I would think that the small "hiss" you hear is the *interaction* between the amp and the speakers. I have this too. Have to put my ear right up against the tweeter, and then actually angle my head specifically to hear it. (Just the amp connected to the speakers.)

But the big "HISS" that you hear that becomes apparent when you adjust the volume from -80db to -79db must be from the 950.

So that's at least 3 people now:

Prefect
Dealcatcher
Tetra500

That have experienced this...