I recall vaguely during my build that the 4.7ohm resistors measured a bit off (perhaps a wide tolerance part, but it shouldn't be almost 100% off).  I'll wait for Matador to chime in and see if that variance is still ok in the circuit.  I may seek a tighter tolerance resistor for future kits in that position.

For PTFE silver teflon wire, I am generally using 20 and 22 gauge stranded. . . and 28 gauge stranded for capsule connections.  I now have kits in hand with all of the original wire colors in the stock psu for $5.  Alternately, you can find various sources on Ebay and such for small quantities in various colors.  I need to clean a bit of my mess before I can take pictures and post to the webstore, but email me and I can send out a wire kit if you like.

Ah, I didn't see this in time! I just ordered some 20gauge from tube depot. At least I know that I picked the right size. As far as quality goes, I'll have to wait and see. Thanks for the info.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Volume11 on March 29, 2013, 05:43:27 AM
Check your battery in the meter, low batteries can cause erratic behaviour.

Regards,
Mark

This could be the case, I did buy it used. Thanks
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Volume11 on March 29, 2013, 05:49:02 AM
It would be odd for both to be in error that much.  Are you using a high-impedance probe?

The tube draws about 300mA of heater current, and the voltage before filtering is about 12.7V.  10 ohms drops three volts a piece, which leaves nothing for the regulator to work on.

We need 6.3V, which means pre-regulator we need about 8.3V.  12.7 - 8.3 = 4.4V of drop at 300mA, which means total resistance (R7+R8) cannot be higher than about 14 ohms worst case.  I picked about 10 ohms to be safe.

I would install them, then measure the regulator output (or heater voltage).  If those really are 10 ohms a piece, you won't be able to dial the heater voltage up to the required 6.3V.  If you can dial it in, then somethings odd with the meter reading(s).

The 5W resistors are overkill:  dissipation in R7 and R8 is 0.3*0.3*4.7 = 0.423W each.  A half watt part would work, or a 1W to be conservative.  Should be easy to find 1% resistors in that value.

I'm not sure about the impedance of the probes but, I believe that they are the original ones that came with the dmm?

I went ahead and soldered them into place, as soon as I get some more wire and a few other parts I will fire it up and take measurements. Thanks for all of the help, I'll report back shortly.

Chad
Title: Re: Official C12 Clone - Build and Support Thread
Post by: bobtheninja on March 30, 2013, 06:11:25 AM
It's odd to think of a mike with a "high cut" switch, but with a C12 it might be just the ticket to a new sonic crayon. ;)

This is an aside, but my Pearlman TM-1 has a high-cut switch on it that is actually really useful. Especially on vocals, but also for room duties, etc. :)
Title: Re: Official C12 Clone - Build and Support Thread
Post by: JessJackson on March 30, 2013, 10:07:02 PM
My readings across my Haufe T14

Title: Re: Official C12 Clone - Build and Support Thread
Post by: JessJackson on March 30, 2013, 10:08:06 PM
And The Reds
Title: Re: Official C12 Clone - Build and Support Thread
Post by: JessJackson on March 30, 2013, 11:58:31 PM
And The Reds

Those readings seem quite high.

Your secondary would present a load of well over 600 ohms to the mic pre, that should normally be around 200 ohms.
Primary would be well over 30K. Doesn't seem right.

What frequency does your meter use for DCR?

Do you have the specs for that transformer?

Regards,
Mark

Thats what I was thinking.

Its a Haufe, it came out of a Telefunken USA C12. Its sold to Telefunken as historically correct T/14 wound at the same specification as the vintage Haufe's.

If you divide the numbers, the step down ratio seems to come out the same though.

I believe the greens are the 50ohm wires which you usually tie together in c12 circuit.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: micaddict on March 31, 2013, 07:06:26 AM
Nice sample again, Mark. Keep them coming.  :P

As much as I like dry percussive sounds, at heart I guess I'm a tone guy. So I have some extra love for ride cymbals. Nice combinations of attack and sustaining, bell tones. Sizzle and crash can be added to taste. I'm no drummer so I hope this makes sense. With a ride alone you can paint many colors and to capture them all, the mic better be good. Sort of like the key test, come to think of it, but more versatile.
Here's an introduction, for those interested:
http://www.youtube.com/watch?v=W-iBfuKvMZo (http://www.youtube.com/watch?v=W-iBfuKvMZo)
Title: Re: Official C12 Clone - Build and Support Thread
Post by: 3nity on March 31, 2013, 10:44:21 AM
Mark Congrats on the building of that room!!
I see its not finished yet but man it looks and sounds sweet.
It has some kind of vibe dude!
How i long to finally set my things up here, but its gonna be for next year!

Good luck!
Title: Re: Official C12 Clone - Build and Support Thread
Post by: chunger on March 31, 2013, 04:20:31 PM
Let's get some nice custom headbaskets on those mics!  The factory begins volume production on Monday.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: HellfireStudios on March 31, 2013, 04:22:48 PM
Let's get some nice custom headbaskets on those mics!  The factory begins volume production on Monday.

How do I pre-order?
Title: Re: Official C12 Clone - Build and Support Thread
Post by: chunger on March 31, 2013, 04:33:08 PM
Let's get some nice custom headbaskets on those mics!  The factory begins volume production on Monday.

How do I pre-order?

As of right now, I'm not taking pre-order.  If lots of people insist, I may change my mind, but due to the long lead times, last time I did reservations for microphones, it was a lot of legwork tracking everyone's requests, and many people who reserved items did not follow through with purchasing.  I refuse to take money until I have product in hand or at minimum I know for sure I still have time to refund the paypal charges if something goes horribly wrong.

I had to order 500 units for the first run.  There is absolutely no way I will sell that many in any reasonable timeframe which means they should be in stock for quite some time when they arrive.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: KMB-AUDIO on March 31, 2013, 09:45:16 PM
Hi guys,

I received my two kits on Friday! Starting on the power supplies tonight.

I've read through this thread and am curious about the 0 Ohm "resistor".  What is the difference between using this jumper and bare wire?

Title: Re: Official C12 Clone - Build and Support Thread
Post by: JessJackson on April 01, 2013, 05:33:52 AM
Strange things this end,

Just finished the build.

Mic Connected:

Bias and Heater are spot on (although heater adj is VERY sensitive)

Im getting 160v on b+... B+ Adj doesn't seem to be doing much but lowering by the decimal. I am able to get it down to about 158v

Out the wall I have 121v, After the PS Xformer Im getting 225v and 10.3v

Any Thoughts?
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Matador on April 01, 2013, 02:01:58 PM
Strange things this end,

Just finished the build.

Mic Connected:

Bias and Heater are spot on (although heater adj is VERY sensitive)

Im getting 160v on b+... B+ Adj doesn't seem to be doing much but lowering by the decimal. I am able to get it down to about 158v

Out the wall I have 121v, After the PS Xformer Im getting 225v and 10.3v

Any Thoughts?

Is this with the mike connected?  What tube are you using?
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Matador on April 01, 2013, 02:03:28 PM
Hi guys,

I received my two kits on Friday! Starting on the power supplies tonight.

I've read through this thread and am curious about the 0 Ohm "resistor".  What is the difference between using this jumper and bare wire?

No difference:  it's just cleaner and looks better. ;)  For the first two prototypes, I used a short section of solder wick directly across the two SMD pins (which is all a zero ohm resistor is:  essentially a piece of wire).
Title: Re: Official C12 Clone - Build and Support Thread
Post by: JessJackson on April 01, 2013, 03:47:47 PM
Strange things this end,

Just finished the build.

Mic Connected:

Bias and Heater are spot on (although heater adj is VERY sensitive)

Im getting 160v on b+... B+ Adj doesn't seem to be doing much but lowering by the decimal. I am able to get it down to about 158v

Out the wall I have 121v, After the PS Xformer Im getting 225v and 10.3v

Any Thoughts?

Is this with the mike connected?  What tube are you using?

Yes with mic connected...

Without is 195v B+

Using stock tube... i have other GE 5 star nos tubes but I don't want to damage them.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: KMB-AUDIO on April 01, 2013, 09:59:41 PM
Finished one power supply last night and all seems well.

Just wanted to give people a heads up using TNC ACM-1200 mics that their power supply may be a little different than the one that Chunger has picture of here (see attached photo).

On mine, the PCB was  a full rectangle with the transformer attached to the PCB, so I had to drill some holes in the enclosure to mount it.  Additionally, the secondary taps are reversed, so I had to extend one of them to reach the new PCB.



Title: Re: Official C12 Clone - Build and Support Thread
Post by: Matador on April 02, 2013, 12:19:57 AM

Yes with mic connected...

Without is 195v B+

Using stock tube... i have other GE 5 star nos tubes but I don't want to damage them.

The stock 12AX7 pulls less current than a 6072A under the same bias conditions:  this can be seen on the tube plate curves.  If you want to run the mike with that tube, the series pass resistors (91K) need to be increased.  Lowering the grid bias down to -0.2V also helps the tube draw more current.

The 180K resistor from B+ to ground right at the 7-pin XLR output jack is the best test to do for getting things right before a real 6072A goes in.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: JessJackson on April 03, 2013, 05:03:28 PM

Yes with mic connected...

Without is 195v B+

Using stock tube... i have other GE 5 star nos tubes but I don't want to damage them.

The stock 12AX7 pulls less current than a 6072A under the same bias conditions:  this can be seen on the tube plate curves.  If you want to run the mike with that tube, the series pass resistors (91K) need to be increased.  Lowering the grid bias down to -0.2V also helps the tube draw more current.

The 180K resistor from B+ to ground right at the 7-pin XLR output jack is the best test to do for getting things right before a real 6072A goes in.

Thanks Matador,

So I threw a 180k resistor across and B+ was able to reach 114v with Adj pot fully gained.

I then threw my 5 Star GE tube in there and we're back to 144v with Adj pot fully down. The Adj pot only seems to be effecting by decimals, adjusting maybe 2 volts max.

This is with stock capsule, awaiting Tim's capsule... I could try a capsule from my vintage C12 but wouldn't really feel comfortable at this stage.

b+ = 144v
Grid = -0.656v
Plate = 72.9v
Heater = 6.30
Bias = - 1.00
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Matador on April 03, 2013, 05:09:08 PM
The capsule plays no part in the tube current and switching it won't matter.

It looks like the variance is much higher on these tubes than the data sheets imply:  can you increase the bias voltage up to -0.5 volts (as measured at the PSU, not right at the tube grid) and see if you can observe B+ lower down to 120V?
Title: Re: Official C12 Clone - Build and Support Thread
Post by: JessJackson on April 03, 2013, 05:46:15 PM
The capsule plays no part in the tube current and switching it won't matter.

It looks like the variance is much higher on these tubes than the data sheets imply:  can you increase the bias voltage up to -0.5 volts (as measured at the PSU, not right at the tube grid) and see if you can observe B+ lower down to 120V?

So my 180k resistor turned out to be a 165k... I replaced it with a 180k and am now measuring 117.2 at highest adj

With Bias at - 0.5 I am getting 141.2v

I'll try another 5 star GE and I have a EEC 81 i can try also.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: chunger on April 03, 2013, 06:14:32 PM
I may be stating the obvious, but are all of the trimmer pot values verified and installed in the correct positions?  Seems odd that the B+ would only have a few volts of adjustment range regardless of where the final voltage lands . . . and that the bias adjustment would be very touchy as that was quite a gradual change on my sample build per turn of the pot.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: JessJackson on April 03, 2013, 07:35:29 PM
I may be stating the obvious, but are all of the trimmer pot values verified and installed in the correct positions?  Seems odd that the B+ would only have a few volts of adjustment range regardless of where the final voltage lands . . . and that the bias adjustment would be very touchy as that was quite a gradual change on my sample build per turn of the pot.

omg.. i'm a dickhead for this but I thought all Adj pots were the same value.. simple mistake..

In Bias I have installed W502
In B+ I have installed W202
In Heater I have installed W104

Is there an easy way to remove these components because I'm having real difficulties desoldering the three legs at the same time.

Cheers
Title: Re: Official C12 Clone - Build and Support Thread
Post by: KMB-AUDIO on April 03, 2013, 07:39:28 PM
I may be stating the obvious, but are all of the trimmer pot values verified and installed in the correct positions?  Seems odd that the B+ would only have a few volts of adjustment range regardless of where the final voltage lands . . . and that the bias adjustment would be very touchy as that was quite a gradual change on my sample build per turn of the pot.

omg.. i'm a dickhead for this but I thought all Adj pots were the same value.. simple mistake..

In Bias I have installed W502
In B+ I have installed W202
In Heater I have installed W104

Is there an easy way to remove these components because I'm having real difficulties desoldering the three legs at the same time.

Cheers

Get some solder wick my friend! or a de-soldering gun...makes these chores so much easier.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Matador on April 03, 2013, 08:02:07 PM
I may be stating the obvious, but are all of the trimmer pot values verified and installed in the correct positions?  Seems odd that the B+ would only have a few volts of adjustment range regardless of where the final voltage lands . . . and that the bias adjustment would be very touchy as that was quite a gradual change on my sample build per turn of the pot.

omg.. i'm a dickhead for this but I thought all Adj pots were the same value.. simple mistake..

In Bias I have installed W502
In B+ I have installed W202
In Heater I have installed W104

Is there an easy way to remove these components because I'm having real difficulties desoldering the three legs at the same time.

Cheers

Thanks Chunger, I was going to suggest this check next.  :o

I've had (limited) success removing these by turning the board upside down, then wiping the iron quickly across the three pins while applying sideways pressure on the pot body.  You can do something similar with a chuck of solder wick or wire that has been tinned.  If you can heat all three joints they should come out easily, then you can suck out the solder from the plated through holes with some fresh wick and some liquid flux or paste.

If you end up cutting them off, you can substitute in temporary resistors across the two outside holes using Ohm's law to your advantage.  This should get you going until new trimmers arrive, as these voltages aren't particularly critical:

1) Heater - average loss is 0.2V (via I*R loss) by the time the voltage makes it to the tube pin.  This means you want 6.5V at the supply side.  Output heater voltage is set by the equation Vout = 1.25*(1+(R12+R10)/R9).  Since R12 is 1K and R9 is 392, then the pot R12 should be set to 646 ohms.  A 640 ohm resistor would be very close.
2) Bias - total return current is the plate current + the bleeder resistor R6.  At 120V, R6 bleeds 0.25mA.  The plate current at -1V bias at B+ 120V is 0.7mA, so we want 1V across R3 with 1mA, which means that R3 should be 1K ohms.  10% bias voltage up or down won't hurt things for testing.

R4 is more difficult, but you can get close by testing with your 180K resistor, trimming to 120V, then cutting out the pot and measuring the resistance between pins 2 and 3.  Then substitute this with a fixed resistance.

Or, barring ALL of this, just get them out or buy new trimmers:  they are only a few bucks for all of them.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: KMB-AUDIO on April 03, 2013, 08:42:24 PM
I may be stating the obvious, but are all of the trimmer pot values verified and installed in the correct positions?  Seems odd that the B+ would only have a few volts of adjustment range regardless of where the final voltage lands . . . and that the bias adjustment would be very touchy as that was quite a gradual change on my sample build per turn of the pot.

omg.. i'm a dickhead for this but I thought all Adj pots were the same value.. simple mistake..

In Bias I have installed W502
In B+ I have installed W202
In Heater I have installed W104

Is there an easy way to remove these components because I'm having real difficulties desoldering the three legs at the same time.

Cheers

I think you have the bias pot in the correct position, looks like the B+ and heater are reversed.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: chunger on April 03, 2013, 10:34:51 PM
I know that it is an expensive investment, but the Hakko 808 desoldering tool would make short work of swapping out those pots.  I've been able to consistently suck out all of the solder in seconds and just have the part fall out of the pcb when desoldering with that tool.

Sooner or later in DIY, you'll wish you had it. . . well, in this instance, it would appear to be sooner.  I seem to need it more often than I would care to admit.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Winetree on April 03, 2013, 11:36:28 PM
+1  Hakko 808 can't DIY without it.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: JessJackson on April 03, 2013, 11:50:39 PM
Thanks for everyones help, Just ordered the hakko (i borrowed my friends but it removed the tin on the circuit board at the same time... I was able to salvage the exsisting trimmers, I had to cut a couple of the pins but just used a small extension of wire and some heat shrink and the trimmers live off the board (for now).... was annoying b/c my build is as neat as changers / or pretty close.

So The Results are in...

1st 5 Star GE Tube

B+ = 121.69 (Adj pot fully minimum) @ PS
Heater = 6.30 @ Tube Base
Bias = -1.00 @ PS
Plate = 48.54 @ OP Cap

Am I good to go?
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Matador on April 04, 2013, 12:12:13 AM
Thanks for everyones help, Just ordered the hakko (i borrowed my friends but it removed the tin on the circuit board at the same time... I was able to salvage the exsisting trimmers, I had to cut a couple of the pins but just used a small extension of wire and some heat shrink and the trimmers live off the board (for now).... was annoying b/c my build is as neat as changers / or pretty close.

So The Results are in...

1st 5 Star GE Tube

B+ = 121.69 (Adj pot fully minimum) @ PS
Heater = 6.30 @ Tube Base
Bias = -1.00 @ PS
Plate = 48.54 @ OP Cap

Am I good to go?

Spot on!   8) Your tube is idling at (121.69-48.54) / 100K = 0.73mA which is exactly what the tube curves suggest under those bias conditions.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: JessJackson on April 04, 2013, 12:15:47 AM
Great Matador!

Things get even more interesting.

Above post is measured with Fluke 115

I made same test with Extech MN42

B+ = 111.0
Bias = -0.54
Heater = 6.32
Plate = 45.5

Both meters give me 10.01v exactly tested on a 9v battery.. so odd

I dont know why but I've never trusted the fluke although its the more expensive meter. Both have new batteries
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Biasrocks on April 04, 2013, 11:57:15 AM
B+ = 111.0
Bias = -0.54
Heater = 6.32
Plate = 45.5

Plate seems low.

Your plate voltage should be closer to 60-70 volts with a healthy tube.

Mark
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Matador on April 04, 2013, 01:30:07 PM
B+ = 111.0
Bias = -0.54
Heater = 6.32
Plate = 45.5

Plate seems low.

Your plate voltage should be closer to 60-70 volts with a healthy tube.

Mark

Plate voltage will be up or down by 20% depending on the tube.

Remember the chart I post earlier:

(http://www.musicalsparks.com/images/c12/12ay7_c12_bias.jpg)

50V is right in the average for a typical tube.  If the tube in question pulls slightly less current, quiescent plate voltage is higher.

As for the meters:  keep in mind that the meters work by placing a large(ish) resistance in parallel with whatever point is being measured, and measuring the current shunted through this resistance.

If the circuit being measured is low impedance (like a battery), then the impedance of the meter doesn't matter much.  If I try to measure a bias voltage on a capsule (supplied from a ~gigaohm impedance), the circuit impedance is 4 orders of magnitude higher than the meter and the meter "takes over".  This is why the polarization voltage collapses when you try to measure it with a typical 1M to 10M DVM).

Plate supply's sit in the middle:  for this design, the supply is "highish impedance", having several hundred kohms in series with the supply.  From my earlier post, we are talking about supplying 1mA at 120V which means the PSU output impedance looks like a 120K resistor.  If your meter is 1M, then it adds 0.12mA or 12% error current into the equation.  A 10M DVM adds 1.2%.  Obviously for these kids of measurements, the higher impedance meters will give more accurate results.

Most Fluke's are 10M input impedance, so it's best to find the meter with the highest impedance for these kids of measurements.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Biasrocks on April 04, 2013, 02:23:55 PM
Both of my microphones are at ~67-68VDC on the plate. GE 5 Star tubes.

Also from Klaus Heyne comes this.

"The plate voltage of a healthy 6072 tube working inside a healthy C12 should be around 65-80 VDC."

http://repforums.prosoundweb.com/index.php?topic=33288.msg493077#msg493077

Regards,
Mark
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Matador on April 04, 2013, 04:02:24 PM
Both of my microphones are at ~67-68VDC on the plate. GE 5 Star tubes.

Also from Klaus Heyne comes this.

"The plate voltage of a healthy 6072 tube working inside a healthy C12 should be around 65-80 VDC."

http://repforums.prosoundweb.com/index.php?topic=33288.msg493077#msg493077

Regards,
Mark

This may imply that AKG might trim the bias resistor more towards the -1.5V to -2V range.  -1V (at least based on my prototyping and experimentation) gave a good compromise between signal swing, input headroom, and linearity.

Does anyone have an original they can measure?
Title: Re: Official C12 Clone - Build and Support Thread
Post by: JessJackson on April 04, 2013, 11:51:54 PM
Thanks Matador, you are in fact correct... its all basic arithmetic and there is no reason that a tube output should be higher than the calculation end point.

Find attached 6072 Data Sheet
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Ericbazaar on April 05, 2013, 04:23:50 PM
I have a question! ::) On my microphone varies the B + voltage. I set the Voltage to 120V and 1hour later ist the Voltage higher at 121V. Is it bad when the voltage fluctuates between 119 and 121V? And Thanks Chunger for sending me a new T14!! :D
Title: Re: Official C12 Clone - Build and Support Thread
Post by: chunger on April 05, 2013, 06:26:55 PM
I have a question! ::) On my microphone varies the B + voltage. I set the Voltage to 120V and 1hour later ist the Voltage higher at 121V. Is it bad when the voltage fluctuates between 119 and 121V? And Thanks Chunger for sending me a new T14!! :D

As I understand it, the B+ section of the power supply is a passive setup without a regulator, so the B+ will fluctuate a bit according to fluctuations in the line voltage.  This is normal.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Pip on April 09, 2013, 03:48:34 AM
Hi:

First post to this forum after being a voyer for awhile.

Just finished this build and wanted to say how rewarding it was, mic sounds great (still has stock capsule Tim Campbell capsule on order) all went well. Hats off and much appreciation to Matador, Chunger and all others who contributed. THANK YOU FOR LEADING US FOLLOWERS!

A few points of possible interest, maybe. I used the Carvin Guitars version of the Alctron HT-11A as a donor. The only difference between it and the one in the thread is the power transformer was mounted on PC board and needed to be remounted to metal case, two holes drilled and some 6/32 screws and nylock nuts later voila. It should also be mentioned that the output wire pairs on my transformer were reversed to those in the build thread pics and not labeled so make sure you check before hooking up! Be sure to attach ground wire as part of this process as well.

As to grounding. I can not stress enough how with this and all mic projects ground integrity is really important so do yourself a favor and really keep on it!

I did have problem with B+ voltage level getting past 113 VDC measured at PSU with both 180K dummy load and Mic attached. I will work on this looking at Matadors suggestion of changing the values on resistors 1 & 2. All seemed to work and mic sounds great. Also no puffs of smoke and blue sparks always a bonus. I will take any and all suggestions on this  and will keep forum informed. I plan to go back at this when Tim Campbells capsule arrives. Stay tuned.

I used a NOS JAN 6072 Phillips USA tube. I have mic rated GE 5 Star 6072 tubes but the glass envelope is bigger on them and as space is a premium and the Phillips tube so far sounds good with no artifacts so be it. No difference by the way with either tube and the B+ issue.

Thats it for now. Once again thank you all for a rewarding build.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: micaddict on April 09, 2013, 03:59:38 AM
Welcome!

Thanks for your contribution and yes, I have a feeling we we will stay tuned.  ;)
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Matador on April 09, 2013, 10:39:30 AM
A few notes based on feedback received from several people:

1) I am changing the BOM/schematic to increase the values of R1 and R2 slightly up to 100K for those using 6072A tubes.  This will give about 20V more adjustment room to B+ for differing tube types (including the stock 12AX7 tube which many are using for testing purposes).
2) Pip pointed out that the schematic indications for front capsule and rear capsule are reversed:  I'll fix this.  The silkscreen on the mike PCB is however verified correct. 
3) On recommendation from Kidvybes, I have ordered a handful of GE and JAN 6201 (12AT7WA and 12AT7WC) tubes, as you can get nice deals on these for NOS 5-star grade material:  I got mine from TC Tubes for about $25 each.  These tubes feature triple micas and extra support rods so microphonics should be excellent.  These tubes are higher mu so a few circuit tweaks will be in order:  mostly lowering R17 down to make the gain about the same as compared to a 12AY7/6072A.  Bias will also need to be tweaked so that the idling point is about the same.  These tubes draw much more quiescent current at idle so tweaks to R1 and R2 may be necessary as well.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: micaddict on April 09, 2013, 01:47:30 PM
OK I didn't want to unnecessarily pollute the thread, but now you've brought it up yourself, here goes.  :)

http://tubedata.tubes.se/sheets/093/6/6072.pdf (http://tubedata.tubes.se/sheets/093/6/6072.pdf)
http://tubedata.tubes.se/sheets/093/6/6201.pdf (http://tubedata.tubes.se/sheets/093/6/6201.pdf)
http://www.thegearpage.net/board/archive/index.php/t-157299.html (http://www.thegearpage.net/board/archive/index.php/t-157299.html)
http://www.gearslutz.com/board/high-end/669136-bock-251-now-using-6201-tube.html (http://www.gearslutz.com/board/high-end/669136-bock-251-now-using-6201-tube.html)

As a warm up, for those interested.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Gilgamesh on April 10, 2013, 09:09:11 AM
Apologies if this has been covered somewhere else already, but what is the maximum diameter for c12 to comfortably fit in the Alctron body?
Title: Re: Official C12 Clone - Build and Support Thread
Post by: JessJackson on April 13, 2013, 12:18:01 AM
A few notes based on feedback received from several people:

1) I am changing the BOM/schematic to increase the values of R1 and R2 slightly up to 100K for those using 6072A tubes.  This will give about 20V more adjustment room to B+ for differing tube types (including the stock 12AX7 tube which many are using for testing purposes).
2) Pip pointed out that the schematic indications for front capsule and rear capsule are reversed:  I'll fix this.  The silkscreen on the mike PCB is however verified correct.
3) On recommendation from Kidvybes, I have ordered a handful of GE and JAN 6201 (12AT7WA and 12AT7WC) tubes, as you can get nice deals on these for NOS 5-star grade material:  I got mine from TC Tubes for about $25 each.  These tubes feature triple micas and extra support rods so microphonics should be excellent.  These tubes are higher mu so a few circuit tweaks will be in order:  mostly lowering R17 down to make the gain about the same as compared to a 12AY7/6072A.  Bias will also need to be tweaked so that the idling point is about the same.  These tubes draw much more quiescent current at idle so tweaks to R1 and R2 may be necessary as well.

Thanks for this info

I just ordered some 71-RN60D-F-100K for R1 and R2 as per your suggestion.



Title: Re: Official C12 Clone - Build and Support Thread
Post by: KMB-AUDIO on April 13, 2013, 09:59:27 PM
How should the backplate connections be hooked up? In the tutorial, on the CT12, you bridge the two backplates together at the capsule and presumably hook them up to FB and RB on the PCB?. I don't understand why there are two connections on the PCB when they are just bridged together.

For now, until I get Tim's capsule, I have a microphone-parts RK12 which has one wire for the backplate.  Do just connect to both RB and FB or just one? If I connect to both,  can I just bridge RB and FB together at the PCB?
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Matador on April 13, 2013, 11:35:11 PM
How should the backplate connections be hooked up? In the tutorial, on the CT12, you bridge the two backplates together at the capsule and presumably hook them up to FB and RB on the PCB?. I don't understand why there are two connections on the PCB when they are just bridged together.

For now, until I get Tim's capsule, I have a microphone-parts RK12 which has one wire for the backplate.  Do just connect to both RB and FB or just one? If I connect to both,  can I just bridge RB and FB together at the PCB?

One connection serves to polarize the capsule, and the second is used to provide a tap point for the coupling cap.  They are there so that you can use three or four terminal capsules easily.

They can be tied together at the PCB if you are using a capsule with only three connections.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: mwrichardson on April 14, 2013, 04:05:03 PM
Any idea when the headbaskets will be for sale?
Title: Re: Official C12 Clone - Build and Support Thread
Post by: chunger on April 14, 2013, 11:39:12 PM
Any idea when the headbaskets will be for sale?

The order has been placed/paid for the production run of 500 units a couple weeks back as I recall.  The factory lead time is officially 2 months (it could be significantly faster).  I am strongly leaning towards bringing in an initial quantity of these via air freight because many people seem to be anxious to get their hands on these.  Due to increased logistics costs on these ~50 or so units, I will price them at $35.  After those initial copies sell out and the main shipment travelling via boat arrives, I'll drop back to the target $30 price point.

Air shipment while expensive only takes a couple of days to ship from China to me.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Winetree on April 14, 2013, 11:44:53 PM
Count me in on 3 headbaskets from the first air shipment.
Are you going to stock some of Tim's capsules?
I've e-mailed him 3 times without any response.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: KMB-AUDIO on April 15, 2013, 04:42:51 AM
Just finished up my two microphones! Just waiting on Tim's capsules and new headbaskets :) I have the microphone-parts RK12 in there for now.

Thanks guys who made this possible.


(http://i1186.photobucket.com/albums/z372/matthewbaker/2013-04-15_01-18-59_415.jpg) (http://s1186.photobucket.com/user/matthewbaker/media/2013-04-15_01-18-59_415.jpg.html)

(http://i1186.photobucket.com/albums/z372/matthewbaker/2013-04-15_01-27-56_898.jpg) (http://s1186.photobucket.com/user/matthewbaker/media/2013-04-15_01-27-56_898.jpg.html)
Title: Re: Official C12 Clone - Build and Support Thread
Post by: chunger on April 15, 2013, 05:21:10 AM
a bit of good news. . . it looks like the factory making the custom headbaskets estimates a 4/23/2013 completion date for the order so these may be available sooner than the main microphone shipment.  This means my headbaskets are actually in process right now.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: gary o on April 15, 2013, 11:22:50 AM
KMB audio proud father of twins ..... look great , be interested in comparing the RK12 to the tim cambel capsule
Title: Re: Official C12 Clone - Build and Support Thread
Post by: KMB-AUDIO on April 15, 2013, 02:06:48 PM
KMB audio proud father of twins ..... look great , be interested in comparing the RK12 to the tim cambel capsule

I'm going to be doing some testing and can post the results if desired.

I plan on testing drum overheads, acoustic guitar, and vocals.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: micaddict on April 15, 2013, 02:21:58 PM
Quote
I'm going to be doing some testing and can post the results if desired.

Desired.





 :)
Title: Re: Official C12 Clone - Build and Support Thread
Post by: hyde maintenance on April 15, 2013, 03:31:55 PM
Quote
I'm going to be doing some testing and can post the results if desired.

Desired.





 :)

Considering I too haven't heard back on the CT12 I'm trying to order, I'm very interested in hearing those comparisons as well.
I'm thinking about using the double layer headbasket for a variety of reasons, so I wonder if I'd be compromising a few of the reputed strengths of the CT12 anyhow?
Title: Re: Official C12 Clone - Build and Support Thread
Post by: KMB-AUDIO on April 15, 2013, 03:48:51 PM
Quote
I'm going to be doing some testing and can post the results if desired.

Desired.





 :)

Considering I too haven't heard back on the CT12 I'm trying to order, I'm very interested in hearing those comparisons as well.
I'm thinking about using the double layer headbasket for a variety of reasons, so I wonder if I'd be compromising a few of the reputed strengths of the CT12 anyhow?

Out of curiosity, what are those reasons?
Title: Re: Official C12 Clone - Build and Support Thread
Post by: HellfireStudios on April 15, 2013, 06:38:25 PM
Dibs on one single-layer headbasket. Should we PM you to be on the first shipment list?

-James-
Title: Re: Official C12 Clone - Build and Support Thread
Post by: JessJackson on April 15, 2013, 11:42:55 PM
Is Tim ok?

I haven't heard back from him either, its now around the time he said my capsule would be ready to pay for.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Tim Campbell on April 16, 2013, 02:21:48 AM
I am fine. I have been in Germany the last week. From checking my email I'm pretty sure that I have answered everyone here. Jess, checking my records, you ordered a capsule about 4 weeks ago but since I have an 8-10 week lead time your capsule won't be ready for a while.

I am extremely busy, because of this, the huge amount of email I receive, and the fact that my current lead time is so long, I answer email as time allows, not every day. All my capsules are handmade, every part, by me alone and this takes time. Orders of multiple capsules take longer because more selection and adjustment must be done.

If I say I have you are on my list you will receive a capsule, when it's ready, but you must be patient. No amount of email will change when it's ready and just slows down the process.

The RK12 capsule is fine. It's inexpensive, sounds decent and made in a factory so you can order as many as you'd like without long delays. Many companies that use my capsule also use the RK12 and offer my capsule as an upgrade. The differences are mostly in the smoothness of the top end and depth of detail.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: chunger on April 16, 2013, 03:15:02 AM
There is no way to significantly ramp up monthly production volumes on Tim's handmade, hand-tuned capsule.   We have a rush right now on capsules because the kits were recently released and the first round of donor bodies (a significant amount) are being build up.

My plan is to attempt to stock Tim's capsule as soon as the dust settles from the 2nd round large-quantity shipment of donor microphones and associated parts from China.  I am also waiting for Tim's evaluation of the microphone kit, but due to the spike in demand for capsules, he has not yet had enough free time to actually build the microphone.  Also, I need to get in line just like everybody else because there is a finite amount of capsules available every month.  I do not want to bump anyone else who has been waiting, and I do not believe Tim does this.

I will say this about Tim Campbell's capsule business that differentiates him from some others in the same custom capsule market.  His lead time estimates are realistic and he does not take money until your capsule is close to completion.  Once it is confirmed that you are in the build queue, please allow for the estimated lead time and requests for updates reasonable/minimal.  Long hours answering emails and doing logistics detracts from time that could be spent building everyone's capsules!

Hopefully, once the initial rush on these microphones subsides a little bit, we will be able to smooth the ordering process.  For now, please be patient.  We want as many folks as possible to enjoy these great mics and are trying our best to make everything easily available.

I have sold through the first order of electronic parts kits, but have attempted to re-stock and pack a 2nd round of components.  I believe I was somewhat successful in that the pipeline is relatively uninterrupted, but these behind-the-scenes scramblings along with taxes have put me 2 weeks behind in shipping, but I hope to catch up this week.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: micaddict on April 16, 2013, 09:11:44 AM
In the good ole days of craft, waiting was normal.

And hey, anticipation is part of the fun.  :P



Talking about anticipation; I'll be needing one single layer headbasket and one dual. FWIW.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: kidvybes on April 16, 2013, 09:45:06 AM
...just as a point of reference for those who are undecided as to what capsule option to go with for their build, I am in the preliminary stages of testing a recent build of this mic, using another of the C12-type capsules available for this application...as previously posted, I employed one of the 3-Zigma GK-Series capsules (manufactured under much more strict QC standards in China for Larry Vilella of ADK)...they also offer a 251-voiced capsule as an additional option...Jim Jacobson at JJ Audio has spoken very highly of these capsules in the past and these originate, to my knowledge, from the best/oldest of the Asian microphone manufacturers under the additional QC oversight of ADK's agent, and are in stock and available from ADK's custom shop:
http://www.adkmic.com/catalog/customshop/ModsAndParts.php
...these are the same capsules ADK employs in their premium Z-Mod Series microphones:
http://www.adkmic.com/catalog/customshop/Z-Mods.php

...I am using the GK-12d, which unlike Tim's capsule, is not an exact replication of the historic C12, but rather an interpretation based on the C12's tonal characteristics...my initial impressions of this capsule is that it has a noticeably smoother top-end than the less expensive TongXin 5-micron (like the RK12) and ShuaiYin 6-micron C12-type capsules, with much less susceptibility towards sibilance...

...these are not inexpensive and I cannot comment as to how they compare in tonality to Tim's capsule, which is clearly the C12 standard in terms of current production, but I can say that the preliminary tests have been quite impressive...this is the same mic/capsule that Matador provided a soundfile for in post #155 of this thread...

...as soon as I have soundfiles worthy of sharing, I will post samples of this build for vocal tracking...I want to thank both Matador and Chunger for helping to facilitate this opportunity to add one of these excellent microphones to my mic cabinet...I look forward to putting it to good use on future projects...
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Tim Campbell on April 16, 2013, 10:10:10 AM
I believe this might be the capsule being used in the Blackspade UM25.
I had no idea anyone would pay so much for a chinese, K67 based, factory made capsule.
I need to rethink my prices.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: kidvybes on April 16, 2013, 11:10:23 AM
I believe this might be the capsule being used in the Blackspade UM25.

...the base level Blackspade UM25 employs, I believe, a variation of the ShuaiYin 6-micron C12-type capsule, similar to those used by Advanced Audio and Stellar Microphones, but with additional QC/modification here in the US...similar capsules are available from Dave Thomas for $95...
http://www.aamicrophones.com/parts.htm

(see pic below)

I had no idea anyone would pay so much for a chinese, K67 based, factory made capsule.
I need to rethink my prices.

...first you need to consider that these inflated prices are "retail", not the cost of these capsules direct from the manufacturing source...there are in fact, quite a few high-priced, respected "boutique" quality microphones employing capsules from this particular factory (I am reluctant to post brand specifics for obvious reasons)...these are clearly a much higher quality and do not share any components/metalwork with the TongXin and ShuaiYin variations...this factory does not offer OEM product like the others in China, but only manufactures for exclusive, branded application...this factory has direct lineage to the Chinese government facility that originally employed German engineers to train it's staff many years ago...

...I'd be interested in your thoughts on the quality of these capsules, particularly in light of your positive comments relating to the RK12 capsule...I have other mics that employ the $100-retail Asian C12 capsules, and I assure you this is on another level entirely...whether or not they offer good value based on the $300-400 suggested retail price is a personal judgement call, of course...

...Tim, you might inquire about (since I know you supply JJ Audio with your capsules) a more specific evaluation from Jim Jacobson since he employs all of these variations in his buillds...
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Tim Campbell on April 16, 2013, 12:56:56 PM
Perhaps Oliver Archut wasn't clear when he told me that their capsule was made by Feilo. I know some of the engineers at Gefell who worked with them.

Pricewise , I meant that someone here would pay (not wholesale prices that someone buying 1 capsule wouldn't receive) 145 dollars more than my capsule would cost them ( the 251 is 500 dollars, my capsule is 355). These capsules are not chambered but simply  edge terminated, K67 backplates with membranes. Building a CK12 is much more labor intensive, that's why T-USA and Josephson charge 1500 dollars for their CK12's.

I am sure these capsules sound terrific, maybe as good as mine and I would encourage anyone to buy them.

As far as the sound of my capsule, Bill Schnee and Toby Foster after a long comparison between their C12's and a pair of FLEA F12's with my capsules concluded I currently make the best CK12 capsule in the world (Toby Foster worked with T-USA developing theirs).



Title: Re: Official C12 Clone - Build and Support Thread
Post by: strangeandbouncy on April 16, 2013, 01:43:38 PM
Guys and Gals,



  It's really very simple. If you want a Capsule that sounds as close as is humanly possible to the original CK12 from AKG, buy a Campbell Transmitter Capsule for a ridiculously small amount of money. I mean ridiculously cheap. They are hand made and tuned by Tim HIMSELF. Personally, I have heard a wide variation of CK12s in different mics (ELAM251, AKG C12, AKG C24, AKG 412, AKG C12a, AKG414eb(?), and they vary greatly in my experience. Tim can make them all the same, or Tim can even match his to an existing capsule! His capsule is "the same" in my book!

  Don't [email protected]@k around with Chinese so-called CK12 capsules. Apart form the fact that they are capsules, they have very little in common with the real deal. I am sure that some of them do sound fairly good, but they are NOT the same thing, and they are made on an assembly line by assembly line workers. Tim is not an assembly line, rather a very skilled and dedicated sound engineer who has been using these puppies all his working life. HE MAKES THEM HIMSELF.


   If you have to wait for one. Wait. It is well and truly worth the wait.


   AndyP



ps I am in no way affiliated with Tim. I do, however, use a home-brewed C12-ish mic on a daily basis. It makes me very very happy. Oh, and my clients!

pps - did I say "HE MAKES THEM HIMSELF"? - perhaps I should repeat myself again . . . .
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Matador on April 16, 2013, 02:26:19 PM
I didn't get a lot of time with the prototype with Tim's CT12, but from what I could tell it sounded fantastic.

What I've noticed with the edge-terminate 67 type capsules:  they really need the electronic de-emphasis to sound natural and balanced.  The edge termination doesn't really change this character:  I assume it must be related to the backplate drilling, diaphragm tension, etc (I'm no expert by any means).

The C12 circuit is, for all intents and purposes, "full range", meaning the gain doesn't start dropping off until the output transformer inductance starts to dominate the frequency response.  I think this happens out past 40K, so for audio the circuit is essentially "flat" (I'm hand waving here, but it illustrates my point nonetheless) in the audio regions of interest.

For those trying these capsules, the ELA 251 plate cap is a good band-aid for taming this peaking response:  values in the 470pF to 1,000pF range are a good starting point. 

Tim's capsule sounds perfect without this cap, but you can dial in a very usable sound with this cap.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: KMB-AUDIO on April 16, 2013, 03:54:23 PM
It's really very simple. If you want a Capsule that sounds as close as is humanly possible to the original CK12 from AKG, buy a Campbell Transmitter Capsule for a ridiculously small amount of money. I mean ridiculously cheap. They are hand made and tuned by Tim HIMSELF.

<snip>
pps - did I say "HE MAKES THEM HIMSELF"? - perhaps I should repeat myself again . . . .

I have heard nothing but the highest praises for his capsule, that's why I don't mind waiting! I hope nobody is giving Tim a hard time about his lead time.  You gotta wait for quality!

When I first started looking into buying a capsule from Tim, I had no idea on the price and figured I was going to have to pay double what he is asking for his.  I was pleasantly surprised to find out that they were only 355 for a hand-made, hand-tuned capsule that is the real deal.

I never intended to keep the RK12 in the mics at all, they were bought so I could get the mic built and functioning until the CT12s arrived.  I have a couple other mics that I want to put the RK12 into to to see how they sound in other circuity.  Who knows, I may just build two more "C12s" with these caps.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Ericbazaar on April 16, 2013, 04:21:23 PM
Hi Matador,

i will replace R1 and R2 for the 6201 Tube.

These tubes are higher mu so a few circuit tweaks will be in order:  mostly lowering R17 down to make the gain about the same as compared to a 12AY7/6072A.

Can you be more specific. R17 can remain in the circuit, or should another resistor to be installed? Which values has the new resistor?
Or better asked, it is better to replace the Electro Harmonix 6072a Tube against a GE Five Star 6201? Is there a sonic advantage?

Thanks

Title: Re: Official C12 Clone - Build and Support Thread
Post by: Matador on April 16, 2013, 05:08:29 PM
I think R17 should be lowered to about 47K.  With -1V bias, idle current looks to be about 1.25mA with a 6201.  R1 and R2 being 100K should still be fine and give adjustment room around the 120V point.  Plate should be sitting at about 60V at idle (same as 6072).

I'm not sure about how the sonics will be different:  the main reason to switch to a 6201 is availability of high quality tubes at this date.  The 6201 has more robust internal construction than the 6072, so it might be quieter (all other things being equal).  With a lower R17, output impedance will be lowered which should make the amp slightly "faster" (for lack of a better term).

I have some parts in transit to me and I'll build a version with this tube.  I'll post my exact tweaks if you don't want to experiment (or be a guinea pig) in this case.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: kidvybes on April 16, 2013, 05:24:41 PM
Perhaps Oliver Archut wasn't clear when he told me that their capsule was made by Feilo. I know some of the engineers at Gefell who worked with them.

...if Oliver says so then the information I received may have been more recently revised...I previously demo'ed serial #10 of the UM17 in August 2011, while the UM25 production was still being finalized, and was informed by my contact at Blackspade in Switzerland that their capsule source was indeed ShuaiYin...(I just reviewed the original correspondence and it clearly states ShuaiuYin was the source for both the original K17 and CK25 capsules)...

...I acquired my GK12d capsule as part of a gear trade, as it was originally intended to be used as an upgrade on a Avantone CV12 by the original owner...if I intended to spend anywhere near the cost of this capsule, I too would opt for your capsule...I only offered up the info as another option...

...my comments were in no way meant to imply that the ADK capsule is a true C12 reproduction, they are clearly an "interpretation" based on K67 backplates...while not an accurate C12 reproduction, I do believe it is a high-quality capsule...no one, certainly not I, questions the integrity of your CT12 capsule...the mic I am currently testing is being evaluated purely based on it's performance and usefulness as a vocal microphone for a particular artist, not it's accuracy as a "C12 clone"...
Title: Re: Official C12 Clone - Build and Support Thread
Post by: hyde maintenance on April 16, 2013, 08:01:53 PM
Quote
I'm going to be doing some testing and can post the results if desired.

Desired.





 :)

Considering I too haven't heard back on the CT12 I'm trying to order, I'm very interested in hearing those comparisons as well.
I'm thinking about using the double layer headbasket for a variety of reasons, so I wonder if I'd be compromising a few of the reputed strengths of the CT12 anyhow?

Out of curiosity, what are those reasons?

Nothing too mind blowing unfortunately. Basically I'd like to play around with a few variables (including tube type, transformer and output cap) to see if anything strikes my fancy. Also on the practical side, I'd like a bit more capsule protection from dust, spit etc than I would get over the single layer basket.
And if I don't like it I can always pull the thin mesh out.

Glad to hear all is well with Tim Campbell, and hope to hear back from him soon.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: gary o on April 16, 2013, 09:12:18 PM
Well its nice to have more and more capsules for DIY clones or otherwise, the big problem is unless you buy them all to try you just dont know which is best for you & you end up reading other users discriptions of the sound they hear, not good

On a technical note I have been wondering how K67capsules are made to sound like other capsules  ....  the ADK for instance, Blue seem to make capsules that sell for a lot of money like this, I myself have a Violet VD67 capsule £500 K67 style meant to sound like the U67 mic its sound good but wouldnt know what real U67 sounds like tho.... but have been wondering how they tune these & can we tune cheap K67 capsule to sound better...... for what its worth I love the sound of my VD67 but also love sound of Tims capsule tho again I dont have a real C12 to compare but I do think Tims its great value..... also for what its worth I have ADK cheap Vienna thats meant to sound like a C12 & it doesnt sound bad at all......

All the best
Title: Re: Official C12 Clone - Build and Support Thread
Post by: chunger on April 16, 2013, 10:51:10 PM


Nothing too mind blowing unfortunately. Basically I'd like to play around with a few variables (including tube type, transformer and output cap) to see if anything strikes my fancy. Also on the practical side, I'd like a bit more capsule protection from dust, spit etc than I would get over the single layer basket.
And if I don't like it I can always pull the thin mesh out.

Glad to hear all is well with Tim Campbell, and hope to hear back from him soon.

The single layer headbasket looks sexy and shows off the capsule, but I have in mind to put the dual layer headbasket on and try.  If the dual layer influences the sonics in a positive way or I'm neutral as to which one I like better, I will keep the 2 layer on there for the added protection.  Plus, I'm hoping these headbaskets are at a price-point where people can use it as another sonic variable to try quickly.

As I understand, it is very hard to predict what changes in the meshing will do to the sound without just throwing different configurations on the mic and trying them out.  There are a lot of complex acoustic interactions that happen in that small space.  With the new shipment of microphones, I'm happy to be able to offer a few different meshing options to try.

Title: Re: Official C12 Clone - Build and Support Thread
Post by: JessJackson on April 16, 2013, 11:15:01 PM
Thanks Tim, yeah your right its been about 5 weeks, felt like longer lol

since the topic went in that direction i'll say that I have a re skinned vintage ck12 by tele usa capsule in my vintage c12 and i'm not overly impressed with the re-skin job... not smooth on the top.

Best,

J
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Ericbazaar on April 17, 2013, 04:10:43 AM
For those trying these capsules, the ELA 251 plate cap is a good band-aid for taming this peaking response:  values in the 470pF to 1,000pF range are a good starting point. 

Hi Again,

I have a question regarding the exchange of the capacitors. It interests me very much, I want to keep my options open, adjust the microphone from the sound. Are you talking about the replacement of the capacitors C10 and C11? Here in Germany, there are NOS 1nF 630V Polystyrene capacitors of "East German RFT", or Sovcor pure glass capacitor 1nF 300V. I have also discovered Output MCAP condensators of German "Mundorf". I would like to experiment a little! I know it is a C12 clone, but I want a great sounding tube microphone, if it sounds like an original C12 is not important to me.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Gilgamesh on April 17, 2013, 05:57:58 AM
I added in the plate cap to a 460 mod and it definitely gave a darker more vintage tone but seemed to rob the mic of some of its class as well. I'm planning on gutting it and doing a 251 proper when that kit becomes available.

I used a 220pf cap, I thought the cap in the original 251s varied a bit but was generally between 100pf - 300pf??
Title: Re: Official C12 Clone - Build and Support Thread
Post by: gary o on April 17, 2013, 06:54:37 AM
 Gilgamesh do you mean cap between plate & ground on 1961 schematic for ELA251 its a 100pf.......
did I read the ELA was a redesigned C12 for broadcast use kind of nobbling the C12 by rolling off bass b& top ...... 

Im currently experimenting with several tube mics to learn & to decide which to build to use for vocals so far I tried ELA250 with 6072 & 5840, Mk47,M49C (5840) MGM Church mic, & a TB1 (like a ELA C12 crossbread i guess) I hated the sound of the ELA compared to others I guess now it was the low 30M grid resistor which I guess make sense if not meant for recording vocals....

Im gonna have play with this here C12 circuit



Title: Re: Official C12 Clone - Build and Support Thread
Post by: Category 5 on April 19, 2013, 09:06:59 AM
Any restrictions on what type of solder to use on this?  I normally use 63/37 but got some lead free solder I'm itching to try too.  Also, is the included 7 pin cable good enough or is that something that should be replaced?

Finally, I plan to test with an JAN AT7 and the stock Alctron capsule.  Is this good enough to trim the voltages, etc?  I wouldn't even think about starting out with Tim's capsule.  Also, since there is a big lead time on Tim's Capsules I think I will use the microphone-parts K12.  Anyone else have experience with this capsule?

BTW  extra thanks to Matador and Chunger who put together a project here that borders on legendary.  The boards look just incredible populated.  it's almost a shame to cover them up!
Title: Re: Official C12 Clone - Build and Support Thread
Post by: mwrichardson on April 19, 2013, 10:59:40 AM
Hi Chunger

I sent you an email directly to your store asking to reserve or pre pay an order of four of the 251 dual mesh head baskets. Did you get that? Do I need to order here? I would be happy to pay the extra to be on the advanced air shipment order.

I also sent Tim Campbell an email ordering 2 capsules. No reply yet. I know I have to get on a waiting list. Tim, if you see this please add me to the order list. I know you get alot of emails and I do not want to add to that.

Thanks guys

Mark Richardson
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Matador on April 19, 2013, 11:11:52 AM
Any restrictions on what type of solder to use on this?  I normally use 63/37 but got some lead free solder I'm itching to try too.  Also, is the included 7 pin cable good enough or is that something that should be replaced?

Finally, I plan to test with an JAN AT7 and the stock Alctron capsule.  Is this good enough to trim the voltages, etc?  I wouldn't even think about starting out with Tim's capsule.  Also, since there is a big lead time on Tim's Capsules I think I will use the microphone-parts K12.  Anyone else have experience with this capsule?

BTW  extra thanks to Matador and Chunger who put together a project here that borders on legendary.  The boards look just incredible populated.  it's almost a shame to cover them up!

Any solder is fine, so long as you have the tools to deal with it.  The electrons won't care!  8)

The 12AT7 pulls more current than the 6072A, but it should still trim out fine.  Is that the tube type you'll stick with?
Title: Re: Official C12 Clone - Build and Support Thread
Post by: KMB-AUDIO on April 19, 2013, 07:00:20 PM
Any restrictions on what type of solder to use on this?  I normally use 63/37 but got some lead free solder I'm itching to try too. 

Before you use that lead free, try it out on something other than your mic first.  It has a different "feel" when soldering that I am not used to yet.  I still have spools of 63/37 to use up though :)
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Category 5 on April 19, 2013, 07:48:40 PM
Any restrictions on what type of solder to use on this?  I normally use 63/37 but got some lead free solder I'm itching to try too.  Also, is the included 7 pin cable good enough or is that something that should be replaced?

Finally, I plan to test with an JAN AT7 and the stock Alctron capsule.  Is this good enough to trim the voltages, etc?  I wouldn't even think about starting out with Tim's capsule.  Also, since there is a big lead time on Tim's Capsules I think I will use the microphone-parts K12.  Anyone else have experience with this capsule?

BTW  extra thanks to Matador and Chunger who put together a project here that borders on legendary.  The boards look just incredible populated.  it's almost a shame to cover them up!

Any solder is fine, so long as you have the tools to deal with it.  The electrons won't care!  8)

The 12AT7 pulls more current than the 6072A, but it should still trim out fine.  Is that the tube type you'll stick with?

No.  I will settle with the recommended GE 6072A.  I want to get as close to original as possible.

Gonna use 63/37 then.  It melts like butter and cools like polished silver.  Scared to go lead free just yet because I just know I'm gonna overheat components getting used to it.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Pip on April 20, 2013, 02:23:52 AM
Any restrictions on what type of solder to use on this?  I normally use 63/37 but got some lead free solder I'm itching to try too.  Also, is the included 7 pin cable good enough or is that something that should be replaced?

Finally, I plan to test with an JAN AT7 and the stock Alctron capsule.  Is this good enough to trim the voltages, etc?  I wouldn't even think about starting out with Tim's capsule.  Also, since there is a big lead time on Tim's Capsules I think I will use the microphone-parts K12.  Anyone else have experience with this capsule?

BTW  extra thanks to Matador and Chunger who put together a project here that borders on legendary.  The boards look just incredible populated.  it's almost a shame to cover them up!

I use 4% silver solder. A specific brand but do a search their out there. Not because of the sound characteristics or anything so readily debatable (so please don't not here anyway). It is because silver oxide (AgO not Ag2O) conducts as well as silver. Nothing more nothing less.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Matador on April 20, 2013, 01:01:55 PM
No.  I will settle with the recommended GE 6072A.  I want to get as close to original as possible.

Keep in mind that since the 12AT7 pulls more idle current, you will dial in less resistance in order to achieve 120V on the top of the plate resistor (B+).  When you sub in the 6072A, the B+ voltage will rise significantly, which means the polarization voltage will also rise, perhaps enough to suck in the diaphragms.

Once everything is up and running with the 12AT7, disconnect the 4 capsule leads and then do the tube swap.  You can then readjust the B+ and bias voltages to the 120V and -1V levels.  After all of that is done, you can then re-attach the capsule leads and everything should be fine.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Gilgamesh on April 20, 2013, 01:15:12 PM
Gilgamesh do you mean cap between plate & ground on 1961 schematic for ELA251 its a 100pf.......
did I read the ELA was a redesigned C12 for broadcast use kind of nobbling the C12 by rolling off bass b& top ...... 

Im currently experimenting with several tube mics to learn & to decide which to build to use for vocals so far I tried ELA250 with 6072 & 5840, Mk47,M49C (5840) MGM Church mic, & a TB1 (like a ELA C12 crossbread i guess) I hated the sound of the ELA compared to others I guess now it was the low 30M grid resistor which I guess make sense if not meant for recording vocals....

Im gonna have play with this here C12 circuit

Yes that's the cap I mean, maybe I will try a 100pf and see if it's a better result with a more modest effect on the highs. IIRC the 251 was a modification of the C12 designed to compete with the U47 which is why they rolled off the tops through the circuit modifications. I have also read that, although the same capsule was used the CK12 capsule in the 251 was tuned more for its specific purpose. I am building a C12 mic but also want to build a second in the 251 style as I think it shines as a vocal mic more than the C12. I compared my modifed 460 with a Tim Campbell CT12 to a Bock in the 251 style and it almost matched its class (quite impressively considering the relatively modest cost) but it didn't have the same width in the mids to give it that thick honey vocal I'm chasing. I'm hoping a genuine 251 circuit and the double layered head basket Chunger is working on will get me a bit closer. The search continues...
Title: Re: Official C12 Clone - Build and Support Thread
Post by: micaddict on April 20, 2013, 02:01:11 PM
Quote
I'm hoping a genuine 251 circuit and the double layered head basket Chunger is working on will get me a bit closer.

Like I've stated before, I'm hoping there'll also be a non-export version, with a subminiature tube (e.g. the 5840) rather than the 6072a. Sort of like Dany does with the M49 and M269. With a little luck they could all use the same (basic) PSU.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Category 5 on April 20, 2013, 02:35:13 PM
Quote
I'm hoping a genuine 251 circuit and the double layered head basket Chunger is working on will get me a bit closer.

Like I've stated before, I'm hoping there'll also be a non-export version, with a subminiature tube (e.g. the 5840) rather than the 6072a. Sort of like Dany does with the M49 and M269. With a little luck they could all use the same (basic) PSU.

I sure hope not.  These kits are so nice I will be forced to build every single one they offer.  This could get wicked expensive.

Any idea when the first 251 project is due out?  If it's soon, I'll pick up an extra headbasket and donor mic with the next batch.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: micaddict on April 20, 2013, 03:07:08 PM
Quote
I sure hope not.  These kits are so nice I will be forced to build every single one they offer.  This could get wicked expensive.

 ;D

Hey, but being able to run different tube mics from the same PSU (like in the old broadcast days) could save you time and money.  ;)
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Pip on April 20, 2013, 11:18:58 PM
Getting back to the B+ adjustment question.

Ok now granted empirical means were used throughout this process. But here are my findings such as they are.

Using the same 6072 tube I have from beginning (this does beg the question is the tube to blame but it sounds good and was bought tested from a reputable source. I will have to breakout the Hickock Tube tester down the line) these are my results.

