I have a strong hiss from my speakers that I have not been able to eliminate. I've tried many things, lifting the ground, unplugging all units hook to the 990, going to balanced interconnects, etc and it still persists. The 7125 I had was dead quiet using the exact same gear and AC outlets. Any ideas what may be causing it?

Have you tried to unplug your cable, it should eliminate 80% of the problem. I have the same problem the other day after I installed the new amp which is Earthquake 3 channel. The hiss was 90% gone after I grounded the cable plug.

Yes, the pre had nothing hooked to it at one time and still produced the same hiss.