Official C12 Clone - Build and Support Thread

[Mikael-ange]

Villemoisson sur Orge (Essonne, 91)

Ok cool
Je suis pas loin de toulouse (dans une petite ville qui vient d'etre connu pour ca defaite contre une equipe de foot parisienne)

 

[Matador]

Sorry, was traveling for the holidays. Glad you got it sorted.

 

[Matador]

For like a 120B+, self Bias should have a 220K plate resistor& 3.8K for cathode for around -4 grid voltage for class A.

-1 at the grid would be for more like a 12AX7 or a 12AU7 on self bias.

Should? That is one operating point out of countless others: the 120v, 100k loadline at a -1V quiescent point is perfectly valid. Also note that 220K with a 120V supply will have little output headroom running near 1mA static. The C12 operating point is a good compromise between noise, input single swing, output headroom, and output impedance.

Class A? What other class can you have with a single tube?

Keep in mind, the more current you pull from the tube, the less series R you can have in the power supply, so all other things being equal, filtering is worse.

 

[HyprDrivr]

Any chance that these boards will be avalible again?

 

[JeffKall]

Any chance that these boards will be avalible again?

+1 on PSU PCB’s …

I miss these boards !!!

 

[geekmacdaddy]

Is there a mic body that fits Dany's D12 boards? I have been searching the forum and understand there are modifications to the board (not quite clear on what they are) to make them fit donor bodies.There are currently 151 pages to this thread so forgive if I missed the info. Any links are helpful, thank you

 

[cariocaman85]

Hello,

I'm having trouble with one of my C12 clones

It's been in service for 8 years and sounding great, but last week I decided to upgrade to AMI T14 transformer. I installed it, and it worked fine.
Then I decided to fine tune bias and B+ has it's been I long time I didn't. Tried to get to 110V because this is a Tim Campbell Capsule and I read they sound better at this voltage, couldn't get any lower than 116V.

Then I plugged it, still monitoring B+, ran a few tests, very good.

After 10 min or so I lost signal, B+ was increasing at fast rate, I stopped PSU at 145V.
I waited, tried again, and the same, fine for 5 mins, then B+ is increasing suddently.

What do you think could cause this ? I think failling tube, but maybe not...

 

[cariocaman85]

With no load, minimum B+ is at 174V.
Now with the mic plugged, B+ minimum, voltage rise. I cut power when it passes 125V. It shouldn't be near this at B+ minimum.