If you have tube equiptment, a hum is all to common. Even you can hear noise from SS amps. The king of hiss is my beloved Reel to reel 4 track. However, if it does not interfere with your listening experience I wouldn't worry about it.
How Much Hiss Is Normal?
I have some Quad 12L Actives that I'm still setting up. I notice an ever so slight hiss from the speaker even when it's not connected to anything. You have to be right next to the speaker to hear it though. The volume setting does not change this. I'm reading that this is not uncommon for (other) powered speakers. They are both connected to a power cord surge suppressor. I assume this is normal??