I first changed the R17 resistor to a 400k as per the original C12 schematic. This resulted in the B+ midpoint adjustment on the pot becoming proper. There was a real midpoint. Voltage now 120VDC.

I then replaced the R17 with the original Matador specced 100K and changed resistors 1 and 2 to 100K. This resulted in the same problem returning could not get B+ voltage up higher than 106VDC (measured with Fluke 289)! ::)

So I then replaced the R17 resistor once again with 400K leaving PSU resistors at the new 100K value. This resulted in a lower midpoint on B+ adjustment pot but it works so I have left it this way for now.

Mic still sounds good with plenty of output. So there you have it.

When Tim Campbells capsule arrives I will go back at this in ernest.

At present:

Measured at PSU with mic connected.
B+ 120VDC
Heater 6.3VDC
Bias -1VDC
Title: Re: Official C12 Clone - Build and Support Thread
Post by: chipss36 on April 21, 2013, 08:02:21 PM
So I have ordered parts for the build, after reading about others finished mics ,
Opted for the 1 uf cap, anyone else tryed both? Suppose more than an exact c-12 clone , just looking to make a great sounding mic.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Category 5 on April 21, 2013, 10:17:29 PM
Contacted Christian about getting a tube for mic 1 and got schooled on the variants.  What a great guy to deal with.  He mentioned he's got some really fantastic 1970's tubes right now so if you're planning on contacting him for this build I'd say do it soon.  He seems really impressed with his current stock.

Also, anyone know the best way to get added to the waiting list for a CT12?  I sent an email to Tim but haven't heard back.  I imagine he's sick of hearing from group DIY'ers and I don't want to badger him but I'd like to get on the list soon so that completing the mic will coincide with my capsule arrival.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: KMB-AUDIO on April 22, 2013, 08:27:44 PM
Getting back to the B+ adjustment question.

Ok now granted empirical means were used throughout this process. But here are my findings such as they are.

Using the same 6072 tube I have from beginning (this does beg the question is the tube to blame but it sounds good and was bought tested from a reputable source. I will have to breakout the Hickock Tube tester down the line) these are my results.

I first changed the R17 resistor to a 400k as per the original C12 schematic. This resulted in the bias midpoint adjustment on the pot becoming proper. There was a real midpoint. Voltage now 120VDC.

I then replaced the R17 with the original Matador specced 100K and changed resistors 1 and 2 to 100K. This resulted in the same problem returning could not get B+ voltage up higher than 106VDC (measured with Fluke 289)! ::)

So I then replaced the R17 resistor once again with 400K leaving PSU resistors at the new 100K value. This resulted in a lower midpoint on B+ adjustment pot but it works so I have left it this way for now.

Mic still sounds good with plenty of output. So there you have it.

When Tim Campbells capsule arrives I will go back at this in ernest.

At present:

Measured at PSU with mic connected.
B+ 120VDC
Heater 6.3VDC
Bias -1VDC

I'm hoping Matador can chime in on this one.  I too am having this issue.  I've built two mics so far, one of them I was able to dial in all the voltages as per Chunger's tutorial.  The other I was not.  I've eliminated the tube (6072a from Christian Whitmore) and capsule (RK12) as possible causes.  When I went back to troubleshoot, I discovered that on the mic that I was able to set the voltages, I made a mistake and put a 500k resistor at R17 instead of the 100k as specified.

So I guess what I would like to know is: what is the consequence of putting a 400k resistor, as per the original design, at R17?
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Matador on April 23, 2013, 10:28:15 AM
Using 400K is fine.

There is obviously much higher tube tolerance than the original datasheets suggest.  Getting more current through the bleeder is one way to get more current flowing through the bias network.  In reality, the original C12 schematic shows a 300K resistor (R9) as the B+ bleeder, but that design was also only half-wave rectified, so it's not apple to apples in any case.  This had to be done in order to make use of the stock transformer in this circuit.

As a general principle, if the B+ voltage is too low (can't be trimmed high enough), then one has several options:  a) reduce R1 and R2 in value, b) increase the value of the bleeder R6, or c) make the bias voltage more negative.  B and C reduce the current through the network which increases B+, and A reduces the voltage drop while keeping the current roughly the same.

If the B+ voltage is too high (can't be trimmed low enough), then reverse the direction of everything above.

I was on the fence about making the B+ part of the supply regulated (with a MOSFET pass element and a Zener diode bias with feedback), however this is a drastic departure from the original supply and likely has more sonic implications. 
Title: Re: Official C12 Clone - Build and Support Thread
Post by: mwrichardson on April 23, 2013, 11:01:15 AM
I built my mic and supply with the parts in the BOM and had no trouble setting all 3 voltages.

Correct me if I am wrong, but R17 is 100k on schematic, not 400k. Look at how the draftsman writes his numeral 1 with a descending top slash and how he writes numeral 4 elsewhere like at power supply R2 (4W). A 400k in R17 would make the output impedance rise dramatically (and change gain) and thus would not be a good match for the T14 transformer. Also the 251 and C24 schematics all have 100k as Plate resistor.

So I don't think R17 at 400k is a good solution. The problem is probably elsewhere.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: KMB-AUDIO on April 23, 2013, 03:08:15 PM
I built my mic and supply with the parts in the BOM and had no trouble setting all 3 voltages.

Correct me if I am wrong, but R17 is 100k on schematic, not 400k. Look at how the draftsman writes his numeral 1 with a descending top slash and how he writes numeral 4 elsewhere like at power supply R2 (4W). A 400k in R17 would make the output impedance rise dramatically (and change gain) and thus would not be a good match for the T14 transformer. Also the 251 and C24 schematics all have 100k as Plate resistor.

So I don't think R17 at 400k is a good solution. The problem is probably elsewhere.

@mwrichardson, I think you are right about R17 on the original schematic.  Which capsule and tube are you using?

@ Matador, which option do you suggest starting with? I am using a T14 from Oliver. Eventually, these will have CT12's in them, but for now I have RK12.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: mwrichardson on April 23, 2013, 03:14:52 PM
I am using a Peluso PK12 capsule and a 6072 I got from him too. I am ordering tubes from Proaudiotubes and waiting to be put on the list for Tim Campbells capsules (Hoping for an email from Tim!). The Peluso capsule has that "U67 type capsule that is not compensated by eq" over brightness. I believe he adds a cap to ground at a junction of 2 resistors that replace the single grid bypass resistor (R15 on Matadors drawing) )to control HF in the P12.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Pip on April 23, 2013, 04:53:41 PM

Thank You Matador. You are very generous with your time to this group. That helps very much, much better explaination too!

Also I have corrected my intial post to reflect the term B+ throughout as I at one point incorrectly used the term bias. Ooops!

Just for information purposes this is the schematic I am referring to as the original:


Title: Re: Official C12 Clone - Build and Support Thread
Post by: Matador on April 23, 2013, 06:55:39 PM
R17 is the plate load resistor: don't change it from 100k unless you know what you are doing.

The resistors I am referring to are the filter resistors R1 and R2, and the bleeder resistor R6 (per my schematics not AKG's).
Title: Re: Official C12 Clone - Build and Support Thread
Post by: KMB-AUDIO on April 23, 2013, 08:40:12 PM
R17 is the plate load resistor: don't change it from 100k unless you know what you are doing.

The resistors I am referring to are the filter resistors R1 and R2, and the bleeder resistor R6 (per my schematics not AKG's).

Understood. I will change R1 and R2 tonight and report back my findings.  Thanks for your help!
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Pip on April 23, 2013, 09:52:28 PM
R17 is the plate load resistor: don't change it from 100k unless you know what you are doing.

The resistors I am referring to are the filter resistors R1 and R2, and the bleeder resistor R6 (per my schematics not AKG's).

There is, I think, the clarification I needed to understand. What would you suggest starting with as a value for substituting R6 if plate resistor (R17)is at 100K. And not enough B+ voltage being obtained.

Thanks again.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Gearsix on April 24, 2013, 01:29:26 AM
Hello, someone can say me if it is possible to replace the SMD 0 ohm resistor with a small jumper?
Thank you!
Title: Re: Official C12 Clone - Build and Support Thread
Post by: KMB-AUDIO on April 24, 2013, 01:39:35 AM
Hello, someone can say me if it is possible to replace the SMD 0 ohm resistor with a small jumper?
Thank you!

Check out post #182: http://www.groupdiy.com/microphones/official-c12-clone-build-and-support-thread/182/

This is the first SMD component I've ever soldered...it wasn't too tough! Quite easy in fact.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Pip on April 24, 2013, 02:40:47 AM
.

Correct me if I am wrong, but R17 is 100k on schematic, not 400k. Look at how the draftsman writes his numeral 1 with a descending top slash and how he writes numeral 4 elsewhere like at power supply R2 (4W). A 400k in R17 would make the output impedance rise dramatically (and change gain) and thus would not be a good match for the T14 transformer. Also the 251 and C24 schematics all have 100k as Plate resistor.

So I don't think R17 at 400k is a good solution. The problem is probably elsewhere.
R17 is the plate load resistor: don't change it from 100k unless you know what you are doing.

The resistors I am referring to are the filter resistors R1 and R2, and the bleeder resistor R6 (per my schematics not AKG's).

Yes I do believe you are right all the way around now that I take yet another look at schematics.

Again Thanks All.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: mwrichardson on April 24, 2013, 09:35:38 AM
I used wire jumped instead of SMD device. I am not a fan of them.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Gearsix on April 24, 2013, 01:28:02 PM
Thank you, I have lost that post!
Another thing: someone has used 4700pf capacitors instead of 5000pF?
Cheers
Title: Re: Official C12 Clone - Build and Support Thread
Post by: mwrichardson on April 24, 2013, 05:34:30 PM
4700pf is fine. They are just filters. and.. I got on Tim Campbells capsule waiting list!! Thanks Tim!
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Category 5 on April 24, 2013, 09:58:47 PM
I got on Tim Campbells capsule waiting list!! Thanks Tim!

How?!  Lucky!
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Gearsix on April 25, 2013, 04:56:58 AM
Someone has verified differences using the 100M Ohm resistors instead of 30M Ohm and 250M Ohm?
Best
Title: Re: Official C12 Clone - Build and Support Thread
Post by: chunger on April 25, 2013, 06:26:26 AM
Just got word from the motherland.  The production run for the custom headbaskets is complete.  These should become available shortly.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: mwrichardson on April 25, 2013, 08:39:54 AM
Where and why are you using 100M resistor? It is not on schematic or BOM.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Gearsix on April 25, 2013, 09:47:23 AM
In the version 3 of the BOM (you can download it in the first page af this thread) the 100M ohm resistors are indicated as alternate to 30M and 250M resistors
Best
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Matador on April 25, 2013, 11:17:08 AM
I tried the 100M versions in the second prototype and could not tell any differences.

They also save almost $10 from the BOM cost alone.  ;D
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Gearsix on April 25, 2013, 11:47:21 AM
Thank you!
Title: Re: Official C12 Clone - Build and Support Thread
Post by: baadc0de on April 26, 2013, 09:40:51 AM
How much of a difference in low cut does a 0.15uF capacitor make vs. 0.5uF or 1.0uF?
Title: Re: Official C12 Clone - Build and Support Thread
Post by: mwrichardson on April 26, 2013, 03:31:46 PM
If you double the cap from 0.5 uf to 1 uf the low end is extended about an octave.

Title: Re: Official C12 Clone - Build and Support Thread
Post by: Winetree on April 26, 2013, 04:29:03 PM
If you double the cap from 0.5 uf to 1 uf the low end is extended about an octave. I might try this.
But aside from this, I read a capsistor review, rating many caps on their sound,
and the ERSE caps were rated 6.5 with some as high as 12.
The cap prices when up with the ratings.
Would a better rated and more expensive output cap (C12)
make a difference in the sound of the C-12?
Title: Re: Official C12 Clone - Build and Support Thread
Post by: JessJackson on April 26, 2013, 09:14:58 PM
If you double the cap from 0.5 uf to 1 uf the low end is extended about an octave. I might try this.
But aside from this, I read a capsistor review, rating many caps on their sound,
and the ERSE caps were rated 6.5 with some as high as 12.
The cap prices when up with the ratings.
Would a better rated and more expensive output cap (C12)
make a difference in the sound of the C-12?

The Elam 251 used a 1uf cap, the c12 used a .5

1uf adds saturation at transformer also, I have not done sonic tests on this yet but many have.

Coupling Cap Reads...

http://www.neumann.com/forums/view.php?bn=neumann_archive&key=992691654&v=f

http://prorecordingworkshop.lefora.com/2011/02/16/c12-v-ela-m251-differences/efora.com/2011/10/23/franken-u47-opinions-welcomed/
Title: Re: Official C12 Clone - Build and Support Thread
Post by: chipss36 on April 27, 2013, 10:47:09 PM
I am wondering, what would happen if i put a m-7 style capsule in this build?
I am loving that capsule  on every mic I have wired it up on, will it work on this build as well?
Title: Re: Official C12 Clone - Build and Support Thread
Post by: baadc0de on April 28, 2013, 10:11:33 AM
Guys, I'm a bit at a loss here with my build.

I have built both the PSU and the mic. In the mic, I have substituted the output cap for a 1uF PIO and the two 5nF styrenes with two 8.2nF films. In the PSU, the pattern switch is built from 390k resistors instead of 400k resistors.

My multimeter has 10M input impedance in voltage measurement mode. With a dummy load (182k resistor) I can get 111V easy. With the mic I can only get about 80V. On the mic, basic voltages check out ok (bias, heater, plate). I have tried injecting some signal after the output cap (before the xformer) to verify that it's working OK and I can certainly get the signal out (so cables, leads, xformer, etc.. are all OK).

But I can't get any signal if I inject at grid. EDIT: with capsule disconnected.

The signal is direct from D/A through a 1uF/630 poly cap, to block DC.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: baadc0de on April 28, 2013, 03:11:48 PM
Found what the problem was... the wire going from plate on the PCB to tube was pinned down by a PCB mounting screw, stripping off a bit of the insulation and making contact to ground. So the tube wasn't getting any voltage on plate, since the electrons didn't feel like going there, instead opting to return to ground. Funny chaps. I'd think the opportunity to visit a springboard was better than home, but there you have it.

My next problem is super-low output, but from some testing it seems to, sadly, travel with capsule. Darn.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: baadc0de on April 28, 2013, 05:30:07 PM
And here I am again. The mic works and sounds nice. The output is still very low (barring my preamp at home not working well - that will need to be checked out in the studio), but it does not in fact travel with the capsule (instead, hum travels with capsule, so some capsules seem to work better as radio antennas than other, hmmm). Anyway, I am now suspecting the tube or preamp. I've tried both -2, and -1V bias and settled on -1V.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: cariocaman85 on April 29, 2013, 04:43:55 AM
Hi,

I built the mic yesterday with a friend. We were very, very careful and kept everything cleen at each step according to the tutorial (with 70% isopropyl alcohol).

PSU worked fine I think. We can easily get +120V on B+ with a 180k screwed beetween B+ and ground; and 6,3 for heater, -1 for bias, checking from the PSU blocks.

Then we removed the 180k resistor and we ran a test with the mike (stock capsule and groove tube 12AT7, FB and RB linked by a jumper). We adjusted the heater from the mic, and B+ and Bias, checking from the PSU blocks. Everything went fine. Then we powered it off, closed the mike's body, plugged it in a preamp (without phantom  ;) ), and powered on.

It took about 40 seconds before we could ear a sound but finaly, sound appeared! It was ok, except the noise seems to be too loud, and the audio signal, a little bit to tiny, regarding the stock Alctron we tested in comparison. I thought it was the tube/voltage, so we adjusted B+ and Bias (heater was fine 6,28V) with the same method I described before. The mike was still a little bit noisy and low output.

Maybe we (ok I  ::) ) made a mistake, I thought the tube as a problem, so I switched it for the 6072 nos tube. We readjusted voltages (B+ was down to 104, we put it at 120V), always checking the heater from the mike and the others (B+  and Bias) from the psu blocks, according to the tutorial. While everything seemed to be fine, we ran an audio test.

And... Still the same: not a lot of audio signal ( stock alctron is at least 5/6 dB higher in comparison ), and constant noise. The noise is not so loud, but enought to be a problem while recording. We tested into several preamps, with the same conclusion.  :'(

Then it was 3am and we didn't want to destroy something, so we stopped...

What do you thinks this could be? Is it normal? I don't think so but maybe someone as already encoutered this issue?

Some help will be very appreciated  :D

thanks,

Remi



Title: Re: Official C12 Clone - Build and Support Thread
Post by: mwrichardson on April 29, 2013, 06:41:17 PM
Cariocaman85.. What transformer are you using?  You need a T14 style. Check that the winding attached to the tube is the higher resistance winding.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: cariocaman85 on April 30, 2013, 02:58:21 PM
Hi, thanks for your reply!

We bought the T14 with the kit (the same as the tutorial). The red wires (21 ohms tested) are attached to the connector, and the blue ones (939 ohms) are connected to X1/X2. Is that correct?

Title: Re: Official C12 Clone - Build and Support Thread
Post by: JessJackson on April 30, 2013, 03:27:41 PM
Hi, thanks for your reply!

We bought the T14 with the kit (the same as the tutorial). The red wires (21 ohms tested) are attached to the connector, and the blue ones (939 ohms) are connected to X1/X2. Is that correct?

This is correct. Make sure primary and secondary left and right sides are correct also.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: cariocaman85 on April 30, 2013, 03:42:28 PM
Checked, they're ok... no phase switching.



Title: Re: Official C12 Clone - Build and Support Thread
Post by: mwrichardson on April 30, 2013, 10:56:26 PM
Here are some voltage measurements in my mic builds. I did 2 mics and had same readings. 

Junction of R12 and R17 .. 120vdc,   at junction of R17  C12 and plate .. 68.8 vdc,  at junction of R12  R13 and R14  (capsule polarization) .. 59vdc,    at  R11 and connector pin  .. 1.1vdc (bias). 

Also do not feed heater voltage to unused tube section (pin 5 if not using second triode) and ground plate, cathode and grid of unused section(pin 6 and 7 and 8 id not using 2nd triode). Might help noise.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: baadc0de on May 01, 2013, 06:35:44 PM
My build has a really low output I think. How could I verify if it's the capsule but not the amp? Could i inject a sine at the grid point and check? What kind of gain should I be expecting (probably about 25dB?). The problem is, currently my gain is about 25dB short of what I would expect...
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Matador on May 01, 2013, 07:28:57 PM
Per above, keep in mind 12AT7 and 6072A's are NOT drop-in replacements for each other in this circuit.  The output impedance of the power supply is just too high and many adjustments need to be made.

As for low-output:  in my testing of 3 prototypes, I observed around 20-25dB of gain as measured at the tube plate.  The 10:1 output transformer throws away 20dB of this gain, so the circuit is somewhere right around unity to about 5dB.  Gain can be made higher with other tube selections and some value tweaking (per above).

The stock Alctron CCDA circuit has a lot more gain, as there is a cathode-follower output stage feeding in to a much lower ratio transformer...perhaps twice the gain if the capsule is kept constant.

My build has a really low output I think. How could I verify if it's the capsule but not the amp? Could i inject a sine at the grid point and check? What kind of gain should I be expecting (probably about 25dB?). The problem is, currently my gain is about 25dB short of what I would expect...

One can inject a signal into the capsule coupling cap, or right at the grid if there is no offset in the signal generator.  If all is well, a 1V peak sine wave should appear as a 1V to 2V peak sine wave as measured at the XLR connector outputs.

As for the noise issues:  can you make a test recording of the noise you are hearing?  A great test (which can be done without taking out the capsule), is to hard ground the grid (e.g. pin 3 if you are using the "first" half of the tube) of your active tube stage and then do a test recording with everything buttoned back up.  What you will be hearing at this point is the self-noise of the tube, and any coupled noise from the power supply and/or cabling.  It will allow you to take the capsule and it's biasing (and the high-impedance section in it's entirety) out of the equation.

If the noise goes away, then we have to look in to the high-impedance parts.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: cariocaman85 on May 02, 2013, 07:21:50 AM
Thanks for all your replies!  :D

We can't test and record the mike before the next week, but we'll post samples and pictures asap!

I'll try with a 6072 EH, in order to preserve the NOS one.



Title: Re: Official C12 Clone - Build and Support Thread
Post by: srdigital on May 02, 2013, 02:44:10 PM
in building the c-12, will the k67 capsule you sell function to tide me over until i have enough cash to buy some of mr. campbell's? trying to mod 2 of the apex 460's, but want to see if the cap is a cheap alternative until i can afford the real deal. thanks!
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Category 5 on May 02, 2013, 02:53:22 PM
in building the c-12, will the k67 capsule you sell function to tide me over until i have enough cash to buy some of mr. campbell's? trying to mod 2 of the apex 460's, but want to see if the cap is a cheap alternative until i can afford the real deal. thanks!

Since those capsules have the 8KHz rise that has to be compensated for in circuit it probably won't give you what you want, even in the interim.  I am planning on using some of these while I wait to hear from Tim.  Cheap, and only positive reviews thus far.

http://microphone-parts.com/rk12-microphone-capsule/
Title: Re: Official C12 Clone - Build and Support Thread
Post by: hyde maintenance on May 03, 2013, 09:45:59 PM
I am wondering, what would happen if i put a m-7 style capsule in this build?
I am loving that capsule  on every mic I have wired it up on, will it work on this build as well?

I've been hoping someone would share any experiences or opinions on this question as I'm drawn to the idea of quality unique or oddball mics vs clones. Unfortunately my budget doesn't allow for multiple capsule purchases to try a bunch of combinations.

Anyone have any thoughts?
Title: Re: Official C12 Clone - Build and Support Thread
Post by: chipss36 on May 04, 2013, 05:16:13 PM
well i have the mic pcbs and p/s  stuffed, nos rca  tube and a russian  back up,  and the mic part c-12 capsule, I also have there 67 capsule but the deal I had on the  mic fell thorough kinda funny all the parts no mic, and have to go offshore for a month, however I guess I may be that guy, pretty sure the c-12 is going to be to bright for my taste ,  matt at microphone parts is a great guy . he did select a c-12 with less high end for me, see how it works out,  cathedral pipes has his caps on sale, I have a second, with a higher capacitance,  so it does overload a bit, however to tone is spot on for me vintage and warm, high end is sweet not ice pick like, just wondering if the voltages and such in this build would support that capsule?
also want to try matts 47 cap and his 7 if this mic supports it ill try them all and report back,  i have a feeling the m-7 is what ill like best though...
Title: Re: Official C12 Clone - Build and Support Thread
Post by: wolan42 on May 05, 2013, 09:53:44 AM
Hello,

maybe some silly questions.

Is another 10:1 transformer like Beyer BV 351 110 005 (1:10) or Neutrik NTE 10/3 also a possibility instead the CM-2480 or the AMI T14?
My goal is not a 1:1 copy of the AKG C12. I will build a good sounding mic.

I've ordered a Dale M7 (originally for my G7, but it is hard to find a not so expansiv body for this) and will now build it into the C12.
Is it also possible?

Andreas
Title: Re: Official C12 Clone - Build and Support Thread
Post by: HellfireStudios on May 05, 2013, 10:52:35 AM
Hello,

maybe some silly questions.

Is another 10:1 transformer like Beyer BV 351 110 005 (1:10) or Neutrik NTE 10/3 also a possibility instead the CM-2480 or the AMI T14?
My goal is not a 1:1 copy of the AKG C12. I will build a good sounding mic.

I've ordered a Dale M7 (originally for my G7, but it is hard to find a not so expansiv body for this) and will now build it into the C12.
Is it also possible?

Andreas

I am not going to say that one capsule is better in for one circuit than another, but doesn't it make more sense to use the capsule designed for the circuit? An M7 is not going to be as bright as the C12. If that is what you wanted, why did you not just build a U-47 clone? It should still work, but seems a roundabout way to get your intended destination.

-James-
Title: Re: Official C12 Clone - Build and Support Thread
Post by: wolan42 on May 05, 2013, 12:59:32 PM
Hello James,

thank you for the answer. You are right about the sense of the capsule alternativ.
But I'm here in the forum to learn. And as a "microphone builder newbee" there is a lot to learn.

My "silly" question about the capsule was, I have the dale capsule here.
Orginally I ordered it for my G7. But for the G7 there is no body here.
At this moment the Equinox body is to expensive for me, and so I think the M7 capsule was an alternative for the C12.

Sometimes, for a non native english spoken user, I feel like an idiot (in german: Depp) to ask such questions. ;-)

I will take your suggestion.
I put the Dale capsule into the G7 and will buy a body from Equinox in summer if I have the money.
For the C12 it is better to order a capsule from Tim or as cheap alternative a RK12 from MicParts.

But what about the transformer alternatives?

In my Takstar Royer Mod, the Beyer sounds very good. But is this also a posible "substitute" for the CM-2480 or AMI T14?
(Sorry about my english, but I am not in practice for the last years.)

Cheers

Andreas
Title: Re: Official C12 Clone - Build and Support Thread
Post by: HellfireStudios on May 05, 2013, 01:39:50 PM
I use and love the CM-2480 in my C12 clone, but using another 10:1 transformer instead is acceptable. Try it. The worst-case-scenario is that you will not like it, and will need to purchase an approved transformer. Good luck.

-James-
Title: Re: Official C12 Clone - Build and Support Thread
Post by: wolan42 on May 05, 2013, 02:15:50 PM
Thanx.

I try and report it.

Andreas
Title: Re: Official C12 Clone - Build and Support Thread
Post by: chunger on May 05, 2013, 04:36:12 PM
I have been pleasantly surprised on more than one occasion putting "the wrong" parts together just because that is what I had on hand at the time.  This is DIY after all.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Pip on May 05, 2013, 10:53:18 PM
Ok the latest on the PSU front and my particular build. In short forget all that other stuff I said and Matador is the man.

I got bored and I have decided I really like what the Microphone-parts people are doing so had some cash and bought there RK-12 capsule (http://microphone-parts.com/rk12-microphone-capsule/). As my original intention still holds this project requires a Tim Campbell capsule and mine is ordered but still weeks off (really good things come to those who wait) I put this in for now.

My build was suffering from not enough B+ voltage and a maxed out adjustment pot. And after much confusion on my part I finally got the CHANGE THE VALUE OF R1 & R2 TO A HIGHER VALUE OR TO A LOWER VALUE IN AN INVERSE RELATIONSHIP TO YOUR PROBLEM DUMMY!(me being the dummy). The annoying part is I know this and I still over thought the problem, don't worry my day job does not include any work with radiation. So I changed the value of R1 & R2 to 75K and voila it is working. I have a real midpoint in my B+ adjustment and all is GOOD! :)

Microphone sounds great and very low noise. The new temporary capsule is really crisp and not too forward but I can hear what the TC capsule will do in this circuit and it will yield perfection. No knock on the Microphone-parts bit of kit at those prices I have zero complaints this thing sounds really good now.

So:

B+= 120VDC
Bias= -1VDC
Heater 6.3VDC Measured at mic
Plate= 59.5VDC measured at output cap  :) ;D ;)
Title: Re: Official C12 Clone - Build and Support Thread
Post by: mwrichardson on May 06, 2013, 03:32:04 PM
Does anyone know what the actual Bias voltage is on a C12. It is not noted on the schematic and is not adjustable as R8 is a 1k resistor. Klaus H. has stated that plate should be 65 to 80 vdc. Someone have a C12 they can measure?  I see Matador recommends -1 volt. I seem to remember that -1.1 was correct. I get a 68 volt reading on my plate with -1.1 vdc bias setting. I wonder what the range in vintage C12's is.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Treelady on May 10, 2013, 08:15:03 PM
Hello James,

Sometimes, for a non native english spoken user, I feel like an idiot (in german: Depp) to ask such questions. ;-)


Andreas

NEVER suggest that you are an idiot when you are writing in a second language!  It is impressive that so many people know more than one language.   Your English is 100 times better that our German.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: cariocaman85 on May 11, 2013, 10:53:21 AM
Hi,

Some news from our C12 built!

Yesterday we ran another test, with a DPA 2011C in comparison.
The preamps were 2 BC315 in an Amek BC3 console (with new caps and lundhal trannies), throught an Apogee PSX100.
And... The sound was good!  ;D

The level of the C12 is about 2/3 db less than the DPA, and the noise is almost identical, very low I think.
I still can hear some very low level hiss, but I think it can decrease with letting the tube burn 24 hours more. Is that correct? How long could it take?

I'm still using the stock capsule (waiting for a Tim's one), and a low noise, tested GE 6072 triple Mica NOS from Tube Depot.
Can I expect more low end with the Tim's capsule?

I will post samples asap.

Thanks again! ;)

Remi
Title: Re: Official C12 Clone - Build and Support Thread
Post by: cariocaman85 on May 11, 2013, 11:59:35 AM
And here are our first samples:

One classical guitar recorded in my room:

The mike is at 35cm from the instrument.
The BC315 gain is set at +50dB:
https://www.dropbox.com/s/wow90uwyeccd2kf/C12_50dB_gain_35cm.wav

The mike is at 20cm from the instrument.
The gain is set at +50dB:
https://www.dropbox.com/s/xcb7exj0717gmn8/C12_50dB_gain_20cm.wav

The mike is at 20cm from the instrument.
The gain is set at +45dB:
https://www.dropbox.com/s/s1xqy3nh3qfpqtl/C12_45dB%20gain_20cm.wav


There is no normalisation nor FX.

What do you think?
Does it sound "correct" to you?

Thanks for your replies!  :)

Remi
Title: Re: Official C12 Clone - Build and Support Thread
Post by: maq3396 on May 11, 2013, 01:42:12 PM
I dont know if it sounds "right" but it does sound beautiful!

Thanks for posting

Cheers
Mac
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Melodeath00 on May 11, 2013, 01:54:11 PM
When you say "stock capsule" you mean the K67 from the donor mic?
Title: Re: Official C12 Clone - Build and Support Thread
Post by: cariocaman85 on May 11, 2013, 02:00:02 PM
Yes, this is the capsule from the Alctron mic, still in place until I get a Tim Campbell's one.

I didn't remove the layers from the headbasket yet, but I'm wondering if it's a good idea, I'm afraid of getting hum/RF.
What do you think?

Title: Re: Official C12 Clone - Build and Support Thread
Post by: micaddict on May 12, 2013, 06:55:55 AM
Not a big fan of the Chinese 32 mm K67, but with this circuit it obviously sounds worlds better than with the stock circuit. Pretty good, actually. Quiet, too. And it will get even better with Tim's capsule.

Before you get the pliers in there, check out chunger's headbasket offerings (due tomorrow). There's a single layer (like the original C12 has) and a dual layer (more towards Ela M251 style).
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Reverend on May 12, 2013, 11:40:43 PM
I'm having a hard time finishing the power supply. I'm not getting any voltage reading for the B+ thru the polar...all of them. I'm wondering if the stock transformer in the Apex 460 power supply could be bad. I noticed it was loose during the build. I tightened it. Should I try to re-solder it? Is there a replacement? Has anyone had this problem?
Thanks.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Reverend on May 13, 2013, 12:49:35 AM
Pip, I somehow messed up when I tried to reply to your message. It's an Apex 460 with the power supply. All wires from stock transformer in the power supply, 200VAC and 9VAC, are to the correct terminal block and I'm in the US so I'm assuming that the 115 setting is correct (that's the way it came too). When I power it up, the light comes on, but there's no voltage reading on my DMM. Thanks for replying.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: chunger on May 13, 2013, 01:40:25 AM
Are you getting A/C voltage at the secondaries?  Did the stock Apex 460 power up as normal before gutting?
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Reverend on May 13, 2013, 01:48:27 AM
I didn't power it up before I tore the whole thing apart. That was dumb, I know. I just checked again and I'm not getting any voltages from anywhere.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Reverend on May 13, 2013, 02:00:32 AM
None at the secondaries either. Do I have a bum transformer possibly?
Title: Re: Official C12 Clone - Build and Support Thread
Post by: chunger on May 13, 2013, 02:11:58 AM
Uh oh. . . I'm not sure if Apex will warranty the psu in its current condition  :o .  I have spare psu's in stock if you need one.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Matador on May 13, 2013, 10:30:35 AM
None at the secondaries either. Do I have a bum transformer possibly?

Disconnect the secondary and measure it right out from the transformer (unconnected).

You may have run afoul of the "mixed up the 4700uF and 100uF caps" problem:  putting a 16V cap in the 120V B+ side of the circuit turns it from a cap to a dead short.  Check to make sure all of the large filtering caps are in the right places.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Reverend on May 13, 2013, 11:40:36 PM
OK. I checked the caps and the 100uf and 4000uf are in the proper places. So, I disconnected the secondaries and no voltage reading at all from the transformer. Chunger, what will you charge for one of your spare power supplies? Thanks. Having fun even with the problems.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: chunger on May 14, 2013, 04:35:27 AM
OK. I checked the caps and the 100uf and 4000uf are in the proper places. So, I disconnected the secondaries and no voltage reading at all from the transformer. Chunger, what will you charge for one of your spare power supplies? Thanks. Having fun even with the problems.

It may be worthwhile to try and put the original PCB back in place and see if you can get the mic replaced under warranty.  Otherwise I have spare psu for $40.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Category 5 on May 14, 2013, 03:22:24 PM
Finally heard from Tim Campbell.  YAY!  Won't be seeing anything until late August/Sept., but at least I got into the queue!

Going to use a pair of these in the mean time.  Cheap enough to get the mics going, and good enough quality to use in future projects.  Maybe even the "anticipated" ELAM 251 I hope Matador may be considering doing.

http://microphone-parts.com/rk12-microphone-capsule/
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Winetree on May 14, 2013, 03:41:31 PM
Congrats, When did you first contact Tim?
Did you build and test the mic with the orginal Chinese capsule?
If so, could you share  the difference in sound with that and the RK-12 when you get there?
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Ericbazaar on May 14, 2013, 03:45:41 PM
Got a Mail from Tim last Friday, my CT12 is on the Way! :) :) ;D And a good GE 6072 Five Star from Christian next Month! Yehah!
But the Mic sounds Great with the RK12 and EH 6072 now! Greets from Germany 8)
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Category 5 on May 14, 2013, 04:36:41 PM
Congrats, When did you first contact Tim?
Did you build and test the mic with the orginal Chinese capsule?
If so, could you share  the difference in sound with that and the RK-12 when you get there?

Haven't built the test mic but have a RK-12 in a Royer style mic and the capsule is smoooooth as can be.

Contacted Tim about a month ago and heard from him today.  So excited!  I had to get in line to get in line to be allowed to purchase...lol.  My wife thinks I'm crazy but just knowing I'm on the list is quite gratifying.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Matador on May 16, 2013, 03:52:01 PM
ELAM251 Conversion Steps
===============================
I've gotten pinged a few times about what to change in the C12 circuit to convert it over to a more 251 type circuit.  Here are the steps:

1) The cathode bias needs to be moved from the PSU up into the mike.  You can remove R3 and bridge from pin 1 to pin 3 of R3, or (recommended) you can dial R3 fully clockwise (so that the negative bias voltage goes from -1V to 0V):  this grounds the bias voltage going out through the cable.

2) A new cathode resistor and bypass cap needs to be added to the tube board.  This can be connected from the "TK" node of the tube side you are using (either TK1 or TK2).  The resistor value should be between 1.4K and 1.8K (original M251 R11 value was 1.82K).  Coincidentally, it's value will be exactly the same as whatever was trimmed to the pot R3 for the original circuit.  :D  So one end of the resistor goes into the "TK" hole on the tube PCB, and the other end goes to any ground node.  I would use one of the heater return pads right under it (both outside solder pads that attach the tube board to the main PCB are ground).

3) In parallel with this resistor goes the cathode bypass cap (C4 on the original schematic).  It's value should be 20uF/16V (although anything from 10uF to 100uF should work).  If you get a radial cap, you can just wrap the leads around the resistor that you added in step 2 since these are in parallel.
4) The last new piece is the plate cap C5.  I believe the original value (at least according to Google) is 1000pF, but other versions show 100pF.  The higher the value, the more treble roll-off.  I've tried 1nF and thought it sounded very good (much more U47 like).

Here's where the plate cap goes:

(http://www.musicalsparks.com/images/c12/c12_to_elam251.jpg)
Title: Re: Official C12 Clone - Build and Support Thread
Post by: HellfireStudios on May 16, 2013, 05:06:35 PM
My 251 schematic shows 1000pF for C5. Though, it would be interesting to hear what a smaller value cap would do to sweeten the top end in the C12 circuit...

-James-
Title: Re: Official C12 Clone - Build and Support Thread
Post by: micaddict on May 16, 2013, 05:13:20 PM
Thanks, Matador.

Here's a comparison by David Bock (who now does his 251 with a 6201 tube BTW). If it's too long or uncalled for, I'll remove it.

"They were both manufactured by AKG, despite the Telefunken badge on the 251.
They do share common a tube type, capsule type, output transformer, psu xfmr, & basic amp topology, all with minor variations and production changes.
For those who don't know the C12 is the skinny one and the 251 the fatter one.
Starting at the capsule, the 251 CK12 was a variant of the CK12, with slightly different backplates, and a little more low end than the C12 CK12. The capsule mount on the C12 hags the capsule, shock mounted with felt, while the 251 capsule sits  on a pedestal which is also shockmounted with felt. The 251 pedestal has a very slight angled face below the capsule, while the C12 has a strictly flat surface below it. I mention this because theoretically, there is high frequency reflection in the headgrille area which is broken up by angles, and not broken up by flat surfaces. This attempt to break up HF reflections may be found in other condenser mic designs as well, and is the basis for the Neumann M49 sloped headgrille.
The 251 mechanical assembly is mostly plastic (!) while the C12's is a metal frame. That 251 plastic often deteriorates & cracks.  The 251 has a pattern select switch just below the capsule, while the C12's is on the power supply. The 251 has two layers of mesh Course and Fine) in the headgrille, whilst the C12 is a very open one layer of mesh.
 The amplifier of both mics is a single triode with resistive load, capacitor coupled to a small output transformer. They differ in how the patterns are achieved, and how the capsule is coupled to the amplifier. The 251 is self biased, meaning the cathode is connected to a resistor and capacitor (in parallel)  to ground, and the C12 is fixed bias with a grounded cathode and negative voltage from the psu. The 251 pattern control is achieved by manipulating backplates in the capsule, with no voltages exceeding 60v, and the C12 varies the voltage from 0-120v on the rear membrane. The 251 capsule is directly coupled to the grid of the tube, while the C12 has a coupling capacitor between the capsule and grid. The output capacitor values vary on  the 251 from 1uF-3.2uF depending upon production.
Original C12's used nice polystyrene & PIO caps, while the 251 used wet tantalums, ceramics, & polystyrenes. Both systems operate off 120v dc generated by their psu's.
The first 200 C12's had a large IE core transformer, as such, sound different that all subsequent C12's. After that both mics used the T14/1 tiny output transformer, with many production variations of that part alone.
They both came with large blade type conductor stand mount connectors, which are heavy duty and have stood the test of time.
Both power supplies are well made heavy duty simple designs that have also stood the test of time.
Many vintage 251 & C12 have had modifications and aftermarket psu's paired with them, be careful as the psu is part of the sound in mics like this.
What does all this mean? Well the 251 has a little more gain and is quieter, as well as a generally more pleasing vocal sound (my opinion). The C12 can be a little too bright on vocalists, and seems to find greater use as drum overheads. I think of the 251 as more "forgiving", and falls more into the "flatter the source" category than the C12's "capture the source" category."

Not from the REP forum this time, but from PRW. The whole thread is here:
http://prorecordingworkshop.lefora.com/2011/02/16/c12-v-ela-m251-differences/ (http://prorecordingworkshop.lefora.com/2011/02/16/c12-v-ela-m251-differences/)
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Melodeath00 on May 16, 2013, 06:53:18 PM
Thanks, micaddict - I've read that post many, many times myself through various google searches haha.

What is interesting/odd is the talk on PRW about how the decaying plastic int he 251 affects the tone. I wonder if anyone can chime in as to how that would be possible.

Matador, are you outlining the mod just so people know, or does this mean there will be no formal/official 251 PCB and build thread? I almost "assumed" it was coming, since it seems like as soon as I registered on this site, slowly but surely a PCB for the U67, M49, M269, and C12 was released. :p
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Matador on May 16, 2013, 07:32:17 PM
Thanks, micaddict - I've read that post many, many times myself through various google searches haha.

What is interesting/odd is the talk on PRW about how the decaying plastic int he 251 affects the tone. I wonder if anyone can chime in as to how that would be possible.

Matador, are you outlining the mod just so people know, or does this mean there will be no formal/official 251 PCB and build thread? I almost "assumed" it was coming, since it seems like as soon as I registered on this site, slowly but surely a PCB for the U67, M49, M269, and C12 was released. :p

Those modifications I posted will get you 95% of the way there without having to spin another PCB and kit.  To truly match the exact circuit configuration means we'd need a mike body that has the proper polar pattern switches, etc.  Seems like a lot of effort for that last 5%. ;)
Title: Re: Official C12 Clone - Build and Support Thread
Post by: chunger on May 16, 2013, 07:48:57 PM
The problem is not spinning another pcb. . . that is easy. . . well, for Matador anyways.  The bigger problem is indeed spinning a new body in order to "delete" what I feel to be a nice feature of the C12 - the 9 position variable patterning.

The turret-board style construction of this mic kit lends itself easily to this kind of component swapping.  We are out of test microphones right now, but another shipment should be inbound soon.  What I'm hoping to do soon after new mics arrive is to document this hybrid ELA configuration clearly and see where that takes us.  A switch can be hacked into the HT-11A body and I don't think it would be terribly difficult, but I'm not sure how many people on forum are keen to taking a dremel and file to their shiny new donor microphones.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Melodeath00 on May 16, 2013, 07:57:51 PM
Those are good points. I don't feel the switch is particularly important, since we are using non-replica mic bodies anyway. I guess it would only matter if the switch caused a difference in sound compared to the 9 pattern PSU. "The 251 pattern control is achieved by manipulating backplates in the capsule, with no voltages exceeding 60v, and the C12 varies the voltage from 0-120v on the rear membrane." I'm not experienced enough to even make a guess if there COULD be a difference in how the capsule reacts in those two different situations.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: JessJackson on May 17, 2013, 12:46:01 AM
just to confirm, I received Tim's TC12 4 terminal capsule. Do I tie together the backplates or keep them separated for this build?

Original c12's are tied together and in chungers build notes they are tied together but when i soldered a bridge across RB and FB on the circuit board, i can hear tube sound but no capsule sound at all.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Tim Campbell on May 17, 2013, 01:45:13 AM
Dear Jess,
Yes, you tie the backplates together. If you get no signal something is very wrong. Did you try the mic with the other capsule?
You must be very gentle when soldering the solder tags. All these screws thread into plastic. If they are over heated at all the screws can become loose. Check that the screws are snug (but don't overtighten them).
Scroll through the pattern selector and see if you get any signal in omni or figure 8.

If you can hear the amplifier then you have a missing connection rather than a short. A picture might help.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: chunger on May 17, 2013, 02:03:46 AM
Did you verify prior to connecting Tim's capsule that the B+ voltage absolutely did not exceed 120V?  When I installed my non-expendable capsule, I adjusted B+ well to the low end of the trimmer pot's range and slowly inched it up after the capsule was installed.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: JessJackson on May 17, 2013, 02:38:54 AM
Dear Jess,
Yes, you tie the backplates together. If you get no signal something is very wrong. Did you try the mic with the other capsule?
You must be very gentle when soldering the solder tags. All these screws thread into plastic. If they are over heated at all the screws can become loose. Check that the screws are snug (but don't overtighten them).
Scroll through the pattern selector and see if you get any signal in omni or figure 8.

If you can hear the amplifier then you have a missing connection rather than a short. A picture might help.

Thanks Tim,

I just checked all continuity, Everything is fine. When soldering the capsule I was very quick and made great connections.

Although one thing i just noticed. On the schematic ( http://musicalsparks.com/images/c12/c12_schematics_v3.pdf )

It shows Front Capsule going to R16 (30M) and Rear Capsule going to GRND

On my circuit board RC PIN goes to R16 and FC seems to be on grnd. although this would just reverse the capsule.

I found that i had accidently r17 and r13 swapped values, so i switched them just now. about to try it.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: JessJackson on May 17, 2013, 02:39:58 AM
Did you verify prior to connecting Tim's capsule that the B+ voltage absolutely did not exceed 120V?  When I installed my non-expendable capsule, I adjusted B+ well to the low end of the trimmer pot's range and slowly inched it up after the capsule was installed.

my B+ sits around 123 at minimum adjustment.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: JessJackson on May 17, 2013, 03:02:19 AM
WORKING! perfect, capsule sounds great tim, looking forward for head basket and ELA mod.

was the plate cap in most 251's 1000pf or 100pf? i see the schematics vary. thats a big difference.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: micaddict on May 17, 2013, 05:27:23 AM
Those are good points. I don't feel the switch is particularly important, since we are using non-replica mic bodies anyway. I guess it would only matter if the switch caused a difference in sound compared to the 9 pattern PSU. "The 251 pattern control is achieved by manipulating backplates in the capsule, with no voltages exceeding 60v, and the C12 varies the voltage from 0-120v on the rear membrane." I'm not experienced enough to even make a guess if there COULD be a difference in how the capsule reacts in those two different situations.

I'm not qualified to offer full proof either, but the word goes that remote pattern control adds some noise and can (relatively) thin out tone. This is why some "remote controlled" tube mics have a hard switch, pure cardioid setting as an extra.
This doesn't have to be a clearly visible toggle BTW. From what I remember, the Horch (now Urton) RM2J has a very small, recessed "button" that has to be pressed with a pen. This completely switches off the back half of the capsule and makes for a considerably fuller tone IME. Added (=extra) proximity effect might play a part, too.

There are zillions (well almost) documentations about polarization. This one is more in depth than most and at the same time concise and readable IMO:
http://www.foxaudioresearch.ca/Polarpatterns.htm (http://www.foxaudioresearch.ca/Polarpatterns.htm)

This one is interesting, too:
http://www.google.nl/url?sa=t&rct=j&q=&esrc=s&source=web&cd=22&ved=0CDsQFjABOBQ&url=http%3A%2F%2Fwww.neumann.com%2Fdownload.php%3Fdownload%3Dlect0003.PDF&ei=swOWUcjJJ-me0QXlvoC4BA&usg=AFQjCNFc6SJ8kStFG5hKFmXMmsARj-7vVA&sig2=C7oCgyyMsmPMG0pmy7ArnQ&bvm=bv.46471029,d.d2k (http://www.google.nl/url?sa=t&rct=j&q=&esrc=s&source=web&cd=22&ved=0CDsQFjABOBQ&url=http%3A%2F%2Fwww.neumann.com%2Fdownload.php%3Fdownload%3Dlect0003.PDF&ei=swOWUcjJJ-me0QXlvoC4BA&usg=AFQjCNFc6SJ8kStFG5hKFmXMmsARj-7vVA&sig2=C7oCgyyMsmPMG0pmy7ArnQ&bvm=bv.46471029,d.d2k)
 
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Matador on May 17, 2013, 12:17:16 PM
Dear Jess,
Yes, you tie the backplates together. If you get no signal something is very wrong. Did you try the mic with the other capsule?
You must be very gentle when soldering the solder tags. All these screws thread into plastic. If they are over heated at all the screws can become loose. Check that the screws are snug (but don't overtighten them).
Scroll through the pattern selector and see if you get any signal in omni or figure 8.

If you can hear the amplifier then you have a missing connection rather than a short. A picture might help.

Thanks Tim,

I just checked all continuity, Everything is fine. When soldering the capsule I was very quick and made great connections.

Although one thing i just noticed. On the schematic ( http://musicalsparks.com/images/c12/c12_schematics_v3.pdf )

It shows Front Capsule going to R16 (30M) and Rear Capsule going to GRND

On my circuit board RC PIN goes to R16 and FC seems to be on grnd. although this would just reverse the capsule.

I found that i had accidently r17 and r13 swapped values, so i switched them just now. about to try it.

I thought I had fixed that schematic. :(  The PCB is correct:  the "front capsule" should be grounded.  The capsule doesn't care either way it's just the patterns will be switched front to back.

I'm not convinced that the polarization changes make any difference, but I haven't A/B'ed them in a scientific manner either.  In one case, the capsule "sees" -60V by having 120V on the back diaphragm and 60V on the center diaphragm.  In the other case, it's zero and +60V, or the exact same bias flipped in polarity.  I don't think the capsule cares either way.

Now using the capsule as the grid coupling element (eliminating the coupling cap) probably makes much more of a sonic difference (comparing the 251 to the C12).  For those who are looking for cardioid/omni only it may be possible to hack up the design to achieve this:  I'll give it some thought.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Tim Campbell on May 17, 2013, 12:24:02 PM
I always find it preferable to have the front membrane at ground. The capsule is usually quieter ( the membrane acting as a shield to the polarized backplate) and it attracts less dust.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: tonycamp on May 17, 2013, 12:32:24 PM
Hi fellas, i got my tim campbell capsules, and my new styrenes for the matachung c12(i apparently burned em, use hemostats instead of alligator clips for heat dissipation), i'm going to be calibrating with christians test tube, and installing Tims capsule this weekend, then i'll let everyone know my results.

In the meantime, i modded my rode K2 with a NOS mullard tube, uped the capacitors with hi Q's in the mic/psu, and put my 2nd Tim Campbell capsule in, it sounds amazing to me, transformerless, scouped mid/extended hi's, modern c12 like? I attached a clip that was done through a VP28 pre.

The mic already sounded really nice to me with the upgrades, but Tims Capsule just raised the bar on it to unreal good, i hope that translates in the clip?

https://soundcloud.com/tonycamp/modded-k2-samples-1
Title: Re: Official C12 Clone - Build and Support Thread
Post by: HellfireStudios on May 17, 2013, 01:11:22 PM
I know it is probably nuts, but I tend to put heat sensitive components (especially germanium diodes) in the fridge for an hour or two before I heat-sink-clip, and solder them. It's like insurance.

-James-
Title: Re: Official C12 Clone - Build and Support Thread
Post by: tonycamp on May 17, 2013, 01:31:50 PM
I know it is probably nuts, but I tend to put heat sensitive components (especially germanium diodes) in the fridge for an hour or two before I heat-sink-clip, and solder them. It's like insurance.

-James-

Hellfirestudios and Ice! never occurred to me James, good one i think ???
Title: Re: Official C12 Clone - Build and Support Thread
Post by: MicDaddy on May 17, 2013, 01:55:12 PM
Are there any negative ramifications from such a temperature swing?  I don't know just posing the question. 
Title: Re: Official C12 Clone - Build and Support Thread
Post by: tonycamp on May 17, 2013, 02:04:56 PM
Are there any negative ramifications from such a temperature swing?  I don't know just posing the question.

Hence the "i think ???" lol! Don't know either, I've done freeze and heat maneuvers with auto fab/mechanics, but i think i'll stick to hi heat, quick touch, with a high mass hemostat heat sink for now, again this may be totally wrong as i'm no expert ::)
Title: Re: Official C12 Clone - Build and Support Thread
Post by: HellfireStudios on May 17, 2013, 03:39:03 PM
Are there any negative ramifications from such a temperature swing?  I don't know just posing the question.

With the heat sink in place, the temperature swing only occurs on the leads from the component. Also, I haven't destroyed anything yet. I got this tip from one of the guitar effects sites (I can't remember which one). BTW, I use the fridge and NOT THE FREEZER. I can't guarantee that your components would like that large of a swing.

-James-
Title: Re: Official C12 Clone - Build and Support Thread
Post by: JessJackson on May 17, 2013, 07:17:04 PM
getting back to plate high freq filter cap.

ela m 251e shows 100pf
ela m 261 shows 1000pf
Neumann M249 shows 500pf
Neumann M269 shows 80 to 160pf
Neumann M250b shows 600pf
Neumann M49 shows 150pf
Title: Re: Official C12 Clone - Build and Support Thread
Post by: jrmintz on May 17, 2013, 10:57:36 PM
Quote
3) In parallel with this resistor goes the cathode bypass cap (C4 on the original schematic).  It's value should be 20uF/16V (although anything from 10uF to 100uF should work).  If you get a radial cap, you can just wrap the leads around the resistor that you added in step 2 since these are in parallel.

Thank you for posting this Matador. For the cathode bypass cap does the negative end go to ground and the positive to the TK hole?
Title: Re: Official C12 Clone - Build and Support Thread
Post by: tonycamp on May 17, 2013, 11:35:22 PM
Calling Matador!

Long time no talkie ;D Hey i got the new styrenes in at all 3 places, and put a christian test tube in, fires up glows nicely, readjusted, b+ to 120v, set 6.3v heater at the tube, set the biasing to -1v, then i rechecked B+v and it went down to 113.4v with the trimmer all the way open? (insert best homer simpson voice) Doouuughp!

Any suggestions? looks like my saga saga continues :-[

Thanx
T

Edit: I read the whole thread, and conclude i need to change the values on resistors R1 and R2, to get the B+ up, does someone know the exact values on those? I read a couple different ones? I'm testing with a 12at7, and going to run a 5star 6072A from christian

thanx boys
T
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Matador on May 18, 2013, 01:09:22 AM
Calling Matador!

Long time no talkie ;D Hey i got the new styrenes in at all 3 places, and put a christian test tube in, fires up glows nicely, readjusted, b+ to 120v, set 6.3v heater at the tube, set the biasing to -1v, then i rechecked B+v and it went down to 113.4v with the trimmer all the way open? (insert best homer simpson voice) Doouuughp!

Any suggestions? looks like my saga saga continues :-[

Thanx
T

How does it sound?
Title: Re: Official C12 Clone - Build and Support Thread
Post by: tonycamp on May 18, 2013, 01:16:16 AM
Hi matador,

thanx for responding!, I just threw an edit on my previous post, I read through the whole thing to get current(no pun ;D) I haven't plugged it in yet, i wasn't even going to bother until i had the 6072A and Tims capsule in it(which i have). Check my edit on my previous, what do you say?

thanx
T

Title: Re: Official C12 Clone - Build and Support Thread
Post by: sr1200 on May 18, 2013, 02:21:14 AM
 8) 8) 8) 3Hrs 51min Start to finish!!! Great guide and great project thank you so much!!!!!!
Title: Re: Official C12 Clone - Build and Support Thread
Post by: micaddict on May 18, 2013, 08:10:35 AM
Matador wrote:
Quote
For those who are looking for cardioid/omni only it may be possible to hack up the design to achieve this:  I'll give it some thought.

Cool, especially if there are sonic advantages.

Anyway, thanks for taking all feedback into account. Much appreciated.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Melodeath00 on May 18, 2013, 02:01:02 PM
Dear Jess,
Yes, you tie the backplates together. If you get no signal something is very wrong. Did you try the mic with the other capsule?
You must be very gentle when soldering the solder tags. All these screws thread into plastic. If they are over heated at all the screws can become loose. Check that the screws are snug (but don't overtighten them).
Scroll through the pattern selector and see if you get any signal in omni or figure 8.

If you can hear the amplifier then you have a missing connection rather than a short. A picture might help.

Thanks Tim,

I just checked all continuity, Everything is fine. When soldering the capsule I was very quick and made great connections.

Although one thing i just noticed. On the schematic ( http://musicalsparks.com/images/c12/c12_schematics_v3.pdf )

It shows Front Capsule going to R16 (30M) and Rear Capsule going to GRND

On my circuit board RC PIN goes to R16 and FC seems to be on grnd. although this would just reverse the capsule.

I found that i had accidently r17 and r13 swapped values, so i switched them just now. about to try it.

I thought I had fixed that schematic. :(  The PCB is correct:  the "front capsule" should be grounded.  The capsule doesn't care either way it's just the patterns will be switched front to back.

I'm not convinced that the polarization changes make any difference, but I haven't A/B'ed them in a scientific manner either.  In one case, the capsule "sees" -60V by having 120V on the back diaphragm and 60V on the center diaphragm.  In the other case, it's zero and +60V, or the exact same bias flipped in polarity.  I don't think the capsule cares either way.

Now using the capsule as the grid coupling element (eliminating the coupling cap) probably makes much more of a sonic difference (comparing the 251 to the C12).  For those who are looking for cardioid/omni only it may be possible to hack up the design to achieve this:  I'll give it some thought.
Ah yes, I forgot about the grid coupling difference. I have read that this extends bass response. Is it not possible to eliminate the coupling cap while keeping the remote pattern switching? It seems then we would have the exact 251 circuit (with your other mods) other than the pattern switch.

By the way, could anyone send me a 251 schematic? I searched google images, but am only finding very small ones I can't read.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: sr1200 on May 18, 2013, 03:02:07 PM
Hey, the mic sounds AMAZING!!!!  I have one small question/gripe and perhaps its something that i did.  The new head basket has a helluva resonant frequency around 430 cps.  Anyone have a good way to dampen that? (besides EQ)
Title: Re: Official C12 Clone - Build and Support Thread
Post by: JessJackson on May 18, 2013, 03:04:02 PM
Went to use mine in session last night... really low output level by about 20db... hiss way too high. damn i was almost there.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: tonycamp on May 18, 2013, 03:48:20 PM
Hey, the mic sounds AMAZING!!!!  I have one small question/gripe and perhaps its something that i did.  The new head basket has a helluva resonant frequency around 430 cps.  Anyone have a good way to dampen that? (besides EQ)

Yes, i have a great way to dampen that, go to home depot, go to the electrical section, find box/duct seal, It comes in the shape of a giant candy bar w/white wrapper, it costs under $2, its for sealing the back of electrical boxes from weather. roll up a small amount into mini hot dog shape the width of the vertical posts, then line it up and push it into the offending rails from the inside. Works awesome, and poses no threat of falling off or damaging anything, and soaks up those resonances. I've done this to a dozen mics with great results. It's not too sticky and messy at all, just make sure you wash your hands before handling the re assembly of the mic.

good luck

anyone know the exact value of R1 R2 resistor change? my B+ is maxed at 113.4V

thanx
T
Title: Re: Official C12 Clone - Build and Support Thread
Post by: sr1200 on May 18, 2013, 03:59:42 PM
Cool ill look into that.  What if its the screen that resonating?
Title: Re: Official C12 Clone - Build and Support Thread
Post by: chunger on May 18, 2013, 04:30:55 PM
Can you check to see if there are any defects physically in the headbasket construction?  Broken/missing solder joints, etc.

