horrible sound out of AV input when nothing is connected

Hello

On my Nac 282 after I tried X-Box on Aux2 with Chinch (holded program button and pushed 6) and it worked perfectly, then I tried Ipot touch with original Mac cable and there got no music out (perhaps it's normal), it worked on a Cambridge Audio A500 !?

Then I pulled out Headline connected to a 2nd Napcs (on Tape input) and I pulled out Phono (Rega P3 by Chinch). I did all this to reduce cables because I had sound problems....long story :-)

So by chance yesterday I switched through all the inputs (a KT 1100 is now connected at Aux2 by Chinch).

and AV (without anything connected at the AV input) there is an awful loud noise coming out of the 2 speakers.

When I hold "prog button pushed" it disappears but comes back.

I never heard such an awful noise

Please help.

There is nothing connected on AV2 !

thanks

hififriend