A normal working example of the REF 3/REF110 combo will not have that level of hiss or tube rush audible from the listening position. I agree with an earlier poster that you have a bad tube, likely one of the small signal tubes that is causing the excessive noise.
I would guess that if you listen carefully, the noise is coming from one channel rather than both. If this is the case, swap the small tubes from one channel to the other and see if the noise moves. If it does, then you know what which tube(s) to replace.
I would guess that if you listen carefully, the noise is coming from one channel rather than both. If this is the case, swap the small tubes from one channel to the other and see if the noise moves. If it does, then you know what which tube(s) to replace.