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Thread: Cad M179 hum?

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    Testing123 is offline Newbie
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    Cad M179 hum?

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    I've noticed that my Cad M179's both seem susceptible to hum in the area of the pattern selection switch. If you put your finger near the switch the hum increases. It doesn't seem to be related to cabling issues.

    Has anyone else noticed this?

    -Keith

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    Not me, mine are DEAD silent. The self noise (including hum) are very low to non existant. So, no it's not normal as far as I can tell.

    What are you using for phantom power?

    Maybe your mic has been damaged. The pattern selection switch changes the pattern by mixing in the 2nd diaphragm. If something came disconnected back there it could instead mix in the 50/60hz hum instead.

    I would try the mic on a different cable and phantom power source (preamp).

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    Quote Originally Posted by Testing123
    I've noticed that my Cad M179's both seem susceptible to hum in the area of the pattern selection switch. If you put your finger near the switch the hum increases. It doesn't seem to be related to cabling issues.

    Has anyone else noticed this?

    -Keith
    I had one that did the same thing, exactly. CAD tech support said it was a faulty capacitor. Contact them and I'm sure they will take care of you.

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    I've got one of them. Just to add, no problems like that with mine. Isolated incident.
    I really...really...REALLY have no idea what I'm talking about...AT ALL.

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    Testing123 is offline Newbie
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    Thanks for the replies. I tried a few different cables. I have one set of cables that have the shield tied to the shell at the microphone end, and one set that don't - neither behaved any differently.

    I'd think if it was a phantom power problem it would hum all the time, but maybe not. I'll check that out.

    I sure don't remember them behaving that way when I first got them, but I can't recall if I ever changed the pattern while I was listening.

    If everything else checks OK I'll give CAD a call.

    -Keith

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    Just wanted to follow up... this ended up being somewhat of a case of operator error. I realized later that I was set up VERY close to a 240VAC power line in the floor under where I was testing. Putting my finger on the pattern switch in such an intense field from the power line was just too much.

    I've since used the mics in some really quiet environments (i.e. recording classical music) and no sign whatsoever of any hum.

    -Keith

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    Quote Originally Posted by Testing123 View Post
    Just wanted to follow up... this ended up being somewhat of a case of operator error. I realized later that I was set up VERY close to a 240VAC power line in the floor under where I was testing. Putting my finger on the pattern switch in such an intense field from the power line was just too much.
    Mics shouldn't care about a power line under your floor. If you can still reproduce the problem in the original spot, that probably indicates that the body of the mic isn't properly grounded, which is a safety issue. Drop CAD a line and see what they think.
    Quote Originally Posted by Obi-Wan
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    travelin travis is offline Been Here, Posted That
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    Quote Originally Posted by dgatwood View Post
    Mics shouldn't care about a power line under your floor. If you can still reproduce the problem in the original spot, that probably indicates that the body of the mic isn't properly grounded, which is a safety issue. Drop CAD a line and see what they think.
    the one i had with the humming problem would give off a little shock sometimes.

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    Quote Originally Posted by Testing123 View Post
    I've noticed that my Cad M179's both seem susceptible to hum in the area of the pattern selection switch. If you put your finger near the switch the hum increases. It doesn't seem to be related to cabling issues.

    Has anyone else noticed this?

    -Keith
    It is a ground loop issue. Somewhere in the circuit there is a ground potential problem. IE: the ground of the mic/preamp circuit is not 0 V compared to someother ground. This is what causes the hum to get stronger and could potentially cause shocking if severe.

    What are you running the mic into? What is the signal chain? This is important to know.
    "Tascam, Fostex or Studers don't make hit records...........people do"
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    Quote Originally Posted by MCI2424 View Post
    It is a ground loop issue. Somewhere in the circuit there is a ground potential problem. IE: the ground of the mic/preamp circuit is not 0 V compared to someother ground. This is what causes the hum to get stronger and could potentially cause shocking if severe.
    Maybe, but if only one mic hums and other condensers don't, it is probably a failed body ground. At most you'll get the leakage across some of the power regulation circuitry in the mic (probably a couple of volts) unless some other part fails and you get a 48v short to the case, in which case you could then get a nasty shock. Not much amperage, but you'd still feel it....
    Quote Originally Posted by Obi-Wan
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