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Old December 4th, 2003, 09:33 PM   #1
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Ignorance Causing Brain Freeze. Need 911

I have a GL2. I own a audio-technica lav mic with a 20 foot cord. I want to video tape interviews, i.e. the standard head and shoulders stuff and use VO over insert shots. I have a horrible time with HUM. I've spent a few days trying to learn but truthfully, to no avail. Length of cord, motor, environment, etc etc. In FCE (I also have FCP) I tried to remove the electronic hum woven into my subject's monologue re the HUM filter. Nada (yeah, I rendered).

1) Please refer me to an excellent book on the subject of AUDIO.

2) Tell me how remove the HUM in existing footage (although I have read the threads on the topic already posted here... my plan now is to rerecord)

3) Do I lose the 1/8 inch lav mic with the really long cord? (Sometimes I get the hum, sometimes I don't...but what do I do when I get the hum and the subject is sitting there, blinking at me? What's Plan B?)

3) MOST IMP: please just tell me what to buy given my objective and equipment. I'd rather pay for quality than take a chance on the cheapest stuff.

Reiterate: GL2. Interviews.

It sounds easy enough. why cant I figure this stuff out?
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Old December 4th, 2003, 09:58 PM   #2
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Hello Diane,
Quote:
1) Please refer me to an excellent book on the subject of AUDIO.
Here it is.
Quote:
2) Tell me how remove the HUM in existing footage (although I have read the threads on the topic already posted here... my plan now is to rerecord)
Get this, too. (Merry Christmas!) Your ability to remove noise, particularly low-frequency hum, depends partly on the range of frequencies it occupies. I'm no sound pro, but my favorite tool for such work is Bias' Peak with their Sound Soap tool.

Without knowing more about the setup you used and the location's environment it's hard to say where the hum came from (no rhyme intended...but's it's cute, isn't it?). Most often, however, hum finds its way into an audio track by not using a balanced cable and XLR connector. unbalanced cabling can pick up electromagnetic noise (and even occasional radio frequencies). A balanced audio setup cancels most of this noise.

Take heart and good luck!
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Old December 5th, 2003, 12:09 AM   #3
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Diane,

I echo everything Ken said. I just got Jay Rose's book (Producing...) and it is awesome...really explains everything you need to know. Not know more about your hum frequency, if it is a low hum you can try the audio filters in FCP, specifically the AUHiPass or Hi Pass filters for low hum, and the AULowPass or Low Pass filters for a high pitched hum. If experimentation with these filters results in nothing you need to isolate the hum and figure out which frequency it is you need to filter if experimentation with these filters results in nothing. This thread might help: http://www.dvinfo.net/conf/showthrea...ht=isolate+hum

Good Luck.

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Old December 5th, 2003, 09:06 AM   #4
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Diane,

Running an unbalanced audio line 20 ft is ASKING for trouble. Highly recommend that you shift to a balanced set up or even go wireless. Hum (especially 60Hz here in the US) can be generated by just about anything and flouresent lamp ballasts are a common cause. Go balanced XLR!
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Old December 5th, 2003, 09:12 AM   #5
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Does wireless "eliminate" the issues related to long wires (I am guessing the answer is "duh." But are there NEW problems I need to be aware of if operating wireless?)

Thanks, everyone, for the links and advice.
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Old December 5th, 2003, 09:14 AM   #6
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Diane,

Wireless can introduce it's own set of problems but I would say it's better than running a 20 ft antenna (unbalanced input) into your audio channel. I recommended that guessing that perhaps you have wireless gear and don't currently have XLR connectability.
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Old December 5th, 2003, 09:20 AM   #7
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Thanks for the link, J. Good, tangible stuff. I just wish I knew how to recognize a FREQUENCY when it popped out at me. Or how to "select a narrow band" or what a "high Q" looked like (Bill Gates keeps popping into mind). I've saved the link and will augment the advice with manuals.

Diane
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Old December 5th, 2003, 10:02 AM   #8
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Thanks, Rob.


So, just to run it by everyone. What I'm planning on doing as of now is to buy an XLR-pro dual channel adaptor. That will work with the GL2, yes? And allow me to run a wireless mic if I go in the direction, yes? And can I use my evil 20 foot condenser lav mic now because the XLR will balance it? (I read that on a thread somewhere, but wait: that means my 1/8 lav goes into the XLR...or should I purchase an XLR fitted lav?)

The second I get a decent budget, I'm hiring a sound guy, and a light guy, and all those other people who make the guy in charge look good...


d
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Old December 5th, 2003, 11:12 AM   #9
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Diane,
If you introduce that "20 foot antenna" (as Rob so aptly called it) into your signal path it will likely cause the same trouble. That is, you can still pick-up E.T. phoning home, the electromagnetic hum from flourescent ballasts downstairs, etc. The hum will just get transmitted wirelessly, since the receiver will hear the hum as source sound, not as a cancellable noise source.

For best results stay balanced from the mic to the camera if you're going to remain using a wired lav. Use that 20' cord to tie up some of your other gear.

Going with a good wireless lav transmitter/receiver can introduce some noise but today's better sets (ex: Sennheiser, Audio-Technical, et.al.) provide plenty of opportunities for you to avoid noise. That is, they're pretty trouble-free under most circumstances.
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