''Hissing'' from speakers....cause ?

I had exactly the same situation that is audiable with some amps and with some amps it's less audiable. When I replaced tweeter, everything had straightened out. I even had come to the point when I had to block the tweeter with soft paralone so it doesn't hiss to loud and listen most of top end from another speaker but it was temporarily to save my sencitive ears.

Tubes hiss. Everything else hums. Good equipment (in proper working condition) is inaudible.

Thar's right Plato, the Monarchy is passive, the Sim active. Never considered that, thanks.
It's noticeable when I'm close to the speakers, or if my small listening room is very quiet.