crackling in random recordings

I’m using WIndows 7. I’m recording with a shure mic and x2u usb converter. WHen recording vocals, many times I get a crackling noise in it. It’s not clipping or anything, so that’s not the reason. I’ve tried both mono and stereo, but neither fixed the problem. I’m recording over a backing track. Some recordings are randomly fine and have no crackling, then I’ll try to re-record the exact same thing without changing any settings, and the crackling will be in the new recording. Any suggestions?

Are you plugged into the computer via a USB hub? That’s a bad idea. USB sound doesn’t like sharing a bitstream.
If the instance of cracking goes up when you’re trying to overdub, then the computer may not be up to holding precise recording, mixing, and playback all at once. When it drops bits that can sound like cracking.

Make sure the computer isn’t doing anything else at the time and make sure your hard drive is error free and completely defragmented.

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