sound distortion in hd channels

[bony]

hi guys , i installed my new Tata Sky hd dth this month on my set up i e Samsung full hd 40 " led and yamaha home theater thru coaxial cable every thing is fine but when i select the audio mode in dloby digital mode in my amp it works but with distortion sound in all the five speakers specially in Sony hd ..i already changed the coaxial cable ....other wise my amp is wrking fine on blue ray player(dts sound ) and sd channels.......any suggestions..........