You can vary values in many locations to EQ or add gain. I use 2-sided alligator clips to swap parts.
A good place to start is the V1 cathode resistor and bypass capacitor. A larger cap will have more bass. On a plexi, the normal channel has a 1.5K resistor and a 330uf cap. Mud City. The bright channel has a 2.7K resistor and a .68uF. It cuts the bass nicely.
Coupling caps and plate resistors can be messed with as well. Build the amp per schematic and get it working well, then spend the time experimenting with one thing at a time and playing through it until you find something you like.
