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Thread: Help needed with noise problem

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    Help needed with noise problem

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    Hi folks:

    I could use some help figuring out the cause of a noise problem that cropped up last weekend when my bluegrass band performed at a local indoor farmers market. We provided a small sound system and I recorded with my Zoom H4n plugged into the system. I noticed the problem when listening to the recordings after the event; we did not notice it while we were playing.

    The issue is a loud snapping noise that can be heard in some of the recordings at moments where the sound level produced by the singer or instrument is high. To me, the noise sounds electrical, like static or a short, but I'm no expert. I'm hoping it sounds like something to you. I realize you probably can't say what the cause is exactly without being there, but maybe you can give me a clue as to what it could be. I'll give you specs on the set up below, but first, here are two samples:

    21 Angelina Baker 2018-02-03.mp3 - noticeable in first 30 seconds over fiddle
    22 Mama Don't Allow 2018-02-03.mp3 - very noticeable in first minute over vocal


    SETUP:
    • Microphones: 1 Ear Trumpet Labs “Mabel” condenser mic, 1 Neumann TLM 102 condenser mic, and 1 unidirectional dynamic (brand/model unknown) mic.
    • Mixing console: Yamaha MG06
    • Sound system: Fender Passport P150
    • Recorder: Zoom H4n



    The two condenser mics were plugged into the mixing console, which was output to the sound system. The Ear Trumpet Labs mic was placed in the center as the main mic for vocals. The XLR jacks on the sound system were set to “line.”

    The dynamic mic was plugged directly into the sound system and the XLR jack was set to “mic.”

    The recorder was plugged into the sound system’s “tape out” RCA jacks with an RCA to XLR cable with two 15 db attenuators going into the H4n combo jacks. Mic level was set appropriately and there was no clipping. Mono mix was on and phantom power was on, though not needed.

    The mics and mixing console were in front of the band, while the sound system was placed behind the band. A braided rug was placed over the cables to prevent people from tripping and for aesthetics.

    Here are some of the possible causes that I've thought of:

    • Phantom power should not have been set to “on” on the recorder?
    • Microphone is faulty?
    • XLR cable wasn’t plugged in securely to mic or jack?
    • XLR cable was damaged (by people stepping on it)?
    • Rug caused static?


    Tonight I tested the Ear Trumpet Labs mic (seemed like the problem was coming from that mic), mixing console and all of my XLR cables. I couldn't replicate the problem. The mic sounded fine, but I did find that one of the cables is noisy. I couldn't test the full set up as the sound system belongs to one of the other band members.

    Any thoughts?

    Thanks for any help you can provide!

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    I'd say it's all caused by clipping. Turn the level down considerably, recording 44.1 or 48/24 WAVs. You can add gain back but that MP3 is over the top. (See the "Highest Reconstructed Peak Level" and "Reconstructed Peaks Above 0dBFS" in the attached image.)
    screen-shot-2018-02-05-9-15-40-pm-png

    Now, if you have original WAV files from the Zoom SD card you can export without MP3 normalization, it might be worth looking at those.
    "... I know in the mornin' that it's gonna be good
    when I stick out my elbows and they don't bump wood." - Bill Kirchen

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    I have had problems with phantom powered mics where the XLR leads are damaged or have dirty connections causing the phantom to produce static in the signal, I still get this in the studio sometimes when there is a dirty XLR, a bit of spray usually fixes it.

    If you have a noisy cable that could be the problem? I would get hold of some contact cleaner, spray all the xlr plugs and connectors on the PA system and see how you go.

    The static may not have been heard at the gig due to ambient noise, but the recording would show it up.

    Alan.

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    "in first 30 seconds over fiddle.." And during the mando right after. Actually throughout both tracks.
    I'd suspect flaky connection somewhere. That includes my previous suspicions that include all mixer internals (remember Mackie's ribbons mess? , and I've seen some 'scratchy pots symptoms on a new Yammi MG.
    -But, if you can determine it's common to only one mic path, that might narrow it down.

    Haven't played 'Mama Don't Allow in while
    Placebo stomps 96k ....... Recent projects
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    Quote Originally Posted by mixsit View Post
    "in first 30 seconds over fiddle.." And during the mando right after. Actually throughout both tracks.
    I'd suspect flaky connection somewhere. That includes my previous suspicions that include all mixer internals (remember Mackie's ribbons mess? , and I've seen some 'scratchy pots symptoms on a new Yammi MG.
    -But, if you can determine it's common to only one mic path, that might narrow it down.

    Haven't played 'Mama Don't Allow in while
    Yeah, it occurs intermittently throughout these and other tracks. Just wanted to point folks to specific examples.

    Listening again this morning, I hear snaps in a few spots that aren't quite as loud, which is one reason why I don't think it's clipping. The other reason is that I've had clipping issues in the past and this sounds different to me. I do hear it in the original .wav file. I will take another look tonight, however, to see if it could be clipping. For what it's worth, I see bright lines on the spectral frequency display at those spots in Audition.

    I do think it's one particular mic path...the center mic, as it seems to happen most when our two loudest singers are leading. I'm a softer singer and it doesn't happen on my songs. The other two mics were on instruments.

    Also, it seems to me that the center mic might have cut out at times as the vocals seem softer on some songs (even with the louder singers). The other condenser, which was lower and pointed toward an instrument, may have been picking up the vocals, albeit more softly due to distance. That's my theory, anyway.

    I don't know if the noisy cable was one used in that mic path, but I'm going to take it out of commission and buy a new one just in case. Also more testing to be done with the whole system.

    Thanks everyone for your input! It will definitely help narrow things down.

    P.S. For any bluegrassers listening to the samples, the percussion you hear in Mama Don't Allow is courtesy of some kids with toy tambourines and shakers. We usually have some on hand when we play farmers markets to engage the little ones in the music on a few kid-friendly songs. Just didn't want anyone to think we actually have percussion in a bluegrass band.

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    Quote Originally Posted by KindaScratchy View Post
    ..P.S. For any bluegrassers listening to the samples, the percussion you hear in Mama Don't Allow is courtesy of some kids with toy tambourines and shakers. We usually have some on hand when we play farmers markets to engage the little ones in the music on a few kid-friendly songs. Just didn't want anyone to think we actually have percussion in a bluegrass band.
    Our 'percussion over here a bit West of you is pops' from the balloon lady in the Farmer's market here in Davis Ca.
    We tell her to get on the beat but...
    Placebo stomps 96k ....... Recent projects
    Ray Catfish Copeland 'Got Love Jim Goodman 'Southern Steel

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    I'd say clipping or static.

    Turn down some gains and clean your contacts.

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