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Mic Hum

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Reave Watkins
Mic Hum
on Oct 27, 2007 at 4:35:49 pm

Hi Guys

I have a project studio for voice-over. the problem is my AKG Solidtube Mic has
a pretty bad hum in it when in record. All my other mics are fine. When i bring the mic
out of the voice-over room and into the control room, the hum lessens. I sent it to be
repaired recently and they could find nothing . I also tried bringing the tube power supply into
the voice-over room. Lastly when I hook it to a small mixing board
there is no hum. Like I said all other mics have no hum! Iam using a digi 002 and G-5. any ideas will be helpful

thanks -Reave


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Ty Ford
Re: Mic Hum
on Oct 27, 2007 at 9:59:28 pm

Hello Reave,

I seem to remember when I reviewed that mic many years ago that the original production model lacked proper conduction of the ground from the lower half of the body to the upper half that covered the capsule. The result was a buzz.

AKG fashioned a retrofit after I brought the problem to their attention. I think it was a little piece of metal that bridged conductivity from the lower body to the top.

Open yours if you feel comfortable and see if that little metal piece is still in place.

Before you try that, try the same cable from one of your mics that doesn't buzz with the AKG mic. Also use a ground lifter on the AKG power supply or plug it into the same strip you have the mixer plugged into to eliminate the possibility of a ground loop.

Regards,

Ty Ford

Ty Ford's "Audio Bootcamp Field Guide" was written for video people who want better audio. More at: http://home.comcast.net/~tyreeford/AudioBootcamp.html
or http://www.tyford.com


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Reave Watkins
Re: Mic Hum
on Oct 30, 2007 at 7:24:05 pm

Hi Ty

As you suggested I opened the the mic up. Didn't see any metal, then put it
Back together and the hum was almost gone! I have been trying to get AKG on
the line to send it. Must have been something rubbing in there you think?

Reave



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Matte
Re: Mic Hum
on Oct 31, 2007 at 1:13:48 pm

[Reave Watkins] "st have been something rubbing in there you think?
"


More likely that something was NOT rubbing and when you put it back together you made some metal contact that's acting as a shield.

Try this as an experiment.

COVER the entire mic with aluminum foil (like a baked potato) and make sure you contact the foil with a wire connected to the mixer's XLR pin 1.

See if that quiets the noise completely.

This will indicate if the hum is coming from OUTSIDE the mic's shell.


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