mic buzz when connected to video monitor

R

redman

Active member
I get a very loud buzz noise in the headphones when I do this with my DVX100A:

Lavalier mic connected with a video monitor also connected. As soon as I disconnect the video monitor cable from the camera the buzz dissapears. Anybody else have this problem? I was trying to simply monitor a talking head I was shooting but couldn't be cause of this problem. I just had to monitor using the LCD screen. Thanks, Reggie.
 
Sounds like you have a grounding problem. I experienced this once with a boom mic on a boom pole. I took the mic off the pole and the buzz went away. Also could be your connector. Could have a short, be dirty or faulty. I use external monitors all the time both through the composite RCA and S-Video and even have hooked more monitors up in series through them with no problem. Sound like the monitor your trying to use and the mic are in conflict with each other.
 
The ground loop problem can be solved by operating the camera on batt. and not
ext. power supply. Try it.

Try also to move the lav. mic cable so it will not go close or parallel to power cables.

If your lav. is a "low cost" 2 wire model, you will have lots of problems when used with ext power devices.
 
it happened to me once before, but on checking the actual recording the buzz wasnt there. In my case anyway it was an unrecorded humm. Thus it was something causing hum on the headphone line not the mic line.
 
I'm using a 3 wire Sony lavalier and a bnc cable connected to a NEC plasma monitor (with an rca adapter on the DVX end). When I disconnect the monitor everything is fine. How could there be a problem with the video cable or connection? Thanks, Reggie.
 
redman said:
Aw this sucks, having the same problem with an HVX200 now. Is it so much to ask that you could use the XLR inputs and externally monitor video at the same time?
Click to expand...

Not really, and most of the time this can be - and usually is - done.

If you have a ground loop, the first thing to try is swapping out cables. Try a new XLR cable, or a new BNC cable. Either or both could have frayed wire or cold-solder joints that are causing the issue.

If you are using AC (wall power) for anything in your system, you could be dealing with dirty power. Isolate everything from the AC and see what happens.

I have found these to be absolute life-savers. They filter the ground loop hum while maintaining a safe ground. The convention center here has notoriously dirty power, and I slap a couple HumX filters on various parts of my PA system and the problem is gone. Much safer than AC ground lifts, and much better than inline ground lifts on the audio cables, which don't always work.
 
Tried a couple different XLR cables and BNC cables. Camera's running on battery power too. This buzz is very loud too, not like a quiet buzz from a mic cable crossing an a/c cable. I'm always aware of where my mic cables run and in this and the previous instance with my old DVX I ensured that the cable was nowhere near my lights' cables etc.
 
Anyone who is electronically inclined could purchase group loop isolators and install them in various places to isolate these problems....I used to do this all the time with various parts of stereo systems, and luckily my video gear hasn't had these problems yet....but the moment it does I'll be buying GLI's, hobby boxes, various connectors, and breakin out the trusty soldering iron.
 
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