Official C12 Clone - Build and Support Thread

[Ericbazaar]

I have make detailed Pictures of the CT 12 Capsule and the Connections. I think its all ok.

 

[Ericbazaar]

and another…

 

[Ericbazaar]

again

 

[Ericbazaar]

I just want to make sure that the capsule is ok ...

 

[Ericbazaar]

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

 

[tonycamp]

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

 

[Ericbazaar]

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?

 

[tonycamp]

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.

 

[strangeandbouncy]

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

 

[Matador]

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.

 

[Matador]

This first page shows the bridging of the two backplates:

...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...

 

[NTJEvan]

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?

 

[JessJackson]

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.

 

[Matador]

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?

 

[JessJackson]

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

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.

 

[JessJackson]

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?

 

[Tim Campbell]

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?

 

[Ericbazaar]

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

 

[Matador]

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.

 

[jrmintz]

Does anybody make nice boxes for these mics?