Noise floor hiss

I've noticed on my setup that the noise floor hiss starts to become noticeable from the listening position after I reach about 90db volume level. (with no record playing) Now normally I don't listen this loud often, but it still annoys me that the hiss is there. Can I do anything to "quiet" the hiss so I may turn the amp up louder without fear of background hiss?
You could try re-routing or changing interconnects and speaker cables, as you could be picking up noise due to shielding (or lack there of) issues. Outside of that you probably will need to get a preamp/amp with a lower noise floor.

If you are using a solid state preamp there's possibly not much that can be done, if it is actually operating normally. Could compare the idle noise levels of each channel (turn it up with no music playing). If about the same then it's probably just inherent in the design, so then you just live with it or try a different model pre. If one side is significantly different then service could be in order.
A tube pre could explain higher idle noise levels caused by differences in tubes and /or degradation thereof. You may be familiar with "tube rush" noise often referred to here. Tube rolling, or swapping like devices between the two channels are some possible paths to disgnosis &/or resolution.