In our testing, a sharp resonance should have been detected, but our primary tracking room inherently has a 500 Hz resonance that we know about and work around, so that could have partially masked the issue in our test environment.

Do you have clips?  Does the stock Alctron headbasket eliminate this resonance?
Title: Re: Official C12 Clone - Build and Support Thread
Post by: HellfireStudios on May 18, 2013, 04:34:03 PM
Cool ill look into that.  What if its the screen that resonating?

You could try dampening the rails with your fingers, and then tap/flick the screen to check. Same idea for testing the rails.
If the screen is the issue, the two screen version may be the only option, but some sort of clear spray-on plastic on the inside of the headbasket could work.
You've got me a little worried. I ordered the from first round of C12 headbaskets...

-James-
Title: Re: Official C12 Clone - Build and Support Thread
Post by: tonycamp on May 18, 2013, 04:37:13 PM
Chungs point aside, if you do the lower circumference and the entire U shaped rail, it should tamp down the mesh very well. At least that has been my experience, it works EXTREMELY WELL.  I'll post a pic of a head basket that has it later on tonight if i can.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: tonycamp on May 18, 2013, 04:56:24 PM
Using 400K is fine.

There is obviously much higher tube tolerance than the original datasheets suggest.  Getting more current through the bleeder is one way to get more current flowing through the bias network.  In reality, the original C12 schematic shows a 300K resistor (R9) as the B+ bleeder, but that design was also only half-wave rectified, so it's not apple to apples in any case.  This had to be done in order to make use of the stock transformer in this circuit.

As a general principle, if the B+ voltage is too low (can't be trimmed high enough), then one has several options:  a) reduce R1 and R2 in value, b) increase the value of the bleeder R6, or c) make the bias voltage more negative.  B and C reduce the current through the network which increases B+, and A reduces the voltage drop while keeping the current roughly the same.

If the B+ voltage is too high (can't be trimmed low enough), then reverse the direction of everything above.

I was on the fence about making the B+ part of the supply regulated (with a MOSFET pass element and a Zener diode bias with feedback), however this is a drastic departure from the original supply and likely has more sonic implications.

Hey fellas, which option is best? my B+ is low at 113.4V, is there an exact value on R1 and R2 for a 6072A?, is a,b,or c a better option? I'm a first year newb, i'm getting better, but i'm just not comfortable making these decisions on my own

help a brother out? :)
Title: Re: Official C12 Clone - Build and Support Thread
Post by: sr1200 on May 18, 2013, 08:37:36 PM
No defects that i can tell in the headbasket.  Only thing i can think of is that the chrome bath that it got made that screen mesh just REALLY hard.  (kinda like when you tune a drum head)

(sorry im trying things as i type this so it may seem all over the place)

I "massaged" the mesh a little (hearing the chrome crackling a bit as i did it) and it actually seems to have helped.  Maybe it was just to solidified from the chrome plating.  To answer your question Chung, no didn't get it with the original head basket and its 15 layers of mesh lol.  Im only hearing the ring now if i tap it with my finger, and if anyone taps this with their finger during a session im gonna be pretty annoyed anyway lol.  So, cheers n beers to you and matador for putting this awesome sauce together!!!!  :D :D :D
Title: Re: Official C12 Clone - Build and Support Thread
Post by: chunger on May 18, 2013, 11:25:32 PM
Just a clarification. . . this is a nickel plating. . . same as the microphone body except the surface is polished instead of bead blasted prior to plating.  And yes, all of the mics I put together for testing required a little bit of bending to straighten out the side rails because I'm anal like that, but when I made those bends, I did hear the crackling.  I'm assuming the plating while thin,  "glued" some of the mesh wires together and when I mechanically moved the mesh, the wires separated back to their original state.  This is all before audio was put through the mics.

I suppose it would not take much to dampen or move the resonant frequencies around (kindof like putting tape or those gel thingy-majigs on a drum head).

Title: Re: Official C12 Clone - Build and Support Thread
Post by: Pip on May 19, 2013, 12:51:12 AM
Using 400K is fine.

There is obviously much higher tube tolerance than the original datasheets suggest.  Getting more current through the bleeder is one way to get more current flowing through the bias network.  In reality, the original C12 schematic shows a 300K resistor (R9) as the B+ bleeder, but that design was also only half-wave rectified, so it's not apple to apples in any case.  This had to be done in order to make use of the stock transformer in this circuit.

As a general principle, if the B+ voltage is too low (can't be trimmed high enough), then one has several options:  a) reduce R1 and R2 in value, b) increase the value of the bleeder R6, or c) make the bias voltage more negative.  B and C reduce the current through the network which increases B+, and A reduces the voltage drop while keeping the current roughly the same.

If the B+ voltage is too high (can't be trimmed low enough), then reverse the direction of everything above.

I was on the fence about making the B+ part of the supply regulated (with a MOSFET pass element and a Zener diode bias with feedback), however this is a drastic departure from the original supply and likely has more sonic implications.

Hey fellas, which option is best? my B+ is low at 113.4V, is there an exact value on R1 and R2 for a 6072A?, is a,b,or c a better option? I'm a first year newb, i'm getting better, but i'm just not comfortable making these decisions on my own

help a brother out? :)

http://www.groupdiy.com/index.php?topic=51377.msg666445#msg666445

I think this is best option. Again 75K was my choice with the same problem. :)
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Pip on May 19, 2013, 01:07:10 AM
No defects that i can tell in the headbasket.  Only thing i can think of is that the chrome bath that it got made that screen mesh just REALLY hard.  (kinda like when you tune a drum head)

(sorry im trying things as i type this so it may seem all over the place)

I "massaged" the mesh a little (hearing the chrome crackling a bit as i did it) and it actually seems to have helped.  Maybe it was just to solidified from the chrome plating.  To answer your question Chung, no didn't get it with the original head basket and its 15 layers of mesh lol.  Im only hearing the ring now if i tap it with my finger, and if anyone taps this with their finger during a session im gonna be pretty annoyed anyway lol.  So, cheers n beers to you and matador for putting this awesome sauce together!!!!  :D :D :D

Hey, the mic sounds AMAZING!!!!  I have one small question/gripe and perhaps its something that i did.  The new head basket has a helluva resonant frequency around 430 cps.  Anyone have a good way to dampen that? (besides EQ)

Yes, i have a great way to dampen that, go to home depot, go to the electrical section, find box/duct seal, It comes in the shape of a giant candy bar w/white wrapper, it costs under $2, its for sealing the back of electrical boxes from weather. roll up a small amount into mini hot dog shape the width of the vertical posts, then line it up and push it into the offending rails from the inside. Works awesome, and poses no threat of falling off or damaging anything, and soaks up those resonances. I've done this to a dozen mics with great results. It's not too sticky and messy at all, just make sure you wash your hands before handling the re assembly of the mic.

good luck

anyone know the exact value of R1 R2 resistor change? my B+ is maxed at 113.4V

thanx
T

Sorry first thing is I am going to share something that was beaten into me by one of my mentor/teachers a true sage in the HIFI community, so forgive me if this is misdirected but it is an important distinction. DAMPENING involves water and a sponge usually, DAMPING is the effect of a force on oscillations. He would still grit his teeth to this day if I said one when I ment the other. Thanks that felt good.

430CPS is rather low this mic is always going to be somewhat vulnerable to handling noise. What capsule and mount are you using and also what tube. It sounds to me like you might have a microphonic issue.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: tonycamp on May 19, 2013, 01:14:05 AM
Using 400K is fine.

There is obviously much higher tube tolerance than the original datasheets suggest.  Getting more current through the bleeder is one way to get more current flowing through the bias network.  In reality, the original C12 schematic shows a 300K resistor (R9) as the B+ bleeder, but that design was also only half-wave rectified, so it's not apple to apples in any case.  This had to be done in order to make use of the stock transformer in this circuit.

As a general principle, if the B+ voltage is too low (can't be trimmed high enough), then one has several options:  a) reduce R1 and R2 in value, b) increase the value of the bleeder R6, or c) make the bias voltage more negative.  B and C reduce the current through the network which increases B+, and A reduces the voltage drop while keeping the current roughly the same.

If the B+ voltage is too high (can't be trimmed low enough), then reverse the direction of everything above.

I was on the fence about making the B+ part of the supply regulated (with a MOSFET pass element and a Zener diode bias with feedback), however this is a drastic departure from the original supply and likely has more sonic implications.

Hey fellas, which option is best? my B+ is low at 113.4V, is there an exact value on R1 and R2 for a 6072A?, is a,b,or c a better option? I'm a first year newb, i'm getting better, but i'm just not comfortable making these decisions on my own

help a brother out? :)

http://www.groupdiy.com/index.php?topic=51377.msg666445#msg666445

I think this is best option. Again 75K was my choice with the same problem. :)


Pip

Thanx brother! So here's what i did just because, i new the mic was working ok(no smoke or sparks or flames ect. ;D), so I backed my B+ trimmer off to about 95v, pulled my tester 12at7, put in the 6072A, and trimmed it up, and now i get B+120v(trimmer is still wide open though), bias -1 and heater 6.3, go figure? Is a 12at7 a poor choice for testing? I must admit, i kinda had a little panic attack sticking a $100 tube in it, but i had a feeling it would change things, Now alls good apparently. Im gonna trow da Tim Campbell capsule in and give her a go, i'll report tommrw.

thanx for the reply Pip

Title: Re: Official C12 Clone - Build and Support Thread
Post by: tonycamp on May 19, 2013, 12:48:36 PM
Check this out my brothers of DIY, considering we are at only 5% of this cost with our builds, even utilizing the best parts available! It truly brings a  :) to my heart, as i have a hard time believing it sounds $19,000 better than my Matachung C12(i'm aware the listing is an ELA M251)

Thank you Matador and Chunger for bringing the dream of Unobtainium to reality! (make sure you scroll down the page, there are some great pictures!)


http://www.ebay.com/itm/TELEFUNKEN-ELA-M-251-E-VINTAGE-ORIGINAL-CLASSIC-TUBE-MIC-MINTY-LQQK-SIR-380-/290774086590?pt=US_Pro_Audio_Microphones&hash=item43b37c73be
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Gus on May 19, 2013, 01:16:52 PM
Be careful with duct seal.  I would use something else.

IIRC it out gasses and anything that out gasses is bad to place by a condenser capsule

Title: Re: Official C12 Clone - Build and Support Thread
Post by: tonycamp on May 19, 2013, 01:41:28 PM
Be careful with duct seal.  I would use something else.

IIRC it out gasses and anything that out gasses is bad to place by a condenser capsule

I don't know what kind you're talking about, I was concerned about that before i used it also, so i looked into it.  I use "IDEAL" duct seal from home depot(thats all they carry out here), a quote from their site

 "The Duct Seal formula is completely nontoxic, and unlike many other chemical-based repair materials on the market, you can handle it without gloves or fear of skin irritation/chemical absorption. It’s also completely non-corrosive, so it’s safe to use on both plastics and metals. Ooooh, and one more thing: Duct Seal also has a relatively high flash point (590°F), so it’s helpful in preventing electrical fires"

I sealed every outlet box, switch box, door knob, damped lamps, and a lot of other things that resonate in an undesirable fashion in my studio. I've put it into a lot of mics, they all still work great, I used bare hands to install all of it, no skin irritation, cant smell it unless you put your nose right on it, and i forget which mics its in until i tap on the basket, so??
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Gus on May 19, 2013, 02:14:43 PM
I have used duct seal in the past for damping things like turntable headshells.  IIRC it left a residue when I removed it from the headshell.

Just because you can't smell or it is nontoxic it does not mean it is not outgassing. 

Title: Re: Official C12 Clone - Build and Support Thread
Post by: tonycamp on May 19, 2013, 02:46:20 PM
Ok then, i'm gonna pull my Thiersch Blueline PVC M7 capsule out of my mic, because PVC out gasses like crazy! And while i'm at it, i'm going to pull out the wire from my mics because they have chemical insulation on them, my carpet, air ducts, paint, acoustic foam, this Mac computer, and every product in the house that contains some form of petroleum based plastic, including my food containers. Also the plating process on my mic bodies is so toxic it's ridiculous, i should throw those away also.

IMO, its no big deal, besides, I'd rather deal with a little poison in the air than a harsh upper mid resonant frequency any day!lol

I'm not forcing anyone, don't use it.  it works really nice though ;)
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Gus on May 19, 2013, 03:03:03 PM
I believe you are misunderstanding my posts.

I have worked on older microphones that had a coating on the mylar, as best I could tell without a test was the foam inside the headbasket broke down and was a part of the coating on the mylar.

Anything that has a plasticizer added can outgass like in a new car. 

My point is what is in the duct seal might/will coat the mylar of the capsule possible causing issues.

I agree duct seal damps very well.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: tonycamp on May 19, 2013, 03:12:16 PM
I have(had) 2 vintage sm81's that are complete junk now due to the shure microphone cases, the foam in them dissolved into oily goo, destroying the mics. I had them perfectly stored with all my other mics.
I believe duct seal is too dense in it's formulation to be flyaway like foam and stick to a capsule. I will just agree to disagree with you, as my results have been problem free and excellent.

BTW, i like a lot of the posts you've done, always informative

Thanx
T
Title: Re: Official C12 Clone - Build and Support Thread
Post by: JessJackson on May 19, 2013, 03:38:21 PM
I still have very low output.

Question, what is the common reason in this circuit for low output level? I feel that I may have the xformer wired wrongly or something simple like that.

on Pg 9. i post images of my transformer. I wired the high number to the circuit board and the low number to the XLR but forgive me if i'm being an idiot but shouldnt the higher resistance go to XLR and lower resistance go to board since its a step down xformer.

Also should my green wires be tied together. like most ela m / c12's are?.. i think im going to have to pull the xformer and re-measure.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: sr1200 on May 19, 2013, 05:10:14 PM
Got the same tube that chunger used in his photo documentary of the build.  Purchased from tube depot, ordered low microphonic yadda yadda.  Its definitely NOT the tube though, since when i swap the head basket for the old one, the issue is not there at all.  As I stated earlier, the problem isn't really a problem anymore since i bent the screen around a little.  The body resonance is way down near about 100 or so best i can tell from handling it.  (not very scientific tests here for this lol)

 BTW chung... how did they buff the nickel to a shine on the screen lol (totally looks like chrome to me and even has pitting like chrome!) ??  Bout to use it for a session in about 20 min. :)
Title: Re: Official C12 Clone - Build and Support Thread
Post by: chunger on May 19, 2013, 07:58:00 PM
Got the same tube that chunger used in his photo documentary of the build.  Purchased from tube depot, ordered low microphonic yadda yadda.  Its definitely NOT the tube though, since when i swap the head basket for the old one, the issue is not there at all.  As I stated earlier, the problem isn't really a problem anymore since i bent the screen around a little.  The body resonance is way down near about 100 or so best i can tell from handling it.  (not very scientific tests here for this lol)

 BTW chung... how did they buff the nickel to a shine on the screen lol (totally looks like chrome to me and even has pitting like chrome!) ??  Bout to use it for a session in about 20 min. :)

I didn't do any of the buffing!  The factory did.  I believe it's surface treatment prior to plating that makes the difference.  Also, it is MUCH more forgiving to do bead blasted matte finish because the blasted surface hides imperfections (and at this price-point, it will have imperfections).  The main reason I ordered the polished nickel finish instead of bead blasted nickel was different factories may have different formulations in their plating process and I did not want to risk the colors being different between the microphone body and the headbasket.  By doing the polished finish on the basket, it contrasts either way so even if the color of the plating is a little off, the mic still looks nice.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Matador on May 19, 2013, 11:35:08 PM
I still have very low output.

Question, what is the common reason in this circuit for low output level? I feel that I may have the xformer wired wrongly or something simple like that.

on Pg 9. i post images of my transformer. I wired the high number to the circuit board and the low number to the XLR but forgive me if i'm being an idiot but shouldnt the higher resistance go to XLR and lower resistance go to board since its a step down xformer.

Also should my green wires be tied together. like most ela m / c12's are?.. i think im going to have to pull the xformer and re-measure.

It's a step-down, meaning the primary has a lot more turns than the secondary.  Since that wire has resistance, you want the side with more resistance on the primary, and the low resistance on the secondary. 

What green wires are you referring to?
Title: Re: Official C12 Clone - Build and Support Thread
Post by: JessJackson on May 20, 2013, 12:27:28 AM
I still have very low output.

Question, what is the common reason in this circuit for low output level? I feel that I may have the xformer wired wrongly or something simple like that.

on Pg 9. i post images of my transformer. I wired the high number to the circuit board and the low number to the XLR but forgive me if i'm being an idiot but shouldnt the higher resistance go to XLR and lower resistance go to board since its a step down xformer.

Also should my green wires be tied together. like most ela m / c12's are?.. i think im going to have to pull the xformer and re-measure.

It's a step-down, meaning the primary has a lot more turns than the secondary.  Since that wire has resistance, you want the side with more resistance on the primary, and the low resistance on the secondary. 

What green wires are you referring to?

ok, cheers matador, so i have it wired correctly in that case.

Wonder what else could be causing the low output.

Im referring to the 50ohm green wires. I have an original Haufe T14. the images are on page 9 of this thread.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: baadc0de on May 20, 2013, 01:33:57 AM
I still have very low output.

Question, what is the common reason in this circuit for low output level? I feel that I may have the xformer wired wrongly or something simple like that.

on Pg 9. i post images of my transformer. I wired the high number to the circuit board and the low number to the XLR but forgive me if i'm being an idiot but shouldnt the higher resistance go to XLR and lower resistance go to board since its a step down xformer.

Also should my green wires be tied together. like most ela m / c12's are?.. i think im going to have to pull the xformer and re-measure.

It's a step-down, meaning the primary has a lot more turns than the secondary.  Since that wire has resistance, you want the side with more resistance on the primary, and the low resistance on the secondary. 

What green wires are you referring to?

ok, cheers matador, so i have it wired correctly in that case.

Wonder what else could be causing the low output.

Im referring to the 50ohm green wires. I have an original Haufe T14. the images are on page 9 of this thread.

I also have extremely low output. Voltages are OK, transformer is wired properly (AMI), tube swaps don't seem to be doing anything..
Title: Re: Official C12 Clone - Build and Support Thread
Post by: HellfireStudios on May 22, 2013, 12:32:11 PM
Hey, I got one of the first-run C12 headbaskets as well, and I had the same ringing problem. My fix was to use Loctite Go2 Glue as a dampener. It reminds me of hot glue when wet, and rubber cement when dry, but dries crystal clear. I added it to the inside of the rails and around the base ring. It seems to have brought the ringing to a dull thud.
I would use painter's tape to cover the visible screen (not covered by rails, etc.) before applying glue, and removing the tape 10 minutes later as the glue tends to settle. Be careful to not use too much glue, and work with one section at a time to avoid dripping.
Sorry to be so long-winded, but I wouldn't want anyone to ruin their brand new headbasket...

-James-
Title: Re: Official C12 Clone - Build and Support Thread
Post by: JessJackson on May 22, 2013, 06:56:51 PM
I still have very low output.

Question, what is the common reason in this circuit for low output level? I feel that I may have the xformer wired wrongly or something simple like that.

on Pg 9. i post images of my transformer. I wired the high number to the circuit board and the low number to the XLR but forgive me if i'm being an idiot but shouldnt the higher resistance go to XLR and lower resistance go to board since its a step down xformer.

Also should my green wires be tied together. like most ela m / c12's are?.. i think im going to have to pull the xformer and re-measure.

It's a step-down, meaning the primary has a lot more turns than the secondary.  Since that wire has resistance, you want the side with more resistance on the primary, and the low resistance on the secondary. 

What green wires are you referring to?

ok, cheers matador, so i have it wired correctly in that case.

Wonder what else could be causing the low output.

Im referring to the 50ohm green wires. I have an original Haufe T14. the images are on page 9 of this thread.

I also have extremely low output. Voltages are OK, transformer is wired properly (AMI), tube swaps don't seem to be doing anything..

Post all your voltages measured at mic, i'm gonna do the same and try to figure this low output issue.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Matador on May 22, 2013, 08:59:19 PM
Can we quantify exactly what "low output" means?  How many DBFS is it lower than what you are expecting?
Title: Re: Official C12 Clone - Build and Support Thread
Post by: baadc0de on May 23, 2013, 01:37:02 AM
Can we quantify exactly what "low output" means?  How many DBFS is it lower than what you are expecting?

Another build I just did seems to be ~ 20dB louder. I'll test at the studio soon to be extra sure. From my measurements, the voltages seem to be OK and since tube swaps are not working, I guess it's either the capsule or transformer. I can probably inject signal on both and see if the gain drop still occurs. If it does, it should be the transformer, if not, the capsule. Let me know if you guys have any other suggestions.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: tonycamp on May 23, 2013, 02:39:08 AM
Can we quantify exactly what "low output" means?  How many DBFS is it lower than what you are expecting?

Another build I just did seems to be ~ 20dB louder. I'll test at the studio soon to be extra sure. From my measurements, the voltages seem to be OK and since tube swaps are not working, I guess it's either the capsule or transformer. I can probably inject signal on both and see if the gain drop still occurs. If it does, it should be the transformer, if not, the capsule. Let me know if you guys have any other suggestions.

Double check your bridge on the back plates??
Title: Re: Official C12 Clone - Build and Support Thread
Post by: tonycamp on May 23, 2013, 02:49:27 AM
Hi Fella's,

I have an interesting clip for you guys, my C12 head basket seems to have a pretty nasty bell resonance to it, so i did what i recommended, DUCT SEAL!! :o  Listen to the clip, and judge for yourself, I could imagine if you were to use the C12 head basket untreated, in a high SPL situation, the ring could be quite problematic, the duct seal helps a lot, but i'm not sure if it's enough??

https://soundcloud.com/tonycamp/c12-duct-seal

let me know what y'all think, and i hope this helps

thanx
T

Edit; I mean this as no slight to chungs head basket, it's a really nice piece!, and for all i know, the resonant thing is part of the C12 sound(i've never used a real one), not to mention, the mic sounds friggin beauty gotta love it!!, seriously stellar!
Title: Re: Official C12 Clone - Build and Support Thread
Post by: sr1200 on May 23, 2013, 02:55:39 AM
Did you "break in" the mesh before you applied the sealant to it?  Im trying to find that go2 glue mentioned by hellfire above, noone in my neck of the woods seems to carry it though.  Gonna try home depot tomorrow.  Most of my issue was taken care of just by loosening up the mesh manually... id only want to further damp it for things like high spl since you can almost kinda hear it still but its so feint on loud vocals it really doesn't bother me anymore.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: tonycamp on May 23, 2013, 02:59:04 AM
Did you "break in" the mesh before you applied the sealant to it?  Im trying to find that go2 glue mentioned by hellfire above, noone in my neck of the woods seems to carry it though.  Gonna try home depot tomorrow.  Most of my issue was taken care of just by loosening up the mesh manually... id only want to further damp it for things like high spl since you can almost kinda hear it still but its so feint on loud vocals it really doesn't bother me anymore.

I did break in the mesh, i gave it a few real good squeezes, and worked the crackling out, I'm worried about the ring on overheads, cause i play loud as f**k!lol!, thats about it though. But again, the mic sounds really great!
Title: Re: Official C12 Clone - Build and Support Thread
Post by: baadc0de on May 23, 2013, 04:02:30 AM
Yeah, good idea. I've had this running through my head too, so it will be the first thing to check!

Can we quantify exactly what "low output" means?  How many DBFS is it lower than what you are expecting?

Another build I just did seems to be ~ 20dB louder. I'll test at the studio soon to be extra sure. From my measurements, the voltages seem to be OK and since tube swaps are not working, I guess it's either the capsule or transformer. I can probably inject signal on both and see if the gain drop still occurs. If it does, it should be the transformer, if not, the capsule. Let me know if you guys have any other suggestions.

Double check your bridge on the back plates??
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Ericbazaar on May 23, 2013, 07:12:10 AM
Hi,
I have build this Mic for a few Weeks. Last Week came Tim's Capsule to me. I have Problems with the Polarity. When i solder the right Capsule-Cables to the right Capsule-Connection-Pins, also Rear-Bias to RB, Front-Bias to FB, Front-Capsule to FC, Rear-Capsule to RC, is the Polarity twisted and the Mic have lower Output. I set the Polarity to Cardioid, the Cardioid is on the Back-Side of the Mic and have low Output. Set the Polarity to Omni, is the Mic quiet. When I set the Polarity to Figure 8, is a Cardioid on Back-Side again but with High Output. I don't understand this. The Mic has not Multipattern yet, no Figure 8 and Omni. I have swapped the Cables RC to FC, RB to FB and back, no change. Does anyone know a solution?

Thanks

PS: I have reinstalled the RK 12 Capsule, same Problem! Damn, what is it! And now installed the CT 12 again, all very careful, right Cables to right Pins. The Microphone Multipattern works, but the Output Level is very low! Any Ideas?
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Tim Campbell on May 23, 2013, 10:08:36 AM
The only problems that be capsule related would be a bad connection, wrong connection, damage or collapsing.
Take off the headbasket and make sure the membranes aren't collapsing.

Ericbazaar it sounds like you've got a short or a missing connection. Check your voltages and look for solder bridges. Make sure the solder tags on the capsule are snug (don't overtighten them).
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Matador on May 23, 2013, 10:47:05 AM
There are only a few things I can think of related to low output:

1) Capsule polarization voltage is too low.  I don't remember the equation off-hand, but the lower the polarization potential across the membranes the lower the sensitivity.  If you've confirmed B+ is around 120V (and it doesn't have to be exact), then confirm that the voltage dividier between R12 and R13 is giving 1/2 of whatever you measured for B+.  If this is good, you might try also replacing R14 (although I would think it would be rare for there to be a problem with R14).  You can't measure the FB side because your meter will clobber this voltage (unless you have a very expensive 10G probe system).

2) Tube gain is too low:  seems like a remote possibility.  The tube gm would have to be WAY off for this to be the problem.  But you should confirm that the plate is idling somewhere near 60V-80V by measuring right at the tube socket (pin1 or pin6 depending on which side you are using).  I would also confirm the heater is set correctly by again measuring right at the tube pins (see prior posts in this thread for details).  The tube should be pulling right around 0.5mA with a 100K plate resistor (R17) and the negative bias at -1V.  Also confirm the negative bias by measuring right where it enters the mike at the P4 node (right before R11).

A slightly higher chance is that either C13 or C10 is cooked (doesn't take much with styrene's).  There is a procedure for checking these in the previous posts half a dozen or so pages back.

3) Transformer primary and secondary reversed:  disconnect the primary at the bottom of the board and confirm you are getting 800-1K ohms across the primary.  If the reading is less than 100 ohms it's backwards and it would explain the low output.

The best way to confirm everything is working post-capsule is to disconnect the capsule FB connection (which goes to the coupling cap C13), and inject a 1VPP signal right into the grid at pin2 (or pin7 if you are using the other half of the tube) and then measure the output at the XLR connector.  A 1VPP signal should go straight through and appear somewhere in the 1V to 1.5V range as measure between the two output pins (5 and 6 I think).  The tube gain is about 25dB, and the transformer reduces this by about 20dB so the total gain through the circuit should be about 5dB.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: baadc0de on May 23, 2013, 01:37:33 PM
Unfortunately, after triple checking about tying the backplates together, the result is the same. The 1st mic I did has about ~20dB less gain. The transformer is correctly wired (remeasured in situ) and it is using the same PSU and cable. Voltages arrive fine to the mic. I'm beginning to suspect the capsule rather strongly. It's the same make / model as the other one.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Ericbazaar on May 23, 2013, 02:21:51 PM
The only problems that be capsule related would be a bad connection, wrong connection, damage or collapsing.
Take off the headbasket and make sure the membranes aren't collapsing.

Ericbazaar it sounds like you've got a short or a missing connection. Check your voltages and look for solder bridges. Make sure the solder tags on the capsule are snug (don't overtighten them).

How do I see a broken capsule? I used 30awg silver teflon wire from capsule to pin connectors and i think are snug enough :)

There are only a few things I can think of related to low output:

1) Capsule polarization voltage is too low.  I don't remember the equation off-hand, but the lower the polarization potential across the membranes the lower the sensitivity.  If you've confirmed B+ is around 120V (and it doesn't have to be exact), then confirm that the voltage dividier between R12 and R13 is giving 1/2 of whatever you measured for B+.  If this is good, you might try also replacing R14 (although I would think it would be rare for there to be a problem with R14).  You can't measure the FB side because your meter will clobber this voltage (unless you have a very expensive 10G probe system).

2) Tube gain is too low:  seems like a remote possibility.  The tube gm would have to be WAY off for this to be the problem.  But you should confirm that the plate is idling somewhere near 60V-80V by measuring right at the tube socket (pin1 or pin6 depending on which side you are using).  I would also confirm the heater is set correctly by again measuring right at the tube pins (see prior posts in this thread for details).  The tube should be pulling right around 0.5mA with a 100K plate resistor (R17) and the negative bias at -1V.  Also confirm the negative bias by measuring right where it enters the mike at the P4 node (right before R11).

A slightly higher chance is that either C13 or C10 is cooked (doesn't take much with styrene's).  There is a procedure for checking these in the previous posts half a dozen or so pages back.

3) Transformer primary and secondary reversed:  disconnect the primary at the bottom of the board and confirm you are getting 800-1K ohms across the primary.  If the reading is less than 100 ohms it's backwards and it would explain the low output.

The best way to confirm everything is working post-capsule is to disconnect the capsule FB connection (which goes to the coupling cap C13), and inject a 1VPP signal right into the grid at pin2 (or pin7 if you are using the other half of the tube) and then measure the output at the XLR connector.  A 1VPP signal should go straight through and appear somewhere in the 1V to 1.5V range as measure between the two output pins (5 and 6 I think).  The tube gain is about 25dB, and the transformer reduces this by about 20dB so the total gain through the circuit should be about 5dB.

I have all measured, the B+ is 120v on PSU, on Plate 67v, heater is 6,3v and Bias is -1v. the measure between R12 and R13 is 59v. I dont understand the measuring method of c13 or c10 :-[Sorry I'm still a beginner. When I exchange cable FC and RC, also RC cable to FC pin and other around, one side of the capsule works with good output. Only when the switch is Figure 8, on Omni is the Mic quiet. transformer is installed properly, 930ohm to PCB and 20ohm to XLR. Is it about the polystyrene caps?
Title: Re: Official C12 Clone - Build and Support Thread
Post by: chunger on May 23, 2013, 02:23:42 PM
due to the recent issues folks have been having with the single layer headbasket ringing, I played around with it again last night and have a few observations.

In general, the dual layer basket is MUCH more sturdy than the single layer.  It is amazing how much more rigid the assembly becomes with the thinner mesh inside all soldered together.  I am not an acoustics expert, but I believe the presence of the 2nd layer pushes the resonant frequency of the basket down significantly and the overall stiffness of the assembly makes it resonate less in general.

There is probably good reason most production microphones use 2 or 3 layer mesh setups or more robust hoop structures to support the single layer meshing.  That being said, the main mechanical weak point that I found in the current single layer basket is around the perimeter where the basket meets the round base assembly.  This is only soldered in 2 locations at the hoop attachment points.  For my 2nd batch, I will discuss with the factory at least spot solder all around the perimeter on the single layer baskets.  For now, it seems folks have been successful using a number of adhesives in the critical areas 90 degrees from the hoop attachment points to mitigate the basket ringing.  FWIW, the ringing here in the untreated headbasket seems on par with the ringing I heard in the stock GT-2B microphone and has not proven problematic for me in practical use yet in studio.  But, I can readily induce the problem by physically tapping on the body.

As I understand it, nickel plate while difficult to solder is not impossible.  I will experiment with dremeling away the little tabs inside the headbasket and manually soldering around the perimeter of the headbasket.  This should be the most robust solution as long as the finish is not damaged.  Fortunately, I have a wonky B-stock headbasket on hand that I can experiment with.

The dual layer headbasket seems solid and does not suffer from this particular problem.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: sr1200 on May 23, 2013, 02:41:32 PM
Whats the chances of not plating the mesh in the next batch?
Title: Re: Official C12 Clone - Build and Support Thread
Post by: tonycamp on May 23, 2013, 02:57:25 PM
perhaps inquire about aluminum on the next batch? takes plating excellently, shouldn't ring near as much? who cares if it adds $20 to the bill?
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Tim Campbell on May 23, 2013, 07:00:16 PM
Ericbazaar,  if the capsule isn't collapsed and the connections are good it can't have a lower output than when I sent it to you. try installing the original caplsule and see how that works. In my experience low output is usually a poor connection, a solder bridge or a wrong value resistor.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Ericbazaar on May 23, 2013, 07:20:09 PM
Ericbazaar,  if the capsule isn't collapsed and the connections are good it can't have a lower output then when I sent it to you. try installing the original caplsule and see how that works. In my experience low output is usually a poor connection, a solder bridge or a wrong value resistor.

I have reinstalled the RK12 Capsule again. Exact the same Problem. I have all checked three times, i don't know what it is. Can I destroy the capsule when I change FC and RC Cables? Change RC and FC works one side of the capsule, switch on Omni the Output is quiet, switch on Cardioid the Output is ok, switch on Figure 8 the Output is high. I hope the capsule is not broken :-[
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Tim Campbell on May 23, 2013, 07:33:49 PM
Eric, do you mean you have the same problem with the RK12 installed? If so then it's not a capsule problem. I still believe you have a missing connection or short in one of the cables leading to the capsule. You could ruin the capsule by getting hot flux or solder (even a microscopic bit) on the membrane. This is why I include covers for the membranes. Don't solder/unsolder at the capsule, desolder it's wires at the pcb.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Ericbazaar on May 23, 2013, 07:49:26 PM
Eric, do you mean you have the same problem with the RK12 installed? If so then it's not a capsule problem. I still believe you have a missing connection or short in one of the cables leading to the capsule. You could ruin the capsule by getting hot flux or solder (even a microscopic bit) on the membrane. This is why I include covers for the membranes. Don't solder/unsolder at the capsule, desolder it's wires at the pcb.

Yes Tim, same problem with RK 12! What is the principle of a double membrane capsule? one side have static voltage of +60volts, the other side is switched from -60 to 0v to +60. http://www.sengpielaudio.com/DoppelmembranKondensatormikrofon.pdf (ftp://www.sengpielaudio.com/DoppelmembranKondensatormikrofon.pdf) can this also be a problem? and yes i will checked all cables and xlr.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Ericbazaar on May 23, 2013, 08:00:27 PM
This is why I include covers for the membranes. Don't solder/unsolder at the capsule, desolder it's wires at the pcb.

I have solder the cables with cover and I have made ​​a small bag over it. I have the capsule viewed through a magnifying glass and did not detect any damage.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Matador on May 23, 2013, 08:13:22 PM
Eric, do you mean you have the same problem with the RK12 installed? If so then it's not a capsule problem. I still believe you have a missing connection or short in one of the cables leading to the capsule. You could ruin the capsule by getting hot flux or solder (even a microscopic bit) on the membrane. This is why I include covers for the membranes. Don't solder/unsolder at the capsule, desolder it's wires at the pcb.

Yes Tim, same problem with RK 12! What is the principle of a double membrane capsule? one side have static voltage of +60volts, the other side is switched from -60 to 0v to +60. http://www.sengpielaudio.com/DoppelmembranKondensatormikrofon.pdf (ftp://www.sengpielaudio.com/DoppelmembranKondensatormikrofon.pdf) can this also be a problem? and yes i will checked all cables and xlr.

Not quite:  the voltages are relative.  The FC sits at a fixed ground potential (0V).  The backplate(s) sit at +60V.  The rear diaphragm goes from ground (omni) to +60V (cardioid), to +120V (figure 8).  When the back is at 120V, the backplate(s) can be though of as sitting at ground (really +60V), then the rear capsule is +60V from that (120V), and the front diaphragm is at -60V (at ground).
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Ericbazaar on May 23, 2013, 08:34:08 PM


Not quite:  the voltages are relative.  The FC sits at a fixed ground potential (0V).  The backplate(s) sit at +60V.  The rear diaphragm goes from ground (omni) to +60V (cardioid), to +120V (figure 8).  When the back is at 120V, the backplate(s) can be though of as sitting at ground (really +60V), then the rear capsule is +60V from that (120V), and the front diaphragm is at -60V (at ground).

Ah ok i understand…almost… ::)…now I still do not know where the problem is :-\. it would be easy it would be boring. and when the micro works, I'll love it twice…
Title: Re: Official C12 Clone - Build and Support Thread
Post by: HellfireStudios on May 23, 2013, 09:22:07 PM
You could take a technique from Neumann, and use solder paste in the perimeter of the base ring to make a complete solder joint between the two pieces. It would be easy enough, and probably cheap too. Just an idea...

-James-
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Ericbazaar on May 24, 2013, 05:56:07 AM
I have make detailed Pictures of the CT 12 Capsule and the Connections. I think its all ok.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Ericbazaar on May 24, 2013, 06:00:42 AM
and another…
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Ericbazaar on May 24, 2013, 06:01:52 AM
again
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Ericbazaar on May 24, 2013, 06:04:05 AM
I just want to make sure that the capsule is ok ...
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Ericbazaar on May 24, 2013, 06:27:33 AM
I have all connections checked, xlr, tube cable, i have build a new cable from Cable company "Sommer Cable" from Netherlands and Neutrix Connectors. Double checked, all ok! I think the best Option is order a new PCB and Part Set? The search makes me mad :'( I have build last Week a Lola Mic Pre, this thing works without problems. although this thing has 1000 parts…dammit
Title: Re: Official C12 Clone - Build and Support Thread
Post by: tonycamp on May 24, 2013, 12:57:44 PM
I have all connections checked, xlr, tube cable, i have build a new cable from Cable company "Sommer Cable" from Netherlands and Neutrix Connectors. Double checked, all ok! I think the best Option is order a new PCB and Part Set? The search makes me mad :'( I have build last Week a Lola Mic Pre, this thing works without problems. although this thing has 1000 parts…dammit

right or wrong, i bridged my backplates AT THE CAPSULE?, working really great.

good luck
T
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Ericbazaar on May 24, 2013, 01:06:12 PM


right or wrong, i bridged my backplates AT THE CAPSULE?, working really great.

good luck
T

have you bridge the pins or on the capsule?
Title: Re: Official C12 Clone - Build and Support Thread
Post by: tonycamp on May 24, 2013, 01:27:31 PM


right or wrong, i bridged my backplates AT THE CAPSULE?, working really great.

good luck
T

have you bridge the pins or on the capsule?

on the capsule, used a .25 watt resistor leg cut off.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: strangeandbouncy on May 24, 2013, 01:50:34 PM
HI,


   I didn't hear it at first, because I had a foam popshield over the headbasket. But I found a slight ring when I actually used it on a vocal "under fire". I put a thin sausage of BluTacK around the inside at the base.


    Sorted! It will probably still be there in 50 years. I probably won't!


      ANdyP
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Matador on May 24, 2013, 07:10:46 PM

right or wrong, i bridged my backplates AT THE CAPSULE?, working really great.

good luck
T

This.

If you tie it together at the capsule, then you have separate wires from FB and RB.  If it's tied together at the PCB, then there should be a wire bridge between FB and RB right on the teflon turrets.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Matador on May 24, 2013, 07:14:59 PM
This first page shows the bridging of the two backplates:

(http://studio939.zenfolio.com/img/s8/v75/p1456848224-4.jpg)

...The CT12 capsule has isolated backplates which we will bridge together at the solder terminals on the capsule.  With this capsule being scavenged from a previous prototype, Matador already soldered in wires for the front diaphragm, rear diaphragm, front/rear backplates, as well as bridge the front and rear backplates together...
Title: Re: Official C12 Clone - Build and Support Thread
Post by: NTJEvan on May 24, 2013, 08:47:56 PM
So i've got the mini-pot backed all the way out, but i cant seem to get the B+ voltage below ~124v This is while strictly function testing with the factory 12ax7 and capsule, but I dont want to put the good parts in and risk roasting them. Any ideas at what I could have done wrong?

Also, does anyone have a source for the 7 pin XLR plug that is inside the mic? I'm thinking about upgrading the factory jacks to neutrik or switchcraft parts, but I havent had any luck finding the raw in-mic parts?
Title: Re: Official C12 Clone - Build and Support Thread
Post by: JessJackson on May 24, 2013, 10:23:02 PM
i have the same very low output problem yet i have bridged my backplates at the teflon pins.

I have checked continuity from the pins to the backplates etc.. and everything seems fine with no contamination. My transformer is wired correctly and my voltages seem fine.

This is seriously boggling me for the past week.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Matador on May 24, 2013, 10:54:22 PM
i have the same very low output problem yet i have bridged my backplates at the teflon pins.

I have checked continuity from the pins to the backplates etc.. and everything seems fine with no contamination. My transformer is wired correctly and my voltages seem fine.

This is seriously boggling me for the past week.

What kind of diagnostic equipment do you have access to?

Can you confirm the printing on the plate load resistor R17?
Title: Re: Official C12 Clone - Build and Support Thread
Post by: JessJackson on May 25, 2013, 07:10:52 AM
i have the same very low output problem yet i have bridged my backplates at the teflon pins.

I have checked continuity from the pins to the backplates etc.. and everything seems fine with no contamination. My transformer is wired correctly and my voltages seem fine.

This is seriously boggling me for the past week.

What kind of diagnostic equipment do you have access to?

Can you confirm the printing on the plate load resistor R17?

hi matador, i have the dale 100k resistor there

i have ddm oscilloscope and sine wave gen

i found this post on klaus forum with someone else who was down 20db a few years ago

Quote
Okay, here's where I'm at. The "cackle" was just a bad cable. For the life of me I couldn't trace the problem of the low output. So out of desperation I reversed the transformer connections, and viola - proper output.

I'm wondering if I can get an explanation. I assumed the secondary connected to the audio output. I assumed the 14/1 xformer was a step up xformer and measured the resistance of the leads and concluded the higher resistance would be the secondary.

So is the t14/1 actually a step down xformer for some sort of impedance matching function with the tube, or am I confused about something? Because as it stands now, the low resistance leads connect to the audio output and all seems working properly.

But my x-former does have the lower resistance value as secondary.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: JessJackson on May 25, 2013, 07:14:44 AM
could it be that the left primary and left secondary aren't wound that way? there is red and blue on left and red and blue on right side but  maybe they are swapped inside transformer?
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Tim Campbell on May 25, 2013, 07:51:59 AM
Eric, from looking at your pictures, Have you done something to the posts above the solder tags leading to the backplates? Perhaps soldered to them or filed them?
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Ericbazaar on May 25, 2013, 08:11:22 AM
Eric, from looking at your pictures, Have you done something to the posts above the solder tags leading to the backplates? Perhaps soldered to them or filed them?

i have solder with your Cover and i have double secure with tapes, i solder quick. and now i have brigde RB and FB, now the mic works with all pattern. your capsule works beautiful and i test the sound in the next few weeks. God damn…this was a strange projekt, I'll take the microphone with in grave ;D.

Tim, Matador and Chunger thanks for your help

ericbazaar
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Matador on May 26, 2013, 10:37:12 PM
hi matador, i have the dale 100k resistor there

i have ddm oscilloscope and sine wave gen

Ok, let's try this:  disconnect the capsule lead connected to FB (the one that leads to C13).  Inject a ground-referenced 1V peak-to-peak sine wave into this node (right at the teflon standoff labeled "FB").  Then read the peak-to-peak voltage coming out of the XLR jack that goes to your preamp.

You should be about 5-6dB of gain through the entire chain to the output jack.  If the signal is way low, move the injection point right to the tube grid (pin2 or pin7 depending on which half of the tube you picked).

Let's start there and we'll debug from there.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: jrmintz on May 27, 2013, 09:13:22 PM
Does anybody make nice boxes for these mics?
Title: Re: Official C12 Clone - Build and Support Thread
Post by: jrmintz on May 27, 2013, 09:27:21 PM
I think I answered my own question:

http://vintagemicrophone.com/JShop/product.php?xProd=18&jssCart=60c6cb4ac8b0e8a4ae959b9a4bbb4564

Will an Apex 460 fit in a C12-sized box?
Title: Re: Official C12 Clone - Build and Support Thread
Post by: HellfireStudios on May 27, 2013, 10:18:06 PM
You can find Telefunken R-F-T style boxes on ebay for a decent price. The ones with the red and yellow velvet are the ones that should fit the Apex 460.

-James-
Title: Re: Official C12 Clone - Build and Support Thread
Post by: pmcorbett on May 28, 2013, 04:28:07 PM
Just got my kit and I'm looking forward to building the mic. I'll be using a CEK-12 capsule and a cinemag 2480 transformer... are there different functioning parameters (metering, voltages...etc) I should be aware of when testing and tuning the mic? Let me know when you can. Thanks!
Title: Re: Official C12 Clone - Build and Support Thread
Post by: ruairioflaherty on May 28, 2013, 06:23:52 PM
... are there different functioning parameters (metering, voltages...etc) I should be aware of when testing and tuning the mic? Let me know when you can. Thanks!

This whole thread is dedicated to those questions - read it in it's entirety before you start to gain an understanding of what's involved.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: tonycamp on May 29, 2013, 12:27:16 PM
been using this mic, getting to know her at bit, It's clearly getting better as she's breaking in, and her bottom is surprisingly large! My kind woman! still much learn Kemosahbee
Title: Re: Official C12 Clone - Build and Support Thread
Post by: jrmintz on May 30, 2013, 04:10:01 PM
Matador, in the 251 variant would the 20uF cathode bypass cap have been a Tantalum electrolytic in the original?
Title: Re: Official C12 Clone - Build and Support Thread
Post by: strangeandbouncy on May 31, 2013, 07:16:03 PM
Hi,



    pretty sure it was an electrolytic . . . . anyone?


   Not sure what would be gained by using a Tant here(?)



     ANdyP
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Matador on May 31, 2013, 08:42:54 PM
I honestly don't know.  The size of the cap puts the gain step way down near DC anyways (like 4Hz):  I can't imagine the cap type would make that much of a difference.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: jrmintz on May 31, 2013, 09:22:05 PM
Thanks gents. Matador, the board design is elegant, easy to build. I love the plated through-holes.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: drumminkiger on June 01, 2013, 01:07:01 AM
Well, I pulled the trigger today and bought all the remaining kit components to make my c12 clones after sitting on my mic bodies and tim's capsules for about 6 months now. The only thing I have left to buy is the tubes. I emailed Christian at pro audio tubes, and he recommended two tubes to me. One of them is a vintage GE and the other is a vintage mullard. He said the GE seems to be the choice tube for most folks, but he said the mullard had a more defined mid prescense and is also about half the price. I'm just curious if anyone has tried the mullard, I'm even somewhat curious if it kinda tilts the mic more towards a 251 response. It might be kinda cool, what do you guys think? Anyone tried it?
Title: Re: Official C12 Clone - Build and Support Thread
Post by: tonycamp on June 01, 2013, 01:41:38 AM
Well, I pulled the trigger today and bought all the remaining kit components to make my c12 clones after sitting on my mic bodies and tim's capsules for about 6 months now. The only thing I have left to buy is the tubes. I emailed Christian at pro audio tubes, and he recommended two tubes to me. One of them is a vintage GE and the other is a vintage mullard. He said the GE seems to be the choice tube for most folks, but he said the mullard had a more defined mid prescense and is also about half the price. I'm just curious if anyone has tried the mullard, I'm even somewhat curious if it kinda tilts the mic more towards a 251 response. It might be kinda cool, what do you guys think? Anyone tried it?

I put a nos mullard in my K2, sounds smoother than the stock tube in that mic, so?? You're building a pair  right?, are your campbell capsules a matched pair? if so, wouldn't you want a couple tubes that are identical? just curious.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: drumminkiger on June 01, 2013, 01:48:10 AM
Yes, I would be buying a matched pair of tubes, so one kind or the other.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: tonycamp on June 01, 2013, 01:59:07 AM
Yes, I would be buying a matched pair of tubes, so one kind or the other.

Gotchya, i got the 6072 $100+ ge from christian, it keeps sounding better and better, this mic is real impressive. As a matter of fact, i can't believe how great the matachung c12 and the ioaudio Mk47 sound! Both these mics are quite literally a dream come true for me ;D
Title: Re: Official C12 Clone - Build and Support Thread
Post by: baadc0de on June 01, 2013, 02:19:37 AM
hi matador, i have the dale 100k resistor there

i have ddm oscilloscope and sine wave gen

Ok, let's try this:  disconnect the capsule lead connected to FB (the one that leads to C13).  Inject a ground-referenced 1V peak-to-peak sine wave into this node (right at the teflon standoff labeled "FB").  Then read the peak-to-peak voltage coming out of the XLR jack that goes to your preamp.

You should be about 5-6dB of gain through the entire chain to the output jack.  If the signal is way low, move the injection point right to the tube grid (pin2 or pin7 depending on which half of the tube you picked).

Let's start there and we'll debug from there.

I did this, and unfortunately the amp is alright, working as it should, identically between the bad and good mic. So... that means the capsule, right? Darn...
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Tim Campbell on June 01, 2013, 02:43:36 AM
Disconnect the mic from audio, remove the headbasket and turn on the mic while looking at the membrane. Is it collapsing? Try the mic with the original capsule. If the problem disappears then it is the capsule. I have never heard of this problem with one of my capsules but there's always a first time.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: baadc0de on June 01, 2013, 02:56:35 AM
Disconnect the mic from audio, remove the headbasket and turn on the mic while looking at the membrane. Is it collapsing? Try the mic with the original capsule. If the problem disappears then it is the capsule. I have never heard of this problem with one of my capsules but there's always a first time.

It's not one of yours, Tim. But thank you for the tips nevertheless.. :)
Title: Re: Official C12 Clone - Build and Support Thread
Post by: jrmintz on June 01, 2013, 12:51:54 PM
Matador, is there any reason I can't mount the board to the underside of the rails rather than the top? I'm using a fatter output cap and I might need more room for clearance. I was thinking about mounting in the center of the rails using nuts as standoffs.

Thanks
Title: Re: Official C12 Clone - Build and Support Thread
Post by: drumminkiger on June 01, 2013, 04:56:37 PM

Gotchya, i got the 6072 $100+ ge from christian, it keeps sounding better and better, this mic is real impressive. As a matter of fact, i can't believe how great the matachung c12 and the ioaudio Mk47 sound! Both these mics are quite literally a dream come true for me ;D

Oh yeah, I hear ya there, I think an MK47 is going to be my next project after these bad boys. I don't have a super solid all around type condenser yet so I figured I would build a pair of c12's so I have something good to kinda stand in that role first and then branch out. I don't doubt that the GE is worth every penny, and I'm sure I'll end up with a pair at some point, but I guess I'm kinda curious because of how christian described the mullards having a little more 47ish mid presence. Will that might give me a little more of a 251 style mic? That might be kinda cool.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: chunger on June 01, 2013, 06:28:16 PM
Be aware that the 12AT7 will shift some of your voltages and you may need to adjust a few values to optimize the PSU and audio circuit.  Details have been discussed earlier in this thread.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Matador on June 01, 2013, 07:35:12 PM
Matador, is there any reason I can't mount the board to the underside of the rails rather than the top? I'm using a fatter output cap and I might need more room for clearance. I was thinking about mounting in the center of the rails using nuts as standoffs.

Thanks

It was mounted to the top to give clearance for the tube:  if you can fit in the tube and the output cap, then really any arrangement is fine.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: pmcorbett on June 02, 2013, 04:47:43 PM
Chunger... My PSU internal layout is a little different from the pics shown in this thread (APEX 460). My transformer was secured onto the circuit board...which I'm sure was attached to some sort of ground. The power cord input ground wire was secured by bolt screw through the transformer casing into the circuit board. It looks like from the pics in this thread that the PSU power cord wire is grounded to the PSU outer casing. Is this so? Can I ground the lead wire from the power cord input to the PSU outer case? Thanks in advance for your advice.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: KMB-AUDIO on June 02, 2013, 05:46:24 PM
Hey guys, I did some drum recording last night with my new Matachung C12s - these mics are exquisite! Using a microphone-parts CK12 and a NOS GE 6072 from Christian, it just kills; so much so that I'm selling my Mojave MA-200s and building 2 more! The high end of these mics are just SMOOTH and the sounds are just real! the high end of the Mojave sounds harsh in comparison.

When I get the other two built (with capsules from Tim), I'll so some more recording and post some sound clips.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: EEMO1 on June 06, 2013, 07:43:29 AM

 anyone know where to buy those haufe t14 transformers? how much are they from haufe?


 just e-mail them?
Title: Re: Official C12 Clone - Build and Support Thread
Post by: tonycamp on June 06, 2013, 11:27:32 AM

 anyone know where to buy those haufe t14 transformers? how much are they from haufe?


 just e-mail them?

? I bought some haufe's from Volker aka silent arts
Title: Re: Official C12 Clone - Build and Support Thread
Post by: KMB-AUDIO on June 06, 2013, 02:44:28 PM
Not sure if this is the correct place to ask, but does anyone have any of Chunger's HT-11A mics that they are willing to part with? Just got word that my Tim Campbell capsules are ready and instead of replacing the RK12 in the mics I already built (I'm thrilled with the mics)...I'm going to build two more.  With Chunger's estimate of late July for the next batch to arrive, that's just too long to wait!! :)

Title: Re: Official C12 Clone - Build and Support Thread
Post by: kidvybes on June 06, 2013, 09:53:33 PM
Not sure if this is the correct place to ask, but does anyone have any of Chunger's HT-11A mics that they are willing to part with? Just got word that my Tim Campbell capsules are ready and instead of replacing the RK12 in the mics I already built (I'm thrilled with the mics)...I'm going to build two more.  With Chunger's estimate of late July for the next batch to arrive, that's just too long to wait!! :)

...in a pinch, Carvin has their version (same as Alctron HST-11A) on sale for $179 each:
http://www.carvinguitars.com/products/CTM100

...more info:
http://recordinghacks.com/microphones/Carvin/CTM100
Title: Re: Official C12 Clone - Build and Support Thread
Post by: KMB-AUDIO on June 06, 2013, 11:05:41 PM
Thanks for the lead, but I really want to get an un-branded mic. If I have to wait, it won't be such a big deal.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Woot on June 06, 2013, 11:19:54 PM

 anyone know where to buy those haufe t14 transformers? how much are they from haufe?


 just e-mail them?

Hi,

I have been in contact with Michaela from Haufe re this recently... Just be aware that they have a 120 euro minimum order, and weren't exactly forthcoming that one trafo is worth 43 euro pre tax. So it's obviously better to buy 2-3 at a time.

If you'd like her email, I'll PM it to you.

Matt
Title: Re: Official C12 Clone - Build and Support Thread
Post by: HellfireStudios on June 06, 2013, 11:41:41 PM
Thanks for the lead, but I really want to get an un-branded mic. If I have to wait, it won't be such a big deal.

The screenprinted brandings on most of those mics comes off easily with rubbing alcohol.

-James-
Title: Re: Official C12 Clone - Build and Support Thread
Post by: chunger on June 07, 2013, 01:52:48 AM
Can someone confirm if the Carvin has a compatible psu?  I direct people to the Apex 460 because I know almost for certain that it comes from the same factory, but the Carvin unit has the tell-tale sign of being supplied by a different factory than Alctron (the dark red plastic pieces holding the tube as opposed to orange).  I am nearly certain I know who makes this mic and the psu should be just fine, but I'd really like to see a photo verification before directing customers who are needing to build immediately to the Carvin product as a suitable donor.

Matador built a prototype on an Apex 460, so we know for sure that one is good to go as a donor.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Winetree on June 07, 2013, 02:23:37 AM
In the White Market, Member Burdij's DIY General Store (Grove Audio) is selling
a complete Mic kit at a reduced price of $150.00
It is manufactured by Alctron and is their model HST-11a.


Title: Re: Official C12 Clone - Build and Support Thread
Post by: Winetree on June 07, 2013, 02:26:02 AM
Beeneez is shipping my K12 capsule on Monday.  :) :)
Title: Re: Official C12 Clone - Build and Support Thread
Post by: EEMO1 on June 07, 2013, 06:00:23 AM

 anyone know where to buy those haufe t14 transformers? how much are they from haufe?


 just e-mail them?

Hi,

I have been in contact with Michaela from Haufe re this recently... Just be aware that they have a 120 euro minimum order, and weren't exactly forthcoming that one trafo is worth 43 euro pre tax. So it's obviously better to buy 2-3 at a time.

If you'd like her email, I'll PM it to you.

Matt


 sure! thanks!
Title: Re: Official C12 Clone - Build and Support Thread
Post by: kidvybes on June 07, 2013, 04:18:35 PM
Can someone confirm if the Carvin has a compatible psu?  I direct people to the Apex 460 because I know almost for certain that it comes from the same factory, but the Carvin unit has the tell-tale sign of being supplied by a different factory than Alctron (the dark red plastic pieces holding the tube as opposed to orange).  I am nearly certain I know who makes this mic and the psu should be just fine, but I'd really like to see a photo verification before directing customers who are needing to build immediately to the Carvin product as a suitable donor.

Matador built a prototype on an Apex 460, so we know for sure that one is good to go as a donor.

