They are for setting a reference level for each channel. You then use the volume control knob. If your getting too much output with them set at 12, set them at an appropriate level to allow the greatest range for the volume control.
Do you have your CD player connected to the CD input? Try connecting it to one of the aux inputs. You may like the sound better. Also, connect your amp to the Main 2 output and see if you prefer the sound to the Main 1 output.
Wendell
Do you have your CD player connected to the CD input? Try connecting it to one of the aux inputs. You may like the sound better. Also, connect your amp to the Main 2 output and see if you prefer the sound to the Main 1 output.
Wendell