humming from speakers

[sparkless]

I just connected my stero amplifier to my plasma using the plasma's 'Audio out' connection, obviously to get the TV's sound through my amp & good speakers. It worked but the trouble is there is now a loud humming sound comming from the speakers. I had my old tube TV hooked up this way with no problem a few years back, using the same amp & speakers and there was no humming.
Can anyone suggest what might be causing the humming?

 

[MikeMl]

Google "ground loop" and "ground loop isolator"

 

[mneary]

You can start with:

(a) The plasma and the receiver are plugged into the same surge strip.
(b) There is a lightning arrestor in the surge strip and the tv/cable "antenna" wire goes through it.
(c) The third prong in the surge strip is present, and it is plugged into a properly grounded outlet.

There's a lot more, and Google can get you more, or you can come back here. Bring photos if you can, they help a lot. The ideal photo is about 600 x 400.

 

[sparkless]

Thanks for the help.
Since posting the question I did some experimenting.
I hooked up a different amp & there was no humming.
So I took apart the problem amp, vacuumed out all the dust and more importantly
I cleaned up the internal earthing connection.
Guess what, that fixed the problem.
Cheap n easy.

 

[flat5]

Good work! Sometimes reversing the AC plug (insert it upside down) helps to reduce hum. Perhaps you also did that.