...Chung, from what I know, the older Apex 460, Carvin CTM100, and the Nady TCM 1150 had the red plastic tube mount supports, and the newer 460/Alctron are shipping with the orange, as are some Carvin...(you can see the older 460 here in comparison to the Telefunken M16:
http://recordinghacks.com/articles/telefunken-m16-and-apex-460-comparison/)
...I know the Nady originated from ShauiYin, as I suspect the Carvin does as well...certainly a confirmation of the PSU would be helpful to corroborate what I suspect (that these all originate from the same manufacturing source)...attached is a pic of the Carvin PSU I found on the net...I hope this helps...
Title: Re: Official C12 Clone - Build and Support Thread
Post by: kidvybes on June 07, 2013, 04:23:37 PM
Chung...and here is a pic of a newer Carvin with the orange parts...

...all of the accessories (case, mount, cables) appear to be identical to the Alctron as well...I only suggested this option as a stop-gap until your newer inventory arrives...I hope you understand...
Title: Re: Official C12 Clone - Build and Support Thread
Post by: chunger on June 07, 2013, 04:31:28 PM
The photos show pcb-mounted power transformers.  I wonder if that was an older style of construction because I have current ShuaiYin and Alctron PSU's, and they both use the same chassis-mounted configuration for the power transformer that our kit is designed around. 

It looks like you can totally build our kit on the older type pcb-mounted power supplies, you would just need to drill 2 holes and mount the power transformer to the chassis since our pcb does not have provision for mounting the transformer.  The chassis looks unchanged between the 2 versions.

I'm hoping someone who purchased the Carvin mic recently can take a photo of the psu internals and confirm.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: MicDaddy on June 07, 2013, 05:15:32 PM
In the White Market, Member Burdij's DIY General Store (Grove Audio) is selling
a complete Mic kit at a reduced price of $150.00
It is manufactured by Alctron and is their model HST-11a.

I just snagged one of these, thanks Winetree.  I'll post how it fits together once it all arrives.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: KMB-AUDIO on June 07, 2013, 06:13:48 PM
The photos show pcb-mounted power transformers.  I wonder if that was an older style of construction because I have current ShuaiYin and Alctron PSU's, and they both use the same chassis-mounted configuration for the power transformer that our kit is designed around. 

It looks like you can totally build our kit on the older type pcb-mounted power supplies, you would just need to drill 2 holes and mount the power transformer to the chassis since our pcb does not have provision for mounting the transformer.  The chassis looks unchanged between the 2 versions.

I'm hoping someone who purchased the Carvin mic recently can take a photo of the psu internals and confirm.

This was the same transformer configuration for the two TNC ACM1200 mics that I modded. I did exactly that, just drilled two holes to mount the transformer to the chassis.

http://www.groupdiy.com/index.php?topic=51377.msg661093#msg661093 (http://www.groupdiy.com/index.php?topic=51377.msg661093#msg661093)
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Dylan W on June 07, 2013, 08:25:23 PM
Recent Carvin PSU.

Title: Re: Official C12 Clone - Build and Support Thread
Post by: chunger on June 07, 2013, 11:21:35 PM
Looks like the current production Carvin psu is compatible as a donor.  I'll pass this along as well as the Grove Audio option.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: JessJackson on June 07, 2013, 11:39:11 PM
I edited your schematic to what I understand is the 251 modification. let me know if this is correct.

Title: Re: Official C12 Clone - Build and Support Thread
Post by: JessJackson on June 08, 2013, 01:05:02 PM
Moved my Elam conversation to its own thread

http://www.groupdiy.com/index.php?topic=52712.0
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Pip on June 08, 2013, 02:16:28 PM
Can someone confirm if the Carvin has a compatible psu?  I direct people to the Apex 460 because I know almost for certain that it comes from the same factory, but the Carvin unit has the tell-tale sign of being supplied by a different factory than Alctron (the dark red plastic pieces holding the tube as opposed to orange).  I am nearly certain I know who makes this mic and the psu should be just fine, but I'd really like to see a photo verification before directing customers who are needing to build immediately to the Carvin product as a suitable donor.

Matador built a prototype on an Apex 460, so we know for sure that one is good to go as a donor.

I built mine with this donor mic and PSU. Granted I had it for a few years so mine is older than the one they sell now but it doesn't mean different. Here are the differences between my build and Chungers:

- No difference in microphone at all. All differences relegated to PSU.
- Transformer in PSU mounted to PC board so had to drill and mount it to case.
- Power Transformer output lines reversed of those in Chungers build. No big deal just had to cross them over each other.
- I did have trouble as others did with my bias adjustment but it was an easy fix and I don't think tied to donor in any way.

More on this here: http://www.groupdiy.com/index.php?topic=51377.msg666445#msg666445
Title: Re: Official C12 Clone - Build and Support Thread
Post by: JessJackson on June 08, 2013, 10:24:10 PM
Moved my Elam conversation to its own thread

http://www.groupdiy.com/index.php?topic=52712.0
Title: Re: Official C12 Clone - Build and Support Thread
Post by: jrmintz on June 09, 2013, 10:55:06 AM
Just did a three-way test recording a 1965 Gibson Hummingbird with my C-12 clone, a KM-84, and a KM-56. Used a Daking preamp and LA-2A. They sound remarkably similar, but I think I preferred my C-12. Thanks, guys!
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Matador on June 09, 2013, 12:10:07 PM
I edited your schematic to what I understand is the 251 modification. let me know if this is correct.

That's all correct.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Biasrocks on June 09, 2013, 12:35:20 PM
Just did a three-way test recording a 1965 Gibson Hummingbird with my C-12 clone, a KM-84, and a KM-56. Used a Daking preamp and LA-2A. They sound remarkably similar, but I think I preferred my C-12. Thanks, guys!

Something must be broken, I find those mics to have very little in common, especially on a source like AGtr.

The difference between a KM-84 and even a 414EB is miles and miles IME.

What is the configuration of your C12?

Regards,
Mark
Title: Re: Official C12 Clone - Build and Support Thread
Post by: jrmintz on June 09, 2013, 09:30:45 PM
Nothing is broken. When I said remarkably similar I think I was really trying to say I was surprised at how good the C-12 clone sounds. They don't sound exactly alike, but rather in the same league.

It's a Peluso capsule I had lying around that I'll replace with one of Tim's, a GE 12AY7, and otherwise the stock kit.

Edit: Since it was working well, I decided to fix it. I put in a 1uF Auricap output cap and did the 251 mods with a 330pF polypropylene cap. I'll give it a try tomorrow and see how it sounds.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: jrmintz on June 10, 2013, 06:55:26 PM
When I first built the kit I did the 251 mods. The mic hissed and spit. I undid the mods and put it stock and it was fine. So I redid the mods and it was hissing and spitting again, so undid the mods again and now it's dead. Could the hissing and spitting have trashed the tube? Everything seems to be working okay, voltages are all right on, just no sound. It's possible I screwed up the capsule, I suppose, though I don't think so.

I had disconnected one backplate by accident. It's working now, though why it was unhappy with the 251 mods I don't know. There's also something weird going on between pro tools and my patch bay. I think it's time to take a nap....
Title: Re: Official C12 Clone - Build and Support Thread
Post by: JessJackson on June 11, 2013, 02:19:37 AM
When I first built the kit I did the 251 mods. The mic hissed and spit. I undid the mods and put it stock and it was fine. So I redid the mods and it was hissing and spitting again, so undid the mods again and now it's dead. Could the hissing and spitting have trashed the tube? Everything seems to be working okay, voltages are all right on, just no sound. It's possible I screwed up the capsule, I suppose, though I don't think so.

I had disconnected one backplate by accident. It's working now, though why it was unhappy with the 251 mods I don't know. There's also something weird going on between pro tools and my patch bay. I think it's time to take a nap....

lol, what exactly were your 251 mods? what values etc..
Title: Re: Official C12 Clone - Build and Support Thread
Post by: sr1200 on June 11, 2013, 11:40:07 AM
Quote
Mr. Warshaw writes:

The Telefunken ELA M 250/251 was made for Telefunken by AKG after Neumann discontinued its OEM production of the Telefunken U 47. Of course Neumann still made the U 47 for many years. Telefunken needed a quality condenser, and AKG stepped in.

The differences between the C 12 and the ELA M 250 are small but important. The C 12 is remotely controlled for pattern by polarizing the rear diaphragm with a separate variable voltage from the power supply, while the ELA M 250/251 has switches in the capsule assembly that change its polarization pattern. The 250 has two patterns, Omni and Cardioid. The 251 included these patterns and also the figure eight.

The second difference is in the circuit. The C 12 and ELA M 250 circuits are similar but not identical. They both use the CK 12 capsule, T/14 transformer and either the 6072A tube (US version) or the AC701 (Europe), but the grid coupling, cathode bias and capsule polarization are different.

Third, the body style of the C 12 and ELA M 250 are not the same. Most important, the head grilles are different, so acoustics are also different.

Found this floating around on the net.  Not sure if the suggested mod was correct based on this description.

Edit: got this too:
http://www.coutant.org/akgc12/elam250_2.jpg (http://www.coutant.org/akgc12/elam250_2.jpg) 250-251 schematic
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Matador on June 11, 2013, 03:38:19 PM
When I first built the kit I did the 251 mods. The mic hissed and spit. I undid the mods and put it stock and it was fine. So I redid the mods and it was hissing and spitting again, so undid the mods again and now it's dead. Could the hissing and spitting have trashed the tube? Everything seems to be working okay, voltages are all right on, just no sound. It's possible I screwed up the capsule, I suppose, though I don't think so.

I had disconnected one backplate by accident. It's working now, though why it was unhappy with the 251 mods I don't know. There's also something weird going on between pro tools and my patch bay. I think it's time to take a nap....

How did you guarantee that the tube boas voltage (sent through the cable and attaches to the "P4" node at the base of the mike) was forced to be ground?  Did you ground it in the mike?  At the PSU?
Title: Re: Official C12 Clone - Build and Support Thread
Post by: jrmintz on June 11, 2013, 04:21:42 PM

lol, what exactly were your 251 mods? what values etc..

I used a 1k82 1/4 watt metal film resistor in parallel with a 25uF 25VDC electrolytic cap for the cathode bypass with the positive end of the cap/resistor at TK1 and the negative end at the ground terminal just below it where the styrene cap is attached, and a 330pF 200V polypropylene cap bypassing the output cap just as in your picture.

Quote
How did you guarantee that the tube boas voltage (sent through the cable and attaches to the "P4" node at the base of the mike) was forced to be ground?  Did you ground it in the mike?  At the PSU?

I turned the bias pot in the psu all the way to the right and measured 0V. That's what I understood to be the 'recommended' way. Did I get that wrong? I checked for 0 V to ground, I didn't actually check for 0 ohms to ground.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Matador on June 11, 2013, 05:35:13 PM
Hard ground the tube grid right at the tube socket and see if the crackling goes away.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: jrmintz on June 12, 2013, 11:08:50 PM
I'm kind of liking the mic the way it is - I think I might wait for the dedicated 251 kit.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: tonycamp on June 13, 2013, 01:02:48 AM
I'm kind of liking the mic the way it is - I think I might wait for the dedicated 251 kit.

Hey!!! did i miss something??? Is there a ELA M251 kit in the works?

I'm with you mintz, I modded up my head basket acoustics a bit, it may not sound exactly like a C12(i wouldn't know, cause i've never worked with the real deal in person), but it sounds as nice as any mic i've ever worked with!!!
Title: Re: Official C12 Clone - Build and Support Thread
Post by: JessJackson on June 16, 2013, 04:53:58 AM
I'm kind of liking the mic the way it is - I think I might wait for the dedicated 251 kit.

Hey!!! did i miss something??? Is there a ELA M251 kit in the works?

I'm working on the pcb now.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: chunger on June 16, 2013, 07:57:40 AM
we've always anticipated doing the ELA version of this build.  It is possible to do so on the existing pcb and I may be wrong, but there are provisions for pattern switching at the mic a-la original ELA if you are handy and able to cleanly hack a physical switch into your donor body.  Unfortunately for our prototyping efforts, I am out of donor bodies right now.  I do have a spare Tim Campbell CT12 capsule designated for the build though.  So, I'll be getting back on the horse when those arrive hopefully next month.  Note: if you are going with the original polarizing scheme, you should make sure your capsule has the required isolated backplates.  Tim's CT12 does.  I am not sure if the Beesneez and Microphone-parts.com capsules have this.

As I am getting near the end of this run of mic pcb's, we may make some topology optimizations on the rev. 2 pcb and make the ELA build a bit more straight forward.  Of course, that would necessitate re-doing the instructional photo set for the C12 configuration also, but that's how the cookie crumbles.

So, yes, we plan to make an ELA-specific version available at some point, but the changes can be easily made to the existing pcb set without much fuss and the necessary alterations have been discussed verbally here and should be clear for the seasoned DIY'er.  We have not, however, had the time to build out prototypes and photo-document the process in detail.

After a few discussions with MAtador on the subject, we determined that the changes to go for the M251 build were trivial enough that an entirely new pcb set was not necessary.  Better to use the existing pcb or make minor modifications to it in the next batch of boards to better accomodate both build versions.

I'm kind of liking the mic the way it is - I think I might wait for the dedicated 251 kit.

Hey!!! did i miss something??? Is there a ELA M251 kit in the works?

I'm with you mintz, I modded up my head basket acoustics a bit, it may not sound exactly like a C12(i wouldn't know, cause i've never worked with the real deal in person), but it sounds as nice as any mic i've ever worked with!!!
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Matador on June 16, 2013, 11:47:24 PM
Here's an updated conversion schematic:

(http://www.musicalsparks.com/images/c12/c12_to_ela251_v2.jpg)

It's only 3 more components, with 3 removed (C13, C10, and R11 removed).  This particular version makes use of the PSU-based polarization mechanism (if you want to keep cardioid, figure-8, and omni selections) so no need for new holes in the mike housing.

This retains what I think are the essential aspects of the 25x design:  no gate coupling cap, a bypassed cathode resistor, and a plate cap to ground (100pF was the original value, but I think 470pF sounds a bit smoother).

And even better yet:  no new PCB is needed!  ;D

If you only want cardioid, you can remove even more parts:  remove R16 and C11, and just let the RC connection float (just like cardioid in a U47).
Title: Re: Official C12 Clone - Build and Support Thread
Post by: pmcorbett on June 17, 2013, 10:35:57 PM
Chunger/Matador....a hearty "Thank You" to you guys. After a little tinkering and some minor trouble shooting ( my first "real" DIY build)... got my mic up and running. This was a very satisfying build. This will most likely be the last bit of major modding for my poor old Apex 460. I'm really looking forward to hearing this mic evolve during it's breakin' in process. Thanks again. You guys do great work. ;D
Title: Re: Official C12 Clone - Build and Support Thread
Post by: drumminkiger on June 18, 2013, 04:47:56 PM
Pretty much done with these mic kits, and the one I have completed sounds amazing! I put in one of tims capsules and a nos GE from christian. The only thing I'm not happy with is the stock 7 pin connectors. For some reason I'm having trouble searching for this particular part on the site here even though I've seen that people have used them several times. I'm thinking the Amphenol 7 pin will do me just fine, can anyone tell me what the part is that they used with the set screw and all for inside the body? Also, what size drill bit did you need to use to bore it out? The pins in the stock style seem like they will break on me at some point when I really need them to work.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Pip on June 18, 2013, 09:35:58 PM
Pretty much done with these mic kits, and the one I have completed sounds amazing! I put in one of tims capsules and a nos GE from christian. The only thing I'm not happy with is the stock 7 pin connectors. For some reason I'm having trouble searching for this particular part on the site here even though I've seen that people have used them several times. I'm thinking the Amphenol 7 pin will do me just fine, can anyone tell me what the part is that they used with the set screw and all for inside the body? Also, what size drill bit did you need to use to bore it out? The pins in the stock style seem like they will break on me at some point when I really need them to work.

All 7 pin xlr are the same. Might try Binder connector. Boring that out ain't gonna be easy.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: drumminkiger on June 19, 2013, 04:09:18 PM


All 7 pin xlr are the same. Might try Binder connector. Boring that out ain't gonna be easy.

That's why I was thinking the amphenol connector, its a little smaller I hear and closer to the size of the xlr but with bigger pins. It's also supposed to have a set screw making it easier to mount.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: shabtek on June 20, 2013, 03:02:35 PM
are'nt the inserts interchangeable? switchcraft male cable mount xlr insert have swapped into other china mics
Title: Re: Official C12 Clone - Build and Support Thread
Post by: JessJackson on June 20, 2013, 03:30:58 PM
are'nt the inserts interchangeable? switchcraft male cable mount xlr insert have swapped into other china mics

Worked for mine, i just brought some switchcrafts.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Matador on June 20, 2013, 06:39:35 PM
I had been wondering if the Switchcraft 7-pin XLR inserts were the same size and would drop right in (Switchcraft part number QG7M to be exact).
Title: Re: Official C12 Clone - Build and Support Thread
Post by: HellfireStudios on June 20, 2013, 08:23:40 PM
In the Royer mod articles, he says that you need to sand or file off the positioning protrusion to make the Switchcraft jack insert fit. He is referring to the 5-pin jack, but the same should ring true for the 7-pin version.

-James-
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Melodeath00 on June 21, 2013, 04:47:11 PM
Does anyone have any new comments on the single layer headbasket ring/resonance?
Title: Re: Official C12 Clone - Build and Support Thread
Post by: srdigital on June 21, 2013, 11:49:03 PM
built one of these based off an apex 460... all voltages etc. are correctly adjusted, using microphone-parts rk-12 capsule and a tested 6072a tube. audio passes, however, there is a bad ground hum present. i have been unable to track it down... any ideas?
thanks
Title: Re: Official C12 Clone - Build and Support Thread
Post by: HellfireStudios on June 22, 2013, 09:14:14 AM
Does anyone have any new comments on the single layer headbasket ring/resonance?

Loctite Go2Glue has been working fine for me as a grill dampener. It dries to rubber-like consistency which does wonders for resonances. Put it all the way around the base ring and support struts, and you should be good to go.

-James-
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Winetree on June 24, 2013, 01:29:12 AM
I'm installing a Beesneez K-12 Capsule. It doesn't seem to have dual backplates
and has one wire coming off of the backplate.
Do I bridge FB and RB together and soldier the single backplate wire to the bridge?
Title: Re: Official C12 Clone - Build and Support Thread
Post by: sr1200 on June 24, 2013, 09:42:36 AM
Thats what i did.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Matador on June 24, 2013, 02:26:37 PM
built one of these based off an apex 460... all voltages etc. are correctly adjusted, using microphone-parts rk-12 capsule and a tested 6072a tube. audio passes, however, there is a bad ground hum present. i have been unable to track it down... any ideas?
thanks

Confirm you have a solid ground connection both to the shell of the mike and the headbacket.

I'm installing a Beesneez K-12 Capsule. It doesn't seem to have dual backplates
and has one wire coming off of the backplate.
Do I bridge FB and RB together and soldier the single backplate wire to the bridge?

Yes.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: pearldrum944 on June 24, 2013, 04:02:30 PM
Hi, I'm having an issue with my second apex 460 build.  My first one from last year works perfectly, I'm using the same parts on the new build, with a different tube.  The only other difference is that the capsule has 2 full backplate wires coming from it where as my first capsule (both from Dave Thomas) has a bracket on the capsule that merged to one wire to the PCB.  Both mics appear to be wired the same after double checking.

Here is the issue: both sides of the capsule sound the same on cardioid, muffled.  They sound as if you were speaking into the backside of my other mic, they sound muffled on figure-8 and omni as well.  The capsule wires also seem to be microphonic, they make a lot of noise when I tap on them while monitoring the mic.  Any ideas?  Thanks.

Edit:I added a backplate bridge at the capsule which didn't help.  It also seems that all of my voltages are the same between mics...I'll fully check this later tonight.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Matador on June 24, 2013, 07:27:34 PM
Hi, I'm having an issue with my second apex 460 build.  My first one from last year works perfectly, I'm using the same parts on the new build, with a different tube.  The only other difference is that the capsule has 2 full backplate wires coming from it where as my first capsule (both from Dave Thomas) has a bracket on the capsule that merged to one wire to the PCB.  Both mics appear to be wired the same after double checking.

Here is the issue: both sides of the capsule sound the same on cardioid, muffled.  They sound as if you were speaking into the backside of my other mic, they sound muffled on figure-8 and omni as well.  The capsule wires also seem to be microphonic, they make a lot of noise when I tap on them while monitoring the mic.  Any ideas?  Thanks.

Edit:I added a backplate bridge at the capsule which didn't help.  It also seems that all of my voltages are the same between mics...I'll fully check this later tonight.

This is Dave Thomas's C12-copy?  If memory serves it doesn't have isolated backplates.  That means that both wires need to go to FB and RB (one to each is fine):  the capsule itself will bridge them together.

From your description, it sounds like you have the polarization reversed:  e.g. the backplate thinks it's the front diaphragm.  Can you take some pictures and then label which wires are going to each connection?

I have some of these capsules I'll take a look for you.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: pearldrum944 on June 24, 2013, 09:26:56 PM
Hi, I'm having an issue with my second apex 460 build.  My first one from last year works perfectly, I'm using the same parts on the new build, with a different tube.  The only other difference is that the capsule has 2 full backplate wires coming from it where as my first capsule (both from Dave Thomas) has a bracket on the capsule that merged to one wire to the PCB.  Both mics appear to be wired the same after double checking.

Here is the issue: both sides of the capsule sound the same on cardioid, muffled.  They sound as if you were speaking into the backside of my other mic, they sound muffled on figure-8 and omni as well.  The capsule wires also seem to be microphonic, they make a lot of noise when I tap on them while monitoring the mic.  Any ideas?  Thanks.

Edit:I added a backplate bridge at the capsule which didn't help.  It also seems that all of my voltages are the same between mics...I'll fully check this later tonight.

This is Dave Thomas's C12-copy?  If memory serves it doesn't have isolated backplates.  That means that both wires need to go to FB and RB (one to each is fine):  the capsule itself will bridge them together.

From your description, it sounds like you have the polarization reversed:  e.g. the backplate thinks it's the front diaphragm.  Can you take some pictures and then label which wires are going to each connection?

I have some of these capsules I'll take a look for you.

Yes, these are the AK12 capsules from Dave Thomas.  I just swapped the capsule from my working mic to the body giving me trouble and I had the same issue...so I guess something is wacky on the PCB/tube connector.

Edit:it looks like I have 110v on tube pin 1 for the working mic, 63v for the non-working mic...  Any ideas?  I'm confused.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: drumminkiger on June 25, 2013, 04:54:32 AM
built one of these based off an apex 460... all voltages etc. are correctly adjusted, using microphone-parts rk-12 capsule and a tested 6072a tube. audio passes, however, there is a bad ground hum present. i have been unable to track it down... any ideas?
thanks

This may seems stupid, but when I first fired up my mic it did something kinda like yours, but I noticed that mine was especially bad near power cables, then I put on the outer casing tube of the mic and like magic it was gone. Then I remembered oh yeah, the mic body shields the electronics (and thought to myself, man, what an idiot!). Now, I'm sure that you were smarter than me, but if you haven't tracked it down yet, and you haven't fully assembled the mic yet, you might want to check it out. :)
Title: Re: Official C12 Clone - Build and Support Thread
Post by: sr1200 on June 25, 2013, 10:08:19 AM
Are you getting correct voltage at the power supply?
Title: Re: Official C12 Clone - Build and Support Thread
Post by: pearldrum944 on June 25, 2013, 10:16:35 AM
Are you getting correct voltage at the power supply?

Yes, I am.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: JessJackson on June 25, 2013, 04:19:03 PM
I think you have wrong resistor on plate, maybe 500k instead of 100k?
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Jaybird on June 26, 2013, 07:56:03 AM
Can't wait to build one of these, just waiting for the next run of donor mics to be in-stock at 939.. My question is: would it be possible to fit a small switch or jumper to select what side of the tube you are using? This can be hidden in the mic body since this is something you would not want to change while the mic is in use, if it's possible how would i do it?
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Reverend on June 26, 2013, 02:18:34 PM
I'm still not getting proper voltage readings from my PS.  On the 7 pin connector, I took out the wire ground bridge that went from the 7 to the 4 pin as per instructions (or as I read them), did I do the right thing. STUCK!
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Matador on June 26, 2013, 07:25:08 PM
I'm still not getting proper voltage readings from my PS.  On the 7 pin connector, I took out the wire ground bridge that went from the 7 to the 4 pin as per instructions (or as I read them), did I do the right thing. STUCK!

Yes that's right.

How are you measuring, what are you measuring, and what were the readings?
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Reverend on June 26, 2013, 09:04:04 PM
I'm a total newbie. I'm really not sure that I have my DMM on the right settings. I'm measuring the B+, GND, Polarity, etc. as pictured in Chunger's pics. Since I'm a newbie, and I've only got a couple of other builds (less complicated than this, but I've done PCB work, still), I was super, super careful to make sure that I populated the PS PCB exactly as necessary. Then, I double checked it. Then, I used my DMM to make sure that all of the connections were made. The only 2 things I'm thinking now are....I used too much heat and ruined a capacitor, or, I've got a bad transformer. I really, really soldered quick at about 300 degrees (or at least that's the setting on my Hakko). Wow. Hope I'm not in over my head here. Still having fun and I love a challenge. I even found another PS for an Apex 460, but it's older and different. I'm thinking now that I may try to fix what I have before getting that thing torn apart. For a newbie like me, getting this working will be monumental.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: scott_humphrey on June 27, 2013, 03:01:22 PM
Outstanding project and documentation! Well done, Matador!
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Gearsix on June 29, 2013, 01:16:59 AM
Hello,  someone knows if it is possible to use 390K Ohm resistors instead of 402K Ohm for the position pattern rotary switch in the power supply?
Title: Re: Official C12 Clone - Build and Support Thread
Post by: MicDaddy on June 29, 2013, 09:47:36 AM
My mic is having some weird behaviors while in Omni (it's possible that it is misbehaving elsewhere, but Omni is most obvious for me to observe)

While in Omni, the front diaphragm (FC) gets extremely 'thin' with insanely low output.  It sounds like a room mic far off in the distance.  The rear diaphragm (RC) gets extremely boomy, woofy, just a lot of low end and sounds muffled.  The difference between the two halves in Omni is not good.  They are supposed to be identical mics back to back, but unfortunately something is not playing right.

Last I verified PSU voltages as follows:
B+ 120V
Bias -1.1V
Heater 6.3V

Polar:
Omni 0V
Card ~60V
Fig 8 ~120V

These voltages are what I expected to see but the sounds are not what I expected to hear.

I've yet to swap the RC/FC connections and see if the problem follows the capsule or the amp circuit.

I've used a Beesneez K12, with a single back-plate connection to FB/RB which I've tied together at the PCB.

One thing that has me still puzzled, tonycamp pointed out on page ~3(?) a discrepancy for audio + & - regarding pins 5 & 6 on the 7 pin XLR.

On page 1 there is still a discrepancy.

See at reply #5:
"Next, because I foolishly disconnect the stock wiring, I need to re-solder the 3 pin xlr.

Pin 5 is audio -
Pin 6 is audio +
pin 7 is ground"


Scrolling a tad further down we find:
"And the wire leads on the 7 pin XLR trimmed to length, stripped, tinned, and installed.

Pin 1 = B+
Pin 2 = heater
Pin 3 = pattern
pin 4 = bias
pin 5 = audio +
pin 6 = audio -
pin 7 = ground"


Scrolling down further we find reply #7 saying:
"Before installing the transformer, do a quick test to verify which side is the capsule side and which side connects to the pcb and which side connects to the output XLR connector on pin 5 (-) and pin 6 (+)."

I'll have to back track and see if I have a (several) polarity flips going on but I don't suspect this would be the issue behind my polar switching observations.

Title: Re: Official C12 Clone - Build and Support Thread
Post by: MicDaddy on July 01, 2013, 05:09:50 PM
I swapped the connections at the pcb, RC & FC.  The only change being my formerly rear diaphragm is now the front diaphragm. 

The audible issues while in Omni follow the capsule.  Meaning, the side which sounded thin, still sounds thin.  The side which sounded woofy still sounds woofy.

I'll stick the stock capsule back in and see what happens.


Title: Re: Official C12 Clone - Build and Support Thread
Post by: Matador on July 01, 2013, 05:21:34 PM
So long as you use the combo of pin 5 and 6, the polarity doesn't matter much, and certainly wouldn't cause what you are hearing.

One thing that comes to mind:  some capsules I've seen place the backplates on a screw on the retaining ring, or actually connect to the diaphragm on the opposite side of the capsule.  I would ask for a terminal connection diagram from Beesneez for your capsule.

The reason I bring this up:  a muffled quiet sounding side is a sure bet that the polarization is reversed, and that the capsule is actually trying to pick up the sound coming from inside the chambers.  It's like if you flipped two cardioid mikes and pointed them inwards towards each other (to the center of the capsule!).  It makes a cardioid mike sound like the front is actually what you would hear from a properly wired mike on the "wrong" side (distant, muffled, dark, etc).

Use the stock capsule as a test, as the center-terminated capsule makes it very clear which connection belongs to each capsule side.

Hello,  someone knows if it is possible to use 390K Ohm resistors instead of 402K Ohm for the position pattern rotary switch in the power supply?

Yes this is no problem.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Gearsix on July 02, 2013, 12:11:21 PM
Thank you Matador
Title: Re: Official C12 Clone - Build and Support Thread
Post by: scott_humphrey on July 06, 2013, 05:30:31 PM
As I dive into this, I decided to search for a schematic of the C12 where the AC701K tube was used, but had no luck finding it. If anyone has this, could you please share?

The reason that I want to see it is that I want to experiment with using a 5840 tube (yes, I'm aware that it is not a direct substitute for the AC701K) in this circuit to take advantage of  the "fixed" biasing technique that was used here with the 6072a tube. I'm just curious to see how AKG approached it with the AC701K. If there is anyone who has played around with this please share your experience.

Thanks,
Scott
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Pip on July 06, 2013, 06:44:46 PM
Unless I am mistaken the C12 never had AC701. The  M251 did but only in europe.

http://www.coutant.org/akgc12/

http://www.saturn-sound.com/Curio's/elam_microphones.htm


http://mixonline.com/recording/applications/audio_microlution/

http://fr.audiofanzine.com/construction-de-micros-amplis-pr/forums/t.517913,ou-trouver-des-petites-capsules-pour-projets-diy,p.9.html

I do have to say I can't remember seeing one for the 251 with ac701 now that i think of it.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: scott_humphrey on July 06, 2013, 11:08:54 PM
Unless I am mistaken the C12 never had AC701. The  M251 did but only in europe.

Ah,   …well     (cough, cough)     …that would explain why I can't find it. Thanks.

Anyone have the schematic of the M251 with the AC701? Curious to know if it's cathode biased. Thanks in advance.

-Scott
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Pip on July 07, 2013, 01:21:25 AM
Well only to chime in with all the others who have the same understanding I now  do. I just installed my Tim Campbell Capsule and it is well worth the wait. It truly is a beautiful thing and Tim is an awesome guy you can just telll by the way he writes his emails.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: JessJackson on July 07, 2013, 07:32:53 AM
Unless I am mistaken the C12 never had AC701. The  M251 did but only in europe.

Ah,   …well     (cough, cough)     …that would explain why I can't find it. Thanks.

Anyone have the schematic of the M251 with the AC701? Curious to know if it's cathode biased. Thanks in advance.

-Scott

Title: Re: Official C12 Clone - Build and Support Thread
Post by: Woot on July 08, 2013, 12:46:12 AM
Well only to chime in with all the others who have the same understanding I now  do. I just installed my Tim Campbell Capsule and it is well worth the wait. It truly is a beautiful thing and Tim is an awesome guy you can just telll by the way he writes his emails.

Hey Pip,

Good to hear about the TC capsule, and congrats on the build. Did it take Tim long to reply to your emails? I emailed him about 4 weeks ago but no reply, and no luck on either phone number either. Any advice in contacting him would be appreciated.

Cheers,

Matt
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Pip on July 08, 2013, 12:56:31 AM
Well only to chime in with all the others who have the same understanding I now  do. I just installed my Tim Campbell Capsule and it is well worth the wait. It truly is a beautiful thing and Tim is an awesome guy you can just telll by the way he writes his emails.

Hey Pip,

Good to hear about the TC capsule, and congrats on the build. Did it take Tim long to reply to your emails? I emailed him about 4 weeks ago but no reply, and no luck on either phone number either. Any advice in contacting him would be appreciated.

Cheers,

Matt


Did you put in a request for a capsule. If so it takes about 8 to 10 weeks to get one. Basically all I did was email him saying I wanted one and then when it was ready he emailed me back. But it was at least 8 weeks between the two.

best
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Woot on July 08, 2013, 02:10:41 AM
Hey Pip,

Thanks. Yeah I wrote an email requesting a pair, asked about a deposit etc. I just presumed he'd write back a confirmatiOn email or whatnot.

So I suppose based on your experience I have a couple of capsules on the brew. Sweet

Regards,

Matt
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Gearsix on July 08, 2013, 02:05:01 PM
Hello, I have just realized the power supply but I can't obtain a B+ voltage higher then 105 Volt
I had no problems to regulate the heater and the bias voltages but as I want to use the original capsule that needs 200 Volt (I have read so in the first page of this thread) I need to increase the B+ voltage
I have read that if the B+ voltage is too low (can't be trimmed high enough) I can reduce R1 and R2 in value in the power supply
Someone can suggest to me the right values for these resistors?
Thank you in advance
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Matador on July 08, 2013, 03:09:59 PM
Hello, I have just realized the power supply but I can't obtain a B+ voltage higher then 105 Volt
I had no problems to regulate the heater and the bias voltages but as I want to use the original capsule that needs 200 Volt (I have read so in the first page of this thread) I need to increase the B+ voltage
I have read that if the B+ voltage is too low (can't be trimmed high enough) I can reduce R1 and R2 in value in the power supply
Someone can suggest to me the right values for these resistors?
Thank you in advance

No capsule should require a 200V B+.  120V should work with any capsule.

What is the adjustment range for B+ that you are seeing (between R4 dialed to minimum and R4 dialed to maximum)?  Of course this voltage also depends on a real load so test with the tube installed.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Gearsix on July 08, 2013, 03:27:41 PM
Hi Matador, I have made the regulations with a 180K Ohm resistor placed between B+ and ground
With R4 dialed to minimum I have 83 Volt
With R4 dialed to maximum I have 105 Volt
Title: Re: Official C12 Clone - Build and Support Thread
Post by: scott_humphrey on July 08, 2013, 05:56:52 PM
Hey Pip,

Thanks. Yeah I wrote an email requesting a pair, asked about a deposit etc. I just presumed he'd write back a confirmatiOn email or whatnot.

So I suppose based on your experience I have a couple of capsules on the brew. Sweet

Regards,

Matt
Well only to chime in with all the others who have the same understanding I now  do. I just installed my Tim Campbell Capsule and it is well worth the wait. It truly is a beautiful thing and Tim is an awesome guy you can just telll by the way he writes his emails.

Hey Pip,

Good to hear about the TC capsule, and congrats on the build. Did it take Tim long to reply to your emails? I emailed him about 4 weeks ago but no reply, and no luck on either phone number either. Any advice in contacting him would be appreciated.

Cheers,

Matt


Did you put in a request for a capsule. If so it takes about 8 to 10 weeks to get one. Basically all I did was email him saying I wanted one and then when it was ready he emailed me back. But it was at least 8 weeks between the two.

best

This was my experience as well. When your capsule is ready he sends an e-mail and requests a bank transfer--no PayPal, no credit card.

Buying a capsule from Tim Campbell reminds me of the Seinfeld Soup Nazi episode (http://youtu.be/uVqBzP0xdKk)...

…yes, it is worth the wait, but you must follow Tim's rules and not bug him, or it's, "NO CAPSULE FOR YOU!!!!"
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Woot on July 09, 2013, 01:51:55 AM
^^ ha ha good to know. Thanks for the heads up.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Gearsix on July 09, 2013, 02:49:50 PM
Any help? :)
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Matador on July 09, 2013, 04:51:59 PM
Hi Matador, I have made the regulations with a 180K Ohm resistor placed between B+ and ground
With R4 dialed to minimum I have 83 Volt
With R4 dialed to maximum I have 105 Volt

This seems odd.  Are you sure you stuffed a 100K resistor in for R4?  A 100K pot with 0.5mA test current should provide almost 50V of adjustment.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Pip on July 09, 2013, 11:32:34 PM
Quote

This was my experience as well. When your capsule is ready he sends an e-mail and requests a bank transfer--no PayPal, no credit card.

Buying a capsule from Tim Campbell reminds me of the Seinfeld Soup Nazi episode (http://youtu.be/uVqBzP0xdKk)...

…yes, it is worth the wait, but you must follow Tim's rules and not bug him, or it's, "NO CAPSULE FOR YOU!!!!"

 I believe he accepts paypal you just cover the fees and shipping. He also puts the tarriiffs if any on you.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Gearsix on July 10, 2013, 12:28:41 AM
Yes, the R4 trimmer is 100K Ohm and I have double checked all the components
May be influent that I use 220 Volt? (I think no, but ...)
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Matador on July 10, 2013, 01:54:03 AM
Yes, the R4 trimmer is 100K Ohm and I have double checked all the components
May be influent that I use 220 Volt? (I think no, but ...)

Maybe...what is the voltage after the diode rectifier (the point where R1 and C1 meet)?  What about the node where R1, R2, and C2 meet?
Title: Re: Official C12 Clone - Build and Support Thread
Post by: tonycamp on July 10, 2013, 02:52:00 AM
This was my experience as well. When your capsule is ready he sends an e-mail and requests a bank transfer--no PayPal, no credit card.

Buying a capsule from Tim Campbell reminds me of the Seinfeld Soup Nazi episode (http://youtu.be/uVqBzP0xdKk)...

…yes, it is worth the wait, but you must follow Tim's rules and not bug him, or it's, "NO CAPSULE FOR YOU!!!!"

Lmao!, tims capsules are silly good, i dialed in a couple builds with the stock capsules and was pretty impressed, then i actually wondered how much of a diff the ct12's would make? I installed them, and kapow! mind blown!
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Gearsix on July 10, 2013, 04:27:39 AM
Hi Matador,
in the point where R1 meets C1 I have 306 Volt, while in the point where R2 meets C2 I have 244 Volt
Thank you for your kindness  :)
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Tim Campbell on July 10, 2013, 05:10:53 AM
"This was my experience as well. When your capsule is ready he sends an e-mail and requests a bank transfer--no PayPal, no credit card.

Buying a capsule from Tim Campbell reminds me of the Seinfeld Soup Nazi episode (http://youtu.be/uVqBzP0xdKk)...

…yes, it is worth the wait, but you must follow Tim's rules and not bug him, or it's, "NO CAPSULE FOR YOU!!!!"

I am extremely busy and so slow to answer. There is currently a 10 week lead time on my capsules. I am never arbitrary or vindictive as to who receives a capsule from me and so find the comparison to Sienfeld's "soup nazi" to be unfair.

It can sometimes be hard to keep track of who I may or may not have contacted when people use alias' and their own name as well as multiple email addresses.

I accept PayPal.

"He also puts the tarriiffs if any on you." I impose no tarriffs on anyone. This is at the discretion of the country in which you live.

I am currently travelling with my family and will return to Denmark on th17th.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: scott_humphrey on July 10, 2013, 12:11:49 PM

I am extremely busy and so slow to answer. There is currently a 10 week lead time on my capsules. I am never arbitrary or vindictive as to who receives a capsule from me and so find the comparison to Sienfeld's "soup nazi" to be unfair.

It can sometimes be hard to keep track of who I may or may not have contacted when people use alias' and their own name as well as multiple email addresses.

I accept PayPal.

"He also puts the tarriiffs if any on you." I impose no tarriffs on anyone. This is at the discretion of the country in which you live.

I am currently travelling with my family and will return to Denmark on th17th.

Hi Tim,

This was meant to be in fun, and I apologize if you did not take it that way. I'm a big fan of your work, and I did not intend to offend.

We've all grown accustomed to visiting an online shop and placing an order with the click of a button. Then we instantly receive an email with a receipt, estimated shipping time, etc. With your product ordering is a little more complicated       …but that is fine. Like the Soup Nazi, you produce a product that is so good that people will put up with an unorthodox method of ordering. I don't mean this to be a complaint.

Best regards,
Scott

P.S. Please don't say "NO CAPSULE FOR YOU!!!" because I'd like to order another one in the future.  ;)
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Winetree on July 10, 2013, 01:48:33 PM
Quote
I am extremely busy and so slow to answer. There is currently a 10 week lead time on my capsules. I am never arbitrary or vindictive as to who receives a capsule from me and so find the comparison to Sienfeld's "soup nazi" to be unfair.

I e-mailed Tim Campbell on 3/5/2013 for capsules.
17 weeks without any response what so ever. What's up with that????
Robert Dire
Mediatalker
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Category 5 on July 10, 2013, 04:18:29 PM
Quote
I am extremely busy and so slow to answer. There is currently a 10 week lead time on my capsules. I am never arbitrary or vindictive as to who receives a capsule from me and so find the comparison to Sienfeld's "soup nazi" to be unfair.

I e-mailed Tim Campbell on 3/5/2013 for capsules.
17 weeks without any response what so ever. What's up with that????
Robert Dire
Mediatalker

Maybe you got missed or went to spam.  I emailed him a couple of times thinking I was being overlooked but he eventually got back to me to let me know I was on the list.  I think it did take about 6 weeks to get on the list, but such is the nature of things when there is insane demand for a product only one man can make.  At least we all know the wait and effort are worth it!

Remember, he doesn't just supply the DIY community (whose demand is high thanks to this project) but several manufacturers who require guaranteed product in order to keep their stock healthy.  I imagine our orders get filled when there is surplus or down time from supplying the likes of FLEA, etc.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Winetree on July 10, 2013, 04:32:08 PM
Quote
It can sometimes be hard to keep track of who I may or may not have contacted when people use alias' and their own name as well as multiple email addresses.

Tim,
Maybe this can help you with your records.
 Mediatalker Emailed 3/05/13,
                                3/14/13,
                                4/14/13       ( all from same Name and e-mail address )
                                5/08/13
                                5/15/13        ( check both of your email addresses for above dates )
                                  P.M.'d          ( Winetree-fourm name )
           
As of now I haven't had any response.


Title: Re: Official C12 Clone - Build and Support Thread
Post by: Matador on July 10, 2013, 05:33:17 PM
Hi Matador,
in the point where R1 meets C1 I have 306 Volt, while in the point where R2 meets C2 I have 244 Volt
Thank you for your kindness  :)

Ok so you are loosing 62V across 91K (R1):  this is 0.68mA.  Looks right on.

Another 62V will be lost across R2 which leaves 182V before the pot.  With R4 at max 100K, this should drop another 68V MAX when dialed to maximum resistance.  This should mean B+ should be at minimum 114V.  Decreasing R4 should be raising it from there.

A 180K load resistor sinks 0.5mA at 100V, and the B+ bleeder R6 should leak away 0.2mA, so this all seems to add up to the current through R1. 

Either:

1) R2 isn't the right value
2) The pot you got for R4 is much higher in value than expected

If you don't care about why it's off, you need about 30V more at a draw of 0.68mA, which is the same as taking a total of 44K away.  Take 22K equally from both R1 and R2.  A 68K for each should work to bring B+ back up to where it should be.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Gearsix on July 11, 2013, 02:25:56 AM
Hi Matador,
I have verified R2 and R4, but they are of the right value
Anyway, as you suggested to me I have replaced R1 and R2 with 68K Ohm resistors, and now I have 117 Volt (with the 180K Ohm resistor placed between B+ and gnd)
From another side I have completed to rebuild the microphone that works perfectly (no noise or other problems)
Do you think it is necessary a further reduction in the R1 and R2 value to obtain 120 Volt?
Thank you
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Woot on July 11, 2013, 07:54:43 AM
I am currently travelling with my family and will return to Denmark on th17th.

Hi Tim,

Thanks for clearing a few things up. I look forward to sometime getting my hands on a couple of your capsules, and echo everyones thanks for this service.

Matt
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Tim Campbell on July 11, 2013, 09:23:06 AM
Robert, I have you on my list for 3 capsules from the 6th of May. I have no idea why you didn't receive my response. My email is unix based and sometimes spam filters kick my mails to the receiver's trash.

Title: Re: Official C12 Clone - Build and Support Thread
Post by: Matador on July 11, 2013, 01:59:35 PM
Hi Matador,
I have verified R2 and R4, but they are of the right value
Anyway, as you suggested to me I have replaced R1 and R2 with 68K Ohm resistors, and now I have 117 Volt (with the 180K Ohm resistor placed between B+ and gnd)
From another side I have completed to rebuild the microphone that works perfectly (no noise or other problems)
Do you think it is necessary a further reduction in the R1 and R2 value to obtain 120 Volt?
Thank you

So 44K less and only an increase of 10V implies a different current than before.  Something odd is happening:  the math isn't working out.

How does the mike sound?  The tube wont care about 117V (it is fine) but the adjustment range seems wrong to me.  I'm beginning to suspect you might have a leaky filter cap (C1 through C4).  Are you also sure C5 is installed the correct way?

Just to confirm:  you are planning on using a 6072A tube?
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Gearsix on July 11, 2013, 04:33:04 PM
Hi Matador,
The capacitors are all in the correct way ... I have just verfied them and they are all ok
Yes, I am using a tube Electro Harmonix 6072A, and the mike seems to work good (but I have not the possibility to compare it with another one)
Title: Re: Official C12 Clone - Build and Support Thread
Post by: tskguy on July 21, 2013, 11:03:02 AM
Hi all,

I had the good fortune of finishing one of these kits, let me just say its a pleasure to assemble and it sounds fantastic!!! A big thanks to Matador and Chunger! Here are a few sound clips. I honestly have never heard an original before so please let me know what you guys think. The capsule in this mic is something I have been working on. I welcome any feedback!!

  https://www.dropbox.com/s/wytabw7qsf7eolf/C12%20ACG.wav
https://www.dropbox.com/s/4i4jinh73hcy9dm/C12%20Vox%206inch.wav

Title: Re: Official C12 Clone - Build and Support Thread
Post by: kcstudiohk on July 22, 2013, 08:16:33 AM
I finish my kit few days ago , with RK12~
fantastic sounding !
thanks all for supporting this project !
Title: Re: Official C12 Clone - Build and Support Thread
Post by: warrenwarren on July 22, 2013, 11:24:53 PM
Hi all,

So I just finished the PSU.  But with a 180k resistor, I can only get B+ to be around 132V~133V.  Any ideas?

Thanks!
Warren
Title: Re: Official C12 Clone - Build and Support Thread
Post by: chunger on July 22, 2013, 11:42:46 PM
Hi all,

So I just finished the PSU.  But with a 180k resistor, I can only get B+ to be around 132V~133V.  Any ideas?

Thanks!
Warren

Most likely you have the trimmer pots switched up.  If you are only getting ~1V of adjustment range, you likely have the bias adjustment trimmer installed in the B+ trimmer location.  This issue has appeared before in this thread.

Please verify correct values/locations for 3 trimmers (All 3 are different values) and it doesn't hurt to verify values/location of the 3 small capacitors as well.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: warrenwarren on July 24, 2013, 04:15:37 PM
Thanks Chunger, that was it.  Mixed up one of the trimmer pots
Title: Re: Official C12 Clone - Build and Support Thread
Post by: taffer on August 09, 2013, 08:48:00 AM
Hi

At first, forgive my English .... I do not speak well and "Google translate" is my best friend!  :-[

I built  the C12 clone. I set the Bias at -1V, the heater at 6.3 V, and the B+ at 120 V.
Everything seemed to work fine except when I plugged my microphone on the microphone preamp.
Here, no sound! And when I hit the slightly the headbascket I hear loud and bad noises  (Creeesshhhh ! : This is the sound of the bad noise !!!!  ;D )
I tested the connections ... It looks good ....
For testing, I used the capsule of my APEX 460 (donor body) and before the build, I tested the APEX 460 and the capsule was working fine ...

I do not know what to do ... Do you know this problem?
What are all the tests to do??
and besides, I do not know much about electronics ....
HELP!!

Title: Re: Official C12 Clone - Build and Support Thread
Post by: taffer on August 10, 2013, 06:27:35 PM
Well, I found my problem !  :)
It was a wiring error of the capsule !
The wiring of the Blackplate was not good.
The rear Blackplate was wired with the front capsule !  :-[
Heu.... Sorry...  :-[
 :)
Title: Re: Official C12 Clone - Build and Support Thread
Post by: ajemutt on August 18, 2013, 03:36:10 AM
Heya everyone,

A bit of a n00b here. First time building a mic for sure.

I'm using a Carvin donor body (chassis mounted transformer, BTW)

I've got most everything populated and cleaned up, and I'm in the process of putting the PSU together, but I think I'm completely turned around on the XLR 7 wiring to the PSU PCB.

A few questions:

A: Is pin 7 on the PSU XLR just a ground to the chassis, or should there be a wire from it (in the build guide photo, there looks like a brown wire coming from that pin, but it's hard for me to see clearly)

B: Are P6,P3,P4,P8,P5 on the X1 terminal block supposed to line up with the XLR7 pin #'s? (P8 has me stumped for instance) I've looked over the guide a few times, but am not finding any other info on how correspond pins to block. Am I missing something obvious?  ::)

B1: It seems like if there was a hi res image of an unpopulated PSU board, I might be able to sort that out. Is there a link to such an image?

C: There are 2 ground points on the PSU PCB that appear to be unused in the build guide. , 1 below the 9.5V terminal block, and the other between C7&C8. are they in fact not used?

D: The XLR connectors that came with my donor mic were a bit toasted with terrible soldering. I'd like to replace them, but they appear to be of a switchcraft style, but with Neutrik(ish) markings, and dimensions that don't quite match either. Is there a source for these exact connectors, or should I just get new ones and re-drill the case?


Thanks!
Title: Re: Official C12 Clone - Build and Support Thread
Post by: chunger on August 21, 2013, 06:36:14 PM

B: Are P6,P3,P4,P8,P5 on the X1 terminal block supposed to line up with the XLR7 pin #'s? (P8 has me stumped for instance) I've looked over the guide a few times, but am not finding any other info on how correspond pins to block. Am I missing something obvious?  ::)


For question B, please refer to the legend screen printed on the PCB describing the function of each terminal.  Different builders and studios will choose to configure their pinouts differently.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Matador on August 21, 2013, 10:57:50 PM
A: pin7 transmits PSU ground to the mike.  The shield tab is tied to this point as well (I never liked this to be honest, as ground is ground and shield is shield, and don't need to be the same).  So yes, P7 comes from the ground plane on the PCB, and is also tied to the XLR shield, which is tied to the chassis via the XLR mounting screw.

B: no, that numbering is the AKG signal naming convention.  Follow Chunger's guide, or define your own standard, just make sure the PSU and mike are the same.

C:just there in case one needs a way to ground the PCB to the chassis.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: ajemutt on August 22, 2013, 09:46:19 PM
Ahh.. trace the wires back to the mic PCB, that's the obvious thing I was missing.

Thanks gents, I appreciate it!


Title: Re: Official C12 Clone - Build and Support Thread
Post by: maq3396 on August 24, 2013, 03:28:00 PM
Happy Saturday!

When the new donor microphone kits become available from Chunger, will this have an impact on the pcb and electronics package that has been prepared for this build?

Just trying to plan.

Thanks
Mac
Title: Re: Official C12 Clone - Build and Support Thread
Post by: chunger on August 24, 2013, 04:19:48 PM
Happy Saturday!

When the new donor microphone kits become available from Chunger, will this have an impact on the pcb and electronics package that has been prepared for this build?

Just trying to plan.

Thanks
Mac

The cargo has landed and is in process of clearing customs.  I should have them in my hands in a week.  This will probably have an impact on electronics packages, and there may be brief shortages, but I am well stocked at this time with electronic components (have parts for >60 kits on hand).  I know a lot of people have been waiting until bodies are available to order their kits.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: cariocaman85 on August 26, 2013, 03:11:48 PM
Hi everyone!

We finish our first C12 with the TC12 capsule and it sounds really great, no hiss at all and good sound!

But I noticed the ring that some of you describe, around 340hz, and I wonder if these tapes might fit with the headbasket:

Butyl tape (translucid) or Terostat tape (white / grey).

I've already got them both, but I want to be absolutly sure that the chemical composition of the tape is not gonna destroy the precious capsule. I've read some post mentionning that probability.

Is the tape supposed to be fixed all around the ring, beetween the mesh and the inside metal ring?

Regarding all this which one could be the best?

 Thanks for your replies,

Rémi

PS on september 10 I will record a piano with 2 of this C12, and post samples as soon as possible!  ;)
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Winetree on August 28, 2013, 02:30:29 AM
E-mailed Tim Campbell on 3/5/13 to get on the list. On 7/11/13 (reply #538) got first and only response.
Quote
Robert, I have you on my list for 3 capsules from the 6th of May. I have no idea why you didn't receive my response. My email is unix based and sometimes spam filters kick my mails to the receiver's trash.
It's been 25 weeks since first contact, 16 weeks on the list.
Quote
Quote
I am extremely busy and so slow to answer. There is currently a 10 week lead time on my capsules.
I check my e-mail everyday. Still waiting.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Category 5 on August 28, 2013, 08:06:35 AM
Wine tree.  I recently had some correspondence from Tim and he is behind on these orders.  He is being used for a lot of oems now and that is making it tougher to supply capsules to the DIY community.  If you are on the list I'm sure you'll get your capsules.  For me the expected lead time doubled so you're not the only one.  Maybe some rk12s can hold you over.

Despite the lead time, Tim makes these avaiable to us for a great price and I for one hope he keeps that up.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Tim Campbell on August 28, 2013, 03:53:39 PM
Robert, when was the last time you contacted me to inquire about your capsules?
I'm finding it hard to locate your email since it seems to have no connection to Winetree or Robert Dire.
If you had asked I would have told you that there are still 17 capsules in front of yours ( not counting my oem customers).
I'm very sorry that you're frustrated by the wait. I make my capsules by hand, completely by myself and have a high demand currently that makes estimating lead times very hard.
There are other capsules available with much shorter lead times.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Spencerleehorton on August 29, 2013, 03:19:37 AM
HI All,

My matador C12 has some bubbly noises and very low output?
I have used an AKG 10:1 transformer and also have a 5:1 which i can use if needed.
Also im using the microphone parts CK-12 for capsule and worked fine in the Apex 460 i have.
Was really excited to compare the C12 to the Apex 460 but as it stands its obviously not working right!
will check all voltages and connections, but any advice as to wear to fault find would be great.

regards

Spence.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Melodeath00 on August 29, 2013, 11:03:01 AM
Hi everyone!

We finish our first C12 with the TC12 capsule and it sounds really great, no hiss at all and good sound!

But I noticed the ring that some of you describe, around 340hz, and I wonder if these tapes might fit with the headbasket:

Butyl tape (translucid) or Terostat tape (white / grey).

I've already got them both, but I want to be absolutly sure that the chemical composition of the tape is not gonna destroy the precious capsule. I've read some post mentionning that probability.

Is the tape supposed to be fixed all around the ring, beetween the mesh and the inside metal ring?

Regarding all this which one could be the best?

 Thanks for your replies,

Rémi

PS on september 10 I will record a piano with 2 of this C12, and post samples as soon as possible!  ;)

Do you have a clip to share where that 340Hz ring is present? It worries me a bit about this kit.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: HellfireStudios on August 29, 2013, 12:31:53 PM
I used Loctite Go2 Glue on my single layer headbasket from Chunger, and it did the trick. Check out my earlier posts on the subject for more details about the glue and how where to apply it. I noticed one person had a hard time finding it. I found it in both Target and Wal-Mart chains (usually in their "hardware" sections).
I realize after reviewing this post that it may look like I own loctite. I am in no way affiliated with them. I just like most of their adhesives.

-James-

BTW, here is the finished mic. Sorry it took so long to get a pic up here.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Melodeath00 on August 29, 2013, 01:10:30 PM
Thanks for posting. The ring is completely gone?
Title: Re: Official C12 Clone - Build and Support Thread
Post by: HellfireStudios on August 29, 2013, 02:09:11 PM
Yeah. I just get a dull thud like tapping the other metal parts of the mic. Just make sure you only do one side of the support ring at a time.
I recommend laying the head basket on its side with supports to keep it from moving, and applying the glue to back of the rail that is facing down. Use a toothpick to push the glue between the holes in the mesh making sure the glue makes contact with the rail. In 30 minutes, rotate the headbasket, and repeat. Next, comes the base ring. Add plenty of glue here to really dampen things. BTW, painter's tape will save you a lot of cleanup later. Let the glue fully cure before reattaching to the mic. If it still rings, add more glue.

-James-
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Spencerleehorton on August 30, 2013, 11:58:34 AM
HI All,

having some bubble ans swooshing noises on my build:

voltages on tube are: 1=53.5v, pin 4=6.24v all others are 0v

voltages on r16 = 38v, 1000j/630v = 1.855v

for both 250m resistors i have used a 200mb + 68M is this ok to get away with?

1uf = 54.1v
r17 100k = 93.4v left leg 53.5v right leg
the lower 250m (268m) 1.929v right leg 45.7v

im not quite sure i have the capsule wired in correctly?

fb =  side
rb = side
fc = front edge
rc = rear edge

and i have connected both side connection together, hope thats right?

any help would be great.

regards

Spence.

Title: Re: Official C12 Clone - Build and Support Thread
Post by: Matador on August 30, 2013, 12:51:24 PM
Looks pretty close.  B+ is low:  should be 120V, but with 93 that's about 45V polarization voltage which means you'll loose 6-10dB off sensitivity.  Would cause what you are describing though.

Pops are fizzy sounds sound like leakage currents to me:  how well did you scrub the area around the telfon standoff's with IPA before you finished everything?
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Spencerleehorton on August 30, 2013, 02:18:28 PM
hi,

i will clean thoroughly and put back together and was gonna put a different connector on there as well.

regards

Spence.
 
