I’ve done some tests. I did a couple of things and the hiss was reduced:
1. I adjusted the H9’s input level. I increased the input level (around +17 dB)
2. I placed a Ep booster before the h9 (minimum gain level)
The hiss is still there but things are getting better.
I think that the situation would be even better with something like this before h9:
A noise gate always have aneffect in the signal, I wouldn’t use a noise gate in my rig.