Strange noise after amp's off ???


Hello,

I'm new to high-end audio.
Simple question: why is there strange noise( something like "dong" sound ) from my speakers right after I turn off my int. amp ??? is it normal ? or what should I do to fix it ?

Spendor SP1/2
Plinius 8100.

Thanks,
xxxjo
You have inadvertently obtained a unit with the patented "Cat Alert" feature. The bong sound advised the household cat that you have finished listening and s/he may now resume sharpening claws on your grill cloth.