Title: Re: Official C12 Clone - Build and Support Thread
Post by: chrispsound on August 30, 2013, 05:40:21 PM
I would like to build Matadors C12 power supply PCB into another enclosure and have a power transformer whose secondary HT winding is rated at [email protected] and 12V 1A on the 2ndd secondary winding.  I know the microphone draws around 1mA (Not including the heaters) so the 10mA spec on the transformers HT winding should not be a problem.  My question is, does having 4 R-C filtering stages effect the power transformers VA limit?  Should one consider getting a transformer that has a higher VA rating if there are a large number of passive filtering stages, or does it not matter?  Thanks, ChrisP
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Matador on August 30, 2013, 06:13:10 PM
In short, it doesn't matter.

The 1mA current flows through the filters.  There is no DC path to ground through the filter caps.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: scott_humphrey on August 30, 2013, 11:51:10 PM
I finished one of these with a Cinemag CM-2480 xformer and Tim Campbell capsule. It sounds GREAT! Worked without a hitch on first power up!

Here's a tip for anyone who might want to improve the build. You can purchase a staking tool to attach the turrets to the board here:

http://www.turretboards.com

Click on the "turret tools" link, and choose the "desktop staking tools kit."

OK, now it's time to build a second one….

THANK YOU, MATADOR!
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Spencerleehorton on August 31, 2013, 03:19:46 AM
Hi All,

pardon my ignorance but what are the teflon stand offs?

Pops are fizzy sounds sound like leakage currents to me:  how well did you scrub the area around the telfon standoff's with IPA before you finished everything?

regards

Spence.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Spencerleehorton on August 31, 2013, 10:32:35 AM
Hi,

to say im a little confused is a small understatement!! maybe having a bad day but here goes!

the labelling im finding very confusing and cant get my head around how to wire up the psu to the mic:

on the psu i have the following to the 7 pin XLR

pin 1 = p5
pin 2 = p8
pin 3 = p3
pin 4 = p4
pin 5 = to pin 3 on XLR output
pin 6 = to pin 2 on XLR output
pin 7 = p6

on the mic pcb i have the following:

pin 1 = p5
pin 2 = p8
pin 3 = p3
pin 4 = p4
pin 5 = transformer +
pin 6 = transformer -
pin 7 = p6

is this correct?

regards

Spence.

Title: Re: Official C12 Clone - Build and Support Thread
Post by: Pip on August 31, 2013, 11:11:06 PM
Hi,

to say im a little confused is a small understatement!! maybe having a bad day but here goes!

the labelling im finding very confusing and cant get my head around how to wire up the psu to the mic:

on the psu i have the following to the 7 pin XLR

pin 1 = p5
pin 2 = p8
pin 3 = p3
pin 4 = p4
pin 5 = to pin 3 on XLR output
pin 6 = to pin 2 on XLR output
pin 7 = p6

on the mic pcb i have the following:

pin 1 = p5
pin 2 = p8
pin 3 = p3
pin 4 = p4
pin 5 = transformer +
pin 6 = transformer -
pin 7 = p6

is this correct?

regards

Spence.

Yes except for audio outs pin 3 should be audio (-) pin 2 audio (+) as per 3 pin XLR audio standard. So just reverse your connections on PSU 3 pin XLR. It is mis-stated in Chungers wonderful build thread.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Pip on August 31, 2013, 11:13:27 PM
Hi All,

pardon my ignorance but what are the teflon stand offs?

Pops are fizzy sounds sound like leakage currents to me:  how well did you scrub the area around the telfon standoff's with IPA before you finished everything?

regards

Spence.

The teflon covered pins you should use for the capsule connections see Chungers build thread.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Pip on August 31, 2013, 11:24:28 PM
So today I changed the Phillips JAN 6072 Tube that I used for the build to a GE 5 star 6072. Big difference. The output went down a bit but so did the annoying sibilant high end.

I am using Mr. Campbells capsule and it was sounding good but now I think it sounds better. A friend of mine is using it in his studio which is very busy right now. It was getting good reviews with the original tube on everything except vocals. It was to sibilant. Stay tuned I will report back.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Spencerleehorton on September 01, 2013, 01:53:33 AM
hi pip,

so just to be 100% clear, this is the correct way to wire the psu 7 pin connector and the mic 7 pin connector:

pin 1 = p5
pin 2 = p3
pin 3 = p8
pin 4 = p4
pin 5 = to pin 3 on XLR output
pin 6 = to pin 2 on XLR output
pin 7 = p6

is this ok?


regards

Spence.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Matador on September 01, 2013, 02:15:53 AM
Just to be clear, you are free to assign your own mapping from signals to wires on the XLR.  What matters most is that you are consistent between the mike PCB and the PSU.

The mapping shown will work fine.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Spencerleehorton on September 01, 2013, 02:21:21 AM
hi matador,

ok thats great thanks, one other thing was that i didnt use teflon stand offs, i used the same bits i used for mounting the resistors and caps, will this be problem?
they are soldered in on the bottom of the board on chungers thread, but are they not ment to be soldered in on the top side?

regards

SPence.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Spencerleehorton on September 01, 2013, 04:31:33 AM
hi all,

have wired back up and seem to be getting much better S/N now, all crackles and bubbles gone, first turned on and got them but they went after about 2 minutes (tube burning in maybe?)
only getting 90v on B+?  and adjusting B+ doesnt do anything? getting correct voltages everywhere else.
Also i suspect i have the wrong ratio transformer in there as i tested the ohms and it was 68ohm and 1428ohm pri/sec on my turns calculator this puts it at 5:1 ratio?
have plugged in and get a very trebly low signal?

getting there now but still a few hurdles!!!

regards

Spence.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Matador on September 01, 2013, 05:17:07 PM
It should be a step down - the higher impedance side should be the primary.

You should have 40-50v adjustment on B+.  I suspect you have the low ohms pot in the incorrect place (the B+ trimmer should be 100K, or read 104 on top).
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Toure14 on September 01, 2013, 08:01:43 PM
I used Loctite Go2 Glue on my single layer headbasket from Chunger, and it did the trick. Check out my earlier posts on the subject for more details about the glue and how where to apply it. I noticed one person had a hard time finding it. I found it in both Target and Wal-Mart chains (usually in their "hardware" sections).
I realize after reviewing this post that it may look like I own loctite. I am in no way affiliated with them. I just like most of their adhesives.

-James-

BTW, here is the finished mic. Sorry it took so long to get a pic up here.

Where did you get the nice badge made for the mic?
Title: Re: Official C12 Clone - Build and Support Thread
Post by: chunger on September 01, 2013, 09:15:20 PM
The recommendation to glue along the edge of the mesh where it meets the base plate is good.  The next production batch of headbaskets will be glued at the factory to eliminatebthe resonance.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: HellfireStudios on September 02, 2013, 12:25:58 AM
I used Loctite Go2 Glue on my single layer headbasket from Chunger, and it did the trick. Check out my earlier posts on the subject for more details about the glue and how where to apply it. I noticed one person had a hard time finding it. I found it in both Target and Wal-Mart chains (usually in their "hardware" sections).
I realize after reviewing this post that it may look like I own loctite. I am in no way affiliated with them. I just like most of their adhesives.

-James-

BTW, here is the finished mic. Sorry it took so long to get a pic up here.

Where did you get the nice badge made for the mic?
I actually obtained this particular emblem from a knife set. It was attached to the knife caddy. I've been on the lookout for badges ever since I started modifying and building my own mics. Surplus military medals, metal clothing/craft buttons, and even the gems off of a vodka bottle have served me well as mic badges.
Most of them need modification of some sort. A dremel will do wonders when it comes to flattening the backs and/or modifying the shape of the badges.
When trying to bend the badges to the rounded shape of the mic, use a smaller diameter pipe than the mic you intend to attach it to (this will compensate for metal's tendency to flex out when the clamp is removed). Then, use a hose clamp wrapped around the smaller pipe (covered in tape to protect the badge), to apply even and consistent pressure to the badge, while using a wooden mallet to shape the piece. I recommend tightening the clamp after every whack of the mallet. Loctite heavy duty construction adhesive has worked well for me as a method of attaching the badges to the mic. If your mic is painted, make sure you sand away a little paint behind the badge to allow the glue something to bond to. Roughing up the surface of the mic under the badge location is a good idea whether the mic is painted, plated, or unfinished to help the glue adhere.

-James-
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Spencerleehorton on September 02, 2013, 01:01:06 AM
Hi Matador,

I am testing these AKG transformers today with scope as they are ment to be 10:1, they have 4 wires each side, i have a ratio calculator and one winding measures 32ohms and the other the same, on the other side one is 720ohms and the other is 720ohms, so i can use one side in parallel and the other in series to get the highest ratio of the transformer but when i put the ohms into the ratio calculator it only says about 7:1 with this config? i have been told not to rely on this calculator and use test tone with scope to be sure.
Will check 100k trim is correct but im pretty sure the 100k trim works fine when mic not plugged in? i was getting 135v without mic plugged in and could adjust voltage but will double check this and get back to you.

regards

Spence.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Spencerleehorton on September 02, 2013, 06:54:30 AM
Hi Matador,

have check the PSU and 100k is correct, has 104 on top, when mic not plugged in 100k has no effect?
When mic plugged in after a couple of minutes it sits around 92v.
All other voltages seem fine.
Which way is the transformer wired cause it was said before its used as a step down so would the higher ohm connect to the mic pcb (10 ratio) and the smaller ohm ((1 ratio) connect to the 7 pin XLR?
I thought ive tried it both ways but im pretty sure i got the config of the transformer completely wrong, i now get the correct ratio at least.
Just need to confirm correct way its wired.
Should i take out the 100k and replace it to see if that sorts it?

regards

Spence.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Spencerleehorton on September 02, 2013, 07:51:50 AM
HI Matador,

Have just tried transformer with the higher ohms(1450) to pins 5/6 on the 7 pin connector much less audio this way.
with the low ohms on pins 5/6 it did pass audio but still very very low?
any ideas what to do next?

regards

Spence.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Matador on September 03, 2013, 01:18:53 AM
If you try to use it as a step-up the loading will kill all of the signal.  The mike PCB side should be the higher DCR side (you want it to step-down).

It's perplexing that with the mike installed and drawing current, that B+ isn't adjustable.  Even with no microphone plugged in, the current through R6 should be enough to at least show an adjustment range through R4.

Just to be clear:  you are saying it's 92V always, no matter how the B+ pot (R4) is adjusted?
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Spencerleehorton on September 03, 2013, 01:42:51 AM
HI Matador,

Yes once it comes up and settles it stays at 92v and the 100k doesnt do anything, bias and heater work fine?

regards

Spence.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Matador on September 03, 2013, 10:49:34 AM
Ok, let's try the resistor trick:  remove the mike, and connect a 180K resistor between the B+ line and the ground line.  You can stick it right into the output 7-pin XLR jack right on the psu.

For safety, do it in this order:  stick a bare resistor into the B+ line, then bend the resistor and stick the other end into the ground line.  Then fire it up, and see if the B+ is adjustable.  You should be able to adjust B+ up and down to a 50V or so adjustment range.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Spencerleehorton on September 03, 2013, 12:27:44 PM
Hi Matador,

so just to make sure your saying:

connect a 180k resistor in the psu on the 7 pin xlr to pins 1 & to pin 7 then adjust the 100k?

regards

Spence.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Matador on September 03, 2013, 05:39:48 PM
Yes, but only if that pin definition is what you used. ;)

To be more clear, you want the resistance between the "P5" node (that comes from pin #1 of the 5-pin connector block), and the "P6" node (that comes from pin #5 of the 5-pin connector block).  If you wired P5 to pin#1 on the XLR, and P6 to pin#7 on the XLR, then yes, that's where you want the resistor.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Spencerleehorton on September 03, 2013, 08:44:53 PM
Hi Matador,

yes thats how ive wired it, will do it in the morning and let you know.

regards

Spence.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Spencerleehorton on September 04, 2013, 04:53:57 AM
Hi Matador,

Put 180k resistor in powered up attached gnd from MM used hot onto B+side of resistor get 92.6v then tried adjusting voltage and nothing happens either way?
Dead pot?
I'm flumexed!!!

you know whats happening?

regards

Spence.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Spencerleehorton on September 04, 2013, 02:26:10 PM
HI Matador,

took out the 100k pot and and put in a new one, cleaned everything with Alcohol and new 100k pot works but i only get 94.5v and when i wind the pot down it only goes down to 77v.
Mic works nice now though, but would like to get the correct voltage going.

regards

Spence.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: chunger on September 04, 2013, 06:54:40 PM
Are you trimmer pots in the correct positions?  Switching these up is a very common build error.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Spencerleehorton on September 04, 2013, 11:48:37 PM
Hi Matador,

the problem i was having with the low output was the transformer, i changed it and hey presto, im pretty sure all the trimmer pots are correct now, how critical are the 392R resistors? or what part of the circuit would limit the voltage supply to the 100k pot?
regards

Spence.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Matador on September 05, 2013, 04:01:38 PM
Hi Matador,

the problem i was having with the low output was the transformer, i changed it and hey presto, im pretty sure all the trimmer pots are correct now, how critical are the 392R resistors? or what part of the circuit would limit the voltage supply to the 100k pot?
regards

Spence.

Critical as in exactly 392 ohms?  Critical as in do you need them at all?  ;)

The 392R sets the divider ratio for the heater supply.  Since there is a heater adjust pot it can be off by 10% and it doesn't matter much.

For the B+ voltage, it's the series drop across R1, R2, and R4 that sets the B+ value.  Increasing R1 and R2 will lower the voltage leading in to the 100K pot (R4), and lowering them will raise it.

The transformer shouldn't effect B+ *unless* you have a wonky output cap (C12).  If this cap is leaking DC current through R17 and dragging down B+ then Bad Things Will HappenTM.

If I were you, I would replace C12 as well.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Spencerleehorton on September 05, 2013, 04:27:29 PM
Hi Matador,

the mic is working fine now i have changed transformer, getting good signal through it, im just not getting 120v on B+, so i think i need to lower R1, R2, and R4 to raise the voltage.
R1 and R2 are 5k and R4 is 27k so should i replace with R1/R2 = 2k and R4=15k ?

regards

Spence.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Matador on September 05, 2013, 06:25:28 PM
Hi Matador,

the mic is working fine now i have changed transformer, getting good signal through it, im just not getting 120v on B+, so i think i need to lower R1, R2, and R4 to raise the voltage.
R1 and R2 are 5k and R4 is 27k so should i replace with R1/R2 = 2k and R4=15k ?

regards

Spence.

 :o

Both R1 and R2 are supposed to be 91K.  R4 is the 100K B+ adjustment pot.

Which schematic are you looking at?  The official version for this build is located here (http://www.musicalsparks.com/images/c12/c12_schematics_v3.pdf).
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Spencerleehorton on September 05, 2013, 06:35:38 PM
Hi Matador,

Im pretty sure i was just looking at the wrong psu schematic and i have 91k in the psu.
what should i lower them too?
regards

Spence.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: cariocaman85 on September 05, 2013, 07:03:12 PM
Hi

Here we are again with the head basket resonance! After your advices we decided to go to the glue solution but I can't get loctite 2go glue where I live, so I wonder if this glue:

Cyanoacrylate Bond MP

Might fit for damping the ring?

On the technical data they precise this glue is for metal, resistant to vibrations, and solvent free (http://instantca.com/industrial-adhesives/cyanoacrylate/)
Do you think it is safe for the capsule?

Thanks for your replies, we have to glue it this weekend because we gonna record on Monday.

Best,
Remi
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Matador on September 05, 2013, 07:11:28 PM
Hi Matador,

Im pretty sure i was just looking at the wrong psu schematic and i have 91k in the psu.
what should i lower them too?
regards

Spence.

Aye.  The best thing is to lower both R1 and R2 equally.  It looks like your tube is drawing a bit more than the expected 0.6mA at idle, so each 10K drop will yield about 50-10V of adjustment.  So if you dial R4 to until the B+ is as high as it can go (let's say 100V), then dropping R1 and R2 by 20K each will raise B+ up to about 140V, when you should be able to drop back down to 120V by adjusting R4 again.

I can help you zero in on it a bit better if you max out R4 (drop B+ as low as it will go), and tell me the new B+ voltage with all resistances at maximum.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Spencerleehorton on September 05, 2013, 07:17:26 PM
Hi Matador,

as it stands i get 77v with 100k turned all the way one way and 94.5v turned the other way.

regards

Spence.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Pip on September 05, 2013, 10:20:26 PM
Hi Matador,

Im pretty sure i was just looking at the wrong psu schematic and i have 91k in the psu.
what should i lower them too?
regards

Spence.
http://www.groupdiy.com/index.php?topic=51377.msg666445#msg666445


Check this out I had a similar problem.

http://www.groupdiy.com/index.php?topic=51377.msg666445#msg666445
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Matador on September 06, 2013, 12:34:20 AM
Hi Matador,

as it stands i get 77v with 100k turned all the way one way and 94.5v turned the other way.

regards

Spence.

You drop ~200V across 182K with the 100K turned to zero.  You are idling at 1mA.  This is a 6072A tube?

In any case, you want 40V more which means ~40K less.  I would drop R1 and R2 down to 75K (16K each), and the pot should make up the rest to give you some room around 120V.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Spencerleehorton on September 06, 2013, 03:06:24 AM
HI Matador/Pip,

Thank you guys, thats great, seems my problem will be over once i change R1/R2 to 75k.
happy days!!! :)

regards

Spence.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Spencerleehorton on September 06, 2013, 05:37:00 AM
HI Guys,

just found my first mistake!!! 150k at R1 100k at R2, have no exchanged for 90k and see what happens!!!

regards

Spence.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: chunger on September 06, 2013, 07:38:09 AM
UPDATE:  Erse changed the specs on their 630V 1uF capacitors. . . . DOH!  They were out of stock for quite a few months and the new shipment is significantly larger diameter than the previous batch. . . beyond the measured interference tolerances I calculated internally for the HT-11A body anyways . . . meaning, the cap touches the tube body.  Because the rails are pretty flexible, the mic still assembled fine with the new capacitor, but I've made some modifications to the build instructions to slightly modify/file the PCB to accommodate the new kit 1uF capacitor.  Thinking to drop down to the smaller 400V version for the next batch of parts.

Also, please note that there are a large number of capacitor brands and types that fit in the provided slot besides the Erse metalized polypropylene unit that i supply with the kits.

(http://studio939.zenfolio.com/img/s10/v101/p2022936913-4.jpg)
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Spencerleehorton on September 06, 2013, 08:28:34 AM
Hi Matador/everyone,

All working perfectly now, voltage B+ is 120v, bias -1.0, heater 6.3v, sounds amazing!!!
thanks again, i think i have a new first choice for vocal mic!!! cuts through the mix so well!!!

regards

Spence.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: ajemutt on September 10, 2013, 12:39:47 AM
Is anyone else using the Peluso CEK-12 capsule with their 34mm mount?

On the capsule and mount I got, the screw holes on the mount don't line up with the holes on the capsule body unless I remove one of the wires and re-insert the screw through the plastic capsule mount - thus holding the ring terminal conductor onto the body of the capsule with the mount, rather than directly with the screw.

Is this really the correct way? I'm worried that the ring terminal isn't going to make good contact unless I really tighten that screw hard, but that's just as likely to strip it out.

Any ideas on that?

Oh, another question - what's the advantage of using the pins to solder the capsule leads instead of soldering direct onto the PCB?


Many Thanks!


AJ

 
Title: Re: Official C12 Clone - Build and Support Thread
Post by: sr1200 on September 10, 2013, 10:09:18 AM
Hey Chung, what about strapping it to the back of the board instead of the front, It should fit between the rails and still clear no?
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Matador on September 10, 2013, 01:53:44 PM
Hey Chung, what about strapping it to the back of the board instead of the front, It should fit between the rails and still clear no?

That's where the tube sits.  :D
Title: Re: Official C12 Clone - Build and Support Thread
Post by: sr1200 on September 10, 2013, 03:20:08 PM
Ahh tis true, i thought the tube was up higher, havent had mine open in a while.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: ajemutt on September 10, 2013, 05:45:50 PM
Hey everyone,

On the CEK-12 capsule mount, I got an email from Peluso this AM with a photo of how it should attach, so I thought I'd share.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: JessJackson on September 10, 2013, 06:42:45 PM
Something interesting i noticed and I'm not sure what kind of difference it may make but in the original schematics the 6072 tube heater is center tapped to pin 9 and pin 5 is connected to ground and pin 4 is floating.

On matador circuit you have pin 4 or 5 (whatever side of the tube you are using) connected to heater with the additional pin left floating. While Pin 9 is also left floating. Is this something you consciously decided to implement?

I am going to mod heater to pin 9 like original schematic and strap pin four (on my build) to ground and see if theres a difference.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Pip on September 10, 2013, 08:36:02 PM
Something interesting i noticed and I'm not sure what kind of difference it may make but in the original schematics the 6072 tube heater is center tapped to pin 9 and pin 5 is connected to ground and pin 4 is floating.

On matador circuit you have pin 4 or 5 (whatever side of the tube you are using) connected to heater with the additional pin left floating. While Pin 9 is also left floating. Is this something you consciously decided to implement?

I am going to mod heater to pin 9 like original schematic and strap pin four (on my build) to ground and see if theres a difference.

I think pin 9 is connected to ground in Matadors schematic. What is interesting is in the original schematic everything that is not used, pin 6, 7 and 8 is tied to ground but the heater pin that is not used pin 5 is not hooked up also in original pin 9 is the 6.3 volt in and pin 4 references ground.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: JessJackson on September 10, 2013, 09:18:33 PM
Something interesting i noticed and I'm not sure what kind of difference it may make but in the original schematics the 6072 tube heater is center tapped to pin 9 and pin 5 is connected to ground and pin 4 is floating.

On matador circuit you have pin 4 or 5 (whatever side of the tube you are using) connected to heater with the additional pin left floating. While Pin 9 is also left floating. Is this something you consciously decided to implement?

I am going to mod heater to pin 9 like original schematic and strap pin four (on my build) to ground and see if theres a difference.

I think pin 9 is connected to ground in Matadors schematic. What is interesting is in the original schematic everything that is not used, pin 6, 7 and 8 is tied to ground but the heater pin that is not used pin 5 is not hooked up also in original pin 9 is the 6.3 volt in and pin 4 references ground.

exactly… we have all been heating both sides of the tube unless you have tied everything on the unused side to ground. Looking at my tube mount there doesn't appear to be a trace from pin 9 to ground. It seems to be floating. Therefore heating both Units of the tube resulting in a 3v heater.

E.G: Say for instance you are using the right side of the tube (as per original schematic)

To my understanding, I don't think it matters where you enter 6.3v (pin 5 or 9)

..

Additionally the right and left sides of the tube are not identical.

The right side (Unit 1) is rated at 0.5 uuf
The left side (Unit 2) is rated at 0.38 uuf

Which is a 20% difference and I'm not nearly expert enough to comment on this area. Could this have something to do with the reason all schematics utilised Unit 1?

Attached is original tube schematic for those needing to reference it.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Matador on September 11, 2013, 01:54:20 AM
On matador circuit you have pin 4 or 5 (whatever side of the tube you are using) connected to heater with the additional pin left floating. While Pin 9 is also left floating. Is this something you consciously decided to implement?

I'm not sure where this is coming from:  on my build, pin 9 is grounded, and is not left floating.  You can attach either pin 4 or pin 5 (or both!) to the heater supply to light up each half of the tube (or both!).  Whatever side (pin 4 or pin 5) is left floating will definitely not be heated.

Think of the heater as two resistors, which happen to share a common node (pin 9).  So long as you put 6.3V across either pin4 and pin 9 or pin5 and pin 9, each half will light up (respectively).

If you declare pin9 as ground, then 6.3V on pin 4 or pin 5 will light each half.
If you declare pin9 as 6.3V, then you must ground pin 4 or pin 5 to light each half.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: JessJackson on September 11, 2013, 06:21:25 AM
On matador circuit you have pin 4 or 5 (whatever side of the tube you are using) connected to heater with the additional pin left floating. While Pin 9 is also left floating. Is this something you consciously decided to implement?

I'm not sure where this is coming from:  on my build, pin 9 is grounded, and is not left floating.  You can attach either pin 4 or pin 5 (or both!) to the heater supply to light up each half of the tube (or both!).  Whatever side (pin 4 or pin 5) is left floating will definitely not be heated.

Think of the heater as two resistors, which happen to share a common node (pin 9).  So long as you put 6.3V across either pin4 and pin 9 or pin5 and pin 9, each half will light up (respectively).

If you declare pin9 as ground, then 6.3V on pin 4 or pin 5 will light each half.
If you declare pin9 as 6.3V, then you must ground pin 4 or pin 5 to light each half.

Hi mate, where is it grounded? There doesn't appear to be a trace from pin 9 on my board to ground. Theres no continuity unless it bridge it myself.

cheers

J
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Deepdark on September 11, 2013, 08:49:57 AM
Is it fit a MXL V67I body? I'm asking that because they are really similar of the AKG C12 (gold headbasket and mesh, green body). Just a matter of look hahaha. Awesome work by the way
Title: Re: Official C12 Clone - Build and Support Thread
Post by: chipss36 on September 11, 2013, 09:20:54 AM
Looks like pin 9 runs to ground at the 2 reinforcement cut resistor leads that help hold the vertical pcb. 
It is just as matador has said...
The smd zero Olm resistor selects witch side of the triode Is used, 4 or 5 , 9 is grounded....
If your not seeing ground there, did you put the cut resistor lead gussets on tube pcb and the head amp pcb?
C
Title: Re: Official C12 Clone - Build and Support Thread
Post by: micaddict on September 11, 2013, 09:44:45 AM
Is it fit a MXL V67I body? I'm asking that because they are really similar of the AKG C12 (gold headbasket and mesh, green body). Just a matter of look hahaha. Awesome work by the way

The original C12s (the early ones anyway) were gray or silverish with a polished nickel ("chrome") headbasket:

(http://www.advancedaudiorentals.com/images/products/AKG%20C12%2001.jpg)


The C12VR ("vintage re-issue", albeit with a totally different circuit) is a bluish green with a gold plated grill:

(http://static.bax-shop.nl/components/com_virtuemart/shop_image/product/AKG_C12VR_vintage_tube_condensator_microfoon_1.jpg)


The MXL V76i does copy the colors of the latter, though not the shape:

http://www.realmusic.ua/images/catalog/products/12833563157893img1_big.jpg (http://www.realmusic.ua/images/catalog/products/12833563157893img1_big.jpg)

The colors on the T-Bone SCT800 are even more complementary (blue/gold). This is the actual Alctron HST11A (Apex 460) body I think, so the PCB should fit perfectly. Unfortunately the PSU is cardioid only:

http://www.thomann.de/gb/the_tbone_sct800_tube_mic.htm (http://www.thomann.de/gb/the_tbone_sct800_tube_mic.htm)
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Matador on September 11, 2013, 10:29:10 AM
Hi mate, where is it grounded? There doesn't appear to be a trace from pin 9 on my board to ground. Theres no continuity unless it bridge it myself.

The plated through hole itself attaches to the ground plane on the tube board via a thermal relief (which are just small traces around the circumference of the pin to the plane).  If you look closely you should see them.  I can upload a zoomed in shot of that area of the PCB if you are interested.

The lack of continuity is puzzling.  Ground is provided to the main PCB via two methods:  the first is the ground wire in the XLR socket, which attaches down at the bottom of the main PCB via the "P6" node.  Additionally, the shield of the cable is shorted to the brass body right at the 7-pin jack, which them transmits ground to the mike PCB via the PCB screws directly in to the body.  This ensures that the body is a solid ground at multiple places.

Ground moves over to the tube PCB via the two outside pads that hold the tube PCB in place.  The heater voltage appears via the middle one.  Pin 9 should show 0 ohms between itself (right at the tube socket), and any ground connection on the board or even the mike body itself.  If not, I would revisit the tube pcb and socket soldering and check it.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: JessJackson on September 11, 2013, 02:23:29 PM
Hi mate, where is it grounded? There doesn't appear to be a trace from pin 9 on my board to ground. Theres no continuity unless it bridge it myself.

The plated through hole itself attaches to the ground plane on the tube board via a thermal relief (which are just small traces around the circumference of the pin to the plane).  If you look closely you should see them.  I can upload a zoomed in shot of that area of the PCB if you are interested.

The lack of continuity is puzzling.  Ground is provided to the main PCB via two methods:  the first is the ground wire in the XLR socket, which attaches down at the bottom of the main PCB via the "P6" node.  Additionally, the shield of the cable is shorted to the brass body right at the 7-pin jack, which them transmits ground to the mike PCB via the PCB screws directly in to the body.  This ensures that the body is a solid ground at multiple places.

Ground moves over to the tube PCB via the two outside pads that hold the tube PCB in place.  The heater voltage appears via the middle one.  Pin 9 should show 0 ohms between itself (right at the tube socket), and any ground connection on the board or even the mike body itself.  If not, I would revisit the tube pcb and socket soldering and check it.

Thanks mat,

I think i see the tiny trace on the underside of the tube board but not on the top side. In my build i only soldered the top side of ground plane (outer pads) i left the bottom side un-soldered, this is probably the issue or did you also provide a trace from pin9 to pad on the top side also?

Cheers
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Matador on September 11, 2013, 04:26:55 PM
Thanks mat,

I think i see the tiny trace on the underside of the tube board but not on the top side. In my build i only soldered the top side of ground plane (outer pads) i left the bottom side un-soldered, this is probably the issue or did you also provide a trace from pin9 to pad on the top side also?

Cheers

Ahh yes, this is the issue, good catch!  The "top" pads (or the pads that are on the opposite side as the tube and socket) are there only for mechanical attachment.  The plane on the top of the board is only to make the soldermask color more consistent and there are no thermal reliefs or ground traces on the top side either.  There has to be a solder connection to the "bottom" pads in order to complete the ground circuit (like you can see in Chunger's build guide, as he actually always solders both sides):

(http://studio939.zenfolio.com/img/s8/v76/p1449658880-5.jpg)

I will add a pour and second thermal relief to the next run of boards as a safety measure.  I had assumed that people would always solder both sides but never explicitly called it out.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: JessJackson on September 11, 2013, 06:38:22 PM
Thanks mat,

I think i see the tiny trace on the underside of the tube board but not on the top side. In my build i only soldered the top side of ground plane (outer pads) i left the bottom side un-soldered, this is probably the issue or did you also provide a trace from pin9 to pad on the top side also?

Cheers

Ahh yes, this is the issue, good catch!  The "top" pads (or the pads that are on the opposite side as the tube and socket) are there only for mechanical attachment.  The plane on the top of the board is only to make the soldermask color more consistent and there are no thermal reliefs or ground traces on the top side either.  There has to be a solder connection to the "bottom" pads in order to complete the ground circuit (like you can see in Chunger's build guide, as he actually always solders both sides):

(http://studio939.zenfolio.com/img/s8/v76/p1449658880-5.jpg)

I will add a pour and second thermal relief to the next run of boards as a safety measure.  I had assumed that people would always solder both sides but never explicitly called it out.

Your right thats the issue, cheers mate… do the 45 degree angled struts pass ground because I have one of those soldered through to the underside of the tube board?

Any knowledge on the different ratings of left and right sides of the tube?

J
Title: Re: Official C12 Clone - Build and Support Thread
Post by: chipss36 on September 11, 2013, 07:34:24 PM
it indeed does ground there, take a meter to one of your extra tube pcbs....and check it out , its where i thought he was running ground, didn't  meter the back side of the PCB, 4 different areas that  run to ground....
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Pip on September 11, 2013, 10:33:36 PM
On matador circuit you have pin 4 or 5 (whatever side of the tube you are using) connected to heater with the additional pin left floating. While Pin 9 is also left floating. Is this something you consciously decided to implement?

I'm not sure where this is coming from:  on my build, pin 9 is grounded, and is not left floating.  You can attach either pin 4 or pin 5 (or both!) to the heater supply to light up each half of the tube (or both!).  Whatever side (pin 4 or pin 5) is left floating will definitely not be heated.

Think of the heater as two resistors, which happen to share a common node (pin 9).  So long as you put 6.3V across either pin4 and pin 9 or pin5 and pin 9, each half will light up (respectively).

If you declare pin9 as ground, then 6.3V on pin 4 or pin 5 will light each half.
If you declare pin9 as 6.3V, then you must ground pin 4 or pin 5 to light each half.

Hi mate, where is it grounded? There doesn't appear to be a trace from pin 9 on my board to ground. Theres no continuity unless it bridge it myself.

cheers

J

Yes I did not mean to imply that Matadors schematic or PCB was wrong quite the opposite. What does intrigue me is why the original design shows the other half of the tubes pins referenced to ground? Yes also it does not matter one bit how you get the 6.3 volts into the heaters.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Matador on September 12, 2013, 01:14:18 AM
Yes I did not mean to imply that Matadors schematic or PCB was wrong quite the opposite. What does intrigue me is why the original design shows the other half of the tubes pins referenced to ground? Yes also it does not matter one bit how you get the 6.3 volts into the heaters.

No worries!  Perhaps it was to minimize the chance of the internal nodes floating to weird voltages and causing noise?  I did try grounding the unused pins and couldn't notice any difference.  But it's certainly easy to do with a few wires if you want to experiment.

I did confirm the tube support pins are grounded as well.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: sr1200 on September 12, 2013, 04:35:58 PM
I want another one sooo bad... Used mine this week for some stuff, its so pretty.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: JessJackson on September 13, 2013, 06:47:18 PM
I was getting 160v at b+

so i increased r1 and r2 to 160k each and now still getting 134v

both measurements with trimmer pot all way down.

weird huh
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Matador on September 13, 2013, 07:10:07 PM
I was getting 160v at b+

so i increased r1 and r2 to 160k each and now still getting 134v

both measurements with trimmer pot all way down.

weird huh

Was it working properly before and now it's changed?
Title: Re: Official C12 Clone - Build and Support Thread
Post by: JessJackson on September 13, 2013, 11:00:16 PM
I was getting 160v at b+

so i increased r1 and r2 to 160k each and now still getting 134v

both measurements with trimmer pot all way down.

weird huh

Was it working properly before and now it's changed?

No it was always high, I just tried to bring it down now.

The trimmer pot is definitely the 100k. I'll try two 200k resistors in r1 and r2
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Matador on September 14, 2013, 01:59:46 AM
I was getting 160v at b+

so i increased r1 and r2 to 160k each and now still getting 134v

both measurements with trimmer pot all way down.

weird huh

Was it working properly before and now it's changed?

No it was always high, I just tried to bring it down now.

The trimmer pot is definitely the 100k. I'll try two 200k resistors in r1 and r2

This is with a tube?  What kind?  Did you try the 180K resistor trick?
Title: Re: Official C12 Clone - Build and Support Thread
Post by: JessJackson on September 14, 2013, 04:36:45 PM
yeah when its loaded.

Whats strange is I'm getting the higher voltages when the mic is open and exposed but the moment i slide the body sleeve up the cable and over the mic the voltage drops slightly and then as I tighten the bell connector on the bottom, the voltage drops dramatically further to my specified 120v.

Ive repeated this over and over and literally changes the moment I tighten or loosen the bell. Ground has continuity over entire body and frame from PS regardless of bell being tight or or even slid down cable.

odd findings huh
Title: Re: Official C12 Clone - Build and Support Thread
Post by: originalmusician on September 14, 2013, 04:55:31 PM
I ordered all the parts for this except for the capsule. I had planned on buying the Tim Campbell CK12. I emailed Tim on August 14th and asked to be put on his waiting list. But I never got a reply from him. So I emailed him again a few weeks later at his other email address but still haven't heard back (checked my spam filter and no return emails were in there).

Has anyone else ordered one of his capsules, and is it typical for it to take a month or more to get an email response when trying to get a spot on the waiting list? I'm not trying to be critical of Tim, as I know he's probably tremendously busy. I'm just trying to figure out if my experience is typical, or if the emails are getting hung up somewhere or something? Or maybe my emails are getting redirected to his spambox? My main concern is, I don't want to bother Tim with relentless repeat emails if it normally takes some time for him to catch up with his inbox.

Thanks  :)
Title: Re: Official C12 Clone - Build and Support Thread
Post by: chunger on September 14, 2013, 05:57:23 PM
I ordered all the parts for this except for the capsule. I had planned on buying the Tim Campbell CK12. I emailed Tim on August 14th and asked to be put on his waiting list. But I never got a reply from him. So I emailed him again a few weeks later at his other email address but still haven't heard back (checked my spam filter and no return emails were in there).

Has anyone else ordered one of his capsules, and is it typical for it to take a month or more to get an email response when trying to get a spot on the waiting list? I'm not trying to be critical of Tim, as I know he's probably tremendously busy. I'm just trying to figure out if my experience is typical, or if the emails are getting hung up somewhere or something? Or maybe my emails are getting redirected to his spambox? My main concern is, I don't want to bother Tim with relentless repeat emails if it normally takes some time for him to catch up with his inbox.

Thanks  :)

Hi,  I know a lot of people have been frustrated lately trying to get into Tim's build queue.  I spoke with him recently regarding sustainable sourcing of capsules moving forward, and as of right now, given his OEM commitments, this project has completely exceeded his current production capacity.  As Tim is a one-man operation hand-building these fine capsules, he is not set up to track many emails and inquiries above his previous baseline of communication volume.  While maintaining his current production volumes, he is working diligently to tool up and increase his production capacity, but this takes significant investments in tools and streamlining of production processes.  This will take time, and he must weigh the long-term prospects of my little DIY venture.  My view is I can continue to bring in new DIY customers and expand the market and make kits essentially perpetually available.  For now, once Tim is finished shipping capsules to his current queue of non-commercial DIY customers (people who he has confirmed), I have let him know I will buy every "extra" capsule he can produce and make them available as they trickle in to kit customers.  Hopefully, once some new production processes come online, Tim will be able to incrementally increase his monthly production volume.

That being said, there is currently a shortage of backplate-correct C12 capsules for this project.  I am now working with tskguy to finalize his C12 capsule in hopes that he will be able to fill the gap with a capsule that is true to the vintage AKG capsule's internal construction and frequency response.  His initial tests and prototypes have been very promising and he is basing development on a pristine vintage C12 that he has access to.  For people who require a premium capsule for their builds, I would wait for these units to hit production.  I am sure tskguy will not release anything that he does not feel 100% about, but his production process for these new capsules is conducive to production volumes that can meet the current demand.  I am hoping to finally be able to stock complete turn-key kits when these come online.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: maq3396 on September 14, 2013, 06:52:15 PM
Thanks Chunger

Hats off to yourself, Tskguy and Tim for helping to not only sustain, but make major contributions to this DIY world. Without the tremendous efforts made by the members of this forum, many of us would never have an opportunity to own microphones such as the U67, U47, C12 and ELAM 251.

Thank you all
Mac
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Woot on September 14, 2013, 07:54:52 PM
Chunger -  Sorry if I missed the point of your reply but is Tim still putting DIY people on the list, or are you saying he has suspended this availability for the DIY'ers until his current OEM/DIY backlog is sorted?

Originalmusician - I had a similar experience to you. Additionally, there's a bit of a discrepancy between some peoples reported experience in ordering capsules and what Tim has said to me. ie there were people saying that they sent an email, received no confirmation but received a request for payment and shipping details when the capsules were ready some 8 weeks later. Tim has told me categorically that everyone who has been placed on his list has received email return confirmation of this fact. So unfortunately if he hasn't replied with confirmation then you're not on the list. It took me a few emails over 3 months to receive a reply (not complaining as we know Tim is very busy, just stating facts).

I am going to build a MataChung c12 today, with a Beesneez K12 capsule. Anyone know if they are considered backplate-correct? Anyone elaborate on what backplate-correct means?? ;) I'll post some samples with this combo if anyone interested.

Lastly, I echo the the sentiments from Mac... it's an awesome service you guys provide (and an addictive one).

Cheers,

Matt
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Matador on September 14, 2013, 08:20:20 PM
I'm not an expert, but I have seen a real one apart so can give a general impression.

So a k67 type capsule has a single backplate element per side.  The number and spacing of the holes determine the amount of resistance between the air in front of the capsule and the inside of the sealed chamber.

C12 capsule have a screw in chamber which makes yet another resonance chamber inbetween the front and middle of the capsule.  A large number of C12 clones are simply k67 type backplates that are reconfigured to utilize an edge terminated diaphragm.

I would construe "backplate correct" to indicate the presence of the isolated resonance chamber.  Both tskguy's and Tim's capsules feature this chamber.  Many/most of the clones do not.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: StaticRick on September 14, 2013, 08:49:35 PM
Well that stinks. I had read a couple of different times here that the process to get one of Tim's capsules was to email him, don't expect any response from him, and wait until you get an email from him saying your capsule is ready.  I sent my email and respected his wishes by not peppering him with followup emails. Now, I read that since I DIDN'T get a response from Tim that means that I WON'T be getting one of his capsules?

I understand that he's busy, but I don't understand operating a business when your policy is to never communicate with customers who contact you.

I guess I'll be looking for other options, but a definitive response from Tim would seem to be a common courtesy.

Title: Re: Official C12 Clone - Build and Support Thread
Post by: chunger on September 14, 2013, 08:55:22 PM
Chunger -  Sorry if I missed the point of your reply but is Tim still putting DIY people on the list, or are you saying he has suspended this availability for the DIY'ers until his current OEM/DIY backlog is sorted?


I cannot speak for what Tim is going to do in the future, but I do know that he is very diligent about fulfilling any and all orders that he confirms.  So, if you are IN his build queue, you can rest assured you will receive your capsule.  I also know that he is over-run with capsule inquiries and that has lead to delays in even responding to requests to get into the queue.  Obviously this is a result of a large backlog of existing orders (commercial and DIY).  The experience some people have been having is difficulty getting a response due to the communications backlog.

I've expressed interest in stocking his capsule for complete kits, but I will not be able to receive large batches of capsules like I would prefer, just a few here and there as they become available.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: chunger on September 14, 2013, 09:12:06 PM
Well that stinks. I had read a couple of different times here that the process to get one of Tim's capsules was to email him, don't expect any response from him, and wait until you get an email from him saying your capsule is ready.  I sent my email and respected his wishes by not peppering him with followup emails. Now, I read that since I DIDN'T get a response from Tim that means that I WON'T be getting one of his capsules?

I understand that he's busy, but I don't understand operating a business when your policy is to never communicate with customers who contact you.

I guess I'll be looking for other options, but a definitive response from Tim would seem to be a common courtesy.

Sorry for the confusion.  I believe I have always been clear to cease perpetual email attempts with tim AFTER confirmation that you are in his build queue.  Prior to that point you are not officially in line.

Please keep in mind that prior to this year's diy mic craze things were relatively quiet for a super niche business.  The fact that tim did and still does everything possible to make these capsules available at a reasonable price to the diy market is a great service to the community.  We have simply upped demand too much too fast.  Others will pick up the slack at least for now.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Pip on September 15, 2013, 12:04:31 AM
This is probably here somewhere and a lot of you have seen this I am sure but here it is again. This is what is involved with a real C12 capsule.

http://www.saturn-sound.com/Curio's/akg's_ck12_capsule.htm
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Woot on September 15, 2013, 01:15:33 AM
Well that stinks. I had read a couple of different times here that the process to get one of Tim's capsules was to email him, don't expect any response from him, and wait until you get an email from him saying your capsule is ready.  I sent my email and respected his wishes by not peppering him with followup emails. Now, I read that since I DIDN'T get a response from Tim that means that I WON'T be getting one of his capsules?

Yes, this is the same info I had read somewhere on here, but I can confirm, at least of 2 weeks ago that you need that return email to be confirmed as on the list. It has cost me an extra 3 months wait (6 total) - but it'll be worth it.

 8)
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Woot on September 15, 2013, 10:37:28 AM
I would construe "backplate correct" to indicate the presence of the isolated resonance chamber.  Both tskguy's and Tim's capsules feature this chamber.  Many/most of the clones do not.

I have just confirmed with Ben from Beesneez Microphones that his K12 is "definitely backplate-correct we have the multichambered capsule with the exact spacing of the original..."

They have them on sale last time I looked on their site for anyone interested. I've decided to do my C12's with them, and then use Tims in my ELAMs later on... PS no affiliation with Ben or BN

Matt
Title: Re: Official C12 Clone - Build and Support Thread
Post by: chunger on September 15, 2013, 11:29:22 AM
I would construe "backplate correct" to indicate the presence of the isolated resonance chamber.  Both tskguy's and Tim's capsules feature this chamber.  Many/most of the clones do not.

I have just confirmed with Ben from Beesneez Microphones that his K12 is "definitely backplate-correct we have the multichambered capsule with the exact spacing of the original..."

They have them on sale last time I looked on their site for anyone interested. I've decided to do my C12's with them, and then use Tims in my ELAMs later on... PS no affiliation with Ben or BN

Matt

Not to take anything away from the great work that Ben does in the microphone and capsule development sphere, but the Beesneez K12 capsule is its own proprietary design and not an attempt to faithfully reproduce the original CK12.  It is quite obvious that the hole pattern is different from the original design.  The K12 is probably a nice-sounding multi-chamber based capsule, but it is a Beesneez proprietary design.  For the purposes of this project, I am advocating a premium capsule that attempts to emulate the exact characteristics of the original CK12.  Tskguy and Tim Campbells capsules do this faithfully.  I am not aware of another commercially available option that does.

Not a knock against Beesneez capsules.  I have a Beesneez K7 and M7 in my hands for my mk47 builds and they are beautiful and have been had outstanding reviews from very high-level folks, but the K12 is not a vintage reproduction design.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: baadc0de on September 15, 2013, 01:09:36 PM
Beesneez K12 I can't compare with Tim's offering since I don't have one around, but I have K12 here and it's quite popular with the other guy sharing the studio who does RnB, hip-hop and commercials. I felt the mic was definitely cool and didn't need any significant EQ to sound the way we wanted it.

The only thing I can share right now is a quickie demo I did for my gf's songwriting course assignment, so that's far from perfect as it was done with great rush :) The mic is this C12 clone, K12 capsule, Oliver's T14, NOS GE 6072, Russian PIO output 1uF. Went into bruno2000 Neve1084 with a mild HF shelf at 10k and some compression from drip's Altec 436 modified to RS-124 and off to fireface 800. I think I have the files somewhere without the reverb, delay and backing track, but we tracked with compression. I can send those on demand.

http://snd.sc/1cvq4IA

That said, I did wait ages for the Beesneez capsules to materialize, I think it was more than half a year .. and then I got some weird bass-heavy K87-like capsule delivered and after some persuasion I got capsules that have a C12-like hole pattern and are not too dark, but nicely smooth. Speaking over the phone with Ben, he assured me repeatedly that the K12 is a design he's most proud of.

*Not affiliated with any of the capsule makers :)
Title: Re: Official C12 Clone - Build and Support Thread
Post by: originalmusician on September 15, 2013, 01:24:57 PM
Thanks Chunger. I just ordered K7 and K12 Beesneez capsules and will hopefully be placed in Tim's queue soon so I can eventually get as close to the original design of your C12 build as possible. I've got another project in mind that Ben's K12 will eventually end up in, and it will also give me the chance to directly compare the two capsules in your C12 build.

Thanks so much for putting this project together! I'm also looking forward to doing a U47 build using one of your mic bodies and the Beesneez K7. It would be interesting to compare the Beesneez K7 against the Beesneez M7, but funds are running a little low over here for that. I have an extra Dale M7 laying around that will make an interesting comparison though. :D
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Pip on September 15, 2013, 02:55:52 PM
I feel compelled to say something here. Tim is and always has tried to aid this community as best he can. The facts are he is a small niche business that does something only a few others have ever done, make CK12 capsules. He is also obligated to major manufacturers as an OEM supplier. In the world we live in that is how it works the people with the lawyers get the goods. Let time march on and we will get to a place where Tim can take care of us again. I have never met the man but I can tell by the scant email dealings I have had he cares and is a good and responsible person.

That being said I need to point out some other realities. First thanks to all who have toiled to make this possible I have purchased two kits from Chunger and one of the latest mics. I always build two of everything! I have one CT12 capsule and thats maybe the way its gonna stay for a while I guess. I have contributed to the build thread and shown my triumphs and failures in the best way I can so that others might avoid the failure moments. But in the end what do I have? I have as close as I will ever get in this life (barring hitting the lottery) to an AKG C12. I am happy! To the point though it is not a C12 by any means. The original was a point to point build that used a transformer of much different core size. It was also arrainged component wise much differently and the PSU and Switching system was seperate and different as well. The tubes were hand picked for a typical set of characteristics and at the time new stock items (the tube in this mic is critical as my posts will show). All of these things can potentially change the sound significantly.

I originally built this mic and used it with a http://recordinghacks.com RK12 capsule. It was a great mic and had a great sound. I put in the Tim Campbell capsule and it became a more classic sounding mic and had a mellower voicing. BOTH SOUNDED REALLY GOOD! That's why I chose to build another, was to AB them firstly as I think I want both.

THIS IS NOT MEANT AS A SLIGHT OR A NEGATIVE TOWARDS ANYONE OR THIS BUILD OR ANYTHING RELATED IT IS JUST MEANT TO PUT SOME REALITY IN THE WIND.

Title: Re: Official C12 Clone - Build and Support Thread
Post by: JessJackson on September 15, 2013, 04:58:17 PM
yeah when its loaded.

Whats strange is I'm getting the higher voltages when the mic is open and exposed but the moment i slide the body sleeve up the cable and over the mic the voltage drops slightly and then as I tighten the bell connector on the bottom, the voltage drops dramatically further to my specified 120v.

Ive repeated this over and over and literally changes the moment I tighten or loosen the bell. Ground has continuity over entire body and frame from PS regardless of bell being tight or or even slid down cable.

odd findings huh

does any one else's mic behave this same way?
Title: Re: Official C12 Clone - Build and Support Thread
Post by: JessJackson on September 15, 2013, 05:14:46 PM
The original was a point to point build that used a transformer of much different core size.

--- It doesn't make any difference, I own a vintage c12. People could argue that the pcb version is more "pure" and less susceptible to RF interference.

It was also arrainged component wise much differently

--- No, matadors version is the exact original schematic. If you mean vertical layout as apposed to horizontal then your obviously not commenting based on the sound.

and the PSU and Switching system was seperate and different as well.

--- The PSU is improved as for the remote switching unit, most original power supply had been modded with XLR on the power supply otherwise the output had to travel all the way from the power supply to the remote which was a lot of cable. the idea was that the remote sat in the control room with the engineer. This was all worst design than we have now.

The tubes were hand picked for a typical set of characteristics and at the time new stock items (the tube in this mic is critical as my posts will show). All of these things can potentially change the sound significantly.

--- This is still the case with NOS

I originally built this mic and used it with a http://recordinghacks.com RK12 capsule. It was a great mic and had a great sound. I put in the Tim Campbell capsule and it became a more classic sounding mic and had a mellower voicing. BOTH SOUNDED REALLY GOOD! That's why I chose to build another, was to AB them firstly as I think I want both.

--- Sometimes a u87ai works well too

THIS IS NOT MEANT AS A SLIGHT OR A NEGATIVE TOWARDS ANYONE OR THIS BUILD OR ANYTHING RELATED IT IS JUST MEANT TO PUT SOME REALITY IN THE WIND.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: originalmusician on September 15, 2013, 05:18:05 PM
Good points Pip, and I agree. But those who build Chunger's kit carefully, will end up with one heck of a mic for the money that has all new parts and will be good-to-go for many years to come. Most of us DIYers aren't recording for major labels, so there's typically a lot more lacking on our records than the slight difference between an original C12 and a Chunger build using Tim's capsule. And at the end of the day, Chunger's mic just might sound better on a particular sound source anyways.

IMO, a lot of this holy grail microphone stuff is hype coming from vendors who are attempting to sell something other than the talent, knowledge, skill, and experience it takes to make a really good record.

Title: Re: Official C12 Clone - Build and Support Thread
Post by: Woot on September 15, 2013, 05:34:42 PM
For the purposes of this project, I am advocating a premium capsule that attempts to emulate the exact characteristics of the original CK12.  Tskguy and Tim Campbells capsules do this faithfully.  I am not aware of another commercially available option that does.

Not a knock against Beesneez capsules.  I have a Beesneez K7 and M7 in my hands for my mk47 builds and they are beautiful and have been had outstanding reviews from very high-level folks, but the K12 is not a vintage reproduction design.

Sorry 'chung, I didn't want to go against your recommendation in any way, I suppose I was sort of just checking out options myself and for anyone who was having trouble sourcing other options/wanted something else.

Ben did mention having 2 drilling plans, one historical and one for better matching across bigger batches. I'm not really sure what this will do to the sound. At any rate, most of this is above my pay grade, so I thank those who are so particular with their craft to explore all of these nuances in capsule production/recreation. I'm just thankful that I get to try them all out and have an awesome end product.

This thanks extends to others who make the bodies/kits too.   ;D
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Biasrocks on September 15, 2013, 05:55:23 PM
His initial tests and prototypes have been very promising and he is basing development on a pristine vintage C12 that he has access to. 

For the purposes of this project, I am advocating a premium capsule that attempts to emulate the exact characteristics of the original CK12.  Tskguy and Tim Campbells capsules do this faithfully. 

So we go from 'initial tests' and 'prototype' to 'exact characteristics' in one day.

Interesting.

Looks like we've slipped into GeerSlutz mode.  ::)

My experience with Tim's capsules have been very favourable. My pair of mics get used all the time around here and there's no shortage of microphones to choose from. I've gotten the absolute best drum overhead sound after 23 years of other options. Acoustic instruments love this mic, distant micing, close micing, all great. Vocals, a legend.

I have a pair of 414eb's w/original brass capsules and even though it's not the same circuit, TC capsules have that sound. I wouldn't be in the least bit surprised if I swapped a CK12 from the EB into the C12 if it sounded very close, if not almost exactly the same. Tim has the benefit of having worked with one of the original AKG engineers on his capsules, the benefits of that are immeasurable. These capsules are complex beasts that surely must have taken years of work to get right.

Tim's capsules are worth the wait and sound fantastic.

Be patient and skip the sharks that are smelling a little blood in the water.

Regards,
Mark
Title: Re: Official C12 Clone - Build and Support Thread
Post by: chunger on September 15, 2013, 07:26:34 PM

Sorry 'chung, I didn't want to go against your recommendation in any way, I suppose I was sort of just checking out options myself and for anyone who was having trouble sourcing other options/wanted something .

This is diy.  All opinions and recommendations are just that.  In the end,  you get to find the sound that works for you without apology.

Regarding a previous statement about the AMI T14 core size being incorrect, there were several iterations of the C12 with at least 3 different transformers spec'd as well as vastly different capsule types.  To my knowlege, the early C12's used a larger core transformer but later ones utilized a small core transformer that Oliver's T14 is modelled after.  So that aspect of the clone build is accurate.

Title: Re: Official C12 Clone - Build and Support Thread
Post by: Pip on September 15, 2013, 10:55:20 PM
yeah when its loaded.

Whats strange is I'm getting the higher voltages when the mic is open and exposed but the moment i slide the body sleeve up the cable and over the mic the voltage drops slightly and then as I tighten the bell connector on the bottom, the voltage drops dramatically further to my specified 120v.

Ive repeated this over and over and literally changes the moment I tighten or loosen the bell. Ground has continuity over entire body and frame from PS regardless of bell being tight or or even slid down cable.

odd findings huh

does any one else's mic behave this same way?

What is the voltage swing again? Because to be master of the obvious. When the body is opened and the shielding is compromised the cicuitry gets bombarded with RFI. This could be throwing circuit into overdrive or even oscillation. That would pull the voltage way up. No?
Title: Re: Official C12 Clone - Build and Support Thread
Post by: JessJackson on September 16, 2013, 02:20:01 AM
yeah when its loaded.

Whats strange is I'm getting the higher voltages when the mic is open and exposed but the moment i slide the body sleeve up the cable and over the mic the voltage drops slightly and then as I tighten the bell connector on the bottom, the voltage drops dramatically further to my specified 120v.

Ive repeated this over and over and literally changes the moment I tighten or loosen the bell. Ground has continuity over entire body and frame from PS regardless of bell being tight or or even slid down cable.

odd findings huh

does any one else's mic behave this same way?

What is the voltage swing again? Because to be master of the obvious. When the body is opened and the shielding is compromised the cicuitry gets bombarded with RFI. This could be throwing circuit into overdrive or even oscillation. That would pull the voltage way up. No?

130 - 160v

I thought that at first also but then came to the conclusion that it would be drawing more therefore voltage becoming lower than greater.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Matador on September 16, 2013, 10:39:20 AM
It sounds like a grounding issue to me.

Please confirm the following:

1) On your 7-pin XLR connector into the mike, that you have whatever wire is carrying ground also bridges over to the brass lug that connects with the XLR screw.  You can clearly see it in Chunger's build pic:

(http://studio939.zenfolio.com/img/s8/v74/p1456807856-4.jpg)

2) That you "loosened" the XLR screw which actually tightens it against the bottom housing.

Barring that, solder a ground wire to the mike PCB right at the tube pin 9, and feed it up through the top plate, and out of the head basket's mesh.  The set your meter to ohms, and ground one side to the PSU right where it comes out of the 5-pin header, and then connect the other side to your new wire.  Then watch the reading and you assemble the housing and tighten it.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: StaticRick on September 16, 2013, 10:54:58 AM
Sorry for the confusion.  I believe I have always been clear to cease perpetual email attempts with tim AFTER confirmation that you are in his build queue.  Prior to that point you are not officially in line.

