Does anybody have any idea why I'm getting such a strange wave on my waveform? It's an SE condenser, going into an m-audio preamp. Damaged mic perhaps?

strange waveform

  • 1
    What was the source? (just in case). But sure looks like the AC coupling cap somewhere is busted -- ideally any DC offset is removed but here it looks like it takes a long time (relatively speaking) for the signal to be rebalanced around zero. Aug 21 '15 at 13:31
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    Do you have another microphone? If so it's worth mentioning if you've done an identical test of the preamp and cable. (Just a thought.)
    – Andy
    Aug 21 '15 at 14:43
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    @Andy has the right idea, switch out the mic, cable, pre-amp, etc to see if changing or removing a particular component removes this form. Also important question: What are you hearing? Is there a white noise? is this waveform inaudible? Have you had to amplify/normalise the signal to get this image?
    – AJFaraday
    Aug 21 '15 at 15:50
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    That's not a waveform, it's a peak diagram. Actually these weird shapes could just be some aliasing artifact that only happens in the creation of the peak display. Could you post the actual sample data somewhere (ideally as a .flac file, since lossy codecs tend not to properly capture such phenomena), or at least insert a proper PDF of the signal? Aug 21 '15 at 23:10
  • Yeah, don't get too caught up on what a file looks like. That's just a picture created by whatever software you're using. It's not necessarily a reflection of the actual audio you're getting. Aug 21 '15 at 23:31

Because I don't know how much time this took place over (what's the length of the sample we're looking at), it's hard to isolate what is causing the DC offset problem, but quite likely, you are using a half-balanced or unbalanced input signal that is tied to some ugly grounding. Low filtering will eliminate the problem if you don't need the low frequencies, but still, you are going to peak early due to this DC offset problem -- which will reduce your effective headroom.

Replacing a bad cable will likely resolve this problem. Use only balanced cables to get to your interface. If your interface uses 1/4" TRS inputs, use TRS to XLR cables.. NOT XLR to 1/4" guitar style connectors.

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