Turn it counter-clockwise to have the effect of increasing the bass and decreasing the treble.
For normal pubs I just stick with Balanced. But then again, High Performance gives my laptop more heat, so I use it sparingly only for Dota 2 on important matches. Tone and EQ controls are an all-in-one control for the bass, mids and treble. In Balanced Mode, even a simple game like Dota 2 experiences occasional FPS drop (as low as 15 fps), as opposed to when I use High Performance - of which its a constant 30 fps Vsync-ed.
The only thing we set with this button is if were using AUTO ISO or setting a fixed ISO value. The PFL/SOLO button acts as a controller over which. Setting the gain for each channel can be done using channel meters within each channel, on the high-end mixers, or the volume meter located on the mixer via use of the Solo/PFL button. AUTO ISO can be set in much more detail in the menus. The job of the Gain/Trim knob is to control those levels so the faders can best control the volume output.