Chunger, thanks for responding to my earlier venting. 
I am willing to wait as long as it takes, but I'm still confused about the "process" of getting in Tim's queue.  In my case, I sent an email requesting a capsule about two weeks ago.  Since I have not heard back from Tim, does that mean that I will need to try again with another email in the future, OR does it mean I'm in the "pre-queue queue" and may still hear from him at some point?

I understand that he is a busy man who is making a great contribution to the DIY community.  I don't want to bug him with too many emails.  Whatever the procedure it, I'm happy to follow it. 

My intention has always been to build the mic with the original capsule and then upgrade once everything else is right.  So, I can wait as long as I need to get the right capsule.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: ln76d on September 16, 2013, 11:14:07 AM
Does anyone knows what is the voltage on both 5000pF capacitors?
Is there any existing voltage chart for C12 clone?
I have two 5000pF Siemens styroflex caps, unfortunatelly rated for 160V (pink ring marking).
I know that the genuine were at least 250V, but if the voltage isn't floating at those points, maybe 160V would work?
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Matador on September 16, 2013, 12:21:24 PM
Does anyone knows what is the voltage on both 5000pF capacitors?
Is there any existing voltage chart for C12 clone?
I have two 5000pF Siemens styroflex caps, unfortunatelly rated for 160V (pink ring marking).
I know that the genuine were at least 250V, but if the voltage isn't floating at those points, maybe 160V would work?

C10 (the tube bias cap) will only ever see perhaps 2 or 3V across it.  C11 (the polarization voltage filter) has max about 120V.  So in short, 160V is fine.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: chunger on September 16, 2013, 01:05:56 PM
Sorry for the confusion.  I believe I have always been clear to cease perpetual email attempts with tim AFTER confirmation that you are in his build queue.  Prior to that point you are not officially in line.

Chunger, thanks for responding to my earlier venting. 
I am willing to wait as long as it takes, but I'm still confused about the "process" of getting in Tim's queue.  In my case, I sent an email requesting a capsule about two weeks ago.  Since I have not heard back from Tim, does that mean that I will need to try again with another email in the future, OR does it mean I'm in the "pre-queue queue" and may still hear from him at some point?

I understand that he is a busy man who is making a great contribution to the DIY community.  I don't want to bug him with too many emails.  Whatever the procedure it, I'm happy to follow it. 

My intention has always been to build the mic with the original capsule and then upgrade once everything else is right.  So, I can wait as long as I need to get the right capsule.

You would need to continue contacting him until he confirms you are in the queue.  Unfortunately, if be is severely backlogged and is receiving high volumes of new inquiries, he is not able to respond to emails in a timely manner and you emails may go unresponded to and float to the abyss of the bottom of the inbox.  Really not a good situation for anybody which is why I am working to confirm another viable capsule for the build.  Once demand loosens up a little bit on tims capsules he will likely get back to normal response times.

for now, it is a bit of a brick-wall.  I just shipped out a ton of mics and kits as they were recently restocked and many people prefer a campbell capsule in their builds.

we are working diligently on an alternate solution and I will be receiving a trickle of campbell capsules at some point but I do not know when.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: ln76d on September 16, 2013, 01:23:59 PM
C10 (the tube bias cap) will only ever see perhaps 2 or 3V across it.  C11 (the polarization voltage filter) has max about 120V.  So in short, 160V is fine.

Thank you very much :)
Title: Re: Official C12 Clone - Build and Support Thread
Post by: teacat on September 16, 2013, 07:00:19 PM
Regarding cheaper capsules, (since I might as well not worry about getting a CT12 for a while) I read a lot of folks install and like the RK-12. What about AA's AK12? Anyone install that one in this mike? I had a Stellar CM-5 that I liked quite a bit and I think they use those.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: chunger on September 16, 2013, 07:10:48 PM
Regarding cheaper capsules, (since I might as well not worry about getting a CT12 for a while) I read a lot of folks install and like the RK-12. What about AA's AK12? Anyone install that one in this mike? I had a Stellar CM-5 that I liked quite a bit and I think they use those.

Matador built the first prototype with an AA AK12 capsule and the microphone sounded nice although we did not subject that original prototype to extensive audio tests.  Dave Thomas (CEO at Advanced Audio) has contributed a great deal of knowledge to the DIY community.  He is a die-hard advocate of the CCDA "cathode follower" circuit in the original HT-11A microphone  ;). . . so hopefully he doesn't get too upset about our plate follower layout.  I know his capsule is a 6 micron as opposed to 5 micron in the Microphone-parts.com unit.  Beyond that, since I don't have direct experience with the microphone-parts rk12, I cannot comment. 
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Matador on September 16, 2013, 07:35:04 PM
Regarding cheaper capsules, (since I might as well not worry about getting a CT12 for a while) I read a lot of folks install and like the RK-12. What about AA's AK12? Anyone install that one in this mike? I had a Stellar CM-5 that I liked quite a bit and I think they use those.

Matador built the first prototype with an AA AK12 capsule and the microphone sounded nice although we did not subject that original prototype to extensive audio tests.  Dave Thomas (CEO at Advanced Audio) has contributed a great deal of knowledge to the DIY community.  He is a die-hard advocate of the CCDA "cathode follower" circuit in the original HT-11A microphone  ;). . . so hopefully he doesn't get too upset about our plate follower layout.  I know his capsule is a 6 micron as opposed to 5 micron in the Microphone-parts.com unit.  Beyond that, since I don't have direct experience with the microphone-parts rk12, I cannot comment.

Indeed I thought it sounded fine:  it wasn't in TC's level of quality (and probably not up to tskguy's either, if his 47-type is any indication).  However it had very smooth highs and a balanced sound all-around.

I think it's hard to beat for the price (which I think is about $30 cheaper than the RK12, which I don't have any experience with).
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Woot on September 16, 2013, 07:56:41 PM
Hi, what is the minimum voltage for C12? Can I get away with 200v?

I presume so as the B+ is 120v but I thought I'd double check.

Cheers,

Matt
Title: Re: Official C12 Clone - Build and Support Thread
Post by: JessJackson on September 17, 2013, 06:41:13 PM
It sounds like a grounding issue to me.

Please confirm the following:

1) On your 7-pin XLR connector into the mike, that you have whatever wire is carrying ground also bridges over to the brass lug that connects with the XLR screw.  You can clearly see it in Chunger's build pic:

(http://studio939.zenfolio.com/img/s8/v74/p1456807856-4.jpg)

2) That you "loosened" the XLR screw which actually tightens it against the bottom housing.

Barring that, solder a ground wire to the mike PCB right at the tube pin 9, and feed it up through the top plate, and out of the head basket's mesh.  The set your meter to ohms, and ground one side to the PSU right where it comes out of the 5-pin header, and then connect the other side to your new wire.  Then watch the reading and you assemble the housing and tighten it.

Thanks brother,

You were absolutely right. the moment i tightened that screw into the base, the problem went away and my voltage stays at a nice solid 120v now.

Granted I have built a cardioid only circuit on this board. (I'll take some pics of my mods) here are my voltages. Mic has never sounded better!

B+ 120v
Heater 6.3v
Plate 67.5v
Front Capsule 33.3v
Front Backplate -0.025
Cathode 1.171v

Cheers J
Title: Re: Official C12 Clone - Build and Support Thread
Post by: teacat on September 17, 2013, 06:59:07 PM
Regarding cheaper capsules, (since I might as well not worry about getting a CT12 for a while) I read a lot of folks install and like the RK-12. What about AA's AK12? Anyone install that one in this mike? I had a Stellar CM-5 that I liked quite a bit and I think they use those.

Matador built the first prototype with an AA AK12 capsule and the microphone sounded nice although we did not subject that original prototype to extensive audio tests.  Dave Thomas (CEO at Advanced Audio) has contributed a great deal of knowledge to the DIY community.  He is a die-hard advocate of the CCDA "cathode follower" circuit in the original HT-11A microphone  ;). . . so hopefully he doesn't get too upset about our plate follower layout.  I know his capsule is a 6 micron as opposed to 5 micron in the Microphone-parts.com unit.  Beyond that, since I don't have direct experience with the microphone-parts rk12, I cannot comment.

Indeed I thought it sounded fine:  it wasn't in TC's level of quality (and probably not up to tskguy's either, if his 47-type is any indication).  However it had very smooth highs and a balanced sound all-around.

I think it's hard to beat for the price (which I think is about $30 cheaper than the RK12, which I don't have any experience with).

Thanks for the input, guys.
(...and the project!)
Title: Re: Official C12 Clone - Build and Support Thread
Post by: kcatthedog on September 18, 2013, 05:45:10 AM
Hi everyone,

My voltage readings are off.  I tested the trimmers before installing them and believe they are correctly placed and I have reviewed the entire pcp:

b+  28.7
H      6.3
B        .31
P     22.1

Typically I can turn the trimmer screws many times to little effect.

Suggestions ?

Thx !
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Christopher L on September 18, 2013, 10:23:36 AM
I understand how to determine where the blue and red wires go on the t14 transformer but still am unsure of how to determine the positive and negative leads.  There is no explanation in the thread. 
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Reverend on September 18, 2013, 12:33:58 PM
The volt reading from my B+, with the stock Alcatron capsule is about 150 volts. However, when I try to adjust the trim pot on the B+, it just turns and turns and turns. Does this mean that it's broken?
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Reverend on September 18, 2013, 01:29:43 PM
"Carefully install the capsule and solder the four connections to the proper lugs on the microphone pcb" is what the instructions say. I'm sorry. I can't figure out which lugs do what. Could you post a little bit more in depth instructions for mounting the capsule. What are the "proper lugs?"
FYI, I'm trying to do this with a Peluso CEK12 capsule. Thanks.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: chunger on September 18, 2013, 01:58:23 PM
RB rear backplate
FB front backplate
RC rear capsule
FC front capsule

The particular capsule screw terminals will vary between capsule manufacturers.  Use a multimeter to confirm connections.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Reverend on September 18, 2013, 02:14:43 PM
RB rear backplate
FB front backplate
RC rear capsule
FC front capsule

The particular capsule screw terminals will vary between capsule manufacturers.  Use a multimeter to confirm connections.
OK. Thanks. I see where they are marked now with closer inspection. But I still may need to know how to use the DMM on the capsule to determine.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Matador on September 18, 2013, 05:58:41 PM
Hi, what is the minimum voltage for C12? Can I get away with 200v?

I presume so as the B+ is 120v but I thought I'd double check.

Cheers,

Matt

Any rating over 160V will work fine (which is about as high as you can trim B+).  Most film types carry a 250V rating but 200V will also work.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Matador on September 18, 2013, 06:00:08 PM
Hi everyone,

My voltage readings are off.  I tested the trimmers before installing them and believe they are correctly placed and I have reviewed the entire pcp:

b+  28.7
H      6.3
B        .31
P     22.1

Typically I can turn the trimmer screws many times to little effect.

Suggestions ?

Thx !

Need more input.  Is this without a mike installed?  Start at the basics...no mike installed, what are all of the voltages as measured right at the PSU 5-pin terminal block?
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Matador on September 18, 2013, 06:02:06 PM
I understand how to determine where the blue and red wires go on the t14 transformer but still am unsure of how to determine the positive and negative leads.  There is no explanation in the thread.

In this design, such a distinction doesn't matter.  Once you know primary from secondary you are good.

EDIT:  this statement is true unless you consider matched pairs of mikes.  The phase on both should be consistent to each other.  Easy way to tell is to set up two of them, and then clap a few times (providing something near an impulse response) while recording on your DAW.  Zoom way in to the sample level, and you should see the transients move in the same direction on both channels.  If one "goes up" while the other "goes down" you should swap the secondary wires on one of the mikes.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Matador on September 18, 2013, 06:02:51 PM
The volt reading from my B+, with the stock Alcatron capsule is about 150 volts. However, when I try to adjust the trim pot on the B+, it just turns and turns and turns. Does this mean that it's broken?

No, it just doesn't feature a hard stop.  Once you go back "the other way" it will start to change back again.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Reverend on September 19, 2013, 01:48:23 PM
The volt reading from my B+, with the stock Alcatron capsule is about 150 volts. However, when I try to adjust the trim pot on the B+, it just turns and turns and turns. Does this mean that it's broken?

No, it just doesn't feature a hard stop.  Once you go back "the other way" it will start to change back again.

Ok. But, with the stock Alcatron capsule and a good 6025 tube, turning the B+ trimmer still does nothing to the voltage. Is this a problem?

Another question. I'm getting hum when I listen. When I touch the top of the capsule or another part, the hum goes away, but I can't hear the capsule. Could I have a problem? Could it be the same problem with a cap (C10 or C13?) as described in earlier posts?

Sorry. Ha Ha. Chunger calls himself a newbie....I'm the real deal!
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Matador on September 19, 2013, 02:32:34 PM
Ok. But, with the stock Alcatron capsule and a good 6025 tube, turning the B+ trimmer still does nothing to the voltage. Is this a problem?

Another question. I'm getting hum when I listen. When I touch the top of the capsule or another part, the hum goes away, but I can't hear the capsule. Could I have a problem? Could it be the same problem with a cap (C10 or C13?) as described in earlier posts?

Sorry. Ha Ha. Chunger calls himself a newbie....I'm the real deal!

Ok let's tackle these one at a time:
1) Please remove the mike from the equation.  Unplug it from the PSU, then place a 180K resistor across the B+ and ground connections.  You can stick the leads right in the 7-pin XLR connector and then fire up the PSU.  Is the B+ adjustable?  If so, you have problems in the mike (leading to part 2).
2) Per my previous post:

It sounds like a grounding issue to me.

Please confirm the following:

1) On your 7-pin XLR connector into the mike, that you have whatever wire is carrying ground also bridges over to the brass lug that connects with the XLR screw.  You can clearly see it in Chunger's build pic:

(http://studio939.zenfolio.com/img/s8/v74/p1456807856-4.jpg)

2) That you "loosened" the XLR screw which actually tightens it against the bottom housing.

If you don't have a solid ground path in the mike, then the tube will not draw any current, and thus the B+ will sit high and appear to have little adjustment.  Make sure you have less than 1 ohm resistance between the ground lug in the PSU (pin5 of the 5-pin PSU connector, labeled "P8" I think) and everywhere inside the mike with everything plugged in (POWER OFF!!!!!!) and the outer tube sleeve removed.

The fact that you have hum changes when you touch the parts leads me to believe you have a bum ground path.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: kcatthedog on September 20, 2013, 06:12:04 AM
Hi Matador,

thx,

no mike plugged in.

I was taking readings from the 5 pin PSU block , like in the thread picture. I have a new  Sperry metre and followed the settings in the pictures.

I have sent cat5 pictures of top and bottom of pcp and he has suggested my soldering is suspect ; probable true .

also, after doing the build of the selector, I realized I had put two wrong resisters  on, so I unsoldered them and did install them on the board, all legs were contacting pads.

Trimmers are correctly placed.

kcat

 
Hi everyone,

My voltage readings are off.  I tested the trimmers before installing them and believe they are correctly placed and I have reviewed the entire pcp:

b+  28.7
H      6.3
B        .31
P     22.1

Typically I can turn the trimmer screws many times to little effect.

Suggestions ?

Thx !

Need more input.  Is this without a mike installed?  Start at the basics...no mike installed, what are all of the voltages as measured right at the PSU 5-pin terminal block?
I understand how to determine where the blue and red wires go on the t14 transformer but still am unsure of how to determine the positive and negative leads.  There is no explanation in the thread.

In this design, such a distinction doesn't matter.  Once you know primary from secondary you are good.

EDIT:  this statement is true unless you consider matched pairs of mikes.  The phase on both should be consistent to each other.  Easy way to tell is to set up two of them, and then clap a few times (providing something near an impulse response) while recording on your DAW.  Zoom way in to the sample level, and you should see the transients move in the same direction on both channels.  If one "goes up" while the other "goes down" you should swap the secondary wires on one of the mikes.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: kcatthedog on September 22, 2013, 05:50:52 AM
So, I still do not get correct readings from the power supply.

In terms of trouble shooting, what is next, removing pcp and checking electrical connections with my metre from the bottom of the board ?

In the interim , I started the mike pcp build and made certain I only applied solder to pad , dabbing until it was melting/flowing to ensure a good solder. Stopped  at wires as I need to buy some, should those wire be 18 or 22 gauge ?

thx!

kcat
Title: Re: Official C12 Clone - Build and Support Thread
Post by: thedude on September 22, 2013, 03:15:16 PM
Mic finally put together an workin. But it seems to be an issue with the PSU voltages. When i tested it with the stock capsule and test tube the voltages where ok. When the Tim Campbell  capsule and the my NOS tube was installed the B+ voltage dropped from 120 to 104.

The problem is that i can't trim it up higher than 114 with the TC capsule. Is that an issue, the mic is sounding great. Maybe a little bit more distortion than i expected but in a good way. :)

Any ideas, where do i start troubleshooting?
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Splunge on September 22, 2013, 10:35:08 PM
 I'm trying to build the ELAM/C12 hybrid version of this project. While tracing the circuit to determine exactly how to attach the capsule for this version, I notice that on the PCB (ver. 1.1A), 'FC' is attached to ground and 'RC' is attached to the junction of R16 and C11, but on the schematic (C12_v3) it is shown as exactly the opposite. So which way is correct?
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Reverend on September 22, 2013, 11:16:50 PM
Ok. But, with the stock Alcatron capsule and a good 6025 tube, turning the B+ trimmer still does nothing to the voltage. Is this a problem?
1)Hello Matador, No, when I strapped the 180k resistor between B+ and ground, the B+ trimmer pot was still not adjusting anything.
2)I didn't want work on the possible grounding issue in the mic until this psu thing is resolved.

Another question. I'm getting hum when I listen. When I touch the top of the capsule or another part, the hum goes away, but I can't hear the capsule. Could I have a problem? Could it be the same problem with a cap (C10 or C13?) as described in earlier posts?

Sorry. Ha Ha. Chunger calls himself a newbie....I'm the real deal!

Ok let's tackle these one at a time:
1) Please remove the mike from the equation.  Unplug it from the PSU, then place a 180K resistor across the B+ and ground connections.  You can stick the leads right in the 7-pin XLR connector and then fire up the PSU.  Is the B+ adjustable?  If so, you have problems in the mike (leading to part 2).
2) Per my previous post:

It sounds like a grounding issue to me.

Please confirm the following:

1) On your 7-pin XLR connector into the mike, that you have whatever wire is carrying ground also bridges over to the brass lug that connects with the XLR screw.  You can clearly see it in Chunger's build pic:

(http://studio939.zenfolio.com/img/s8/v74/p1456807856-4.jpg)

2) That you "loosened" the XLR screw which actually tightens it against the bottom housing.

If you don't have a solid ground path in the mike, then the tube will not draw any current, and thus the B+ will sit high and appear to have little adjustment.  Make sure you have less than 1 ohm resistance between the ground lug in the PSU (pin5 of the 5-pin PSU connector, labeled "P8" I think) and everywhere inside the mike with everything plugged in (POWER OFF!!!!!!) and the outer tube sleeve removed.

The fact that you have hum changes when you touch the parts leads me to believe you have a bum ground path.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Matador on September 23, 2013, 01:47:26 AM
I'm trying to build the ELAM/C12 hybrid version of this project. While tracing the circuit to determine exactly how to attach the capsule for this version, I notice that on the PCB (ver. 1.1A), 'FC' is attached to ground and 'RC' is attached to the junction of R16 and C11, but on the schematic (C12_v3) it is shown as exactly the opposite. So which way is correct?

The PCB is correct.  FC goes to ground.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Reverend on September 23, 2013, 08:53:37 AM
OK. With the mic unplugged, I put a 180k resistor between B+ and Ground. The trim pot did not do anything - no adjustment possible. The voltage was quite high. 195 Volts. Since it was cheap, I've already ordered another trim pot off the BOM from Mouser.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: teacat on September 23, 2013, 12:49:08 PM
Finally got the funds together and ordered the parts package. So, I already have a late 50's ge 5-star 6201, and am thinking of using it instead of buying a nos 6072 for now. So, all I have to do is change R17 to 47K? Has anyone done this yet?  What's the diff sonically?

I think R17 should be lowered to about 47K.  With -1V bias, idle current looks to be about 1.25mA with a 6201.  R1 and R2 being 100K should still be fine and give adjustment room around the 120V point.  Plate should be sitting at about 60V at idle (same as 6072).

I'm not sure about how the sonics will be different:  the main reason to switch to a 6201 is availability of high quality tubes at this date.  The 6201 has more robust internal construction than the 6072, so it might be quieter (all other things being equal).  With a lower R17, output impedance will be lowered which should make the amp slightly "faster" (for lack of a better term).

I have some parts in transit to me and I'll build a version with this tube.  I'll post my exact tweaks if you don't want to experiment (or be a guinea pig) in this case.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Matador on September 23, 2013, 02:17:55 PM
OK. With the mic unplugged, I put a 180k resistor between B+ and Ground. The trim pot did not do anything - no adjustment possible. The voltage was quite high. 195 Volts. Since it was cheap, I've already ordered another trim pot off the BOM from Mouser.

With the 180K resistor still in:  tell me the voltages at:
1) The junction of R1 and C1
2) The junction of R1, R2, and C2
3) The junction of R2, R4, and C3
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Reverend on September 24, 2013, 12:32:05 AM
OK. With the mic unplugged, I put a 180k resistor between B+ and Ground. The trim pot did not do anything - no adjustment possible. The voltage was quite high. 195 Volts. Since it was cheap, I've already ordered another trim pot off the BOM from Mouser.

With the 180K resistor still in:  tell me the voltages at:
1) The junction of R1 and C1
2) The junction of R1, R2, and C2
3) The junction of R2, R4, and C3

180k resistor is still in. So, for #1) do I touch black from my DMM to the ground and the red to the lead coming off of the resistor R1 towards C1?
#2) Black on ground and red on the lead coming off of R1 going toward C2?
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Melodeath00 on September 25, 2013, 10:07:39 PM
Quick question...

Is the original C12 power supply regulated or non-regulated? What is the modified Alctron PSU?
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Matador on September 25, 2013, 10:14:15 PM
180k resistor is still in. So, for #1) do I touch black from my DMM to the ground and the red to the lead coming off of the resistor R1 towards C1?
#2) Black on ground and red on the lead coming off of R1 going toward C2?

Ground always stays ground.  If black is ground, and red is your test probe, then touch it in sequence at the places I mentioned above.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Matador on September 25, 2013, 10:14:57 PM
Quick question...

Is the original C12 power supply regulated or non-regulated? What is the modified Alctron PSU?

Non-regulated, but heavily filtered.  I don't understand the second question.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Reverend on September 25, 2013, 10:58:07 PM
180k resistor is still in. So, for #1) do I touch black from my DMM to the ground and the red to the lead coming off of the resistor R1 towards C1?
#2) Black on ground and red on the lead coming off of R1 going toward C2?

Ground always stays ground.  If black is ground, and red is your test probe, then touch it in sequence at the places I mentioned above.

OK. I understand the black to ground thing. Should I touch the red to the lead coming out of the resistor R1 on the side going to C2? And so forth? Thanks and sorry.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Melodeath00 on September 25, 2013, 11:36:33 PM
Quick question...

Is the original C12 power supply regulated or non-regulated? What is the modified Alctron PSU?

Non-regulated, but heavily filtered.  I don't understand the second question.
Second question is in regards to your PCB for the PSU for this project. Is it the same? Non-reg, but heavily filtered? Thanks!
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Matador on September 26, 2013, 12:53:17 AM
180k resistor is still in. So, for #1) do I touch black from my DMM to the ground and the red to the lead coming off of the resistor R1 towards C1?
#2) Black on ground and red on the lead coming off of R1 going toward C2?

Ground always stays ground.  If black is ground, and red is your test probe, then touch it in sequence at the places I mentioned above.

OK. I understand the black to ground thing. Should I touch the red to the lead coming out of the resistor R1 on the side going to C2? And so forth? Thanks and sorry.

That's right.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Matador on September 26, 2013, 12:57:42 AM
Quick question...

Is the original C12 power supply regulated or non-regulated? What is the modified Alctron PSU?

Non-regulated, but heavily filtered.  I don't understand the second question.
Second question is in regards to your PCB for the PSU for this project. Is it the same? Non-reg, but heavily filtered? Thanks!

Oh I see what you meant.

My PSU is identical to the original with the following exceptions:
1) Linear regulator (LM317) for heater in mine, C12 original used Zener reference
2) Full-wave rectifier for B+ in mine, C12 used half-wave rectifier

Both are filtered but non-regulated B+ supply.  Polarization supply and bias supply is identical.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Reverend on September 26, 2013, 02:04:40 AM
OK. With the mic unplugged, I put a 180k resistor between B+ and Ground. The trim pot did not do anything - no adjustment possible. The voltage was quite high. 195 Volts. Since it was cheap, I've already ordered another trim pot off the BOM from Mouser.

With the 180K resistor still in:  tell me the voltages at:
1) The junction of R1 and C1
2) The junction of R1, R2, and C2
3) The junction of R2, R4, and C3

1) R1 and C1  Not getting a good reading. It flashes several different readings but very quickly goes to 1 (left side 1 on DMM read out) and stays there.
2) R1 and C2 Same thing as #1...no real reading 196 for a split second then back to one
    R2 and C2  no real reading.....one
3) R2 and C3  no real reading...one
    R4 and C3  no real reading again except when I touch the top of the trim pot (R4), it goes to zeros

One more thing. R5 to C5 - 1.2
Heater 6.3
Bias -1.1
Title: Re: Official C12 Clone - Build and Support Thread
Post by: cariocaman85 on September 26, 2013, 05:01:30 AM
Hi,

I'm really happy with these C12, but I'm wondering if some Deoxit applied on the tube pins (which are a little bit oxydated, 50 years old nos) might improve the signal/noise ratio?

I currently have deoxit d100L, but I was about to buy deoxit gold, which seems to be better for this application (no lubricant I believe).

What is your opinion?

Thanks,

Rémi
Title: Re: Official C12 Clone - Build and Support Thread
Post by: HellfireStudios on September 26, 2013, 09:35:27 AM
Hi,

I'm really happy with these C12, but I'm wondering if some Deoxit applied on the tube pins (which are a little bit oxydated, 50 years old nos) might improve the signal/noise ratio?

I currently have deoxit d100L, but I was about to buy deoxit gold, which seems to be better for this application (no lubricant I believe).

What is your opinion?

Thanks,

Rémi

DeOxit Gold is for gold plated connectors. Regular DeOxit is for the the other types of connectors, pots, etc.

It couldn't hurt to try it out, but a google search about using DeOxit on a tube wouldn't hurt either (to avoid any mishaps). Let us know how it goes for you.

-James-
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Matador on September 26, 2013, 02:19:34 PM
Hi,

I'm really happy with these C12, but I'm wondering if some Deoxit applied on the tube pins (which are a little bit oxydated, 50 years old nos) might improve the signal/noise ratio?

I currently have deoxit d100L, but I was about to buy deoxit gold, which seems to be better for this application (no lubricant I believe).

What is your opinion?

Thanks,

Rémi

What exactly do you mean by "improve"?  Is it too quiet?  Too much background hiss?  To little capsule signal?

Before you do anything else, did you make sure you scrubbed the area around the capsule connections on the PCB with good quality IPA?  This area needs to be clean and free of solder flux.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: cariocaman85 on September 26, 2013, 07:13:00 PM
I explain myself:

The mics are both fonctionning very well, we did a great piano record few days ago.

But one of the mic had a few crackles, and intermittent hiss on last monday, so I was worried about the tube. I opened the mike, removed the tube, then replaced it, and everything went fine. But yesterday, the same thing happened so I started again the procedure, but without good results. When I gently touched the body I clearly could hear bad contacts, and crackles.

So this morning I retensioned the socket which I believe was a little bit to much loosen during the building, then I replaced the tube and it went fine, no more crackle nor hiss.
So It appears that it solved my problem.

By the way I noticed some oxydation along the tube pins, which I believe it's normal for a 50 years old tube, but I was in the process of troubleshooting this crackles and I thought about removing this oxydation in order to get a better contact.

That's why I'm wondering if deoxit might improve this connection between the tube and the socket. The PCB is absolutly clean of flux, we were very carreful during the building of the mic.
As I looked since this minute every forum on the web to find a clear answer to this question, I noticed that deoxit gold is designed to improve tube to socket contact dixit the manufacter (high temps rates and every metal connexion).
But apparently some people recommand it, and some don't. That's why I'm a bit confused.

So for the moment I have 2 mikes working perfecly. I hope it will last  ;)

Thanks for your comments,

Best,

Rémi

Title: Re: Official C12 Clone - Build and Support Thread
Post by: originalmusician on September 27, 2013, 02:34:26 AM
About how many AC volts should I get at the 200v connector shown in the attached picture when measured in circuit?


Title: Re: Official C12 Clone - Build and Support Thread
Post by: Matador on September 27, 2013, 12:44:17 PM
About how many AC volts should I get at the 200v connector shown in the attached picture when measured in circuit?

You should get 200*SQRT(2) = ~280V across the two terminals.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: chunger on September 27, 2013, 01:37:07 PM
I explain myself:

The mics are both fonctionning very well, we did a great piano record few days ago.

But one of the mic had a few crackles, and intermittent hiss on last monday, so I was worried about the tube. I opened the mike, removed the tube, then replaced it, and everything went fine. But yesterday, the same thing happened so I started again the procedure, but without good results. When I gently touched the body I clearly could hear bad contacts, and crackles.

So this morning I retensioned the socket which I believe was a little bit to much loosen during the building, then I replaced the tube and it went fine, no more crackle nor hiss.
So It appears that it solved my problem.

By the way I noticed some oxydation along the tube pins, which I believe it's normal for a 50 years old tube, but I was in the process of troubleshooting this crackles and I thought about removing this oxydation in order to get a better contact.

That's why I'm wondering if deoxit might improve this connection between the tube and the socket. The PCB is absolutly clean of flux, we were very carreful during the building of the mic.
As I looked since this minute every forum on the web to find a clear answer to this question, I noticed that deoxit gold is designed to improve tube to socket contact dixit the manufacter (high temps rates and every metal connexion).
But apparently some people recommand it, and some don't. That's why I'm a bit confused.

So for the moment I have 2 mikes working perfecly. I hope it will last  ;)

Thanks for your comments,

Best,

Rémi

For what its worth, I user deoxit on matador's first prototype build when I put a nos ge 6072a in for testing.  I used it primarily to lube the pins because the socket was so tight.  There were no ill effects.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: originalmusician on September 27, 2013, 10:31:32 PM
About how many AC volts should I get at the 200v connector shown in the attached picture when measured in circuit?

You should get 200*SQRT(2) = ~280V across the two terminals.

Thanks Matador!

I just bought a used Fluke 87V of Ebay because my el cheapo Harbor Freight meter appears to finally have given up the ghost and be spitting out whack readings in AC mode.

http://www.ebay.com/itm/Fluke-87V-TRMS-Digital-Multimeter-/141063307290?ssPageName=ADME%3AL%3AOC%3AUS%3A3160&nma=true&si=ajvyb1JvHX5QOXh17x7EIC3561k%253D&orig_cvip=true&rt=nc&_trksid=p2047675.l2557

Since the Fluke is used and of unknown history, I was a little concerned about it being accurate. So I put in a new battery, set the meter to Ohms mode, plugged a lead into the Ohms jack, and carefully touched the ohms probe tip to the top of the the mA/uA output jack. This bypassed the LEAD alarm and gave me a reading of 1.000K Ohms. Apparently, this measures the reference voltage and part of the precision resistor network, and it is spot on for this meter.

I was trying to figure out a good test of the AC function, and after work tonight, my neighbor stopped by with a CircuitSpecialist.com meter. Both meters tested ~240V across the transformer winding. I'm guessing this is a realistic real world measurement vs. the theoretical measurement you provided that is free from inefficiencies and losses.

I think my new meter is good to go!  :)

Title: Re: Official C12 Clone - Build and Support Thread
Post by: Matador on September 27, 2013, 11:01:24 PM
Yeah, 280 assumes no current draw....sorry I should have specified that.  But 240 before the rectification sounds a tad low, but if you can trim out the B+ voltage I wouldn't worry about it.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Reverend on September 28, 2013, 01:13:46 AM
180k resistor is still in. So, for #1) do I touch black from my DMM to the ground and the red to the lead coming off of the resistor R1 towards C1?
#2) Black on ground and red on the lead coming off of R1 going toward C2?

Ground always stays ground.  If black is ground, and red is your test probe, then touch it in sequence at the places I mentioned above.



OK. I understand the black to ground thing. Should I touch the red to the lead coming out of the resistor R1 on the side going to C2? And so forth? Thanks and sorry.

That's right.

1) R1 and C1  Not getting a good reading. It flashes several different readings but very quickly goes to 1 (left side 1 on DMM read out) and stays there.
2) R1 and C2 Same thing as #1...no real reading 196 for a split second then back to one
    R2 and C2  no real reading.....one
3) R2 and C3  no real reading...one
    R4 and C3  no real reading again except when I touch the top of the trim pot (R4), it goes to zeros

One more thing. R5 to C5 - 1.2
Heater 6.3
Bias -1.1
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Christopher L on September 28, 2013, 10:37:32 AM
Thanks Chunger and Matador for such a fun diy project.  I have a working mic, but one that is a bit noisy.  When replacing the stock capsule with Tim's I damaged one of the 5000pf capacitors by touching my iron against it a bit.  I found some on ebay but with 160v rating(will this work), this was not the culprit.  All my measurements are correct except the bias fluctuates so much that I'm unable to get the -1.0v. Testing the mic last night there were times when I heard a pop and one time the mic completely cut off for a second or two.  Should the two ground traces on the psu be connected to something. Please help.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Matador on September 28, 2013, 12:31:29 PM
1) R1 and C1  Not getting a good reading. It flashes several different readings but very quickly goes to 1 (left side 1 on DMM read out) and stays there.
2) R1 and C2 Same thing as #1...no real reading 196 for a split second then back to one
    R2 and C2  no real reading.....one
3) R2 and C3  no real reading...one
    R4 and C3  no real reading again except when I touch the top of the trim pot (R4), it goes to zeros

One more thing. R5 to C5 - 1.2
Heater 6.3
Bias -1.1

That behaves like a meter that is over it's limit.

What's the max voltage the meter can read on it's DC setting?  It's often printed right on the meter itself.

I'm guessing 200V.  ;)
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Reverend on September 28, 2013, 12:46:15 PM
1) R1 and C1  Not getting a good reading. It flashes several different readings but very quickly goes to 1 (left side 1 on DMM read out) and stays there.
2) R1 and C2 Same thing as #1...no real reading 196 for a split second then back to one
    R2 and C2  no real reading.....one
3) R2 and C3  no real reading...one
    R4 and C3  no real reading again except when I touch the top of the trim pot (R4), it goes to zeros

One more thing. R5 to C5 - 1.2
Heater 6.3
Bias -1.1

That behaves like a meter that is over it's limit.

What's the max voltage the meter can read on it's DC setting?  It's often printed right on the meter itself.

I'm guessing 200V.  ;)

For those readings, I had it set on 200V for all. There is a 600 setting. Here's my results measuring on the 600V setting.

1) R1 and C1 ....300V
2) R1 and C2 .....242V
    R2 and C2 .....252
3) R2 and C3......208
    R4 and C3......not sure how to take this reading. Touching the top of the trim pot, 000

Thanks for walking me through this.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: kcatthedog on September 28, 2013, 07:36:31 PM
hi, i have a new mastech ms8268.  I am trying to test the AMI T14 transformer. i am using the pairs of reds and blue wires separately as the pictures but the readings never stabilize.  i have the metre set for ohms and it has an auto ranging function.

i am working on the mike. I took the pcp for the power supply to a tech to diagnose. He confirmed my solders were good, so I am curious to learn what I did wrong to explain incorrect variable resister readings ?

 
thanks ,

kcat
Title: Re: Official C12 Clone - Build and Support Thread
Post by: brewbacca on September 28, 2013, 09:23:09 PM
Hi there, I have a couple of these I'm trying to do, but I'm a little confused about some of the readings I'm getting off the power supplies, and want to make sure those are ok before moving onto the microphones.

In the picture you can see that I'm trying to check the power transformer's voltage, and on both I'm getting around 6-7V on each of the 9.5V terminals, and around 110V on each of the 200V terminals. It this normal? I checked the second power transformer before modding the power supply and was getting similar reading at that point. Also, when I check B+ the voltage starts around 100V on each and climbs to around 210V over the course of a minute or two. Is that normal? This is the first power supply I've modded so I'm kind of a newbie about voltage, although I know not to touch anything with my hands that isn't made out of rubber :)

Thanks!
Title: Re: Official C12 Clone - Build and Support Thread
Post by: originalmusician on September 28, 2013, 09:37:36 PM
Hi there, I have a couple of these I'm trying to do, but I'm a little confused about some of the readings I'm getting off the power supplies, and want to make sure those are ok before moving onto the microphones.

In the picture you can see that I'm trying to check the power transformer's voltage, and on both I'm getting around 6-7V on each of the 9.5V terminals, and around 110V on each of the 200V terminals. It this normal? I checked the second power transformer before modding the power supply and was getting similar reading at that point. Also, when I check B+ the voltage starts around 100V on each and climbs to around 210V over the course of a minute or two. Is that normal? This is the first power supply I've modded so I'm kind of a newbie about voltage, although I know not to touch anything with my hands that isn't made out of rubber :)

Thanks!

You are measuring the transformer incorrectly. You need to touch your negative meter probe to one blue wire connector and touch the positive probe to the other blue wire connector. That should give you somewhere around 250vac. Then use your meter probes to jump across the yellow transformer wires in a similar manner. For this, you should get somewhere around the 10v.

Post back with your readings.

I got a similar slow reading to you when I checked my B+. I'm unsure of the explanation of why this occurs.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: brewbacca on September 28, 2013, 09:42:01 PM
Ah! Ok, those readings are much better (~212V and ~11V).  Thanks for the heads up!
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Matador on September 28, 2013, 10:03:40 PM
Yes if you ground the negative probe and then touch each primary, you are only getting half the winding (wrt ground).  Measuring across the secondary will show you what you are testing for.

Remember that we derive the ground by referencing the split between the rectifier diodes:  hence we can only ever measure one half of the AC signal on our meter.

Stealing a Wikipedia image:

(http://upload.wikimedia.org/wikipedia/commons/thumb/d/d5/Gratz.rectifier.en.svg/1200px-Gratz.rectifier.en.svg.png)

If you measure right across the secondary, your meter will see the full signal swing just like the right side of the picture.  If you ground the meter, your meter will only see the rectified peaks which is exactly half of the peak-to-peak swing.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: originalmusician on September 28, 2013, 10:11:06 PM
Ah! Ok, those readings are much better (~212V and ~11V).  Thanks for the heads up!
Interesting.

My mic PS came with the same alternate transformer as you (the windings are reversed compared to the one in Chunger's photos). I got ~242v and 11.4v readings. With these values, the variable resistors allowed for plenty of adjustment on either side of the B+ target  (120v) when I put a 180K resistor across B+ and ground.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Matador on September 28, 2013, 10:11:23 PM
1) R1 and C1 ....300V
2) R1 and C2 .....242V
    R2 and C2 .....252
3) R2 and C3......208
    R4 and C3......not sure how to take this reading. Touching the top of the trim pot, 000

Thanks for walking me through this.

Hmmm...R1, R2, and C2 are all the same node:  why you measure 242V then 252V is odd.

So you are dropping 50V across R1 which (is supposed to be) 91K, which means there is 0.55mA flowing through R1.  You loose another 45-50V across R2 which is consistent with 0.55mA flow.

Can you tell me what the printing is on the top of R4?  It's behaving like the wrong trim pot is installed in there (like several have done previous in the thread).
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Reverend on September 29, 2013, 04:43:21 AM
1) R1 and C1 ....300V
2) R1 and C2 .....242V
    R2 and C2 .....252
3) R2 and C3......208
    R4 and C3......not sure how to take this reading. Touching the top of the trim pot, 000

Thanks for walking me through this.
I took great care in making sure that I got each component in  right and followed directions to a t.
That being said I still could have made mistakes of course. Ha Ha.
My trim pot still doesn't change the voltage value .....can't be adjusted.
Thanks and sorry for the confusion. Still having fun...but I want to use this mic on my session this week....probably not possible now, but I would appreciate your help. My plan was to build two of these, but now, I had better focus on just one.

Hmmm...R1, R2, and C2 are all the same node:  why you measure 242V then 252V is odd.

So you are dropping 50V across R1 which (is supposed to be) 91K, which means there is 0.55mA flowing through R1.  You loose another 45-50V across R2 which is consistent with 0.55mA flow.

Can you tell me what the printing is on the top of R4?  It's behaving like the wrong trim pot is installed in there (like several have done previous in the thread).
Wow. On the blueprint of the pcb for the power supply, there is an R4 resistor where, on my pcb, and in the pictures, that's where the B+ adjust trim pot goes. Confusing. I would not have put the trim pot there except that it's that way it is on my pcb, with the dotted line around the B+ adjust and all.
So, is my power supply ok? Still not getting the trim pot in the B+/R4/whatever to adjust the voltage.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Pohjamonni on September 29, 2013, 05:01:07 AM
Hi!

Any word on Tim Campbell?? I haven't been able to reach him via email.

I've been on his list for two capsules since may 14th and at that time he told that capsules will be ready in 10-12 weeks. I know that Tim is extremely busy but it has been almost 20 weeks now and I'm afraid that my order is lost or something... I also have checked my spam folder regularly.

Thanks for the great project. I have a pair of mics ready and working, only missing those capsules.

-Pohjamonni
Title: Inconsistency
Post by: kcatthedog on September 29, 2013, 09:26:37 AM
"Wow. On the blueprint of the pcb for the power supply, there is an R4 resistor where, on my pcb, and in the pictures, that's where the B+ adjust trim pot goes. Confusing. I would not have put the trim pot there except that it's that way it is on my pcb, with the dotted line around the B+ adjust and all."

Is there an inconsistency in our directions  ?
Title: Re: Official C12 Clone - Build and Support Thread
Post by: scott_humphrey on September 29, 2013, 10:23:13 AM
Hi!

Any word on Tim Campbell?? I haven't been able to reach him


I recently requested two additional capsules by email, but haven't yet received a confirmation email....

I'm fortunate to have a TC capsule in this C12-style mic and it sounds great. I ordered it in 2010 before the gold rush.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Matador on September 29, 2013, 10:51:24 AM
Wow. On the blueprint of the pcb for the power supply, there is an R4 resistor where, on my pcb, and in the pictures, that's where the B+ adjust trim pot goes. Confusing. I would not have put the trim pot there except that it's that way it is on my pcb, with the dotted line around the B+ adjust and all.
So, is my power supply ok? Still not getting the trim pot in the B+/R4/whatever to adjust the voltage.

I'm not sure how to answer this:  R4 is the trim pot. 
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Melodeath00 on September 29, 2013, 04:48:56 PM
Hi!

Any word on Tim Campbell?? I haven't been able to reach him via email.

I've been on his list for two capsules since may 14th and at that time he told that capsules will be ready in 10-12 weeks. I know that Tim is extremely busy but it has been almost 20 weeks now and I'm afraid that my order is lost or something... I also have checked my spam folder regularly.

Thanks for the great project. I have a pair of mics ready and working, only missing those capsules.

-Pohjamonni
Just to give you some consolation, I am in the same boat as you. I was put on the list on May 14, as well, with a 10-12 week lead time. After 13 weeks I asked for an update, and Tim estimated another 4 weeks. It's been 6 or 7 weeks since then, I believe. Luckily I'm not in a rush, but I'd love to start building my C12. I haven't gotten another update from Tim. I hope the backlog of capsules can be alleviated soon. It must be overwhelming for Tim haha
Title: Re: Official C12 Clone - Build and Support Thread
Post by: kcatthedog on September 29, 2013, 05:24:56 PM
a technician i spoke with yesterday called the trimmers, variable resisters : perhaps that explains this misunderstanding ?
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Pip on September 29, 2013, 10:02:48 PM
a technician i spoke with yesterday called the trimmers, variable resisters : perhaps that explains this misunderstanding ?

They are one and the same. If you look back in the thread and follow Chungers awesome build thread there is little chance to get lost. The most common mistake is putting the wrong trimmer in the wrong place as they all look the same yet all three are different values.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Reverend on September 30, 2013, 12:53:01 AM
Wow. On the blueprint of the pcb for the power supply, there is an R4 resistor where, on my pcb, and in the pictures, that's where the B+ adjust trim pot goes. Confusing. I would not have put the trim pot there except that it's that way it is on my pcb, with the dotted line around the B+ adjust and all.
So, is my power supply ok? Still not getting the trim pot in the B+/R4/whatever to adjust the voltage.

I'm not sure how to answer this:  R4 is the trim pot.

Ok. What I did was measure by putting the red lead of the DMM on the metal screw on top of the trim pot/R4, and of course the black on ground, and I get straight zeros.
My main problem now is that the B+ trim pot has never adjusted the voltage. I have a new trim pot or R4 that I got from Mouser. Should I install it and see what happens? Thanks.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Matador on September 30, 2013, 01:09:43 AM
Measuring the screw won't tell you anything useful:  it isn't part of the circuit (unless the pot is busted).

As I asked before, please tell me the markings on the top of R4.  I'm guessing you just have the wrong value (which has happened on a few other occasions in this thread).  Measuring B+ is as good as measuring the voltage across the pot though.

Let's go back to basics:  how exactly are you measuring B+?  How did you connect the 180K resistor and connect it to the PSU?
Title: Re: Official C12 Clone - Build and Support Thread
Post by: chunger on September 30, 2013, 01:10:38 AM
Ok. What I did was measure by putting the red lead of the DMM on the metal screw on top of the trim pot/R4, and of course the black on ground, and I get straight zeros.
My main problem now is that the B+ trim pot has never adjusted the voltage. I have a new trim pot or R4 that I got from Mouser. Should I install it and see what happens? Thanks.

To measure B+, use your DMM on the 5 point terminal block at P6 and P5.

(http://studio939.zenfolio.com/img/s8/v85/p1434208124-4.jpg)
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Reverend on September 30, 2013, 01:35:15 AM
Ok. What I did was measure by putting the red lead of the DMM on the metal screw on top of the trim pot/R4, and of course the black on ground, and I get straight zeros.
My main problem now is that the B+ trim pot has never adjusted the voltage. I have a new trim pot or R4 that I got from Mouser. Should I install it and see what happens? Thanks.

To measure B+, use your DMM on the 5 point terminal block at P6 and P5.

(http://studio939.zenfolio.com/img/s8/v85/p1434208124-4.jpg)
OK. That makes sense. I was thinking "check the voltage at the junction" or something crazy, I don't know. Anyway it measures 187V. Thanks again.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Pohjamonni on September 30, 2013, 01:48:12 AM
Hi!

Any word on Tim Campbell?? I haven't been able to reach him via email.

I've been on his list for two capsules since may 14th and at that time he told that capsules will be ready in 10-12 weeks. I know that Tim is extremely busy but it has been almost 20 weeks now and I'm afraid that my order is lost or something... I also have checked my spam folder regularly.

Thanks for the great project. I have a pair of mics ready and working, only missing those capsules.

-Pohjamonni
Just to give you some consolation, I am in the same boat as you. I was put on the list on May 14, as well, with a 10-12 week lead time. After 13 weeks I asked for an update, and Tim estimated another 4 weeks. It's been 6 or 7 weeks since then, I believe. Luckily I'm not in a rush, but I'd love to start building my C12. I haven't gotten another update from Tim. I hope the backlog of capsules can be alleviated soon. It must be overwhelming for Tim haha

Hi!

Thanks. That was kind of an information I was expecting/hoping to hear. Maybe they will be ready soon.

-Pohjamonni
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Reverend on September 30, 2013, 02:42:10 AM
Measuring the screw won't tell you anything useful:  it isn't part of the circuit (unless the pot is busted).

As I asked before, please tell me the markings on the top of R4.  I'm guessing you just have the wrong value (which has happened on a few other occasions in this thread).  Measuring B+ is as good as measuring the voltage across the pot though.

Let's go back to basics:  how exactly are you measuring B+?  How did you connect the 180K resistor and connect it to the PSU?
I connected the 180K resistor by putting it in the #5 and #6 pin holes in the cable.
OK. I had the trimmer pots in all the wrong places. I'm a dumba**. I'll desolder them and put them right and start this whole process again as per Chunger's build instructions and see what I get. I'm hoping that this solves my problems with my this build or at least with the psu. If you think that I should replace those trimmers with new ones, let me know - in the meantime I'll try to re-use the trimmer pot resistors. Back to work. I hope not to bug you much more, but I may have some ground issues with the mic.  I'll get to that later. Thanks again.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: brewbacca on September 30, 2013, 05:07:45 PM
I decided to try the micandmod mk-12 capsule since I also wasn't able to get a response from Tim. I finished up the mod on one of my two mics and it seems to be working. How am I supposed to know what voltage should be going through B+, heater, bias etc with a different capsule? I looked for some information on it, but didn't see anything that stood out.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Matador on September 30, 2013, 11:01:30 PM
I decided to try the micandmod mk-12 capsule since I also wasn't able to get a response from Tim. I finished up the mod on one of my two mics and it seems to be working. How am I supposed to know what voltage should be going through B+, heater, bias etc with a different capsule? I looked for some information on it, but didn't see anything that stood out.

Changing the capsule should not effect any of the voltages.  If it worked with one capsule it should be the same with any other.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: brewbacca on September 30, 2013, 11:49:38 PM
Ok, cool. I tried setting it up for B+ 120V, but my B+ is jumping around a bit and I can't quite get it up to 120V. Without the mic it's around ~210V but with the mic it's around ~100V. The highest I can get it is around 114V before the trim pot maxes (minimums?) out. Is that an issue? (It sounded pretty good to me). I double checked and my trim pots are all in the correct places.

Thanks! (Also, thanks for putting this project out there! It's been fun to work on)
Title: Re: Official C12 Clone - Build and Support Thread
Post by: kcatthedog on October 01, 2013, 07:41:33 PM
your state to connect the two red leads from the tranny to the positive and negative pins on the input to the microphone.

I thought the tranny gives AC voltage therefore, start is the common or neutral  and the finish is the high lead voltage?

or does it not matter which red lead is soldered to the positive and which to the negative ?

thx.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Matador on October 01, 2013, 10:59:52 PM
your state to connect the two red leads from the tranny to the positive and negative pins on the input to the microphone.

I thought the tranny gives AC voltage therefore, start is the common or neutral  and the finish is the high lead voltage?

or does it not matter which red lead is soldered to the positive and which to the negative ?

thx.

The primary connects to the output cap and ground.  The secondary connects to the XLR jack pins 5 and 6.

And no, it doesn't matter which of the primary leads goes to the output cap (assuming that your red wires are the primary).  If you check earlier in the thread, the primary will have a much higher DC resistance than the secondary so that's a good way to check.

If you are building a matched pair, it's probably best to match the phases between the two (so that a positive going sound pressure when the mike capsules are close) so that they can be easily summed together without phase issues.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: kcatthedog on October 02, 2013, 11:30:46 AM
thank you,

my understanding is the blue thicker leads are the primary and the thinner red wires are the secondary

I understand this is a standard transformer protocal

I have built an ms kit before and am really appreciating the thread and support.


kcat
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Matador on October 02, 2013, 01:36:14 PM
thank you,

my understanding is the blue thicker leads are the primary and the thinner red wires are the secondary

I understand this is a standard transformer protocal

I have built an ms kit before and am really appreciating the thread and support.


kcat

I would caution about making any such assumptions:  if you read the U87 thread, many users got stuck because the wires were the opposite color as the spec sheet indicated.

I would suggest you measure the transformer to be sure, otherwise you'll have all sorts of problems.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: jplebre on October 03, 2013, 06:22:32 AM
Hey guys

I got a bit over-excited with the filing and I'm afraid I might have done some dudu. The cover for the traces is green, and so is other stuff like the cap boundaries etc.
I still have connection between R17 and plate, and P4 and R11, but there are other green traces around there that seem to be cut.

Is there anything else going right next to the cap (C12) box?
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Matador on October 03, 2013, 01:30:30 PM
Hey guys

I got a bit over-excited with the filing and I'm afraid I might have done some dudu. The cover for the traces is green, and so is other stuff like the cap boundaries etc.
I still have connection between R17 and plate, and P4 and R11, but there are other green traces around there that seem to be cut.

Is there anything else going right next to the cap (C12) box?

There's nothing really near the C12 cutout.  Can you take some photo's of what you are referring to?  I can't make it out.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: jplebre on October 04, 2013, 09:11:30 AM
Thanks for the reply. I've checked connections with continuity and all seems good just afraid I may have cut something that I'm missing.
You can see that on the bottom one I eat away a bit of the green line (solder mask? trace?) and on the top "cut" there's a glare of copper.

(http://caffeinatedaudio.co.uk/wp-content/uploads/2013/10/photo-2.jpg)
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Matador on October 04, 2013, 10:23:30 AM
I see!  You should be fine.

Most of the cutout is surrounded by a ground pour, so that is the thin shiny line of copper that you see.  The green is the FR4 board material (the soldermask is the yellow part).  I don't see anything wrong there, just be sure of a few things:

1) There is no continuity between the P4 trace (the one that bends down on the top and goes alongside the cutout) and the ground pour (P6 node).  Based on the picture the space between them along the top looks clear but a whisker of copper will ruin your day.  Simple ohms check between the two points should read "infinite", or a continuity check should read "open" (or no sound if your meter uses a speaker)
2) Apply some nail polish (or clear lacquer) anywhere you see shiny copper exposed on the cutout:  the soldermask normally protects it from corrosion but now that it's exposed you'll want to reseal it
Title: Re: Official C12 Clone - Build and Support Thread
Post by: ArnoldLayne on October 04, 2013, 11:07:57 AM
Hello,
My mic has the same symptoms as Ericbazar had on page 20.
Apparently, he solved his problem by bridging FB and RB on his CT12, but I am using a RK-12, and had the same problem with the stock capsule.
Does it make sese to bridge FB and RB even though it's single backplate capsule ?

Also, I have found a continuity between xp2, P8 and ground on the mic PCB. I can't read the schematics, but surely this isn't normal ?
Title: Re: Official C12 Clone - Build and Support Thread
Post by: jplebre on October 04, 2013, 11:32:30 AM
Thanks Mat!
no continuity between P4 and ground! so all honky dory!

I keep telling myself I shouldn't put my favourite album of the month whilst I'm DIY, but I keep insisting on it. Then this happens! Too much headbanging  8)

So far, so good! PSU built in an hour and working fine (voltages read fine, HT takes a bit to ramp to 190v but other than that all good!
Title: Re: Official C12 Clone - Build and Support Thread
Post by: chunger on October 04, 2013, 08:11:22 PM

(http://caffeinatedaudio.co.uk/wp-content/uploads/2013/10/photo-2.jpg)

File only one side!!! . .  . the one without a critical trace. 
Title: Re: Official C12 Clone - Build and Support Thread
Post by: zandru on October 05, 2013, 10:48:44 PM
Greetings to all fellows Group Diy,

This particular C-12 clone build has kept me intrigued for quite some time.
I'm about to start this build. I've been a audio electronics designer & builder
beginning in the early 1970's, working closely will Tube mics, HiFi and pro
recording equipment since then. A professional spanning my earliest days.

I very much enjoy the follow-up after posts to chunger's easy to understand
and follow instructions.

It's also nice to read that Diy'ers have pointed out a some inconsistencies
and many questions of interest pertaining to this or that , and also making
suggestions.

I have a sizable hoard of original CK-12 capsules , mostly collected from
Noreclo, AKG C12A's-B's and some other later mics that used the CK-12.
I will not be using any one of these high quality CK-12's for this build.

My only true concern revolves around Tim Campbell's CT12 capsule,
"mystery / availably". I'm curious about Tim's manufacturing process etc!.

It would be interesting to find out that Tim edge-threads the secondary
backplate that threads into the primary backplate which is mounted into
the insulated backplate mounting ring ; just like the original CK-12 capsule.

I'm very familiar with the CK-12 capsule; based on my evolving experience,
when I dismantled my first of many which had been damaged in the early
1970's.  I was very curious to see, learn and understand the inner workings.

Soon after, I contacted AKG with the help of a dear old friend (Manfred
Krauter) who as a teenager working consecutive springs seasons at AKG
in the early 60's as an apprentice machinist which was part of his technical
school training. As It turned out, Manfred had contacts over at AKG.

I explained to Manfred what I hough I would need for an CK-12 Capsule
restoration.  So! Manfred wrote a letter to AKG and a week or so later,
Manfred received a call all from from an old friend from AKG, informing
him that for a nominal fee (shipping that is) he would mail out a Care
package.

Three weeks go by and the care package arrives at Manfred's place
As soon a as I open the way larger box than I had expected, I was totally
floored by the contents within the box.

The contents included:

Well over two dozen prepared diaphragms that were obviously tensioned
and mounted to a thin flat square frame that were individually enclosed in
protective container-like packet.

A spiral bound CK-12 assembly persons instruction binder

A diagram with instructions pertaining to the construction of a rather simple
to build multi-station assembly Jig for assembling the CK-12 capsule.

Now! The Mother Load, " I think my My Heart stopped for ten seconds.

Every Part; Yes! every part needed to assemble at least a dozen plus capsules.
Yah!  The brass mounting rings, Insulated mounting rings with primary & secondary
backplates, spacing rings, screws and whatever else that wonderful AKG friend of
Manfred had sent.

Of course this was to be a one shot deal at the time, which I'm very grateful for.
But enough about me.

I do feel that there's somewhat of a concern over tim Campbell's CT12, to which
I have mentioned the capsule being shrouded in mystery. His webpage lacking
in info, No detailed specs etc!.  About the only thing I know is the capsule costs
2,000 Kroner or $365 U.S. Also it's said that Tim uses a CNC to mill some of the
components; for that to me still puts the price into question. There are questions
that I would most like to Know. How about you?. So! please chime in to help
advance this thread.

