Trying to reduce noise while listening to tube phono

Let me start by staying that I'm in love with how my system sounds right now. Hagerman Trumpet and Decca London Super Gold (paratrace stylus) is a ridiculously good combo. The only "but" is that if I raise the level to 3 o'clock on the preamp (Herron) I start to get tube hiss... or some hiss from somewhere. It used to be worse but then I got all new very low noise tubes and it improved a ton but I want to see if I reduce it some more. I'm wondering if the issue is the amount of gain on my preamp? Should I try another preamp with more gain and see if that solves the problem? On other inputs there's no hiss even at full volume so there's nothing technically wrong with preamp.