I'm having a bit of a brain cramp here. See the attached schematic. It is a tube preamp with an input transformer. The transformer is a step up as shown and there is way too much gain. I could put an attenuator between the tranny and tube, but I found one resistor across the windings (resistor that is circled) works quite well, and brings the level down almost perfectly. What I am concerned about is input and output impedances of the transformer. What's the math. Please note I cannot make wholesale changes. The gain solution must be simple.