CHEERS…ZANDRU...
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Tim Campbell on October 06, 2013, 02:34:49 AM
Zandru,
I have no idea what you are implying by your first ever post on this forum. I have been a member of this group for more than 10 yrs. Many of the members here know me personally. I don't post using an alias and all my personal information is easily accessible. If you search this forum you'll find many contributions from me about all aspects of capsule manufacture going back 10 years.
I first offered my CT12 capsule for sale here more than 6 years ago. Probably close to 2000 of my capsules are in use out in the world at large.
This is a build thread for Chunger's mic not a capsule thread and so I'm not sure how hijacking this thread to discuss me or inconsequential details of my capsules serves that end especially given the current limited availability of my capsule for this project. Your time might be better served investigating a capsule you could actually use in this build since my OEM customers currently consume almost all of my output leaving very few of my capsules for sale to private customers.
Ultimately if you have any doubts about my capsules please buy someone elses or use one of your original AKG's.
Currently Josephson, 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.

Title: Re: Official C12 Clone - Build and Support Thread
Post by: Phrazemaster on October 06, 2013, 05:40:45 AM
I'm not sure that requiring a manufacturer to divulge all the details of their manufacturing process is fair. The art of capsule creation is indeed one "shrouded in mystery" and very few capsule makers share their secrets. It is a business, after all. I very much doubt if Stradivarius went around telling everyone what varnish he used or how he created his signature sound.

For example, if you visit Neumann's own site, you'll find that although they do devote a page to a general description of their capsule making process - http://www.neumann.com/?lang=en&id=about_us_history_part_7 (http://www.neumann.com/?lang=en&id=about_us_history_part_7), they in fact do not discuss intimate details such as hole placement, patterning, how to machine the backplates, etc. Nor would one expect them to.

In addition, Tim never claimed to create "original C12 capsules" - how could he? He is not AKG. It is always clear from the beginning that, as close to the originals as they may be,  these are "clones" or "recreations" or "C12-like." And judging by the number of high-end customers he has, they are particularly excellent. As DIY guys/gals we have to recognize the limitations of the forms we are creating. Some parts are just not available, or are simply out of reach. Like a VF14 tube for a U47 clone - or an actual C12 capsule for a C12 clone. But that's the fun of it all, DIY - not buying original everything and sticking it together. For that, we could all just save up and buy an original. There's something thrilling about creating something ourselves that makes it all worthwhile, and the fact that our microphones are not the "actual" microphone we are cloning is obvious from the get-go.

I must agree with Tim, Zandru, the post sounds inflammatory. If you are sharing because you want to sell your hoard, please post in the black market. But singling out Tim seems wrong. I did not hear you denigrating any of the other C12 capsule manufacturers in Tim's list, who most likely have left the details of their capsules "shrouded in mystery" too, and if you visit their website the best you will come up with is their capsules are "faithful recreations" and not much else in the way of technical details.

Having said all that, it's great you have a hoard of C12 capsules. But nobody ever expects a recreated capsule to be micron-perfect to the originals. This is, after all, DIY.

Thanks, Tim, for making your capsules available to this DIY community. I understand you are so swamped you have a 10-week wait time. This only speaks to the quality of your work. Thank-you.

Cheers,

Mike
Title: Re: Official C12 Clone - Build and Support Thread
Post by: zandru on October 06, 2013, 09:06:39 AM
chunger… If You please,  I hope It's ok by you…fellow Group Diy'er & cohort may need relief from emotional distraught…
I'm not trying to step on your toes…

Tim,

It seems that you have no Idea what I'm implying on my first ever post on this forum. You have gone to some length referencing yourself (which is most applicable).
However my post deals with a fervent interest in building the C-12 clone in which I came to embrace chunger's easy to understand assembly instructions that has
caused me to proceed with the project. My post is in no way an attempt to (as you claim) Hijack chunger's thread".

Tim, You and your CT12 are by no means inconsequential within chunger's "official C12 Clone-Build and Support Thread". The CT12 is in fact of considerable
relevance and if you sense that you were disrespected in any way by me , you have been mistaken. I myself have also referenced myself to some length in my
first post but certainly not as a ploy to sell anything as referred to by you; and definitely did not attempt to draw any attention away from any possible revenue
that might blow your way from this thread.

chunger, I admire your build, assembly explination, simplicity and that Tim Campbell's CT12 custom designed & practically hand built capsule was your chose for the build.
This is why I would like to know more about the CT12…. Cheers  to all…  (My so-called alias) …Zandru… I will post My profile ASAP…For those persons who demand
transparency and full dislcosure...
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Tim Campbell on October 06, 2013, 10:41:03 AM
Zandru,
I made no reference to you selling anything. You're mixing me up with Phrazemaster.
My capsule is in very short supply and so no longer the primary one for this build. I believe it's unlikely that my CT12 will be the capsule you use in your construction. There are at least 10 or 12 other capsules that would work well in this mic but their mechanical construction has nothing directly to do with assembling this kit. A discussion of capsule construction would indeed hijack this thread from the intended purpose of helping DIYers assemble this mic.

"I do feel that there's somewhat of a concern over tim Campbell's CT12, to which
I have mentioned the capsule being shrouded in mystery. His webpage lacking
in info, No detailed specs etc!.  About the only thing I know is the capsule costs
2,000 Kroner or $365 U.S. Also it's said that Tim uses a CNC to mill some of the
components; for that to me still puts the price into question."

Why would you feel concern over this? What could you question about the price?
Ben Sneesby's capsule currently costs $370 US, Tskyguy plans on selling his at $350 US , MBHO's capsule is only slightly more expensive, AKG's current capsule is just over $200,
Telefunken and Josephson's capsule cost about $1500 US. I have no idea about prices for the other manufacturers. Only Telefunken of all these manufacturers post any details about their capsule construction. This doesn't seemed to have caused much concern to their many users.

On a lighter note you wrote," There are questions
that I would most like to Know. " believe me I'm a guy who knows a lot of questions.

Welcome to the forum and good luck with your build.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Pip on October 06, 2013, 01:44:02 PM
Do it yourself!
Title: Re: Official C12 Clone - Build and Support Thread
Post by: jplebre on October 06, 2013, 04:22:00 PM
@Tim, sent you an email, but I'm guessing you are not doing one off capsules for forum members anymore?
Title: Re: Official C12 Clone - Build and Support Thread
Post by: ArnoldLayne on October 06, 2013, 11:31:34 PM
Hi Matador,
I'm still having problems with my mic.. I fixed the polarity issues by bridging FB and FC, but I noticed some pops and sometimes loud, windy sounds.
I thoroughly scrubbed the area on the PCB around the teflon standoffs (will take some pictures tomorrow).  Should I clip off the extra leads ?

There is also a big hum which goes away once I put the mic inside its metal tube.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: chunger on October 07, 2013, 01:24:16 AM
Hi zandru,

I am a bit perplexed at the reason for your original post.  I am quite glad you have a stash of original akg c12 capsules and variouas parts and internal assembly procedure documents.  If you are interested in helping to refine the available capsules for this build, please feel free to either post knowledge and documentation on forum or forward the info along to any number of capsule builders here to help refine their clone capsule specs.  That should alleviate some of the mystery you seem concerned about.

As for Tim's capsules, he is a long-standing contributor to the diy community and the construction, consistency, and sonic performance of his capsules speak for themselves.  Top tier is the only possible conclusion in all regards.

I do hope that his efforts to scale up production are successful and these can once again be readily available for diy.

if you are interested in loaning original capsule parts to me I would be happy to generate photos and precise drawings of all critical dimensions so the general knowledge base can be broadened.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Matador on October 07, 2013, 01:44:46 AM
Hi Matador,
I'm still having problems with my mic.. I fixed the polarity issues by bridging FB and FC, but I noticed some pops and sometimes loud, windy sounds.
I thoroughly scrubbed the area on the PCB around the teflon standoffs (will take some pictures tomorrow).  Should I clip off the extra leads ?

There is also a big hum which goes away once I put the mic inside its metal tube.

The hum is expected.  The outer tube shields everything inside.

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.

Board leakage from solder flux sounds like sizzling to my ears.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Spencerleehorton on October 07, 2013, 04:14:48 AM
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.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: jplebre on October 07, 2013, 05:50:58 AM
the original C12's I used do feel rather airy and bright on the top end. Not overly, just nice - like icing on a cake.
(oh dear! the lingo I'm adopting these days).

They did not have the mid range energy and body as some neumanns.

does it feel like it's excessively unbalanced? I don't know the capsule.
Which cap did you use?
Title: Re: Official C12 Clone - Build and Support Thread
Post by: ArnoldLayne on October 07, 2013, 01:37:45 PM
Quote
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
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Matador on October 07, 2013, 01:46:26 PM
Quote
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.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Matador on October 07, 2013, 01:56:09 PM
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.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: ArnoldLayne on October 07, 2013, 02:07:58 PM
Quote
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..
Title: Re: Official C12 Clone - Build and Support Thread
Post by: scott_humphrey on October 07, 2013, 04:31:44 PM
Quote
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!
Title: Re: Official C12 Clone - Build and Support Thread
Post by: scott_humphrey on October 07, 2013, 05:03:11 PM
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!
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Matador on October 07, 2013, 06:00:50 PM
Fox Audio has a good page for this. (http://www.foxaudioresearch.ca/Polarpatterns.htm)

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". ;)
Title: Re: Official C12 Clone - Build and Support Thread
Post by: ajemutt on October 07, 2013, 07:32:22 PM
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
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Matador on October 07, 2013, 07:57:51 PM
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.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: ArnoldLayne on October 07, 2013, 08:03:14 PM
@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
Title: Re: Official C12 Clone - Build and Support Thread
Post by: ArnoldLayne on October 07, 2013, 09:14:20 PM
Looking at the schematics, couldn't C13 be a possible culprit ?  ???
I'm going to replace it anyway, along with C10 & C11.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: scott_humphrey on October 07, 2013, 10:04:00 PM
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.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: ArnoldLayne on October 07, 2013, 10:40:15 PM
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..
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Matador on October 07, 2013, 10:58:36 PM
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?
Title: Re: Official C12 Clone - Build and Support Thread
Post by: melodeath on October 07, 2013, 11:22:27 PM
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
Title: Re: Official C12 Clone - Build and Support Thread
Post by: ArnoldLayne on October 07, 2013, 11:33:38 PM
Yes (see post # 762).
Since C10 and C11 have been damaged, it's possible that C13 has been too..
Title: Re: Official C12 Clone - Build and Support Thread
Post by: OPR on October 08, 2013, 12:29:19 AM
 
Quote
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.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: chunger on October 08, 2013, 01:12:16 AM
Quote
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.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Matador on October 08, 2013, 01:27:09 AM
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?
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Spencerleehorton on October 08, 2013, 07:58:05 AM
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
Title: Re: Official C12 Clone - Build and Support Thread
Post by: ArnoldLayne on October 08, 2013, 08:19:24 AM
Quote
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.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: teacat on October 08, 2013, 10:09:13 AM
Regarding capsules- I just found this: http://www.tab-funkenwerk.com/id131.html (http://www.tab-funkenwerk.com/id131.html) It must be pretty good. Maybe, chunger, since you are already selling AMI's trafo, this could be an option for that 'turn key' kit.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Matador on October 08, 2013, 10:21:31 AM
Actually, omni sounds edxactly like cardio.

Ahhh, that changes things a bit. ;)  What capsule are you using, and can you take some photo's of how it's connected?

One thing:  most edge terminated capsules have the capsule connections under one of the mounting screws on the front face(s)...sometimes the screw connects to the opposite diaphragm.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Randallizer on October 08, 2013, 02:57:51 PM
Order arrived yesterday. The kit looks great and I was actually quite surprised with the build quality of the Alctron mic. Obviously its not German, but with some cosmetic tweaks, I think it'll look quite impressive.

I actually have some original CK12 capsules and I will be using one for this project.

Will I be the first to do so or has anyone else tried this?

I look forward to posting some audio clips once finished and I'll probably borrow/rent an original C12 for comparison.

Interesting times ahead!

Title: Re: Official C12 Clone - Build and Support Thread
Post by: ArnoldLayne on October 08, 2013, 04:53:47 PM
Quote
What capsule are you using, and can you take some photo's of how it's connected?

I'm using Mic & Mod MK12 (http://groupdiy.com/index.php?topic=53177.0 (http://groupdiy.com/index.php?topic=53177.0)), which looks like the microphone-parts RK-12 but a little bigger I think. They don't have an installation guide yet so I just followed the one on microphone-parts..
Yannick from Mic & Mod said that they are currently working on tutorials.

Only one of the backplates are wired, so I considered that side to be the front.
Will take a picture as soon as I can.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: chunger on October 08, 2013, 05:05:51 PM
Order arrived yesterday. The kit looks great and I was actually quite surprised with the build quality of the Alctron mic. Obviously its not German, but with some cosmetic tweaks, I think it'll look quite impressive.

I actually have some original CK12 capsules and I will be using one for this project.

Will I be the first to do so or has anyone else tried this?

I look forward to posting some audio clips once finished and I'll probably borrow/rent an original C12 for comparison.

Interesting times ahead!

Please report back!  Any objective comparisons against good-condition original C12's are greatly appreciated for development.  Your use of an original "aged" capsule is also informative for evaluating the preamp.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: ArnoldLayne on October 08, 2013, 07:18:02 PM
Problem solved ! ;D
After replacing C10, C11 and C13, the mic is 100% functionnal.

Here are the pictures anyway, for those interested in the CK12
Title: Re: Official C12 Clone - Build and Support Thread
Post by: ArnoldLayne on October 08, 2013, 07:18:47 PM
And the back
Title: Re: Official C12 Clone - Build and Support Thread
Post by: OPR on October 08, 2013, 11:02:59 PM

Quote
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.

Re: the Mhbo Haun capsule: I think reply #7 on the propound web forum says it all...

 "Yesterday Kerstin Haun answered my email regarding the correct capsule designation. To my surprise she wrote "our large diaphragm capsules are called KA1000 (the cardioid) and KA1100 (the omni). We don't have other designations for it."
She also confirmed the possibility of retuning a capsule (within certain limits).

Hmmm. So I fear this "Haun CK12"- thing will go on (and on)... Sad
Perhaps David Bock can tell us under which designation he bought the capsules (please!).

But I can understand Kerstin Haun's answer. Because of it's high quality this capsule was (is) quite desirable for Mic-DIYers. However, MBHO seems to dislike the use of their capsules in homemade microphones.
I found a post from 2004 by Marcus Demuth (US representative of MBHO) in a DIY-forum which I'd like to quote: "MBHO Germany, or its US distr. MTC-MBHO US is not planning to expand its current OEM business (s.a. capsules) to additional companies, or individuals, such as DIY'ers."


http://repforums.prosoundweb.com/index.php?topic=22037.0

For what ever reason I dont think MHBO wants to advertise that their capsule is based on the CK12
I is the info on the capsule in question???

http://www.mbho.de/pdf/ka1000n_ka1100k.pdf (http://www.mbho.de/pdf/ka1000n_ka1100k.pdf)

Distributed by Dale proaudio

 http://www.daleproaudio.com/p-13274-mbho-ka1000n-large-diaphragm-cardioid-microphone-capsule.aspx (http://www.daleproaudio.com/p-13274-mbho-ka1000n-large-diaphragm-cardioid-microphone-capsule.aspx)
Title: Re: Official C12 Clone - Build and Support Thread
Post by: ajemutt on October 09, 2013, 12:41:33 PM
Thanks Mat, I look forward to reading your thoughts.

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.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: kidvybes on October 09, 2013, 02:28:23 PM
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.

...I thought this had already been discussed...I've been substituting NOS GE 6201 (12AT7WA) tubes in many of my mics that originally were equipped with a 6072 (12AY7) variant...it has slightly different tonal qualities in comparison to the 6072, as well as slightly higher output, but in most cases, it's a very viable option...I've found it to be more mid-forward with less top-end extension than the 6072...I prefer it over other 12AT7 variants for microphone purposes...

...it should be noted that David Bock has also chosen to equip his 251 clone (his Soundelux version formerly a 6072 equipped mic) with NOS 6201 tubes:
http://www.bockaudio.com/251.html

...here is a post by another respected microphone designer commenting on Mr. Bock's decision to substitute the 6201 for the 6072:
http://www.gearslutz.com/board/7252716-post17.html

...my personal vintage/variant preference for microphone application:
http://www.nostubestore.com/2010/06/general-electric-jg-12at7wa6201-tmbp.html
Title: Re: Official C12 Clone - Build and Support Thread
Post by: micaddict on October 09, 2013, 05:07:26 PM
Quote
...my personal vintage/variant preference for microphone application:
http://www.nostubestore.com/2010/06/general-electric-jg-12at7wa6201-tmbp.html

Have you tried their Raytheon, Sylvania and Siemens & Halske 6201/12AT7/ECC81 vintage tubes?


Henk
Title: Re: Official C12 Clone - Build and Support Thread
Post by: kidvybes on October 09, 2013, 06:17:01 PM
Quote
...my personal vintage/variant preference for microphone application:
http://www.nostubestore.com/2010/06/general-electric-jg-12at7wa6201-tmbp.html

Have you tried their Raytheon, Sylvania and Siemens & Halske 6201/12AT7/ECC81 vintage tubes?


Henk

Hi Henk...in researching the military-grade variants of the 1620/12AT7WA, I repeatedly saw references to the Sylvania "12AT7WA GOLD BRAND" as being one of the sonically premium versions...I purchased a few of those and tested them against a number of different GE 6201/12AT7WA/B/C tubes I had...IMHO, the GE 12AT7WA triple-mica blackplates that I tested worked best in the mic circuits where they were utilized...to my ears, the Sylvanias sounded thinner and brighter in those particular instances...I have not tried the Raytheon or Siemens variations...
Title: Re: Official C12 Clone - Build and Support Thread
Post by: micaddict on October 09, 2013, 06:28:01 PM
Thanks, Dennis!

Oh, and do you get the ones with balanced sections or doesn't that matter much to you in these microphone applications?
Title: Re: Official C12 Clone - Build and Support Thread
Post by: kidvybes on October 09, 2013, 07:34:38 PM
Thanks, Dennis!

Oh, and do you get the ones with balanced sections or doesn't that matter much to you in these microphone applications?

...no, I didn't...as long as both triodes tested strong, most of the mics I used these in employed plate-follower circuits that only utilize one triode...I actually purchased a number of these rather cheaply on eBay (quite a while back), tested a few and chose the one I liked best at the time...
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Aaronrash on October 09, 2013, 09:43:35 PM
Does anybody know where I could acquire one of Tim's CK12 capsules? I've tried several emails with no response

Thanks!
Aaron
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Phrazemaster on October 10, 2013, 01:27:39 AM
Does anybody know where I could acquire one of Tim's CK12 capsules? I've tried several emails with no response

Thanks!
Aaron
From what I hear this is normal...you probably will get an email in x number of weeks saying your capsule is done...at least that's what I read from another guy. I also sent Tim a request for a CK12 but did not get a response; but again I think this is because he is so incredibly backlogged...guy is in high demand.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Woot on October 10, 2013, 04:06:14 AM
Does anybody know where I could acquire one of Tim's CK12 capsules? I've tried several emails with no response

Thanks!
Aaron

Hey Aaron/Phraze,

I thought the same also, but if you haven't received a response confirming you are on the list, then you are not on the list. At least this is what Tim told me about 6 weeks ago. Good luck!

Cheers,

Matt
Title: Re: Official C12 Clone - Build and Support Thread
Post by: jplebre on October 10, 2013, 05:46:38 AM
Good catch. . . I've corrected the discrepancy.

Pin 5 -
Pin 6 +

 :o

I'm confused. on the batch from august/september, the PSU comes wired with 5+ and 6- as default.
I think i'll just stick to this through the hole build.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Aaronrash on October 10, 2013, 06:14:15 AM
Ok thanks guys,

I'll keep my fingers crossed on a response

Aaron
Title: Re: Official C12 Clone - Build and Support Thread
Post by: jplebre on October 10, 2013, 06:39:28 AM
Guys, quick question.
I'm trying to understand what Chunger is trying to achieve when he wired 2 cables to one of the backplates and then to FB and RB on the PCB.
I may have misunderstood the drawing.

He also says it's optional.

right now, I have the front "back" plate wired to FB. do I need to jump FB to RB or do I need to run a second cable from RB (capsule) to RB (PCB)?

.... am I making sense? :P
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Matador on October 10, 2013, 10:33:06 AM
Guys, quick question.
I'm trying to understand what Chunger is trying to achieve when he wired 2 cables to one of the backplates and then to FB and RB on the PCB.
I may have misunderstood the drawing.

He also says it's optional.

right now, I have the front "back" plate wired to FB. do I need to jump FB to RB or do I need to run a second cable from RB (capsule) to RB (PCB)?

.... am I making sense? :P

It's an either/or thing.  You can bridge the FB and RB right at the capsule (the preferred way), or you can bridge them at the PCB.  Bridging in both places neither helps nor hurts.  If you have a capsule with a single backplate you don't have to run two wires, and you can bridge them right at the PCB.

I debated making them a single PCB connection but figured people wanted the connections as close to the original as possible.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Phrazemaster on October 10, 2013, 10:38:03 AM
Does anybody know where I could acquire one of Tim's CK12 capsules? I've tried several emails with no response

Thanks!
Aaron

Hey Aaron/Phraze,

I thought the same also, but if you haven't received a response confirming you are on the list, then you are not on the list. At least this is what Tim told me about 6 weeks ago. Good luck!

Cheers,

Matt
Thanks Matt. I guess I'm not on the list then. I may get a Sneesby C12 then; his work looks top notch.

Mike
Title: Re: Official C12 Clone - Build and Support Thread
Post by: jplebre on October 10, 2013, 11:34:22 AM
Guys, quick question.
I'm trying to understand what Chunger is trying to achieve when he wired 2 cables to one of the backplates and then to FB and RB on the PCB.
I may have misunderstood the drawing.

He also says it's optional.

right now, I have the front "back" plate wired to FB. do I need to jump FB to RB or do I need to run a second cable from RB (capsule) to RB (PCB)?

.... am I making sense? :P

It's an either/or thing.  You can bridge the FB and RB right at the capsule (the preferred way), or you can bridge them at the PCB.  Bridging in both places neither helps nor hurts.  If you have a capsule with a single backplate you don't have to run two wires, and you can bridge them right at the PCB.

I debated making them a single PCB connection but figured people wanted the connections as close to the original as possible.

Thank you!
Would this also matter for capsules like the stock Alctron with 2 separate backplates (no continuity between the 2 backplate screw holes)?
Is the objective to bridge them both?
What would happen if one of them is not?

Just trying to understand a bit better what I'm about to do. I don't like it when it becomes to simple as I learn less :)
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Matador on October 10, 2013, 01:00:27 PM
Thank you!
Would this also matter for capsules like the stock Alctron with 2 separate backplates (no continuity between the 2 backplate screw holes)?
Is the objective to bridge them both?
What would happen if one of them is not?

Just trying to understand a bit better what I'm about to do. I don't like it when it becomes to simple as I learn less :)

The net-net is that you need to convert any 2 backplate capsule into a single backplate capsule with a wire bridge.  The single-backplate scheme is implicit in the design of the C12.

Here is my preference (and it really is just a preference: the electrons don't care ;)):  run the FB wire from the FB turret to the FB of the capsule.  So the same with a second wire from RB to RB of the capsule.  Then run a jumper wire across the two terminals on the capsule itself.  That is also what is documented in Chunger's build pics.

For those with a single backplate capsule:  run a single wire from FB to the capsule backplate.  Then run a jumper from the FB turret to the RB turret right on the PCB itself.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Matador on October 10, 2013, 01:12:40 PM
Here's another way to conceptualize what is going on.

The node/turret labelled "RB" is connected to the junction of the two 499K resistors to B+.  These form a 50% voltage divider and provide a 60V reference to polarize the backplate.  Put a little piece of tape over the PCB "RB" label in your mind, and write "Backplate Polarization Send".

The node/turret labelled "FB" is connected to the gate coupling capacitor that goes to the grid.  Put another little piece of tape over the "FB" label in your mind that says "Backplate signal tap".  So a wire from RB to the capsule sends the "power", and the wire back to FB taps the signal and allows it to be amplified.

Because the capsule is supposed to be a single metal piece (from an electrical point of view), this all works.  If you have a capsule with isolated backplates, they need to be jumpered together to make them "a single metal piece".
Title: Re: Official C12 Clone - Build and Support Thread
Post by: chunger on October 10, 2013, 04:36:20 PM
Does anybody know where I could acquire one of Tim's CK12 capsules? I've tried several emails with no response

Thanks!
Aaron
From what I hear this is normal...you probably will get an email in x number of weeks saying your capsule is done...at least that's what I read from another guy. I also sent Tim a request for a CK12 but did not get a response; but again I think this is because he is so incredibly backlogged...guy is in high demand.

This is NOT the case. . . you are only on the build list if you receive a confirmation email from Tim.  He may or may not be accepting new orders at this time from the DIY community.  Right now, it would be very difficult to get into the build queue as Tim does not seem to respond to all email requests when he has a full backlog of orders that need to be filled.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Phrazemaster on October 10, 2013, 04:57:03 PM
OK...thanks for clarifying that 'Chung. Would be nice from a customer standpoint to know such things, as now I will look for other sources, but I understand he is a world class capsule maker, a one-man shop, and he is crazy busy.

Thanks,

Mike
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Woot on October 10, 2013, 05:02:27 PM

[/quote]
Thanks Matt. I guess I'm not on the list then. I may get a Sneesby C12 then; his work looks top notch.

Mike
[/quote]

Ill be receiving a pair of Bens C12'sin a couple of weeks which I will drop into these c12's. I was intending on posting some samples soon after.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: jplebre on October 11, 2013, 04:00:11 AM
Thank you Mat now it makes perfect sense!
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Tim Campbell on October 12, 2013, 06:17:45 AM
This is one of the few forums that I actually consider myself a member of and so I'm so sorry to have inconvenienced any of you.
Contrary to what some of you may imagine that I'm lying under a palm tree, waited on by bikini clad women building a capsule or two when the mood strikes me I actually work round the clock and produce a steady and growing amount of capsules every month.
I have been hesitant to contact inquirers for my capsules because I am currently swamped with orders and have no way of giving a realistic time frame for when I could deliver. Some of my private customers have waited months and still are unsure when they'll receive their capsule.
My OEM customer accounts must always be serviced first because their business' rely on having a product in time. Those OEM orders have been growing exponentially of late, slowing down delivery to private customers.
I'm am honestly doing all I can to increase my output and hope to have a solution soon.
I am honestly sorry about the delays. If you're still interested please contact me in a month or two.
Kind regards,
Tim
Title: Re: Official C12 Clone - Build and Support Thread
Post by: tonycamp on October 12, 2013, 12:00:25 PM
This is one of the few forums that I actually consider myself a member of and so I'm so sorry to have inconvenienced any of you.
Contrary to what some of you may imagine that I'm lying under a palm tree, waited on by bikini clad women building a capsule or two when the mood strikes me I actually work round the clock and produce a steady and growing amount of capsules every month.
I have been hesitant to contact inquirers for my capsules because I am currently swamped with orders and have no way of giving a realistic time frame for when I could deliver. Some of my private customers have waited months and still are unsure when they'll receive their capsule.
My OEM customer accounts must always be serviced first because their business' rely on having a product in time. Those OEM orders have been growing exponentially of late, slowing down delivery to private customers.
I'm am honestly doing all I can to increase my output and hope to have a solution soon.
I am honestly sorry about the delays. If you're still interested please contact me in a month or two.
Kind regards,
Tim

Tim, it's all good man, don't compromise the way you do things, your capsules are things of beauty, i'm looking for 2 more, i'll contact you in a month or so, and be happy to get em when i get em.

thanx for building the best
T
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Phrazemaster on October 12, 2013, 02:56:10 PM
This is one of the few forums that I actually consider myself a member of and so I'm so sorry to have inconvenienced any of you.
Contrary to what some of you may imagine that I'm lying under a palm tree, waited on by bikini clad women building a capsule or two when the mood strikes me I actually work round the clock and produce a steady and growing amount of capsules every month.
I have been hesitant to contact inquirers for my capsules because I am currently swamped with orders and have no way of giving a realistic time frame for when I could deliver. Some of my private customers have waited months and still are unsure when they'll receive their capsule.
My OEM customer accounts must always be serviced first because their business' rely on having a product in time. Those OEM orders have been growing exponentially of late, slowing down delivery to private customers.
I'm am honestly doing all I can to increase my output and hope to have a solution soon.
I am honestly sorry about the delays. If you're still interested please contact me in a month or two.
Kind regards,
Tim
Hi Tim, I have great respect for your situation, and looked at differently, this is the result of being absolutely phenomenal at what you do! So congrats are in order, although the day-to-day experience for you is currently mounting work and increasing delivery times. Time to increase prices/limit customers? Or perhaps take on some apprentices to help with the work? You have entered the world of the elite highly sought after, well done.

I feel no unkindness towards you for not responding; I understand and I will try contacting you in a month or two as I'd love to have one of your capsules too.

Thanks for your many contributions and we appreciate you here buddy.

Best,

Mike
Title: Re: Official C12 Clone - Build and Support Thread
Post by: micaddict on October 12, 2013, 03:29:21 PM
+1



Henk
Title: Re: Official C12 Clone - Build and Support Thread
Post by: robomatique on October 13, 2013, 11:24:45 AM
Hi,

Another one with a problem...

FInished my vuild yeaterday but have some porblems:

1. B+ only goes up to 115 or so, I will change R1 and R2 to 75k as suggested elsewhere. I have a lot of 0,1W resistors at hand, would that work or should I get 0,25W as in the kit?

2. The output is extremely low and does not have any bottom/bass at all. I can't hardly to get the microphone to distort with my simple yamaha soundcard preamp with 60db of gain. Everything seems to be wired correctly so I am worried that the (Campbell) capsule is dead (had problems when bridging the backplates so I heated more than I usually do) or... anything else? Where do you think I should start looking?

For the info I use a 6072a tube and the polar patterns seems to work correctly. The voktages seem ok except for B+ is 115V (which I will fix but I guess it is not the major problem here). The oputput transformer was measured and has been checked, it should be wired correctly. Just the low output/no bass problem that I have no clue about...
Title: Re: Official C12 Clone - Build and Support Thread
Post by: pasarski on October 13, 2013, 12:17:05 PM

...The output is extremely low and does not have any bottom/bass at all....

Could be transformer hooked up incorrectly.


...I am worried that the (Campbell) capsule is dead (had problems when bridging the backplates so I heated more than I usually do) or...

Not sure but doesn't seem like a capsule problem, because:


...polar patterns seems to work correctly...


...The oputput transformer was measured and has been checked, it should be wired correctly...

I would double check.

One thing to check for is if anything is touching the mic casing?  Is it buzzing as loud as your other condensers with out the body tube or is the buzz also reduced in level?
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Tim Campbell on October 13, 2013, 02:11:46 PM
"2. The output is extremely low and does not have any bottom/bass at all. I can't hardly to get the microphone to distort with my simple yamaha soundcard preamp with 60db of gain. Everything seems to be wired correctly so I am worried that the (Campbell) capsule is dead (had problems when bridging the backplates so I heated more than I usually do) or... anything else? Where do you think I should start looking?"

You should never be heating the capsule. That's what the solder tags are for.  Turn on the mic without the headbasket and make sure the membranes aren't collapsing ( your description sounds like this). If they are, it could be caused by damage, incorrectly wiring the capsule, or incorrect polarization voltage (most likely). Too high a polarization voltage can over time cause permanent damage to the membranes.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: robomatique on October 13, 2013, 02:47:02 PM
Thanks for your answers!

I guess it is not the capsule (phew) as the polar patterns work correctly and the membranes looks as they should when powered on!

So far so good!

I will try to hook up the T14 again, but I have already tripkle checked it, measuring the output at the pins I get the 20R as expected and I remember that I measured the primary before mounting it and that it was correct.

Assuming it is not the T14, anyone has any suggestions? I can also mention that it not onlly have lost the bass/bottom, the highs are very present, much more treble than expected...

Thanks agian for your help on this!!!

Robert
Title: Re: Official C12 Clone - Build and Support Thread
Post by: robomatique on October 13, 2013, 02:56:11 PM
One thing to check for is if anything is touching the mic casing?  Is it buzzing as loud as your other condensers with out the body tube or is the buzz also reduced in level?

I get a lot of hum without the body tube...?

THanks!!!
Title: Re: Official C12 Clone - Build and Support Thread
Post by: pasarski on October 14, 2013, 03:37:17 AM
One thing to check for is if anything is touching the mic casing?  Is it buzzing as loud as your other condensers with out the body tube or is the buzz also reduced in level?

I get a lot of hum without the body tube...?

THanks!!!

Not sure about my reasoning, but that could imply it's not the trafo, the hum would be low level also.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: RuudNL on October 14, 2013, 07:39:00 AM
I have the intention to build a C12, but I still have one question:

The capsule boosts the higher frequencies (just like a K67 capsule).
In the schematic there is no de-emphasis or other frequency correction.
Won't this microphone sound 'over bright'?
Would it be an idea to add a capacitor between the anode and ground (just as in the ELA M251) to roll-off the HF a bit?

(Sorry, but I did not read all 247 posts...)
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Matador on October 14, 2013, 04:09:23 PM
One thing to check for is if anything is touching the mic casing?  Is it buzzing as loud as your other condensers with out the body tube or is the buzz also reduced in level?

I get a lot of hum without the body tube...?

THanks!!!

This is normal.

Can you post a clip of what the mike sounds like?
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Matador on October 14, 2013, 04:11:25 PM
I have the intention to build a C12, but I still have one question:

The capsule boosts the higher frequencies (just like a K67 capsule).
In the schematic there is no de-emphasis or other frequency correction.
Won't this microphone sound 'over bright'?
Would it be an idea to add a capacitor between the anode and ground (just as in the ELA M251) to roll-off the HF a bit?

(Sorry, but I did not read all 247 posts...)

The C12 response peak is significantly higher in frequency that a K67.  It should sound fine in a flat response circuit.

The cap-to-ground trick will work, but not the default 100pF ELA M251 value.  I would suggest 470pF as a starting point to reduce  a K67-ish peak down (although you'll be making a very different mike as compared to a flat C12 circuit/capsule combo).
Title: Re: Official C12 Clone - Build and Support Thread
Post by: robomatique on October 15, 2013, 06:18:19 PM


Can you post a clip of what the mike sounds like?

THanks for getting back to me! I just recorded a few word. I have attached the file as a txt file, download and change the ending to mp3 and it should work (?).

By the way, would R1 and R2 be ok as .1w resistors?

Thanks!
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Randallizer on October 16, 2013, 07:32:34 PM
Okay, so last night we completed work on our kit with an immaculate original c12 capsule. We also picked up a NOS GE 5 star 6072.

Today we gave it it's first run out and the results were....


Unbelievable!!

Hopefully in the next couple of weeks we'll give it a shoutout against an original C12, but at this stage we aren't too worried about how it'll measure up because we've clearly got a fantastic mic on our hands.

Huge credit and appreciation to Chunger and Matador for their work on this project and I have no reservation in recommending others to give it a go.

At this stage I would also recommend to others with old 414s to not be scared of using the capsule in this project. The results are pretty spectacular.

I'll post a clip in the morning.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Matador on October 16, 2013, 11:30:35 PM


Can you post a clip of what the mike sounds like?

THanks for getting back to me! I just recorded a few word. I have attached the file as a txt file, download and change the ending to mp3 and it should work (?).

By the way, would R1 and R2 be ok as .1w resistors?

Thanks!

Borderline:  those resistors have about 1mA, which is 0.001*0.001*91000 = 0.091W.  You can probably get away with it due to the sandbagging by the manufacturer, but those really should be 0.25W parts if you want to count on them for the long haul.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: BryanJHarris on October 17, 2013, 03:03:15 AM
Getting ready to dive into this project pretty soon, but I was wondering who used the Beesneez k12s and what their thoughts were about them?  I doubt I have to patience to hang around until Tim is taking new orders so this seems like a potentially good option. 

Bryan
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Aaronrash on October 17, 2013, 08:39:40 PM
Hello Matador,

I have a few questions for you. I've been talking with Andreas Grosser recently about building a U47 with a EF12 tube. He sent me the schematic and it's a pretty straightforward build. Seems pretty simple and he cleared all the mystery of using a EF12 with a U47 up for me.

The EF12 heats off of negative voltage. The power supply you designed for the C12 actually seems like a perfect candidate for the U47 build with a few modifications. I need +A 120V that will be sent to a voltage divider in the mic and then it will polarize the capsule and power tube operations. Then I need -6V for the heater and that's it, I'll be good to go.

I spoke with Chunger about this and he suggested that turning the diodes and capacitors in the the filament section on the power supply along with a LM337 regulator should give me the -6 for the heater. And I can use the adjustable 200V line for the +A120V. I just wanted to run this by you as Chunger suggested and see what your thoughts are. Hopefully it will help other people in the future looking to build a U47 with a EF12 as well.

Title: Re: Official C12 Clone - Build and Support Thread
Post by: jplebre on October 18, 2013, 06:43:03 AM
Hi guys

the mic is alive and sounding stunning, even with the stock alctron capsule.
I'm hoping with the more accurate edge terminated capsules that cheap feeling on the transients will get improved ;)


I have a few questions, I'm not sure if this is normal:
- with no body cover on, the microphone is incredibly hum-y. Enough to bury signal (if signal is spoken words, low level singing).
- With body cover on, mic is spotless clean!
I know some members mentioned hum problems and other people answered to put the body on, but I still feel it's weird there's SO MUCH hum without the cover.

- the voltage takes a while to ramp up to 120v (a few minutes at least) and takes a very long time to ramp down (+10min).
in fact, the mic stays "operational" for 2-3min before start loosing signal.
Is this normal? I'm used to seeing bleed resistors on PSU designs but not on this one, so I'm unsure if it's normal.
(I don't think R6 - 470kOhm qualifies as bleeding resistor?)

- Bias: I'm using a fluke 175 but I'm not sure I'm measuring Bias accurately. Every time I probe P-ground and P-Bias, the voltage shown is lower (-1.3/-1.5v) and creeps up to -1v where I've set it previously. Is this normal? if so, should I aim for the DMM-free voltage or loaded by the DMM?
If it's not normal, any ideas?

- there's a windy sound but I'm 100% sure it's my room and windows and computer and etc. I'm in the studio 3 days this week so I'll be able to try that out.

If you have rumble and hiss noises, try ditching the stock altron capsule. even a £10 EH6072 is free of most of those issues and sounds quite acceptable.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Matador on October 18, 2013, 01:23:32 PM
The EF12 heats off of negative voltage. The power supply you designed for the C12 actually seems like a perfect candidate for the U47 build with a few modifications. I need +A 120V that will be sent to a voltage divider in the mic and then it will polarize the capsule and power tube operations. Then I need -6V for the heater and that's it, I'll be good to go.

Do you have a schematic?  I bet you can use a positive heater supply just fine.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Matador on October 18, 2013, 01:44:35 PM
I have a few questions, I'm not sure if this is normal:
- with no body cover on, the microphone is incredibly hum-y. Enough to bury signal (if signal is spoken words, low level singing).
- With body cover on, mic is spotless clean!
I know some members mentioned hum problems and other people answered to put the body on, but I still feel it's weird there's SO MUCH hum without the cover.

The air is awash in 60Hz radiation, and even microamps of noise current across very high impedance sections will generate significant noise voltages that be happily amplified by the tube.

In short, completely normal, the the entire reason why the circuits are encased in metal tubes in the first place. ;)

- the voltage takes a while to ramp up to 120v (a few minutes at least) and takes a very long time to ramp down (+10min).
in fact, the mic stays "operational" for 2-3min before start loosing signal.
Is this normal? I'm used to seeing bleed resistors on PSU designs but not on this one, so I'm unsure if it's normal.
(I don't think R6 - 470kOhm qualifies as bleeding resistor?)

The time constant of each filter section is 9 seconds:  there are 3 cascaded together, so it takes a few minutes to charge up.  Yes, R6 is a bleeder, and yes it takes quite a while to ramp down.  One of the side effects of a high-impedance supply!  You can lower the bleeder resistance but all of the passive networks need to be retuned.

I have a 1K/10W discharge resistor on alligator clips for this exact reason.  When I shut off the PSU, I clip the resistor to the B+ supply and it discharges quickly enough to do immediate work on the supply.

- Bias: I'm using a fluke 175 but I'm not sure I'm measuring Bias accurately. Every time I probe P-ground and P-Bias, the voltage shown is lower (-1.3/-1.5v) and creeps up to -1v where I've set it previously. Is this normal? if so, should I aim for the DMM-free voltage or loaded by the DMM?
If it's not normal, any ideas?

Where exactly are you measuring?  If you measure at the tube plate it is expected.  The best place to measure is in the PSU (at the 5-pin connector block), or right where P4 enters the mike.  If you measure on the "other" side (or tube side) of R11 then the meter impedance will foul up the measurement.

- there's a windy sound but I'm 100% sure it's my room and windows and computer and etc. I'm in the studio 3 days this week so I'll be able to try that out.

If you have rumble and hiss noises, try ditching the stock altron capsule. even a £10 EH6072 is free of most of those issues and sounds quite acceptable.

Wind noise typically means the tube needs more burn-in time.  Leave it on for a few days and check again.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: jplebre on October 18, 2013, 04:19:03 PM
Hi Mata!

Thanks once again for your patience!
Quote
Where exactly are you measuring?  If you measure at the tube plate it is expected.  The best place to measure is in the PSU (at the 5-pin connector block), or right where P4 enters the mike.  If you measure on the "other" side (or tube side) of R11 then the meter impedance will foul up the measurement.

I am actually doing this at the PSU molex terminal Pin4 and P6 (I think.... ground one...), using the tightening screw as the probe point.

Also, I see you left provision for ground wiring. Chunger never mentioned adding extra ground wire.
Is the little jumper between the Xlr Pin 7 and the ground tab really enough?

Cheers
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Aaronrash on October 18, 2013, 05:21:57 PM
The EF12 heats off of negative voltage. The power supply you designed for the C12 actually seems like a perfect candidate for the U47 build with a few modifications. I need +A 120V that will be sent to a voltage divider in the mic and then it will polarize the capsule and power tube operations. Then I need -6V for the heater and that's it, I'll be good to go.

Do you have a schematic?  I bet you can use a positive heater supply just fine.

Yes here's the schematic from Mr. Grosser. He also said it's the same schematic Flea uses in their U47/EF12 mics. However he emphasized on how important the -6V is 

Here is also the EF12 data sheet: http://www.hifitubes.nl/weblog/wp-content/telefunken-ef12.pdf

Edit: I removed Andreas schematic because a member here messaged me telling me Andreas doesn't want his work posted anywhere publicly, although Andreas didn't tell me not to post it anywhere I've taken it down anyways.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Matador on October 18, 2013, 11:44:51 PM
That would be trivial to convert to a positive heater supply (much like the U47):  far easier than converting the C12 supply to negative heater:  mainly because the LM337 and LM317 don't share a pinout, and the heater supply has a fixed ground connection to the plane which would be difficult to break (lots of cutting and dicing).

If you are interested I can show you:  it will end up looking very much like a G7 in fact and should sound exactly the same.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: chunger on October 19, 2013, 12:06:41 AM
Hey Matador,

Are you able to provide a bullet point list of component flops and trace re-routes that need to happen in order to change over to negative voltage heater? 

I'm personally interested for U67 PSU application.  I have a dremel and am not afraid to use it  ;D  I figure the LM337 is easy enough to switch by mounting it upside down in the heatsink and running individual wires down to the PCB.  The rest of it might get a bit more involved, but I'm good with my hands and reasonably confident I can execute even extensive re-routes on the board.

From a cost perspective, it might still be advantageous to use this PCB and OEM Alctron donor PSU for the project.

I know.. . it's probably the same thing. . . easier to change the mic over to positive heater on the U67 circuit as well. . .  :o  But I want to build both the kit provided PSU in Dan's enclosure as well as our modified PSU to compare side-by-side to validate.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: robomatique on October 19, 2013, 07:19:28 AM


Can you post a clip of what the mike sounds like?

THanks for getting back to me! I just recorded a few word. I have attached the file as a txt file, download and change the ending to mp3 and it should work (?).

By the way, would R1 and R2 be ok as .1w resistors?

Thanks!

Borderline:  those resistors have about 1mA, which is 0.001*0.001*91000 = 0.091W.  You can probably get away with it due to the sandbagging by the manufacturer, but those really should be 0.25W parts if you want to count on them for the long haul.

THanks Matador, I will get some new resistors!

Did you ever have a chance to listen to the clip? Did it say anythiung to you?

THanks again for all your help!!!
Robert
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Matador on October 19, 2013, 10:58:48 AM
Hey Matador,

Are you able to provide a bullet point list of component flops and trace re-routes that need to happen in order to change over to negative voltage heater? 

I'm personally interested for U67 PSU application.  I have a dremel and am not afraid to use it  ;D  I figure the LM337 is easy enough to switch by mounting it upside down in the heatsink and running individual wires down to the PCB.  The rest of it might get a bit more involved, but I'm good with my hands and reasonably confident I can execute even extensive re-routes on the board.

From a cost perspective, it might still be advantageous to use this PCB and OEM Alctron donor PSU for the project.

I know.. . it's probably the same thing. . . easier to change the mic over to positive heater on the U67 circuit as well. . .  :o  But I want to build both the kit provided PSU in Dan's enclosure as well as our modified PSU to compare side-by-side to validate.

Makes sense:  I'll take a look.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Aaronrash on October 19, 2013, 02:34:36 PM
I'm definitely interested in going this route as well
Title: Re: Official C12 Clone - Build and Support Thread
Post by: scott_humphrey on October 21, 2013, 01:09:25 AM
The EF12 heats off of negative voltage. The power supply you designed for the C12 actually seems like a perfect candidate for the U47 build with a few modifications. I need +A 120V that will be sent to a voltage divider in the mic and then it will polarize the capsule and power tube operations. Then I need -6V for the heater and that's it, I'll be good to go.

Do you have a schematic?  I bet you can use a positive heater supply just fine.



Yes here's the schematic from Mr. Grosser. He also said it's the same schematic Flea uses in their U47/EF12 mics. However he emphasized on how important the -6V is 

Here is also the EF12 data sheet: http://www.hifitubes.nl/weblog/wp-content/telefunken-ef12.pdf

Edit: I removed Andreas schematic because a member here messaged me telling me Andreas doesn't want his work posted anywhere publicly, although Andreas didn't tell me not to post it anywhere I've taken it down anyways.

This seems a bit off topic, and I agree that you shouldn't post Mr. Gosser's schematic without his permission. I'll bet that there is a simple way to accomplish the same thing without having to modify the board. I'm glad to explain. If you're interested just PM me.

I've used the power supply board from this project for another home brew mic with good results. It's great in that you can easily adjust the B+ and bias voltage, so you theoretically could use this board with a variety of different tubes. I'm using it with a 6ak5w and Beesneez K7 in an Equinox body and am very happy. I'll post this separately once the circuit is finalized.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: chunger on October 21, 2013, 03:52:26 AM
Important Note!!!

The new revision 1.2A PCB's have a screen printing difference from rev. 1.1A.  The indicator for "cath" was originally at the C10 junction in the older pcb and is now at C11.  Both nodes are ground points and will work for connecting the wire, but the build documentation reflects connecting at C10.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: jplebre on October 21, 2013, 06:12:25 AM
Yikes! I was actually running to my mic before I realise that if the cathode was not plugged in I would have noticed :P

Matador, did you have any thoughts on the Bias measurement drift?
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Matador on October 21, 2013, 01:10:34 PM
Yikes! I was actually running to my mic before I realise that if the cathode was not plugged in I would have noticed :P

Matador, did you have any thoughts on the Bias measurement drift?

What kind of meter are you using?  Do you know what it's input impedance is?
Title: Re: Official C12 Clone - Build and Support Thread
Post by: jplebre on October 22, 2013, 05:02:41 AM
For the fluke 175 what I found on the manual for voltage DC the input impedance is 10Mohm, 100pF
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Matador on October 22, 2013, 01:37:31 PM
- Bias: I'm using a fluke 175 but I'm not sure I'm measuring Bias accurately. Every time I probe P-ground and P-Bias, the voltage shown is lower (-1.3/-1.5v) and creeps up to -1v where I've set it previously. Is this normal? if so, should I aim for the DMM-free voltage or loaded by the DMM?
If it's not normal, any ideas?

How long does it "creep"?  If I understand this correctly, the meter shows -1.5V at first then settles down to -1V after some period of time?

This is not unexpected:  the bias supply is low pass filtered via R5 (1M) and C5 (4.7uF).  The time constant is 4.7 seconds.  So long as it settles at the proper value it should be fine.  The absolute value, so long as it's around -1V it will be fine.  ;)
Title: Re: Official C12 Clone - Build and Support Thread
Post by: jplebre on October 22, 2013, 03:32:17 PM
Yes, indeed, it's about 4/5 seconds, then it stabilizes on the new reading.
It starts at -1.6v ish and then creeps down to -1v.

I was just wandering if I did something wrong :P

And if that +-0.5v difference would matter.

:)
Title: Re: Official C12 Clone - Build and Support Thread
Post by: kcatthedog on October 23, 2013, 08:02:38 PM
just a status report , i have had my build checked by Brain fox and i had built mike fine but one of my large caps on power supply pcp was not operating properly and I had not done the ground properly: the shunt.

So no wonder I couldn't get proper readings , so mostly right but need to be more careful next time. I remember one cap wasn't seated flush so i redid it: too much apparently.

Anyway, I'll be more careful next time: thx for the thread and parts etc.!
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Nagskof on October 25, 2013, 05:54:24 AM
Hi Metador, hope you are well.
I am down here in South Africa  :'( and I bought the kit from Studio 939 for the C12. WOW, I am impressed!
But the postal service sent the Alctron PSU back to Chunger that he sent me  :o, so I am stuck. Could you tell me the rating of the secondary windings of the power transformer so that I can get one wound in SA to at least test the mic until I get the real power supply please? I asked Chunger and he said I must talk to you on this technical manner.
I would appreciate your feedback.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Matador on October 25, 2013, 10:17:51 AM
Hi Metador, hope you are well.
I am down here in South Africa  :'( and I bought the kit from Studio 939 for the C12. WOW, I am impressed!
But the postal service sent the Alctron PSU back to Chunger that he sent me  :o, so I am stuck. Could you tell me the rating of the secondary windings of the power transformer so that I can get one wound in SA to at least test the mic until I get the real power supply please? I asked Chunger and he said I must talk to you on this technical manner.
I would appreciate your feedback.

I don't know the specs of the Alctron unit, but I can still tell you what you need. ;)

The B+ supply is modest:  200V secondary @ about 5-10mA (which equates to about 5VA) would be sufficient.  No center tap is needed.  For the heater, a 9.5V secondary rated at about 500mA is good:  again, about 5VA.  Again, no center tap needed.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: RuudNL on October 26, 2013, 11:51:11 AM
Just wanted to check: what is the voltage you are measuring at the anode? (At 120 V from the power supply)
Thanks!
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Matador on October 26, 2013, 03:53:06 PM
Just wanted to check: what is the voltage you are measuring at the anode? (At 120 V from the power supply)
Thanks!

Anode?

Those are the transformer secondary ratings.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: RuudNL on October 27, 2013, 12:06:19 PM
Maybe I wasn't completely clear.
The 120 V. is the voltage coming from the power supply, 'on top of' the anode resistor (100 K)
There is a voltage drop across the anode resistor, depending upon the bias voltage.
So: I am interested in the voltage on the anode (referred to ground), to check the bias of the tube!
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Matador on October 27, 2013, 12:23:10 PM
Maybe I wasn't completely clear.
The 120 V. is the voltage coming from the power supply, 'on top of' the anode resistor (100 K)
There is a voltage drop across the anode resistor, depending upon the bias voltage.
So: I am interested in the voltage on the anode (referred to ground), to check the bias of the tube!

Oh sorry. ;)

I can't answer in this specific case, but the "typical" 6072A/12AY7 tube under these conditions draws 0.7mA, and that across 100K implies a 70V drop from 120V, which is about 50V.  In the three mikes I've built, I've seen anywhere between 50V and 70V right on the tube plate.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: scott_humphrey on October 27, 2013, 01:58:34 PM
From Klaus Heyne on the R/E/P forum: "65-80v."

Mine runs at 68v with a 5 star GE. Of course, it depends on the tube. There is variation from tube to tube (NOS vs new, one brand vs another). Each is going to draw a slightly different amount of current, so the voltage will vary.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: RuudNL on October 27, 2013, 02:28:37 PM
Ok, that's all I wanted to know. Thanks!!!
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Aaronrash on October 27, 2013, 04:12:32 PM
Any news on converting the heater voltage to negative voltage?
Title: Re: Official C12 Clone - Build and Support Thread
Post by: chunger on October 27, 2013, 10:37:48 PM
Any news on converting the heater voltage to negative voltage?

I suspect one of the hard-to-execute steps would be to grind and isolate the "-" terminals on the filter capacitors.  Seems like there will be a lot of hacking to make it happen.  I've asked Matador for a bullet point list of mods that need to happen to convert.  I'm sure he just ran into a busy spell or discovered more hurdles than previously known regarding the mod and is thinking it over.

FWIW, the new fully regulated PSU board will be designed to easily accommodate the negative heater supply.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Category 5 on October 28, 2013, 01:00:38 AM
Completed both PSUs tonight.  Mic PCB's done, but mics themselves not assembled yet.  Stuck a 180K resistor between B+ and Ground and was able to dial in a solid 120V on one PSU, but can't get higher than 92V on the other (R4 screwed in all the way).  Both heater and bias voltages can be dialed in on both PSUs.

Wondering if I need to troubleshoot the second PSU B+ before finishing the mics themselves.  Looked all over both and assembly is perfect, everything is where it should be, solder joints are perfect and output at the transformer looks good.  Without the 180k dummy load the second PSU was up around the 180s (V) on B+.  Bad pot a possibility?  There is plenty of adjustment range, just won't go high enough.

EDIT - Don't know if accidentally shorting B+ to Ground before the caps discharged has anything to do with this, but there was a scary pop and spark between the resistor legs.  Accidentally shorted it with by screwdriver.

Anyway here are the voltages with and without the dummy load

Without dummy load - 275 going into r1, 235 going into r2 and 196.6 coming out of r2.  B+ at the terminal is 169.5

With dummy load - 274 going into r1, 205.2 going into r2 and 137.5 coming out of r2.  B+ at the terminal is 92.2  (was 110 before the accidental short of B+ to ground)

R4 fried?

Also maybe worth noting that after the short the bias voltage went from -1 to -.5 but was adjustable to -1.1 thereafter.  Thought it could help lead to an answer.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Aaronrash on October 28, 2013, 03:04:46 AM
Any news on converting the heater voltage to negative voltage?

I suspect one of the hard-to-execute steps would be to grind and isolate the "-" terminals on the filter capacitors.  Seems like there will be a lot of hacking to make it happen.  I've asked Matador for a bullet point list of mods that need to happen to convert.  I'm sure he just ran into a busy spell or discovered more hurdles than previously known regarding the mod and is thinking it over.

FWIW, the new fully regulated PSU board will be designed to easily accommodate the negative heater supply.

Cool,

So there's a new power supply board in the works?
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Melodeath00 on October 28, 2013, 09:59:00 AM
Wasn't the original C12 PSU non-regulated? Can we still get the old-style board? I'd like to get as close to vintage C12 as possible.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: ln76d on October 28, 2013, 10:55:27 AM
Wasn't the original C12 PSU non-regulated? Can we still get the old-style board? I'd like to get as close to vintage C12 as possible.

If you want the "vintage" close as possible, make it without pcb, use selenium rectifiers etc :)
Am planning to make the "close" copy :) Heaters were regulated!
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Melodeath00 on October 28, 2013, 11:05:41 AM
Wasn't the original C12 PSU non-regulated? Can we still get the old-style board? I'd like to get as close to vintage C12 as possible.

If you want the "vintage" close as possible, make it without pcb, use selenium rectifiers etc :)
Am planning to make the "close" copy :) Heaters were regulated!
Well I am not going for exact clone, as I don't have the know-how or the money to do this. But if the older PCB for the PSU is closer to the original than the new, I'd like to get the older one. My Tim Campbell capsule is on the way, as well as my early 1960s 6072 :)
Title: Re: Official C12 Clone - Build and Support Thread
Post by: chunger on October 28, 2013, 12:15:31 PM
Both PSU types will continue to be available.

I will make head-to-head recordings to validate the new PSU.  FWIW, there are differences between our PSU and the original circuit.  Ours is full wave rectified.  The original was half wave rectified.  Reasonable improvements were made but the overall scheme retained.

The reason we are moving forward with the fully regulated PSU is about 90% of the build problems encountered so far relate to the passive B+ section of the PSU and, there should be much more adjustment range in the new setup for experimenting with different tubes, etc.  If Matador was not confident that he could design a system that is as clean or cleaner than the current passive B+, I don't think he would move forward with the design.

If the new fully regulated PSU design proves on the bench and in the studio to perform as good or better than the passive setup, I will encourage less experienced DIY people to build the new one to reduce the chance of build failure.  Again, both will continue to be available.  Nothing is being phased out.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Melodeath00 on October 28, 2013, 12:42:26 PM
Both PSU types will continue to be available.

I will make head-to-head recordings to validate the new PSU.  FWIW, there are differences between our PSU and the original circuit.  Ours is full wave rectified.  The original was half wave rectified.  Reasonable improvements were made but the overall scheme retained.

