Speaker feedback

[a128wed]

Hello,
I have a mini home theatre system hooked up to my tv via the audio out on the tv. when I am watching cable through my digital box I get the buzzing feedback sound in the background. When I am watching a dvd there is no feedback. So it seems like the feedback must be coming from the cable box. Any ideas on solving the feedback issue?

 

[Guest]

It's not feedback, it's hum.

Two possible causes: unscreened/defective audio cable OR lack of mains earth or duplicated mains earth.

To explain the latter: in an audio chain -- for example a CD player connected to an amplifier -- the CD's power cable will not include an earth wire but the audio wiring's neg (screen) is connected to the amplifier casing via the input sockets. The amplifier's power cable must include an earth wire.


That's the principle, I hope it helps.