ive currently got my sky hd box linked to my sony av amp using a hdmi lead for the picture and a coaxial lead for the sound , on the amp display for when i listen using the coax it displays dolby digital and all the speaker icons are lit up , but when i switch to just the hdmi it doesnt light all the speaker display up and doesnt sound as clear , if i remove the coax cable will it alter the hdmi sound and display.