use disable_audio_dither=1 in /boot/config.txt this solved my audio hissing
I fiddled with the buttons from the LCD controller and screen the menu in retropie gives me 1920x1200x60HZ. I am not sure why is this since i have also the 8" LCD and I understood that the display should be 800x600? Maybe the is related to the display cutting off(see my other posts) and the increasing of max power through the USB ports.