very basic, bear with me...

I have a Supratek pre-amp.
This appears to have about half the gain of my previous Syrah. It uses 6H3n's as opposed to 6SN7s.
Sinnce the specs look very similar for the valves, is it possible to do something to up the output of this pre-amp?
It is better than the Syrah but struggles a bit with my Audiopax 88s which like a hefty gain.
Would bigger transformers up the gain or is it maybe the stepped attenuator volume that's limiting the output?
Who knows certainly not me although I imagine gain is dependant on the circuit/design, hoping for input.
Very basic response- some Suprateks have gain control (rotary) or hi/lo gain switch. Does yours?