The reason we are moving forward with the fully regulated PSU is about 90% of the build problems encountered so far relate to the passive B+ section of the PSU and, there should be much more adjustment range in the new setup for experimenting with different tubes, etc.  If Matador was not confident that he could design a system that is as clean or cleaner than the current passive B+, I don't think he would move forward with the design.

If the new fully regulated PSU design proves on the bench and in the studio to perform as good or better than the passive setup, I will encourage less experienced DIY people to build the new one to reduce the chance of build failure.  Again, both will continue to be available.  Nothing is being phased out.
I appreciate the reply, chunger. Thanks! I guess we are using the term "cleaner" as in a general improvement to the circuit. I have no idea how "clean" a vintage PSU would be, but I imagine we are capable of building cleaner PSUs these days.

What exactly does "full wave rectified" mean compared to "half wave rectified," and what effect does it have?
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Matador on October 28, 2013, 01:30:48 PM
The new fully-regulated PSU design is quite a bit more flexible than the previous design:

1) It is agnostic of tube type.  Once set for 120V, you can run any tube type and the supply will adjust itself to maintain 120V.  Currently different tubes of the same type require adjustment of the B+ trimmer, and switching to a different tube type (e.g. 12AT7 or others) require removing and changing filter resistors
2) B+ supply is adjustable from 120V up to 245V
3) It provides true fixed bias, or a low impedance negative supply
4) It can accommodate both "positive" and "negative" heater supplies, all from a fixed regulator type (to switch requires only a jumper be moved)
5) Isolated grounds - there are three supplies that each have their own "ground" plane (think B-, HEATER-, and BIAS+).  This means you can float the heater supply up, etc.  Or you can strap all three together, it's your choice.
6) Optimized BOM with fewer component values that need to be ordered

The B+ supply is good up to about 10mA, and the heater up to 12V, so it's even possible to use this with quite a few tube preamp projects as a nice clean, low-noise tube preamp supply.

In any case, as Chunger said the intention is to offer both, so anyone can pick which variant they want.  :D
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Category 5 on October 28, 2013, 01:42:13 PM
The new fully-regulated PSU design is quite a bit more flexible than the previous design:

1) It is agnostic of tube type.  Once set for 120V, you can run any tube type and the supply will adjust itself to maintain 120V.  Currently different tubes of the same type require adjustment of the B+ trimmer, and switching to a different tube type (e.g. 12AT7 or others) require removing and changing filter resistors
2) B+ supply is adjustable from 120V up to 245V
3) It provides true fixed bias, or a low impedance negative supply
4) It can accommodate both "positive" and "negative" heater supplies, all from a fixed regulator type (to switch requires only a jumper be moved)
5) Isolated grounds - there are three supplies that each have their own "ground" plane (think B-, HEATER-, and BIAS+).  This means you can float the heater supply up, etc.  Or you can strap all three together, it's your choice.
6) Optimized BOM with fewer component values that need to be ordered

The B+ supply is good up to about 10mA, and the heater up to 12V, so it's even possible to use this with quite a few tube preamp projects as a nice clean, low-noise tube preamp supply.

In any case, as Chunger said the intention is to offer both, so anyone can pick which variant they want.  :D

Awesome!  please make a PSU only kit available.  In the mean time can you peruse my post from late last night and give your thoughts.  If I need to make a component order I'd liked to try and get it in with another order tonight.

Thanks a million guys!
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Matador on October 28, 2013, 02:00:40 PM
Awesome!  please make a PSU only kit available.  In the mean time can you peruse my post from late last night and give your thoughts.  If I need to make a component order I'd liked to try and get it in with another order tonight.

Thanks a million guys!

I am highly suspecting C4.  Can you remove it and try the loaded and unloaded readings of all of those points as before?  Unloaded voltages seem very low, which implies leakage current.  The bleeder resistor R6 is sized to bleed away (120V/470K) = 0.25mA, but your unloaded measurements indicate 40V lost across R1 (91K) which is 0.5mA, which is 0.25mA too much.  R4 is the only cap not protected by a series resistor and would suffer the effects of a B+ short the most.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: chunger on October 28, 2013, 02:39:33 PM
I hope to make PSU kits will be available separately. . . it seems there is a surge of interest in DIY tube mics of various types and this particular PSU package (based on the economical Chinese case, power transformer, and mains wiring) is a very nice option for one of the toughest parts of any tube mic build.

I'll likely order loose power supplies from Alctron to bundle with the PSU pcb's.  I am moving towards making both passive and regulated options available separately in full kits and bare PCB's.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Melodeath00 on October 28, 2013, 03:13:34 PM
The new fully-regulated PSU design is quite a bit more flexible than the previous design:

3) It provides true fixed bias, or a low impedance negative supply


Matador, is this to imply that the original PSU PCB design does not provide "true fixed bias," or am I reading this wrong? I'm still very new to this whole electronics thing :P. Many thanks!

Also, I second the motion to have PSUs available separately on their own. I may be using an alternate body for my C12, but will still need a PSU. Thanks!
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Matador on October 28, 2013, 03:48:42 PM
Matador, is this to imply that the original PSU PCB design does not provide "true fixed bias," or am I reading this wrong? I'm still very new to this whole electronics thing :P. Many thanks!

Indeed:  the original C12 design is not fixed bias, despite the cathode being "grounded".  I think I answered it previous in the thread if you care for the details.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Matador on October 28, 2013, 05:21:21 PM
For any interested in alternate build configurations, I am building another mike with a slew of other BOM and stuffing options to show everyone what is possible with this design.

If you are interested in seeing a build for this, please "like" this post and I'll take photos and generate docs for this config.  But in short:
Title: Re: Official C12 Clone - Build and Support Thread
Post by: chunger on October 28, 2013, 06:27:28 PM
Pitchers!!!

Really sensible options posted by Matador.  I am very interested in the specific resistor values used for 12AT7 application because premium 12AT7's are a lot cheaper.  I have a NOS Mullard and Siemens that I would like to try in circuit.  We tested the cinemag 2480 head to head with the AMI T14 and they were really close.  It was only with direct side-by-side evaluation that differences were detected.  I really wanted to like the cinemag better because it is about $40 cheaper, but in this application, with the "premium" mic configuration that we were testing (NOS GE 6072A tube/Tim Campbell capsule), the AMI T14 was a little more transparent/open but had less bass.  Cinemag was much prettier looking though and the build quality of the Cinemag fantastic!  Differences were NOT by a large margin and different ears and different applications could very well favor the cinemag.  Perhaps a better match to the K67 based budget capsules as well.

At the end of the day, the "budget build" should come in at around $500 and the "premium" build around $1000.  That's a big difference.  Hopefully we can put some sound clips up side-by-side once Matador is done. . . assuming the mic doesn't disappear to a paying customer as soon as it rolls off the bench.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Melodeath00 on October 28, 2013, 07:40:43 PM
Matador, is this to imply that the original PSU PCB design does not provide "true fixed bias," or am I reading this wrong? I'm still very new to this whole electronics thing :P. Many thanks!

Indeed:  the original C12 design is not fixed bias, despite the cathode being "grounded".  I think I answered it previous in the thread if you care for the details.
Ah yes, I remember now in the Tube Biasing thread you explain the C12 is not really true fixed bias. However, my question is, is this new PSU design different in the fixed bias portion from the older design? I wasn't sure if you were listing "true fixed bias" as a new feature, or just as a general feature of the new PCB. Thanks!
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Matador on October 28, 2013, 09:45:01 PM
Ah yes, I remember now in the Tube Biasing thread you explain the C12 is not really true fixed bias. However, my question is, is this new PSU design different in the fixed bias portion from the older design? I wasn't sure if you were listing "true fixed bias" as a new feature, or just as a general feature of the new PCB. Thanks!

Yes, it is different.  It is low impedance and regulated from a separate rectifier.  It's level doesn't change as a function of tube current like in the C12 design.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Matador on October 29, 2013, 02:37:51 PM
12AT7 Conversion - The Microphone

Here are some details around the mike changes needed to run a 12AT7 tube.

First, let's look at the load line for the 6072A and we can gather why AKG picked some of the components they did.

(http://www.musicalsparks.com/images/c12/12at7/c12_6072_bias.jpg)

So a 100K plate resistor across a 120V means that the maximum current is 120V/100K or 1.2mA.  We can draw the load line from the 120V, 0V point to the 0V, 1.2mA.  The idle current @-1V bias is about 0.7mA:  if we want to fake this load to test the PSU we need a 120V/0.7mA = 171K load resistor.  180K is close enough.  The Q point at -1V looks to be in the middle:   plate voltage idles at about 55-60V, idling current looks like about 0.7mA.  Bias resistance of -1V bias at plate current of 0.7mA implies a 1.42K "cathode" resistor (really just R4 in the PSU).

For gain:  we can see from the load line, a 0V to 2V swing on the grid equates to a 60V swing on output, which is gain of ~30dB.

So let's try to replicate this with a 12AT7 tube.  Another tube chart is in order:

(http://www.musicalsparks.com/images/c12/12at7/c12_12at7_bias.jpg)

So we need about 60V swing with 2V input to match 6072A gain.  Load line intersecting at 2.5mA gives approximately this.  120V / 2.5mA implies a plate resistor of 47K.  Q point at -1V looks to be in the middle:   plate voltage idles at about 55-60V, idling current looks like about 1.1mA.

So to generate this bias a cathode resistor of -1V/1.1mA = 900ohm is implied.  Easily settable with R3 (EDIT: fixed this should be R3, not R4), or can be an external resistor for those wanting to try true "cathode bias".  A 0V to 2V swing on the output causes a 75V swing on the output, which is a gain of about 31dB.  Understandable since the 12AT7 transconductance is higher.

Output impedance of the head amp is half the stock C12 design (due to lower plate resistor).  Transient response is probably better.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: chunger on October 29, 2013, 02:50:08 PM
So, what I'm reading here is. . . to use the 12AT7, we change R17 in the mic from 100K to 47K, reset the bias via trim pot (R4) in the PSU to -1V and we are done?  EDIT:  NO!  See below.

I should include a 47K resistor in the parts kit and modify the build documentation to reflect this option  ;D
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Matador on October 29, 2013, 03:46:55 PM
Bah Chunger posted before I could get to the PSU part.  :-[

12AT7 Conversion - The PSU

So the two big changes from above (from the PSU perspective) are:  a) the idle bias current draw increases from 0.7mA to 1.1mA, and b) the "cathode" resistance decreases from 1.4K down to 900ohms.  "B" is not an issue because we have R3 which can easily accommodate this change.  With the default 91K values of R1 and R2, the additional 0.4mA of current will drop cause an additional 72V drop in B+, which means there would be no way to get 120V out of the PSU.  So some re-calculations are in order.

Let's assume that R4 is set for half, which is 50K.  We have about 270V coming out of the rectifier diodes and we want 120V out of the PSU, which is a 150V drop across R1+R2+R4.  Total current should be 1.1mA + 0.25mA (through R6) which is 1.35mA.  150V drop at 1.35mA implies a total resistance of 112K.  Since R4 provides 50K, then R1+R2 needs to equal about 62K.  R1 = R2 = 33K sounds pretty good to me.  This gives an adjustment range of about 160V down to about 50V.

12AT7 Conversion - Summary

Microphone:  Change R17 from 100K down to 47K
PSU:  Drop R1 and R2 down to 33K.  Adjust R3 down to about 900ohms, then tweak with the actual tube.
Test load: decreases from 180K down to (120V/1.35mA) = 88K.  91K would work as a substitute for a real tube for PSU testing.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: micaddict on October 30, 2013, 04:34:14 AM
 :D
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Category 5 on October 30, 2013, 02:10:31 PM
Hey Matador.  I haven't had the chance to trouble shoot the psu since your last response but did notice I a pic I took of it that the secondary of the transformer is labeled 175v instead of 200v like my first one. 

Anyone else see this?  Is 275 out of the diode bridge about right?  Maybe they just mislabeled it. 
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Matador on October 30, 2013, 02:17:38 PM
Hey Matador.  I haven't had the chance to trouble shoot the psu since your last response but did notice I a pic I took of it that the secondary of the transformer is labeled 175v instead of 200v like my first one. 

Anyone else see this?  Is 275 out of the diode bridge about right?  Maybe they just mislabeled it.

Probably mislabeled:  200VAC should give about 280V after the rectifier diodes.  275V seems really close to that. ;)
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Aaronrash on October 30, 2013, 03:56:14 PM
This is great news. Any estimate on when the new PSU boards will be availible?
Title: Re: Official C12 Clone - Build and Support Thread
Post by: micaddict on October 31, 2013, 06:14:29 AM
Being dual triodes, both the 6072/12AY7 and the 6201/12AT7 can be had with balanced sections/triodes, cherry picked by the supplier. Obviously, for some applications this is more important than for others. Still, it is suggested that those with balanced triodes have better odds for low noise and microphonics, regardless of application.
Any feelings about this?
Title: Re: Official C12 Clone - Build and Support Thread
Post by: micaddict on November 01, 2013, 03:44:06 PM
Anyone?
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Matador on November 01, 2013, 05:56:56 PM
Balanced halves are good for things like phase splitters:  I can't imagine it being very critical for microphone use.  It may be there is some correlation between balanced sides and noise but I can't imagine what it would be.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: micaddict on November 01, 2013, 06:22:03 PM
Thanks.  :)
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Nagskof on November 04, 2013, 04:36:16 AM
Thank you for a great support thread on this build and an awesome mic! Finished mine with your headbasket, PCB and parts kit, I used a Microphone Parts RK12 Capsule and a Electroharmonix 6072A tube. PSU case and microphone body is custom built and transformer wound locally South Africa. Everything worked 100% the first time! I want another one... :-).
Title: Re: Official C12 Clone - Build and Support Thread
Post by: mica on November 04, 2013, 07:21:12 AM
I just finished the PSU and have the following readings:

B+ : 162V
Heater: 7.67V
Bias: -0.86

Wrong?

/M
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Matador on November 04, 2013, 10:21:31 AM
I just finished the PSU and have the following readings:

B+ : 162V
Heater: 7.67V
Bias: -0.86

Wrong?

/M

Looks correct.  If you are using the 6072A tube, please install the test 180K resistor and you'll be able to measure close to the real operating conditions.  You can stick the resistor right into the appropriate pins of the 7-pin XLR connector (between B+ and ground).
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Category 5 on November 05, 2013, 01:29:01 AM
Awesome!  please make a PSU only kit available.  In the mean time can you peruse my post from late last night and give your thoughts.  If I need to make a component order I'd liked to try and get it in with another order tonight.

Thanks a million guys!

I am highly suspecting C4.  Can you remove it and try the loaded and unloaded readings of all of those points as before?  Unloaded voltages seem very low, which implies leakage current.  The bleeder resistor R6 is sized to bleed away (120V/470K) = 0.25mA, but your unloaded measurements indicate 40V lost across R1 (91K) which is 0.5mA, which is 0.25mA too much.  R4 is the only cap not protected by a series resistor and would suffer the effects of a B+ short the most.

Did some troubleshooting tonight and ended up not quite where I wanted to .  ;)

Replaced C4 as you recommended but got the same results.  I then replaced c1, c2, c3 and the 100K pot and I'm back where I was before the short.  B+ is adjustable to about 108 before I run out of turns.

After replacing C4 loaded volts were, diodes-268 -> R1-200.8V - > R2-134.2V -> B+ 98V

After replacing C1, C2, C3 and R4  diodes-267V - > R1-186V -> R2-108V -> B+ 108V

Not sure why the drop across R1 went up so much.

Checked the "good" PSU and indeed the transformer is different.  I get 225VAC out of the secondary wheras the one labeled 175V gives me 198.3VAC

The voltages (loaded) for the good PSU are

diodes-303.2V - > R1-215.4V -> R2-125.5V -> B+ 120V

This is with the same 180K resistor simulating load.  I'd swap PCBs and see if the tranny is to blame but I'm reluctant to go through that just yet.  I get a solid 120VAC from the line.  One transformer is giving me 12.5% more volts at the input to the PCB.  If that 12.5% translated all the way through to the output of B+ that would explain the difference.  If the transformer is to blame, then I assume I could just use lower values for R1 and R2 to get the required output.

If some of these PSUs are using different parts without making it clear, I can see where the regulated PSU boards that are in the works would be an even greater benefit to this project.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Matador on November 05, 2013, 10:32:36 AM
You have a 30V difference post regulator:  if you measured and only get 198VAC that would explain the difference.  It looks like there is a lot more spread from transformer to transformer.

I redid some maths for you based on your readings, and I think you can safely adjust R1 and R2.  Assuming your readings hold, and you want to target 120V at B+ with the test resistor of 180K, and R4 dialed to 50K (to give maximum adjustment), then changing R1 and R2 to 56K each will do it.  The filter action is essentially unchanged, having a pole below 1 mHz.

The nominal B+ voltage at R4=50K should be about 125V.  R4 at maximum would give about 80V, and R4 at minimum would give about 170V.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Category 5 on November 05, 2013, 11:16:53 AM
You have a 30V difference post regulator:  if you measured and only get 198VAC that would explain the difference.  It looks like there is a lot more spread from transformer to transformer.

I redid some maths for you based on your readings, and I think you can safely adjust R1 and R2.  Assuming your readings hold, and you want to target 120V at B+ with the test resistor of 180K, and R4 dialed to 50K (to give maximum adjustment), then changing R1 and R2 to 56K each will do it.  The filter action is essentially unchanged, having a pole below 1 mHz.

The nominal B+ voltage at R4=50K should be about 125V.  R4 at maximum would give about 80V, and R4 at minimum would give about 170V.

Thanks a lot Mat.  Would Carbon composition resistors 1/4 watt be okay here?  I think I have some metal films somewhere but I know I have some carbon laying around.  I can measure them to get closest to actual value.

This was bumming me out.  Assemble is impeccable, soldering joints are shiny and look great.  I just couldn't imagine what had gone wrong here.

One of the problems with sourcing overseas is that they will do these component swaps when convenient and not mention it.  Bring on the regulated version. ;-)
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Matador on November 05, 2013, 02:58:23 PM
Yes carbon comp would be no problem. 

Even 5% is good enough for this style of jazz. ;)
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Conviction on November 05, 2013, 04:06:44 PM
Hi!

Does the PCB's fit an Avantone CV-12 body?
Any need for changing the PSU (polar patterns, pinouts etc)?

I'm planning a build here and got a Avantone very cheap :-)
And by the way: Beautiful PCB's!

Thanks!

Edit: I see now that they most likely do!
Title: Re: Official C12 Clone - Build and Support Thread
Post by: chunger on November 05, 2013, 05:12:21 PM
It looks like it will likely be compatible.  Depending on how cheaply you got your Avantone, you might consider selling to at profit and then using a cheaper donor.  As i understand it the Avantone has upgraded capacitors, better Q/C'd capsule, and possibly a few other tweaks onboard that make it a nice mic someone else may be able to use as-is.  It would also have extra "ventilation" in the body as it has pad and low-cut switches that our clone does not utilize and there would not be space inside to retain the stock switch pcb.

Hi!

Does the PCB's fit an Avantone CV-12 body?
Any need for changing the PSU (polar patterns, pinouts etc)?

I'm planning a build here and got a Avantone very cheap :-)
And by the way: Beautiful PCB's!

Thanks!

Edit: I see now that they most likely do!
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Melodeath00 on November 05, 2013, 09:03:45 PM
Matador, I wanted to PM you some questions, but your box was full the last time I tried, so I will just put my questions here. I am gearing up to buy the PCB as I now have a nice tube and my Tim Campbell capsule, but had these remaining (newbie) questions before I purchase the rest of the components and begin...

When I look at pictures of the PCB build in this thread, I am confused by the Grounding scheme. I do not see a connection from the unused side of the tube to ground, and I see several ground points on the PCB that don't seem to be connected to each other. Am I missing something, or are there multiple floating ground points? I may have a misunderstanding of ground, but I thought all ground points would be connected. Maybe I am just not able to see the trace in the pictures?

Do you have an opinion on using the teflon standoffs for the capsule connections as is, versus drilling holes in the PCB to push the standoffs in, and wiring the capsule point to point?

Somewhat unimportant, but do you know exactly how much wider the Alctron mic is compared to a vintage C12 body? Is it about 4mm?

I have never soldered a PCB before, but I have built one mic point to point. Do I need to take extra precaution to clean the board with alcohol, since it is a PCB? I did not do any cleaning really on my first mic, and it sounds great.

Lastly, I saw your answer about the new regulated C12 PSU having a low impedance fixed bias feature. My question is: the older PSU PCB is more "true" to the C12 design, correct? I know it is not exactly the same, as you've mentioned specifically that it utilizes a half wave rectifier instead of full wave. What effect, if any, does that have? I just want to be sure that the older design is "truer" to the original C12 PSU design so that I know which to order.

Thanks a lot!
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Matador on November 05, 2013, 11:55:49 PM
When I look at pictures of the PCB build in this thread, I am confused by the Grounding scheme. I do not see a connection from the unused side of the tube to ground, and I see several ground points on the PCB that don't seem to be connected to each other. Am I missing something, or are there multiple floating ground points? I may have a misunderstanding of ground, but I thought all ground points would be connected. Maybe I am just not able to see the trace in the pictures?

The default config doesn't have the unused tube side grounded.  You certainly can if you want:  I noticed no difference in the prototypes.  Grounding all of that stuff makes it much more difficult to swap tube sides later however.

Can you be more specific about the other points?  Which points do you think aren't connected?  There is a ground plane on the bottom of the board which connects all ground points:  there aren't individual traces for ground.

Do you have an opinion on using the teflon standoffs for the capsule connections as is, versus drilling holes in the PCB to push the standoffs in, and wiring the capsule point to point?

Today we have nice, well controlled manufacturing processes, and have well-characterized PCB materials, so we can apply science to see where we will get a benefit and where we won't.  I ran through all of the calculations and went back and forth with the PCB manufacturer to make sure that we could use PCB tracks (with a good-quality soldermask) and not suffer noise or other filtering penalties as a result of running the connections right up to the capsule connection points.

Provided the PCB is cleaned well with IPA, there isn't much to be gained by performing surgery just to re-establish the same connections (only this time up in the air).

Somewhat unimportant, but do you know exactly how much wider the Alctron mic is compared to a vintage C12 body? Is it about 4mm?

I'm not sure:  perhaps others can answer this?

I have never soldered a PCB before, but I have built one mic point to point. Do I need to take extra precaution to clean the board with alcohol, since it is a PCB? I did not do any cleaning really on my first mic, and it sounds great.

Per above, absolutely.  In return for good cleaning, you'll have an easier time assembling and results from mike to mike will be much more consistent.

Lastly, I saw your answer about the new regulated C12 PSU having a low impedance fixed bias feature. My question is: the older PSU PCB is more "true" to the C12 design, correct? I know it is not exactly the same, as you've mentioned specifically that it utilizes a half wave rectifier instead of full wave. What effect, if any, does that have? I just want to be sure that the older design is "truer" to the original C12 PSU design so that I know which to order.

Thanks a lot!

Yes, the old PCB is more "true" to the original design:  in fact, the bias supply is identical.  Full-wave puts the PSU hum at twice the frequency (120Hz vs. 60Hz), so the filters are 18dB more effective at quieting this hum.

In short, yes, the older design is truer to the original design:  however both the old design as well as the new "fully regulated" design are both full-wave rectified.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Category 5 on November 06, 2013, 01:47:52 AM
You have a 30V difference post regulator:  if you measured and only get 198VAC that would explain the difference.  It looks like there is a lot more spread from transformer to transformer.

I redid some maths for you based on your readings, and I think you can safely adjust R1 and R2.  Assuming your readings hold, and you want to target 120V at B+ with the test resistor of 180K, and R4 dialed to 50K (to give maximum adjustment), then changing R1 and R2 to 56K each will do it.  The filter action is essentially unchanged, having a pole below 1 mHz.

The nominal B+ voltage at R4=50K should be about 125V.  R4 at maximum would give about 80V, and R4 at minimum would give about 170V.

Thanks again for taking the time to help here Matador.  The 56K resistors did it.  With the 180K dummy load all my voltages were easily adjustable and well within the middle of the adjustment range.

If anyone else has this problem (B+ Adjustable to about 110 maximum) double check the AC voltage at the output of the transformer.  The good one output 225VAC.  The bad one was only outputting 198VAC.  FWIW, the bad one was labeled 175V whereas the good one was labeled 200VAC.   56K for R1 and R2 instead of the specified 91K (as Matador kindly calculated for me) did the trick!


I am betting I am not the only one who got a lower output transformer.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Melodeath00 on November 06, 2013, 11:40:41 AM
When I look at pictures of the PCB build in this thread, I am confused by the Grounding scheme. I do not see a connection from the unused side of the tube to ground, and I see several ground points on the PCB that don't seem to be connected to each other. Am I missing something, or are there multiple floating ground points? I may have a misunderstanding of ground, but I thought all ground points would be connected. Maybe I am just not able to see the trace in the pictures?

The default config doesn't have the unused tube side grounded.  You certainly can if you want:  I noticed no difference in the prototypes.  Grounding all of that stuff makes it much more difficult to swap tube sides later however.

Can you be more specific about the other points?  Which points do you think aren't connected?  There is a ground plane on the bottom of the board which connects all ground points:  there aren't individual traces for ground.

Are you saying you did not notice a sound difference when you grounded the unused side versus not grounding? I agree grounding it would make switching sides more difficult, but I asked only because in the schematic the unused side is grounded.

As for the parts that don't look grounded: P6 at the bottom of the board looks like it is not connected to anything else. Same with FC at the top, and C10 and C11 near the tube deck. Am I just not seeing the ground plane?


Do you have an opinion on using the teflon standoffs for the capsule connections as is, versus drilling holes in the PCB to push the standoffs in, and wiring the capsule point to point?

Today we have nice, well controlled manufacturing processes, and have well-characterized PCB materials, so we can apply science to see where we will get a benefit and where we won't.  I ran through all of the calculations and went back and forth with the PCB manufacturer to make sure that we could use PCB tracks (with a good-quality soldermask) and not suffer noise or other filtering penalties as a result of running the connections right up to the capsule connection points.

Provided the PCB is cleaned well with IPA, there isn't much to be gained by performing surgery just to re-establish the same connections (only this time up in the air).

Thanks for the info. To be perfectly honest, I'm not even sure I understand the point of the teflon. Why not just use normal keystones?

I ask about drilling and making p2p connections because in another thread you mention that your "PCB is flat down to roughly 40-50Hz," when it seems like it should be flat down to 20Hz. However, you do mention increasing the value of the output coupling cap and using the AMI T14 would help to flatten the response. Which transformer was used in your freq sweep test? Does increasing the C12 cap not just lower the high end roll off point? Does it also extend bass response?


Lastly, I saw your answer about the new regulated C12 PSU having a low impedance fixed bias feature. My question is: the older PSU PCB is more "true" to the C12 design, correct? I know it is not exactly the same, as you've mentioned specifically that it utilizes a half wave rectifier instead of full wave. What effect, if any, does that have? I just want to be sure that the older design is "truer" to the original C12 PSU design so that I know which to order.

Thanks a lot!

Yes, the old PCB is more "true" to the original design:  in fact, the bias supply is identical.  Full-wave puts the PSU hum at twice the frequency (120Hz vs. 60Hz), so the filters are 18dB more effective at quieting this hum.

In short, yes, the older design is truer to the original design:  however both the old design as well as the new "fully regulated" design are both full-wave rectified.

The filters of the original are 18dB more effective at quieting 120Hz than your half-wave is at quieting 60Hz? I guess I'm confused.
I'm looking forward to hearing your thoughts on the new regulated PSU since such a big deal is made about regulated versus non-regulated among mic gurus. It's especially interesting since the new regulated PSU has the full-wave like the original as well.

I read David Bock state that the original C12 used polystyrene caps and paper in oil. Does anyone know which were which? Was it only the coupling cap that was PIO?

I apologize for so many questions. I am a newbie and trying to learn. Thanks so much!
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Matador on November 06, 2013, 06:27:22 PM
Are you saying you did not notice a sound difference when you grounded the unused side versus not grounding? I agree grounding it would make switching sides more difficult, but I asked only because in the schematic the unused side is grounded.

As for the parts that don't look grounded: P6 at the bottom of the board looks like it is not connected to anything else. Same with FC at the top, and C10 and C11 near the tube deck. Am I just not seeing the ground plane?

I assume you mean the original schematic?  Mine shows these nodes floating.  And yes, I didn't notice any difference after grounding them.

Flip the PCB and look at the bottom:  everything that is yellow is the ground plane. ;)  All of those nodes are connected to the plane via thermal reliefs.  If you look very closely, you see 4 little yellow stubs on the bottom that stitch the nodes to the plane itself.

Thanks for the info. To be perfectly honest, I'm not even sure I understand the point of the teflon. Why not just use normal keystones?

I ask about drilling and making p2p connections because in another thread you mention that your "PCB is flat down to roughly 40-50Hz," when it seems like it should be flat down to 20Hz. However, you do mention increasing the value of the output coupling cap and using the AMI T14 would help to flatten the response. Which transformer was used in your freq sweep test? Does increasing the C12 cap not just lower the high end roll off point? Does it also extend bass response?

Telfon is used because it is damn near a perfect insulator (something like 1018 ohms per centimeter).

There are many filters:  the capsule to tube, the output cap into the transformer, the tube capacitance w/Miller effect, etc.  With stock values, C12 (at 0.5uF) into a worst-case 150ohm mike pre has a 3db down point at roughly 40Hz.  You can move this lower in frequency by making C12 bigger, finding an output transformer with more Henries, or both.  I measured with a Cinemag CM-2480.  High end roll-off is not really modulated by the capacitance of C12, it's by the transformer primary inductance and winding capacitance.

The filters of the original are 18dB more effective at quieting 120Hz than your half-wave is at quieting 60Hz? I guess I'm confused.
I'm looking forward to hearing your thoughts on the new regulated PSU since such a big deal is made about regulated versus non-regulated among mic gurus. It's especially interesting since the new regulated PSU has the full-wave like the original as well.

I read David Bock state that the original C12 used polystyrene caps and paper in oil. Does anyone know which were which? Was it only the coupling cap that was PIO?

I apologize for so many questions. I am a newbie and trying to learn. Thanks so much!

The filtering action is different between the regulated PSU and the original.  The original uses 3 cascaded RC filters to try and make the B+ line look like "ground" to AC signals, the strongest of which will have a 120Hz signature due to the full-wave rectification.  It's a brute force approach, however a time-tested one that's been used successfully in countless designs.  It's also cheap and repeatable and pretty much indestructible.

The regulated version uses a modern IC, which has a bandwidth about six orders of magnitude faster than the ripple frequency.  It's so fast in comparison to the ripple that it can turn 120Hz ripple into a constant voltage by applying fast corrections to the internal pass element(s).  It's a different way to solve the same problem.

The key:  the IC uses feedback to make the PSU look like an ideal voltage source, with much lower output impedance.  This means that the PSU can essentially supply any current at fixed voltage, and makes it so it doesn't care which tube (or which tube type even) is used (within reason).

So which is "better"?  That's up to our ears to decide. ;)
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Matador on November 06, 2013, 07:28:52 PM
So let me spend some time to write about why older designs used isolated high-impedance sections, and why we don't always have to anymore.

Let's boil this down to basics:  the capsule and the input impedance of the active element (in this case, a tube) form a high pass filter.  Given a worst-case "typical" capsule of 50pF, and a 1M input impedance (e.g. a 1M grid resistor, or R15 on the C12 schematic), the -3dB point is 3.1kHz.  This is obviously no good, unless you only close-mike coins falling on a table or perhaps whistling.

So R15 has to be higher:  if you do the math, in order to have a -3dB point at 20Hz, the grid resistance must be at least 150M on the worst capsule.  So the C12 uses 250M, probably because it was a part they could source at the time.  250M with 50pF gives about 13Hz, so life is good.

But what else is going on here?  Some of the capsule connections sit at the polarization voltage (FB and RB, for instance) or 60V (or higher, up to 120V!).  At these impedances, small leakage currents start to look like resistors that are of the same magnitude as R15, so now we have to look at our math again.

Let's pretend we have one of these connections to 60V on a dirty, untreated PCB.  A "hole" (or lack of electron) at this high potential sees all of the potentials that are around it that are less (like ground!), and it wants to go there.  If the PCB has a bunch of flux on it that is slightly conductive then we might have a leakage current there.  Let's pretend we have 1uA of leakage from the 60V potential.  Ohms Law says this leakage path looks like a 60V/1uA = 60M resistor:  no different than if we had soldered a 60M resistor there!

But we were counting on the 60V node seeing only the grid impedance, which was 250M above.  But now this new leakage impedance appears to the capsule to be in parallel with this grid impedance (which is ground referenced as well), and being that this hole doesn't want to violate Ohms Law it says "I see 60M in parallel with 250M, not just 250M!".  Knowing that two resistances in parallel always net to something less than the lowest of those resistance, there's no way the hole sees 250M any more:  in fact, it sees something (by definition, without doing any math) slightly less than 60M!

So now the leakage current has formed a phantom resistor, and demolished our carefully calculated high-pass filter.  Instead of a 13Hz high-pass filter, the capsule and the grid + leakage current appears to the system as a high-pass filter of 53Hz.  All from just 1uA of leakage current.  You can do more analysis and see that moving to 2uA leakage current makes the total resistance fall below 30M, which puts the HPF above 100Hz!  Our bass is melting away!

If we could lower the polarization voltage, then the leakage current would shrink, and the phantom resistor would increase in value.  But then sensitivity would suffer.  So we must increase the impedance between these high impedance sections and ground to minimize the magnitude of the leakage currents.

So air is a good insulator:  1014 ohms per centimeter or thereabouts.  Teflon is better (about 1000 times!).  But even 1 cm of air looks like a 1000G resistor, which means only infinitesimally small leakage currents are possible, certainly nothing to move the location of a filter pole.

But modern soldermask is a good insulator as well:  typical UV cured polymerized formulations (Taiyo UVR-150G is a common one) have insulation resistances on the order of 1012 per centimeter:  still 100 times worse than air, but still two orders of magnitude higher than the circuit impedances in question, provided they are clean.  Obviously flux sitting on top of the soldermask is in effect "in parallel" with the soldermask itself, and can cause problems per above.

These technologies didn't exist when the original C12's were produced:  air is a good free insulator in any case. ;)  But part of the challenge of these things is balancing easy-of-assembly with the electrical requirements.  In my opinion, having a stable, repeatable, and easy-for-the beginner layout and design took precedence over gaining some extra giga-ohms, given that I knew I could arrange a design that rendered the differences manageable and inaudible.

So in case it hasn't become clear from my protestations, and Chunger's 14134234982452 detailed photos of a toothbrush and a plate of 95% IPA:

CLEAN YOUR PCB's, and you'll have great sounding, repeatable results without all of the component lead gymnastics!  ;D
Title: Re: Official C12 Clone - Build and Support Thread
Post by: OPR on November 06, 2013, 08:44:47 PM
Great explanation Matador!! But when I built my first acrylic mounted point to point C-12 and compared it to my modded apex 460 sonic differences were mainly in the firmness of the sound and higher air band frequencies rather then the lows as you describe I also did the same with my 251 P to P and had the same results.This is not to say that your board would suffer the same issues as I'm sure you did your homework.  ;)

It's interesting to note that AKG used acrylic for the 251 and C-12 circuit boards and so too did Neuman in the high impedance section of the U47when they could have easily just used the standard circuit board material of the time.


Here is a comparison.

https://soundcloud.com/open-planrecording-studio/c12-point-to-point (https://soundcloud.com/open-planrecording-studio/c12-point-to-point)

https://soundcloud.com/open-planrecording-studio/c12-apex-pcb-mod (https://soundcloud.com/open-planrecording-studio/c12-apex-pcb-mod)
Title: Re: Official C12 Clone - Build and Support Thread
Post by: chunger on November 06, 2013, 09:50:28 PM
Great explanation Matador!! But when I built my first acrylic mounted point to point C-12 and compared it to my modded apex 460 sonic differences were mainly in the firmness of the sound and higher air band frequencies rather then the lows as you describe I also did the same with my 251 P to P and had the same results. This is not to say that your board would suffer the same issues as I'm sure you did your homework.  ;)

Here is a comparison.

https://soundcloud.com/open-planrecording-studio/c12-point-to-point (https://soundcloud.com/open-planrecording-studio/c12-point-to-point)

https://soundcloud.com/open-planrecording-studio/c12-apex-pcb-mod (https://soundcloud.com/open-planrecording-studio/c12-apex-pcb-mod)

It is important to reiterate that this posted test was performed on the OEM stock Alctron PCB's the specific properties of which we do not know, but likely they are "lowest cost possible".  They are NOT the boards we are peddling in this thread.  Matador's boards are manufactured with tightly controlled  specification, materials, and processes. 

Plus, you put a yellow PCB next to a green one of the same composition, and no question, yellow will win hands-down  ;D

Also, teflon standoffs are provided in the parts kits.  It is a simple matter to drill out the capsule connection solder lugs and press fit the provided teflon standoffs.  Silver teflon wire is also available for making your high impedance connections if you choose to drill.  It's DIY!  You get to choose your own adventure.

I suspect if there is a sonic difference, it would be non-existent or so slight that outside of a head-to-head test with 2 identical microphones (capsule, matched tubes, transformer, electronic components) the only difference being air isolated high impedance vs. board soldered, you would not be able to detect the difference.  I do encourage someone to make that head-to-head test.  If proven wrong and sonic advantages (even slight) are derived from floating part of the circuit, I will gladly concede and change the board or at least the official build documentation/procedure.

Short of conclusive, objective test results, I defer to Matador's design specifications.  There are now hundreds of these mics in service.  Among them, a few have gone head-to-head with point to point vintage originals and held their own admirably.  Also, given the high number of "new" diy'ers building this kit, I am happy with the success rate and that has much to do with the intuitive kit layout.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: OPR on November 06, 2013, 09:54:26 PM
 
Quote
It is important to reiterate that this posted test was performed on the OEM stock Alctron PCB's the specific properties of which we do not know, but likely they are "lowest cost possible".  They are NOT the boards we are peddling in this thread.  Matador's boards are manufactured with tightly controlled  specification, materials, and processes. 
+1 8)
Title: Re: Official C12 Clone - Build and Support Thread
Post by: OPR on November 07, 2013, 02:40:36 AM
Hey Chunger,
 I'm not trying to be controversial or undermine your self or Matador and I highly respect the work you guys have put into this build it's very admirable indeed! I was considering buying your boards as an alternative to modding the apex pcb by applying the C-12 circuit to it but I saw no need thinking the modded pcd should be the same :o . But then I ordered one of Tims capsules I thought if I'm going to spend  $400 + on a capsule then I'm going all the way with the circuit board and building one from scratch which would give me the original point to point layout on acrylic! I didn't really expect to hear any difference but I knew I could sleep at night knowing that it was as close as I could possibly take it, so I was plesently surprised when it not only looked awesome but sounded way better! Also I don't think it has anything to do with the standoffs as the Apex board have them too.

Again I'm not implying that your board has the same issue! test so far have only been with modded Apex boards... Have you tested your boards up against an Apex modded with identical circuit and components?

Quote
I do encourage someone to make that head-to-head test.

I'd be happy for us to send a set of boards to each other to run our own tests if your interested? It's really the only definitive way to know where the differences if any lie.


Title: Re: Official C12 Clone - Build and Support Thread
Post by: Matador on November 07, 2013, 01:17:32 PM
The only way to be completely fair would be to build up a mike with a given set of components, do a slew of measurements, then completely rebuild the mike again with the exact same components and hope nothing changed in the process. ;)  And it has to be double blind...and probably repeated a few times...otherwise the experiment becomes simply to show that different mikes sound different.  Microphones are doubly-difficult to do this test because even 1 inch difference in positioning in a room can yield many dB of frequency response differences.

First off, the Apex 460 is a completely different circuit:  it's a cathode follower / CCDA circuitry, different ratio transformer, cathode bias (with different values for the bypass cap), plate coupling cap is a different value (and is electrolytic!), the polarization string is different, the plate resistor as an extra plate cap, the transformer secondary has *very* large RF suppressors, the PSU is Zener regulated, the backplate polarizer has a HUGH bypass cap (they call it C2) missing from the C12 ... the list goes on and on.

What exact mods did you do on your Apex?  Did you pull all of those exact same components out to build the P-2-P version or did you build a new mike with different components?

The devil is always in the details. ;)
Title: Re: Official C12 Clone - Build and Support Thread
Post by: MicDaddy on November 07, 2013, 01:49:58 PM
I hate to interrupt this 'comparison' discussion  ;) but I thought I'd better put this here for all to see:

Hi Matador,

I’ve really appreciated your recent posts regarding the more in depth theory as to what is happening with the electrons within the circuit.

Specifically the mention of the hi z section of the c12 project.

I’ve been experiencing some hissing/buzzing down in the noise floor and am not sure but suspect it to be related to the hi z section and my admittedly poor cleaning of heavy rosin flux.  I’m not getting any significant low end roll off, perhaps this suggests my problem lies elsewhere?  In fact I was surprised at how beefy it sounds, even with the hissy/buzzy noise floor.  Not a ground hum but buzzy fizzy, ha love the audio adjectives.

Transformer is AMI, capsule is Beesneez k12, tube is 6072a from Christian Whitmore (BOWIE)

My question, what symptoms would one expect should these sections have high resistance paths to ground or leakage current.  I read what you said about the filter frequency being influenced, would added noise be a result as well?

I used 91% ISA and can unfortunately still see a film of residue.

My initial thought is to lift connections between both backplates and Teflon pins at the pcb.  Lift the capsule side legs of c13 and r14.  Jumper my backplates and pry to the microphone gods… but first I thought it best to consult with you.

Thank you for your time and for the project!

Best Regards
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Matador on November 07, 2013, 01:52:08 PM
As another aside:  this debate has raged on for years in the guitar amp world.  Google "fender pcb amp versus point to point" and the internet will explode.

I was asked what flux residue sounds like, if not causing a noticeable frequency shift.  My analogy before was flawed on purpose for simplicity - I said it's "no different" from soldering a 60M resistor.  In reality, it's quite different.  The impedance here isn't exactly well known, and is highly voltage dependent.  What this means is that this phantom resistor can appear and disappear at random, causing all number of weird noises.

One is a sizzling, crackling noise - this is as this resistor pops into being, changes the charge on the capsule, then disappears rapidly.  Tubes can also cause this noise so it's hard to diagnose.  Sometimes, the noise floor appears to rise.

The best way to clean is right after the resistors and tube board + socket are soldered in, but before any styrene caps are installed.  Fill up a cup with about 1 inch of IPA and dunk the whole board in.  Scrub with a toothbrush as Chunger showed, then dunk again.  Keep doing this until the PCB looks shiny and clear, and you can run you finger across the surface without it feeling "sticky".  PCB houses use ultrasonic cleaners with various solvents to do the job.

If this still doesn't work, you can use a high-strength solvent, but you have to be more careful where it goes.  Most of the components used in this design are epoxy coated and will not be harmed with stronger solvents (like mineral spirits and acetone) but I would stick with IPA...it will just take longer.

Title: Re: Official C12 Clone - Build and Support Thread
Post by: OPR on November 07, 2013, 03:09:04 PM
Quote
The only way to be completely fair would be to build up a mike with a given set of components, do a slew of measurements, then completely rebuild the mike again with the exact same components and hope nothing changed in the process. ;)  And it has to be double blind...and probably repeated a few times...otherwise the experiment becomes simply to show that different mikes sound different.  Microphones are doubly-difficult to do this test because even 1 inch difference in positioning in a room can yield many dB of frequency response differences
.

I'm not thinking of anything quite that complex if we cant hear a substantial difference with our ears then the debate would be over. The mics would obviously have the same brand/value components, each of us could test the mics and then test again but swap capsule, tube input and output caps and transformer to eliminate differences in those parts or swap all of the components if you feel that's necessary.

Quote
First off, the Apex 460 is a completely different circuit:  it's a cathode follower / CCDA circuitry, different ratio transformer, cathode bias (with different values for the bypass cap), plate coupling cap is a different value (and is electrolytic!), the polarization string is different, the plate resistor as an extra plate cap, the transformer secondary has *very* large RF suppressors, the PSU is Zener regulated, the backplate polarizer has a HUGH bypass cap (they call it C2) missing from the C12 ... the list goes on and on.
I thought I had made this clear already :o I compared it to an Apex 460 with a 100% 1:1 copy of the C12 circuit.

Quote
What exact mods did you do on your Apex?  Did you pull all of those exact same components out to build the P-2-P version or did you build a new mike with different components?

The devil is always in the details. ;)

Yes the devil is in the details  ;) Both mics had the same circuit, brand,value of caps and resistors and matched tubes I have a few sets of these mics lying around with the same components that I also tested against the Pt to pt mic with the same results... The differences are obvious I can hear them on a cheep set of computer speakers. If even flux residue effects a high impedance section then why wouldn't a completely different material used as a circuit board?

Again I will repeat the fact that AKG and Neuman both used acrylic mounted components in the high impedance sections of the C-12 Ela 251M and U47, They actively did this for a reason as there were other circuit board materials around. Point to point was a given, a standard for the time but to specifically select acrylic for the Hi Z section in the U-47 or the whole mic in the case of the C12 and 251, I think there just might be more to it then the old tired point to point argument ;)
(http://www.saturn-sound.com/images%20-%20microphones/akg%20c12%20-%20inside.jpg)
(http://farm4.staticflickr.com/3141/3284455275_d62d922a6b.jpg)
(http://www.telefunken-elektroakustik.com/images/mics/photo_galleries/u47-01.jpg)

Acrylic was also used in the Ck12 capsule as an insulator :)
(http://www.saturn-sound.com/images%20-%20microphones/akg%20ck12%20capsule%20-%20see%20through%20the%20backplate.jpg)

I would still love to run the tests between the two methods as it would be a great learning opportunity as this would be a very telling test and pretty clear cut if we both do it and present it here.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Matador on November 07, 2013, 05:52:58 PM
They actively did this for a reason as there were other circuit board materials around.

Do you have a primary source for this?  What materials did they have to choose from?  What were their properties?  Could they be manufactured in-mass? What decisions were made, experiments run, that ultimately led to the final design choices?

Impedance controlled / polymerized PCB coatings were invented at least 35 years after these mikes were produced.  I'm not sure exactly what the point is here:  they used what was available at the time.  Even crude hand-drawn PCB's didn't arrive in "mass production" until the mid 60's.  I think even the lowly FR-4 material wasn't being used for mass-produced PCB's until the late 60's.

PET/Acrylic resin(s) was/were probably a good choice at the time:  it was inexpensive, easy to machine/cast, could be repeatably assembled, and most important of all, caused very low yield loss (e.g. $$) when built in the many thousands.

So back to your point:  I remember your test, and I remember they sounded different.  They still sound different to me.  Was the same capsule, same tube, and same components used?  Not the same type, or same value, or even same brand... the exact same physical components used?  Caps have high tolerance, as do transformers and capsules...to that point even two otherwise identical C12's/U47's/ELA M251's will sound different from each other.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: OPR on November 07, 2013, 06:31:40 PM
Quote
Do you have a primary source for this?  What materials did they have to choose from?  What were their properties?  Could they be manufactured in-mass? What decisions were made, experiments run, that ultimately led to the final design choices?

I'm not going to pretend that I know why they made the choices they did be they sonic economic or otherwise but I feel  that these decisions have left a sonic footprint on these mics for the better or worse.

Quote
Impedance controlled / polymerized PCB coatings were invented at least 35 years after these mikes were produced.  I'm not sure exactly what the point is here:  they used what was available at the time.  Even crude hand-drawn PCB's didn't arrive in "mass production" until the mid 60's.  I think even the lowly FR-4 material wasn't being used for mass-produced PCB's until the late 60's.

Yes they did use what was available at the time..I'm not arguing better or worse just that they would most likely sound different for better or worse.

Quote
PET/Acrylic resin(s) was/were probably a good choice at the time:  it was inexpensive, easy to machine/cast, could be repeatably assembled, and most important of all, caused very low yield loss (e.g. $$) when built in the many thousands.


Again the U47 only used acrylic in the Hi Z section the other parts look to be be the standard board material. why didn't they feel the board material was up to scratch for the Hi Z? there must be some sort of sonic impact..and even with today's Impedance controlled  / polymerized PCB coatings it would be interesting to know how they compare and what sort of impact the different substrates have on the sound.

Quote
So back to your point:  I remember your test, and I remember they sounded different.  They still sound different to me.  Was the same capsule, same tube, and same components used.Not the same type, or same value, or even same brand... the exact same physical components used?  Caps have high tolerance, as do transformers and capsules...to that point even two otherwise identical C12's/U47's/ELA M251's will sound different from each other.

 Not the same physical components but same value/brand...I did swap capsule and tube between the mics with the same results. I've also built quite a few mics p to p and pcb hacked with the same results over and over.

Bar the Chinese capsule, I doubt the difference would be this big between the components otherwise no body on the planet could make a consistent mic ;)

Anyhow the only way to know is to test and listen  ;D
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Matador on November 07, 2013, 10:33:25 PM
Edit: nevermind...there's no way to advance this debate in a substantive manner.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: OPR on November 07, 2013, 10:59:12 PM
Quote
there's no way to advance this debate in a substantive manner.
The only way would be to do the tests and listen to the results.  ;)  Anyhow if your not keen on it that's fine keep up the great work!
 I really hope I haven't offended or upset yourself or Chunger as I really do appreciate and respect you both and the work you do!
 peace! 
Title: Re: Official C12 Clone - Build and Support Thread
Post by: chunger on November 08, 2013, 12:12:07 AM
Someone somewhere will test this. . .there are plenty of these builds in circulation now in all parts of the world.  For now, my development and testing efforts are focused on getting the ELA build documented as well as comparatively testing the various tube options that are now prototyped and functioning in the circuit. . . so that we can make a decisive recommendation for full kits (for budget variant).  Development resources are also allocated to building a set of test mics for capsule evaluation. . . specifically finding a good tuning for tskguy's upcoming capsules and testing a variety of Chinese capsule options from various factories.

Eventually, I will build a teflon extravaganza of an isolated point to point variant to test based on the proto board that is currently available, but operationally as far as this enterprise is concerned, I defer to Matador's expertise on technical matters of layout, materials, development priorities, and BOM.  This is, after all, a build and support thread for his design!

Other threads including OPR's own support thread for his commercial venture can further debate the issue and run tests as he designs and sees fit.  There are a myriad of reasons we structured our kit the way we did, and those choices were not made blindly.  Cost, repeatability, longevity, flexibility, intuitive build process, ease of post-build diagnostics, and integrity of the circuit implementation all figured in and when executed correctly with good components, the resulting build is by any standard a great mic.

OPR has a pretty retail point to point mic at a great price-point and provides parts for the build if people are so inclined.  I've referred people to buy his mic who I felt were not quite ready to jump into a DIY project of this type and desire a point to point C12 clone built with care.  At just ~$500 above an all-out premium build on our kit, I felt it to be a superbly reasonable recommendation (Assuming that model carries Tim Campbell's capsule or equivalent reproduction chambered capsule).

That being said, there are no magic bullet materials (even old ones). . . prominent restoration shops have reported acrylic ELA M251's have been known to develop strange issues as the material ages and all manner of problems that were only resolved by re-manufacturing the entire base structure.  Know what you're using and why.  I do not think Tim Campbell is using Acrylic in his reproduction capsules. . . likely it is because a better material is being used as he is not one to compromise and holds to vintage specs more closely than anyone else in the business.

If Matador does not find it constructive to go back and forth on this thread further concerning PTP vs. PCB (much information has already been presented along with beautiful sound clips of "not this kit"), I think it probably good to start another thread elsewhere or pick up the subject on OPR's support thread because quite honestly, we need Matador here to help answer technical questions as they relate to this kit!
Title: Re: Official C12 Clone - Build and Support Thread
Post by: OPR on November 08, 2013, 01:44:53 AM
Thanks for the Kind words Chunger! :) I really love you work too! Those head baskets are glorious! and I cant wait to see your u47 bodies!! are they far off?

 
Quote
prominent restoration shops have reported acrylic ELA M251's have been known to develop strange issues as the material ages and all manner of problems that were only resolved by re-manufacturing the entire base structure.  Know what you're using and why.  I do not think Tim Campbell is using Acrylic in his reproduction capsules. . . likely it is because a better material is being used as he is not one to compromise and holds to vintage specs more closely than anyone else in the business.

Just to be clear I use Uv stabilized Acrylic in my boards which is made to take a beating in outdoor applications and in direct sunlight doesn't degrade like the the old material... Also I wasn't aware that Tim wasn't using acrylic in his capsules, can you post a link where he discusses this? Not that it matters too much as I'm sure he is using something with similar electrical properties.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Matador on November 08, 2013, 10:05:55 PM
I really hope I haven't offended or upset yourself or Chunger as I really do appreciate and respect you both and the work you do!
 peace!

No worries!  I'm fine to continue the discussion, just not here. ;)  This thread is about building C12's! :D
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Matador on November 08, 2013, 10:21:25 PM
Speaking of building mikes:  shots of the mica caps and 12AT7 conversion.  It's very simple actually:

C13 becomes silver mica:

(http://www.musicalsparks.com/images/c12/12at7/IMG_2433.JPG)

A huge 2uF cap for C12, and R17 (plate resistor) goes down to 47K:

(http://www.musicalsparks.com/images/c12/12at7/IMG_2434.JPG)

Small filter caps (C10 and C11) go under the board as before, silver mica's as well:

(http://www.musicalsparks.com/images/c12/12at7/IMG_2437.JPG)

And of course, the tube swap:

(http://www.musicalsparks.com/images/c12/12at7/IMG_2438.JPG)

All fired up and sounded fine with my test capsule.  Now I need a real capsule to test with before I turn it over to the studio for more abuse!

The mica caps are from JustRadios.com, and I think go for about $4 a piece in small quantities.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: micaddict on November 09, 2013, 05:50:14 AM
Matador, you da man.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: OPR on November 09, 2013, 05:53:10 PM

Quote
No worries!  I'm fine to continue the discussion, just not here. ;)  This thread is about building C12's! :D
me too!  :D But I think we've exhausted the topic bar running and actual 1:1 comparison to see if the theory and specs matches with the real a world test. My offer remains open ;D
Title: Re: Official C12 Clone - Build and Support Thread
Post by: scott_humphrey on November 10, 2013, 09:21:20 AM

I’ve been experiencing some hissing/buzzing down in the noise floor and am not sure but suspect it to be related to the hi z section and my admittedly poor cleaning of heavy rosin flux.  I’m not getting any significant low end roll off, perhaps this suggests my problem lies elsewhere?  In fact I was surprised at how beefy it sounds, even with the hissy/buzzy noise floor.  Not a ground hum but buzzy fizzy, ha love the audio adjectives.

Transformer is AMI, capsule is Beesneez k12, tube is 6072a from Christian Whitmore (BOWIE)

My question, what symptoms would one expect should these sections have high resistance paths to ground or leakage current.  I read what you said about the filter frequency being influenced, would added noise be a result as well?

I used 91% ISA and can unfortunately still see a film of residue.

My initial thought is to lift connections between both backplates and Teflon pins at the pcb.  Lift the capsule side legs of c13 and r14.  Jumper my backplates and pry to the microphone gods… but first I thought it best to consult with you.

Thank you for your time and for the project!

Best Regards

Before doing this I'd suggest trying another tube. A bad tube is the usual suspect for the symptoms that you are describing. Second most likely is a bad solder joint.

I've modded my board to use teflon standoffs for the high impedence sections. I wasn't very scientific in comparing before and after results, but to my ears the post-mod mic seems to have a slightly increased bass response. I'm not advocating that everyone do this mod. This mic sounds great either way. I just did it because, in theory, it made sense to me. The mod had no effect on the mic's self noise level.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Category 5 on November 13, 2013, 01:35:43 PM
Anyone know if this could be an issue?  I think not, but why not ask.

(http://www.pbase.com/sbushman/image/153363368/large.jpg)

(http://www.pbase.com/image/153363371.jpg)
Title: Re: Official C12 Clone - Build and Support Thread
Post by: OPR on November 13, 2013, 02:42:56 PM
I had a few all crooked like that also, l asked Oliver about them and told me it would have no impact on the sound.
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Category 5 on November 13, 2013, 02:51:25 PM
I had a few all crooked like that also, l asked Oliver about them and told me it would have no impact on the sound.

Thanks OPR.  After the super neat installation I did inside the bell housing that's what I wanted to hear.   I hate disassembling my builds.   ;-)
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Volume11 on November 13, 2013, 03:29:18 PM
Hey guys, I'm having trouble digging up info on the gac7 wiring in the search section. Am I correct by using the thicker blue and red wires for the heater and B+ connections? Also, should I ground the shield to the correct ground pin, or do I use one of the colored wires? If the second option is correct, do I ground the shield to the xlr housing, or just leave it out of the circuit all together?

Sorry if this has been mentioned already, but I had trouble finding any info for this specific mic.

Thanks,
Chad
Title: Re: Official C12 Clone - Build and Support Thread
Post by: Matador on November 13, 2013, 06:34:57 PM
Ok I read that a few times and couldn't get what you were asking...but a quick Google search tells me you must be asking about Deltron GAC-7 power supply cable. ;)

Here's how I would use this:  the two thick cables (red and blue according to the datasheet) I would use for heater and ground, since these have the lowest resistance per foot.  So declare red for heater+ and blue for ground.  The current flow through B+ is minuscule compared to the heater so your ohms are best spent on heater and ground.

Here's the ground scheme:
1) Inside the PSU:  PSU board ground connects to the 7-pin XLR connector.  The docs use pin #7 right in the middle.  This ground is also connected to the PSU enclosure via a short jumper to the brass tab on the XLR connector which goes to the chassis via the housing itself.
2) Inside the PSU, the 3-pin XLR connector has pin 1 connected to the shell via a similar brass lug.

Inside the mike:  pin 7 goes to the PCB "P6&