Help with some misbehaving gear!

[Matt C.]

So in a session the other day I had an issue with some gear and I'm hoping someone can point me towards what might be causing it.

I was using a pair of modded Oktava MK-012 mics (with pads and cardioid caps) in a Recorderman setup. Both sent into a Vintech 1272 with identical gain settings, then into a MOTU 24i/o and into Nuendo. The mic directly above the snare was the one misbehaving - several times it made some unusually loud thumps that sounded like some kind of electrical issue somewhere (they weren't the drummer hitting the mic). The tone was also pretty muffled and the output was low, and seemed to change throughout the day,

Here's a link to some sound clips I compiled of the issues. the first three are the thumping sound, then there's a Left-Right comparison of the two overhead mics, one sounding bad and one sounding fine.
http://soundcloud.com/matt-castore/mk012-issues

Basically before I start sending everything off to be repaired I'm wondering whether anyone has any insight into what specifically could cause this. Is it the mic itself, or a bad connection somewhere, or a flaky phantom supply from the preamp? something else? if anyone has any ideas I'd love to hear them. thanks.

[Snarl 12/8]

I'm assuming you tried a few different mic cables. Was phantom turned on?
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Carl Keil

[Matt C.]

phantom power was definitely on

[Nate Dort]

Since they were both connected to the same pre, I'd be more inclined to suggest that it was the mic itself with the problem. The pre has a single 48V phantom supply, so if it was the problem, it would have manifested itself with both mics. Granted, there can still be issues with one channel of phantom (bad switch, bad 6.81k resistors), but it's much more likely that the mic itself has the issue, especially if you can swap pre channels and see if the problem follows the mic. These mics are pretty simple, so they're fairly easy to troubleshoot. I've been inside a bunch of them.
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[Matt C.]

thanks. ran some tests today and it looks like the mic itself is to blame. the whole thing just weirded me out because when i first noticed the problem, the mic's behavior seemed to change over time. and I haven't been able to recreate those thumps, but the mic is definitely sounding bad.