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Thread: Weird power noise/interference

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    Tim Julian's Avatar
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    Default Weird power noise/interference

    Hi All,

    my studio is being plagued by weird noises. I've got a horrible intermittent burst noise coming through amplifiers - my Fender KXR keyboard amp picks it up with out anything being plugged into it and one of my session guys Fender DeVille picks it up amazingly well - enough to shut down a session last week. It is in random bursts, but the bursts are 10ms (100hz) apart, 20ms if you take the alternating view of it. I can't hear it if I turn up my monitors without anything plugged in. If I plug my bass into my DI (even with the ground lift) I get it through that channel. If I put my hands on the strings the noise goes away - this isn't the case with Mikes Les Paul/DeVille combo, it carries on making the noise. I've put screen shots of the noise on this post.
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    Tim Julian
    The Colour Field Recording Studio
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    Cell phone?
    Harry Butler Photography, Videography and AV Production
    www.harrybutlerphotoav.com

    "I'm CDO. That's like OCD, but the letters are in alphabetical order. As they should be." Seen on a T-Shirt.

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    Quote Originally Posted by Tim Julian View Post
    Hi All,

    my studio is being plagued by weird noises. I've got a horrible intermittent burst noise coming through amplifiers - my Fender KXR keyboard amp picks it up with out anything being plugged into it and one of my session guys Fender DeVille picks it up amazingly well - enough to shut down a session last week. It is in random bursts, but the bursts are 10ms (100hz) apart, 20ms if you take the alternating view of it. I can't hear it if I turn up my monitors without anything plugged in. If I plug my bass into my DI (even with the ground lift) I get it through that channel. If I put my hands on the strings the noise goes away - this isn't the case with Mikes Les Paul/DeVille combo, it carries on making the noise. I've put screen shots of the noise on this post.
    The first question is always "what is new or different?" If there is anyone that has never heard cellphone interference, it would be on 3dB, but what you have looks more like arcing than anything.

    Send us an audio sample.


    DC
    Dave Collins Mastering
    www.collinsaudio.com
    +1 323 467 5570

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    Tim Julian's Avatar
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    Hi Dave,

    I've sent an MP3 through via your website, can't seem to attach MP3's to the PMs in the forum.

    Thanks,

    Tim
    Tim Julian
    The Colour Field Recording Studio
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    HG is offline Gold Club Member (1000+ posts)
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    Lighting dimmers can do it. Even if the lights are off. Cheap inductors are notorious for making problems. Doesn't even have to be in the room, can be the other side of the building but interference is in the entire circuit. You have to remove the fuse ie. break the circuit to diagnose it. PPL say, it can't be the lights cause the lights were turned off but sometimes the circuit has to broken ie it could be a fridge setting off an inductor in another room while the lights aren't even on. I think it was Alberts that had a problem like like that, intermittent buzz.

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    Tim Julian's Avatar
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    Hi HG,

    I've been through the power circuits today - the studio is in a seperate building to my house, but on the same mains. I turned off the mains in the house, so no house interference, then turned off all the breakers in the studio switchboard apart from the power line feeding my KXR amp - still had that noise. Of course, in the screen shots I've turned up the waveform and cranked the audio, but it's still very noticeable.

    I've organised a sparkie to come out next week and plug a scope thing into the power sockets to see if the noise is coming down the power lines or if it's in the air.

    Scratching my head on this one!
    Tim Julian
    The Colour Field Recording Studio
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    My guess is it's a radiated RF problem. Appears to be synchronized to the power line (assuming 50 hz power), so yeah, dimmers are a prime suspect. Also street lights. If it's a big enough arc, it could be a mile or more away.
    You may need someone with a radio direction finder. Know any radio amateurs in the area? They may be fighting the same problem.


    Wayne

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    Tim Julian's Avatar
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    Hi Wayne,

    yeah, I'm thinking along the RFI lines now. I did some messing about with the cell phone as per previous suggestion, it didn't make any difference to the noise I'm hearing, although fiddling with the controls did seem to introduce a different noise. However, when looking at it today I noticed that I had the reverb turned up on the KXR amp I've been using to monitor it. Once I turned that off (it's a spring reverb) the buzzing went away. It only seems to affect those things with coils in. I'll get the sparky out with his meter on Friday and see if he can find anything, but after that I think I might get in touch with my friend who's a radio ham. Thanks for the suggestion.
    Tim Julian
    The Colour Field Recording Studio
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    Have you systematically eliminated equipment from both the electrical and audio chains? Just totally disconnect stuff one at a time from the mains and also from the audio chain to see if it stops.
    Sam Clayton

    We are who we are because of what we know.

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    iPhones are really bad about sending "digital chatter" down the line. I had a friend lay one on top of my Neve rack one time, and the interference was crazy. Might be worth checking...
    Todd Robbins
    TX3 Productions, Inc.
    www.toddro.com

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