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I get background noise on a a new CAD U1 USB Mic but not on a Logitech USB mic.

Same issue when tried on a different computer. Clearly a problem with the CAD.

What's wierd is the noise is only in the negative cycles.

enter image description here

Scale: the peak noise is about -.013 db (I think it's db !) Here is another screen shot where you can see the normal vocals

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That looks like one of the most severe cases of DC Offset I've ever seen. I can't really make out the scale, but it looks pretty out-zoomed to me, and if so, I would return that card if I were you. It doesn't necessarily mean the audio is screwed though. Most editor-programs I've seen have the option "Remove DC Offset", which SHOULD fix this completely.

I must admit I've never seen this negative before, but the way to treat it should be the same no matter what. Still, this can't be a normal thing, I seriously advise replacing it altogether as soon as possible.

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  • You will of course still have noise after the Offset, but it will remove all that horrible solid green bulk plaguing the timeline. Another way to deal with this, should the program seriously not have a DC Offset, is to just plain use a highpass filter set exactly where ever you want above 20Hz. Or virtually anywhere above 1Hz, to be frank, but filters aren't cutting straight, so better to safe as anything below 20 isn't audible anyway. Oct 28, 2014 at 2:00
  • Okay, one more addition. As I said, I've never seen this negative before. Though the program theoretically should have no problem whatsoever fixing this, stil, if it for some reason actually did, all you have to do is phase-reverse the file, and do the Offset on the now positive DC. This shouldn't be needed, but I mention this anyway just in case. Oct 28, 2014 at 2:11
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    BTW, right click the picture, open in new tab will allow you to zoom it, peak of the offset is -0.015 [though there are no units, assuming dB] +1 for DC offset, btw.
    – Tetsujin
    Oct 28, 2014 at 19:32
  • Ah! Thanks mon! Made the pictures a lot more accessible :-) Oct 30, 2014 at 19:44
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I think it's just broken. I've seen this on an AKG C451 before which needed to be repaired. It's probably something wrong with the electronics as it is impossible for the capsule to move in this way. I'd send it back asap.

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