Faint speaker hiss


Was wondering if anyone here might be able to help me out. I recently acquired a new naim integrated (XS2) to pair with my Harbeth p3esr. I am using straightwire speaker cables which I've had for years. I noticed when I plugged everything in that the speakers have the ever so slightest hiss coming from them. I cannot hear it unless I get extremely close to to tweeter and te sound becomes non-existent once music starts playing. I have had the amp for about a week now and have kept it on 24/7. Does anyone know where the small hiss could be coming from? I tried different speaker cables/power cord and that didn't change anything. I also tried unplugging all my sources and left just the amp and speakers plugged in ad still had the faint hiss. Like I said, it's not audible unless I really get my ear close to the tweeter (about 3 inches). I might be nit picking but was wondering if anyone has had experience like this before? Should I try a different outlet? I am in an apartment so only have one or two places to put everything. Any help would be greatly appreciated. Thanks!
mgrec42
This.  All brands and models of amplifiers vary, as will individual examples of each.  Above all, don't go crazy throwing $$$ at this problem because you'll never eliminate it.  The most quiet integrated I've ever heard is the Ayre AX-7, probably because of built-in filtering and the unusual design/configuration of its transformer.
They almost all do. I never had a speaker/system that was completely silent. But Can't hear a thing if my ear is few inches away. 
While as others have stated the "hiss" is normal, there is something to keep in mind/try. The hiss should only get so "audible" and then cranking the volume further clockwise should NOT increase the volume of the hiss. Usually the volume of the hiss maxes out around the 12 O’clock position. If the hiss continues to get louder as you crank the volume I’m pretty sure this would not be considered normal.

Something else to try. RCA shorting plugs on the unused inputs of the amp. Can’t hurt and could help.

And yet something else.... gee I've learned so much from this forum over the years :).... the efficiency of your speakers do play a role. The more efficient they are, the more hiss you will (or could) hear.
Sorry for a late response but I appreciate all the feedback! I thought I should mention too based off some responses that no, the hiss does not get worse with more volume. It is a minor constant sound that goes away once music is played. The speakers I have are inefficient to say the least (83 db)  I did do a quick a/b with an old pair of paradigms that are around 90 db and yea the hiss was more audible but still nothing dramatic. As others have stated, it really shouldn't be a worry as it is so minor but this is a lot of money for me and I just wanted to make sure there wasn't a stupid mistake on my part that could have been causing it. Thank you all so much for the feedback