What you are hearing is precisely why I have changed over to a solid state preamp. I have the tubes in the amp. It is even more troubling when listening to a tube phono preamp. The tube noise of the phono signal is very noticible. I prefer solid state phono pre for that reason. Amplifying the signal through a preamp is where you do not want extra noise. Finding good tubes that are quiet enough for preamp use is a particularly difficult feat. They may advertise them as quiet, but when you exchange out the tubes for solid state, the difference can be pretty significant.