[SOLVED] Noticeable hiss in S-DJ05 when idle

I recently purchased a set of S-DJ05 and I am really quite pleased with their performance and looks. But I have an issue were the speakers produce a slight hiss when idle. I tried multiple power sockets and connections and also tried all inputs, but this hiss is still there.

Now I am wondering, whether I should be returning them to let them get checked out, or whether the hiss is normal in these speakers because of their active amplifier. I would hate to return them and get back a set which are similar..