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[brucekaphan]

I own an AKG C414EB that was working well until it wasn't.

I was in session recently when the mic suddenly began blasting out self-noise that I would describe as sputtering—my use of that word isn't necessarily technically direct: the noise was not constant—it was loud enough to render the microphone useless. I tried exercising the onboard switches (polar pattern, rolloff, and pad). I tried cleaning the XLR connector. I tried swapping cables, preamps, patch points, and DAW inputs. I had been using the mic set to 75Hz rolloff. When I switched to no rolloff, the problem disappeared. When I switched it back to 75 Hz or 150Hz, the problem reappeared.

I was able to find schematics online. It's my guess that condensers C5 or C6 are suspect. Hopefully there's someone out there who might be knowledgeable and willing to share that knowledge: do you think my relatively uneducated guess that C5 and or C6 are suspect might be a good start for part replacement?

If so, the parts list associated with the schematic I found indicates that the condenser is a 0.1µF. The caps themselves have the following graphics: "+, .1, 35V." The "Order Number" listed on the parts list is "0035 E 1004."
In the photo of the circuit board, the two small green capacitors are the ones in question.
Does anyone know what type of condensers these are?

[Kai]

These caps are 0.1 uF / 35 V Tantal-Capacitors and very likely the source of this problem.
Tantal- or Tantalum-Caps age and quite often cause the described effect.

Replace both with same type or film caps, if you find mechanically fitting ones.
The 35 V is minimum, film caps often have 63 V at least.

[klaus]

Goods advice on the fix.
I just question using that filter in that cicuitry in the first place. As it's rather steep, it kills the beauty of the CK12 (audible phase shift).
I'd rather you use a post-mic filter with less artifacts in tow.

[brucekaphan]

Thanks to both Kai and Klaus for your posts. Much appreciated!

[klaus]

P.S.: I am big fan of Bruce's pedal steel playing. He is a master of heavenly chord progressions.

[brucekaphan]

Klaus,

Thanks for those kind words. Those words, coming from a meticulous master of microphony makes them all the more poignant.

The only mic in my collection that you've worked on, the C12 you restored/improved for me will be in use all day today—it's a magnificent, superlative tool. One client was so in love with that mic that he declared that he was going to name his album "C12." The album didn't end up with that title, but he was so bowled over by the experience of singing into that mic that he was truly inspired for weeks.

I feel fortunate to be able to write to you and to have access to your posts. Your recent analysis of the new M 49 V was inspiring to read, being that I'm a huge fan of the original...

[afterlifestudios]

Keep us posted, Bruce.  I had a C414eb with a similar sounding problem (and switching roll-off cleared it up sometimes too).  But it ended up being from capsule contamination.  All good now...

[brucekaphan]

Thanks for your reply, John. In the back of my mind, I wondered if the capsule might be the culprit, so thank you for bringing this up. Though I'm handy enough with a soldering iron, I've never attempted to service a capsule. Did you service your own, or did you send it somewhere for service, and if you sent it somewhere for service, where was that?

[klaus]

Make the breath test and observe whether the noise changes at all, or whether it's steady-state, regardless of trigger.
Posting an audio clip of the noise will put this baby to rest.

[afterlifestudios]

Make the breath test and observe whether the noise changes at all, or whether it's steady-state, regardless of trigger.
Posting an audio clip of the noise will put this baby to rest.

Indeed.  Breath test will shine a light.

[Kai]

I had been using the mic set to 75Hz rolloff. When I switched to no rolloff, the problem disappeared. When I switched it back to 75 Hz or 150Hz, the problem reappeared.

... It's my guess that condensers C5 or C6 are suspect.

This is a clear evidence C5 or C6 is the cause, not the capsule.

[brucekaphan]

capacitors just arrived today... will be replacing them and will report back in once I have. Thanks to all for the suggestions and help! Much appreciated!

[brucekaphan]

I'm very happy to report that after replacing C5 & C6 late yesterday and initial test sounded good, then leaving the mic fired up all last night, I woke this morning to an apparently healthy C414EB. Capacitors C5 & C6, and possibly some general cleanup of loose-looking wiring, a couple of potentially cold solder joints, and removing excess gobs of solder did the trick. Thanks again to all for your advice and counsel! Case closed! At least for now...

[afterlifestudios]

Glad to hear it!