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Author Topic: Weird Uneven Waveforms  (Read 2326 times)

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Offline robgronotte

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Weird Uneven Waveforms
« on: August 23, 2023, 07:07:06 PM »
Thread title courtesy of null dogmas.

I've never really understood the + and - portions of the wave form visualizations in most music editing software. ND tried to explain, and I read some online, but I was never much of a physics guy and anything I once knew is long gone.


Anyway, some of my recordings have always been a bit top or bottom heavy, but I have never paid much attention to it. Lately though, some of my recordings, have been far weighted to the negative (down) side.  I got more concerned when I noticed that it's only significant in one channel.

I can't actually hear anything unusual, but I don't know what I would be listening for. I've read some things online saying it's likely to be some issue from the venue PA, but these recent recordings are at different venues, and I've been to both places in the past without these issues. The fact that it's only in one channel just makes me worry that there may be a problem with one of the mics, which are still pretty new.

Would appreciate any thoughts on the issue.


Offline robgronotte

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Re: Weird Uneven Waveforms
« Reply #2 on: August 23, 2023, 11:45:55 PM »
I had already found one of those articles. The other one does explain it a little more, but the types of things that both articles say are often asymmetrical are not present on my recordings with the issue. The problem would bother me less if it were in both channels because I can't think of any reason it would always be in the right channel.
I don't think it could even be my position while recording, because it has happened for shows where I was on either side of the venues.

Online opsopcopolis

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Re: Weird Uneven Waveforms
« Reply #3 on: August 24, 2023, 12:03:34 AM »
Do you have any screenshots? It’s not just DC offset?

Offline nulldogmas

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Re: Weird Uneven Waveforms
« Reply #4 on: August 24, 2023, 12:30:48 AM »
Rob, can you post the screenshots you showed me?

Offline robgronotte

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Re: Weird Uneven Waveforms
« Reply #5 on: August 24, 2023, 02:31:55 AM »
Rob, can you post the screenshots you showed me?

I tried when I made the OP, but the file type wasn't allowed.  Then when I took a screenshot on my phone of what you sent you, the file size was too big.

Alright, I just renamed the png file as jpg and it worked.
« Last Edit: August 24, 2023, 02:36:07 AM by robgronotte »

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Re: Weird Uneven Waveforms
« Reply #6 on: August 24, 2023, 01:22:05 PM »
My recording last night has both channels but similar except to the positive.

Offline grawk

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Re: Weird Uneven Waveforms
« Reply #7 on: August 24, 2023, 01:23:30 PM »
Assuming you're using separate microphones, if you swap channels (physically), does the imbalance stay on the same channel?  Or if you use a different recorder, does it continue to happen?

You could try cleaning the connections with a deoxidizer.
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Offline nulldogmas

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Re: Weird Uneven Waveforms
« Reply #8 on: August 24, 2023, 02:19:18 PM »
I'm curious if a fresh battery fixes the problem, as a dying battery is usually what triggers uneven waveforms for me.

Offline rigpimp

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Re: Weird Uneven Waveforms
« Reply #9 on: August 24, 2023, 04:54:35 PM »
DC offset?
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Offline robgronotte

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Re: Weird Uneven Waveforms
« Reply #10 on: August 24, 2023, 04:59:10 PM »
Assuming you're using separate microphones, if you swap channels (physically), does the imbalance stay on the same channel?  Or if you use a different recorder, does it continue to happen?

You could try cleaning the connections with a deoxidizer.

I haven't tried that, and it would be very difficult to do. My mics are on separate cables and mounted on my hat. Never know when it's going to happen either.

Where would I get deoxidiser? The mics, battery box, and  recorder are all very new, wouldn't think they would have dirty connections yet.

Same thing for the battery, but maybe I will try a new one anyway.

I don't really understand DC offset, but these don't look like the photos of that I found online.
« Last Edit: August 24, 2023, 05:04:36 PM by robgronotte »

Offline nulldogmas

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Re: Weird Uneven Waveforms
« Reply #11 on: August 24, 2023, 06:06:33 PM »
DC offset?

No DC offset in that image, just uneven waveforms around the X axis.

Offline loughney

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Re: Weird Uneven Waveforms
« Reply #12 on: August 24, 2023, 11:06:58 PM »
I'm curious if a fresh battery fixes the problem, as a dying battery is usually what triggers uneven waveforms for me.
Same with me.

Offline Gutbucket

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Re: Weird Uneven Waveforms
« Reply #13 on: August 25, 2023, 11:53:07 AM »
Yeah, most frequently a dying preamp battery in my experience.

90% isopropyl alcohol works well to clean the connections.  Deoxit or some other electrical contact cleaner a bit better.  Brake cleaner is magic for a lot of things but may melt plastic parts.

If the mics are 2-wire and terminate to a stereo miniplug (or stereo whatever plug) you could make simple cross channel adapter to easily swap left/right channels before or after the battery box to aid in trouble shooting.  Just need a stereo female connector, a stereo male connector and three short wires.

Connections as follows:
Mini jack in > Mini plug out
Tip > Rig
Ring > Tip
Sleeve > Sleeve


Doesn't look too bad in the image. If it sounds OK don't worry about it too much.
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Offline robgronotte

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Re: Weird Uneven Waveforms
« Reply #14 on: August 30, 2023, 06:37:18 PM »
Just an update - I'm less worried about one of my mics having a problem now, because another show I recorded last week has the same negative skew, but this time it's much more prominent in the opposite channel it was before.

So hopefully it was a quirk with the sound of the particular bands/venues, but I also replaced the battery just in case.  Thanks to everyone for their input.

 

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