Shielding video and audio cables from AC current interference?

Question

Trying to clean up some minor sound and audio problems in the sound booth at our church. Most of the wiring, including the armored cable that brings AC power to everything is in the same chase. Would a simple divider made of something other than metal, be enough to keep the "trash" off of the audio and video lines? I'm an electrician by trade, and in new constr., we keep the two out of the same chase, or at least run the 110V power in conduit to help keep any possible inductance off the "low voltage stuff". Thanks

Answer 1

The guys at blockemf.com have several items to choose from that would be helpful. Some items are specifically for 60 hz electomagnetic field effect reduction. Here's a link to one sample:

http://www.blockemf.com/catalog/product_...

Answer 2

First make sure that none of the low voltage (audio-video-data) cables run parallel to the ac lines. If the l.v. lines run parallel for more than the length of a 60 cycle wave, they will adopt that signal, shielded or not in many cases. Shielding is never 100%. Also, make sure you dont have a ground loop or any cross phased ac lines. You can buy a hum reduction unit fairly cheap but will need one for every ac line. You can trick your lv lines into rejecting 60 cycle by looping it  or wrapping it but that is hit and miss. If all this fails you can add a choke to your speaker wires at the speaker. Cut off everything from 80hz and below. Hope this helps.

Answer 3

In my experience it is most always a conducted emissions issue and will require power filtering at the source. However a shield like what you describe will work only if properly grounded.

Answer 4

When I was in the army I worked on radars, alot of our radars failed a RF leakage test. They worked fine just small amounts of energy were leaking somewhere after months of work we ended up wrapping a cable in tin foil as a temp fix till we got the manufacturer to send us a new better cable.

Answer 5

Yeah, you have the right idea.  Maybe a wood or rubber divider would greatly decrease the interference.