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Author Topic: Audio interfering with video projector  (Read 2168 times)

Stephen Swaffer

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Audio interfering with video projector
« on: December 30, 2013, 12:51:23 pm »

I posted on this a few years ago and as never able to resolve the issue-and since have changed out some equipment so as to eliminate some possible issues.

When playing videos in our church we get multiple, random horizontal bars on the video projection.  We have a projector hanging from a pole about 10 feet in front of the platform, a center cluster of speakers above that and monitor wedges on the platform.  The ONLY way to eliminate them is to turn down the monitor wedges.  I can run full volume on the house with no trouble-and that wiring is closer to the video wiring than the monitor wiring.  Monitor amp was replaced about a year ago-from a QSC 1450 to a Crown XLS2000 with no change in interference issues.  Interference occurs both on playback from a DVD player and from a PC.  I have tried running power from another area to amp-again no change. If I back off monitor setting to about 30% the problem goes away-but often those on the platform want to be able to hear clearly as well-plus we use both the PC and DVD for audio playback only at times and it would be helpful to not have to change settings
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Steve Swaffer

Mac Kerr

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Re: Audio interfering with video projector
« Reply #1 on: December 30, 2013, 01:14:41 pm »

I can run full volume on the house with no trouble-and that wiring is closer to the video wiring than the monitor wiring.  Monitor amp was replaced about a year ago-from a QSC 1450 to a Crown XLS2000 with no change in interference issues.  Interference occurs both on playback from a DVD player and from a PC.  I have tried running power from another area to amp-again no change. If I back off monitor setting to about 30% the problem goes away

Are your monitor speaker lines installed in the building, or portable cable run across the floor? If it is installed in the wall, try disconnecting all the speaker cables from the outputs of the monitor amps and run portable cable to see if anything changes. If it does, you have a bad speaker line possibly shorting to conduit or something else. Narrow your search by replacing one at a time till you find the one causing the problem, and then measure each of its wires to ground and each other, and inspect any part of the cable you can to find the problem.

Mac
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Jerome Malsack

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Re: Audio interfering with video projector
« Reply #2 on: December 30, 2013, 06:31:54 pm »

In the home theater world we see this with the ground from the cable box and the sub woofer.  Recommend using Ground lift between PC and Mixer, and DVD and mixer. 

Disconnect audio from DVD and PC to the mixer and see if this eliminates the problem.
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