This is more for a mic used in live performance that the studio, although any mic that's used for vocals is naturally somewhat contaminated by the saliva, spittle, and in many clubs, smoke. It's a good idea to clean those mics if for no other reason that simple hygiene. Keep in mind that what we're talking about is a microphone with a removable grill, like our old friend the SM58 or Beta 58.
1) Unscrew the grill from the microphone and remove anything stuck on it with a toothbrush.
2) Now clean both the grill and foam windscreen with some plain water and mild dishwashing detergent. This should be enough to chase any unwanted smells away.
3) Let grill air-dry, but if you're in a hurry, you can use a hair dryer set on low. Don't put the grill back on the mic if it's still wet, since this can cause damage to the capsule if any moisture sifts into it.
4) For mics with grills that aren't removable like an SM57, turn the mic upside down and scrub with a toothbrush soaked in a weak solution of water and detergent. Don't turn it right-side up until it's dry.
Want a quick solution for a stinky mic? Get a very diluted solution of mouthwash and water, turn the mic upside down, and gently scrub. As in #4 above, don't turn it over until it's dry.
Be especially careful with condenser mics, since any moisture at all equals disaster. In fact, don't even think about it unless you can take the windscreen completely off and leave it over-night to dry.
Once again - be careful, be careful, be careful. Moisture and electronics do not mix. That being said, if you're careful your mics will now smell nice and clean and be good for you too.
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