Scratched, 8 bit sound

hello, I can´t get nothing but a hollow, like backround from the telefon sound in my system. I´ve tried to different cards, the M-box2 mini with ASIO4ALL and the MAYA with its own driver, sounds exactly the same. It goes somehow allright with headphones, but the digital output and recorded wavs on cd played in the stereo sounds just awfull, it even damaged one speaker. Any clue? Thanks a lot

i7 3.4 ghz 16 gb ram Win 7 64 bit Cubase 6 elements