mic trouble at DVinfo.net

Go Back   DV Info Net > The Tools of DV and HD Production > All Things Audio

All Things Audio
Everything Audio, from acquisition to postproduction.


Reply
 
Thread Tools Search this Thread
Old December 1st, 2010, 02:25 PM   #1
Major Player
 
Join Date: Jul 2006
Location: Chicago, IL
Posts: 937
mic trouble

I need to do some more investigating but I ran into this today

We had a Sennheiser ME66 / K6 on a boom pole plugged into a EX1 that was running on battery power. There was a hum in the audio signal, and when you touched the mic it would get substantially louder.

Switched AA batteries in the mic, changed XLR cables, turned off mic battery power & tried 48v on the camera (made it worse). Only thing that worked was plugging the mic into a wireless cube transmitter.

Any ideas what could cause this?

thanks
__________________
Nothing says you're a serious video maker like S-VHS
Zach Love is offline   Reply With Quote
Old December 1st, 2010, 02:52 PM   #2
Inner Circle
 
Join Date: Jan 2004
Location: Boca Raton, FL
Posts: 2,979
In my experience, hum in audio is almost always from a grounding issue. Going wireless seems to point to that too. Sounds counter intuitive but I might have tried switching the camera to use mains power. <grasping at straws here> Did the boom operator have a personal monitor inline? Was the op suited up with other electrical equipment? Was the ground wet?
Les Wilson is offline   Reply With Quote
Old December 1st, 2010, 03:21 PM   #3
Major Player
 
Join Date: Jul 2006
Location: Chicago, IL
Posts: 937
Going to shore power.... hmmm... didn't think to try that. Does seem counter intuitive, but wouldn't be the first time that something works by doing something that shouldn't make it work.

Boom was on a stand, shoot was in doors, so no water around & mic was wired directly into the camera.

I also tried a ground lift XLR in line filter, which didn't help. I searched some more around google & someone had a similar problem that there was a loose screw in the power unit. So I'm going to try to take a look at that.
__________________
Nothing says you're a serious video maker like S-VHS
Zach Love is offline   Reply With Quote
Old December 1st, 2010, 03:39 PM   #4
Regular Crew
 
Join Date: Feb 2007
Location: Toronto, ON
Posts: 186
Were you using balanced XLR cables?
Jeffery Magat is offline   Reply With Quote
Old December 1st, 2010, 06:03 PM   #5
Regular Crew
 
Join Date: Feb 2009
Location: Melbourne Australia
Posts: 41
mic trouble

I had a simliar problem with a Sen mic.Turns out it was a simple fix in that the "Philips Head" screw was very loose on the mic causing an earth problem. Check the screw.
__________________
Neil McClure
Canon C100, Panasonic GH3, Sony EX1, FCPx, Motion 5.1
Neil McClure is offline   Reply With Quote
Old December 1st, 2010, 06:33 PM   #6
DVCreators.Net
 
Join Date: Oct 2001
Location: Seattle, WA
Posts: 888
Just out of curiosity, is there any other cables running out of the camera? S-Video, HD-SDI, component etc? These can create ground issues as well, especially when the camera is running on AC as well.

I've heard of a few people that travel a lot having issues with screws coming loose on shotguns and causing rattles - so double check your mics and tighten everything up.
__________________
Guy Cochran
DVinfo Sponsor, Cool Gear - DVeStore!
Guy Cochran is offline   Reply With Quote
Old December 2nd, 2010, 09:52 AM   #7
Trustee
 
Join Date: Aug 2008
Location: New York
Posts: 1,844
I've had instances where a ground type hum can emanate from a mic cable being in close proximity to a power amp or other power supply generating a strong electromagnetic field. A laptop PS was the culprit in one instance, a audio power amp in the other. Moving a cable eliminated the problem. The cables belonged to a hotel's A/V dept. and were of unknown quality.
Rick Reineke is offline   Reply With Quote
Old December 2nd, 2010, 10:39 AM   #8
Tourist
 
Join Date: Sep 2010
Location: London UK
Posts: 2
Yes, if the small Philips screw on the body by the XLR input is loose, you'll get an earth hum on the output. Tighten this and the hum disappears.
Luke Finn is offline   Reply With Quote
Old December 11th, 2010, 03:05 PM   #9
Inner Circle
 
Join Date: Jul 2002
Location: Albany, NY 12210
Posts: 2,650
Only time I've experienced this with the ME66 is when the capsule wasn't screwed into the power module tightly.
Marco Leavitt is offline   Reply
Reply

DV Info Net refers all where-to-buy and where-to-rent questions exclusively to these trusted full line dealers and rental houses...

Professional Video
(800) 833-4801
Portland, OR

B&H Photo Video
(866) 521-7381
New York, NY

Z.G.C.
(973) 335-4460
Mountain Lakes, NJ

Abel Cine Tech
(888) 700-4416
N.Y. NY & L.A. CA

Precision Camera
(800) 677-1023
Austin, TX

DV Info Net also encourages you to support local businesses and buy from an authorized dealer in your neighborhood.
  You are here: DV Info Net > The Tools of DV and HD Production > All Things Audio

Thread Tools Search this Thread
Search this Thread:

Advanced Search

 



Google
 

All times are GMT -6. The time now is 10:17 AM.


DV Info Net -- Real Names, Real People, Real Info!
1998-2017 The Digital Video Information Network