i have a digital cable box that outputs sound to an old tandberg amplifier and noticed that there is a light background hum/noise that is heard no matter what source i am listening to (CD/DVD/AUX). the only way to get rid of the sound is by disconnecting the coaxial cable from the cable box.
thinking that it was the cable box that was the issue, i went out and swapped it out, but as you guessed, no cigar.
i then changed amplifier to an semi-burnt adcom (playing only one channel) and the problem was solved (but only one channel).
i then buy another amp NAD 7400, and the after hooking it all up, the sound is still there, revealing that the tandberg amp was not the issue. the only difference between the adcom setup and the NAD/tandberg setup was the position of the amps. from this i can only theorize that either the adcom isn't sensitive to the interference, or it was the positioning of the amp relative to the cable box.
should i call the cable company (timewarner) and ask them to clean the signal? is there any rf coaxial filters that can help? if so, any suggestions? or am i to resort connecting an a/b box at the input of the cable box with one of the splits not connected to anything so that when i want to listen to music i simply flick the switch (which would disconnect the box from the cable feed and eliminate the rf noise)?

http://www.jensen-transformers.com/datashts/vrd1ff.pdf

http://www.klipsch.com/products/details/magic-splitter.aspx

thanks for the prompt response. i shall try this out.