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Thread: 60 cycle hum - help!

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    kiddakota is offline Registered User
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    60 cycle hum - help!

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    i just moved into an older house and just one of my microphones is picking up 60 cycle hum. it's a tube condenser mic built by scott hampton and it's of the highest quality.

    none of my other mics are picking up any 60 cycle hum. i just purchased an eb tech hum eliminator and it did not solve the problem.

    any thoughts on how to fix this would be much appreciated.

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    cobaltaudio's Avatar
    cobaltaudio is offline Force of Nature
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    Are your other mics dynamic? If so, it's probably getting the hum from the phantom power source. I'd check your cables too, make sure they're not near mains or transformers etc. If all else fails, you can just stick in a very fine notch filter and the hum will just disappear!!

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    kiddakota is offline Registered User
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    some of mics are dynamic but i'm also using an at 4060 which is a tube condenser and it's dead quiet. no mains or transformers near my cables and i've tried multiple outlets in the house with no success. what kind of filter would you suggest?

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    cobaltaudio's Avatar
    cobaltaudio is offline Force of Nature
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    any EQ that's handy to be honest. You just want a really narrow frequency band, i.e. a high 'Q' and set the center frequency to match the hum frequency and take as much gain out of it as your EQ will let you!!
    Does hummy mic have a seperate power supply or anything odd like that? The bulletproof test is to try it on a different mains supply. I.e. a completely different building. If it still hums, then it's probably a problem with the mic's power supply, and if not then it's got to be something to do with the original location or how it was installed.
    Sorry I can't be any more specific. Let me know how you get on trying it elsewhere.
    Andrew
    (if you still have trouble, feel free to PM me or respond here, either works!)

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    cobaltaudio's Avatar
    cobaltaudio is offline Force of Nature
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    If and when you do try it somewhere else, make sure you check the 4060 too, just to be 100% sure that mains supply is clean too)

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    miroslav's Avatar
    miroslav is offline Been Here, Posted That
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    You can try running a ground wire from the mic's PS case to some other gear...like the preamp (or anything in your racks), and see if that takes it out. Just make sure it's bare metal to bare metal. I usually pick a screw on the case, then scrape the paint off under the screw head (it's a very small amount, and the screw head will cover it).

    Get a real long piece of wire...connect to the PS case...and then just touch various cases of your other gear...you may find one connection that solves the problem. I've used this grounding "trick" a few times on my rack gear....and even on my guitar pedals.

    Since you say it's an older house...at some point you may want to check all the wiring for proper Hot/Neutral/Ground connections, and for any loose wires at outlets. Remember...electricity can kill you...so be careful.

    Is the PS plugged into the same outlet as your AT4060 PS and your other gear...?
    If yes...try moving to a different outlet...if no...plug in same outlet...etc. You have to experiment a little.

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    cobaltaudio's Avatar
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    Quote Originally Posted by miroslav View Post
    You can try running a ground wire from the mic's PS case to some other gear...
    At the risk of being controversial, I feel compelled to say: Please be really really careful if you decide to do this. If there is a fault in either of the two pieces of equipment you connect together, and/or you earth something that isn't supposed to be earthed (like a guitar pedal) to something that is (like an amplifier), then it can be really dangerous. Even if the chances of a fault being present are small, it's not worth the risk to get rid of a single tone, which you can easily get rid of a notch filter in an eq plugin. It takes maybe 5 seconds.

    (Sorry for being a party pooper, but my conscience wouldn't allow me to just let it go.)

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    miroslav's Avatar
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    Well..if there is already fault, he's going to find out about it before ever trying an external ground wire...
    ...like the minute he touches that mic!
    Star grounding is common in a studio environment...that's all I'm saying he should basically do (which I'm sure you know), and it's easy enough to see what if any voltage there might be at the case (to see if there was a ground fault) with a simple DVM.

    I don't care for the notch filter approach as it doesn't solve the problem...it only "filters it".
    Last edited by miroslav; 04-02-2011 at 14:17.

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    Steenamaroo's Avatar
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    what interface are you using, and are you on a laptop?

    i ask because some of my mics buzz using mbox and dell vostro.
    The mics that buzz are grill modded mics (nt1a and oktava mk219s)

    They don't buzz if i ground the mic body or laptop body to mains ground.

    I made up a cable that connects spdif shield to mains ground pin to work around this problem.
    I've since bought a motu 828 mk2 that doesn't suffer from this issue, thankfully.
    Quote Originally Posted by Grawlf View Post
    That's a tad too much terminology. What do you mean by 'mix'?

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    cobaltaudio's Avatar
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    Quote Originally Posted by miroslav View Post
    Star grounding is common in a studio environment...
    True, but we're not talking about a studio. It's an "older house" (which means no RCD's either) with either suspect mains or suspect equipment, or hopefully and most probably it's just hum being induced on the mic cable. Even in a studio, it's really bad practice because to re-earth kit through other kit, because if you happen to connect two bits of kit on different phase power supplies (fortunately this is HUGELY unlikely, and you need to try quite hard to do it) star grounding won't help you if the one of the cases becomes live from a fault.

    I do hate myself for being 'that guy' and having to say all this so I'm reeeeally sorry for coming across like that, but "then just touch various cases of your other gear..." is just not a solution. You say you don't care for the filter approach as it's not a solution, well at best re-earthing a PSU puts off the problem, it definitely doesn’t make anything any safer, and at worst it could be lethal.

    I totally see that the required situation to arise for there to be an unknown fault in one or two bits of kit is unlikely, usually you would notice something before. But my point is that I just have difficulty seeing how re-routing the earth is a good solution, because however you look at it you’re not making it safer. Surely the safest thing is to find where the hum is being induced, and if it’s not being induced then to get the equipment checked? Which as I understand it is what kiddakota is asking how to do, which is why I suggested trying a completely different mains supply.

    I don’t see why given the choice, taking any sort of risk with mains or even just a PSU is a good idea.

    Once again, I apologize most profusely for seeming to have my 'safety hat' welded on to my head today.

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