Are there any vintage C12 owners? Couple questions here!

[dirty1_1garry]

Hello!

I work on the studio which has a beautiful vintage AKG C12 mic. It sounds just amazing on vocal^ acoustic gtrs and strings… but has a pretty low gain and pretty hight noise level.

So when I'm recording for example vocal tracks, my sound chain:
C12 mic > mic pre (at hight gain settings) > AD (with +16dBfs settings) > ProTools
If I get peaks in PT somewhere between minus 3 - 6 before zero I get noise about minus 40-45dB. It's really hight.
Sound of this mic overshadows any other aspects like noise and in some kind of music hight noise level not a problem aseptically in rock music. But sometimes I have to use another mic because noise C12 could became a real problem during mixing.
I hear tube'sh type of noise (like a white noise) but C12 consist pretty fresh GE 6072.

More then that i want to build C12 clone mic and noise aspects important for me.

Does your vintage C12  work with same things?
Could that be the bad tube or troubles with PSU? Or should I take it easy and drink some vodka for C12's great sound?))

 

[gyraf]

Just had a pair of 1953 C12's in our studio.

No, they're not noisy.

Well, they're not as low noise as the U47 or the M269 - but difference is some 6-8dB of self-noise at worst.

Which may be a problem when distance-miking soft material, not in usual use.

Have it checked by someone in the knows. Relatively easy to try with a new (old) tube.

Jakob E.

 

[MHanson]

If you have the amount of noise you are describing ... your C12 has issues.

You can swap tubes ... but make sure you have a few ... if you swap it with another tube that is noisy you haven't found anything out.  Try several.

If that doesn't solve the problem then as Jakob said, "Have it checked by someone in the knows."

 

[Dark1]

I have compared several C12s side by side, different vintage with different components (different capsules, transformers, and capacitors/resistors), and they are all a little noisier than your average CMV563 or U47 mic. A friend has a NOS C12, later model, and it still confirms this observation. But the noise is rarely a problem with vocals, as it is nothing drastic, only slightly noticeable on quiet passages, and the C12s usually sound fantastic to outweigh this disadvantage. But the self-noise should not be that high.

Almost every C12 I have ever seen required some love to get it working properly. If it is a steady-state noise, the tube may be the first culprit. If it is a crackling noise, the tube, pattern selector, tube socket or capsule can cause the problem. Since this is a DIY forum, you are probably determined to try repairing it yourself, aren't you.   Perform some basic test and maintenance procedures first: check the PSU, pattern selector, and microphone for modifications (very common problem, esp. with N12k/N12 PSUs, some were modified for fixed pattern etc.!) or component failures. Check the PSU for proper voltages (note: do not kill yourself in the process). Test the tube on a tester for leaks and shorts to make sure it is working properly. Gently clean the tube socket pins with interdental brush and high purity alcohol (do not spill it anywhere else), clean the tube pins with cotton swab/alcohol; avoid touching anything in the high impedance section. Carefully re-install the tube. Clean the connector pins, in the microphone, and on the cables, with cotton swabs and pure alcohol. Clean/lube the pattern selector switch. Test functionality after these basic restoration procedures. Try different tubes. Also, check what kind of an output transformer you have, the secondary may be soldered to a less than optimal tap (earlier Henry Radio transformers have taps for 40/250/500 Ohm).

If this does not help, it is time for the C12 to see the doctor.

 

[dirty1_1garry]

Thanks you guys for that great great recommendations!

 

[fazer]

Don't have a C12 but experience with a tele 251.    The Tube is critical.  some tubes with more liquid sound on high's are noisy and some tubes with lower noise are harsh.  As stated above get many  tubes to try.  The best tubes I've used are 6072 Amperx.  On the 251 I had a problem with the heater voltage set to high due to a  Selenium Rectifer /filter circuit and had to modify the circuit to get it in spec.  Noise dropped but the tube sounded better when the heater was elevated.    It however stripped the cathode and made the tube noisy so this is not a good solution.  I'm just saying check all voltages and make sure they are in spec to not ruin a good tube you just purchased.  Very delicate and old plastic to be careful with at least on the 251.