A critical factor influencing the 'brightness' of beer flavor is wort pH. If it is too high, there are a number of negative results that occur. One of the biggest is the coarse or rough nature of hop expression produced at higher wort pH. Keeping the pre-boil wort pH below 5.4 is critical. Starting with a pre-boil wort pH in the 5.2 to 5.4 range is ideal.
The main thing that creates higher than desirable wort pH is excessive alkalinity in the water source. Be sure to find out what your water alkalinity is and how to treat it.