How important is EMI and RFI rejection?

Not important on power cords and speaker cables. Important in IC's if the system components have poor design. Another words it's mostly component's fault to pick up RFI.

EMI is usually 60 cycle hum that is picked up from power cords into your audio components. This is usually fixed by moving the power cord away from the component that is picking up the hum. Another "trick" is to make sure interconnects are not to close (six or more inches) from the power cord and are perpendicular to it (ie not running right beside it).

RFI is usually not an issue unless you live near a radio station, your neighbor talks on CB or HAM radio, or you put your WiFi brouter next to your turntable (ouch!).

That said, a well designed interconnect will likey take care of both issues. Blue Jean Audio provides cables that excel at EMI and RFI rejection. They have some good articles to read on the topic, too.

You can also block RFI from entering your system from the wall with a ferrite core that clamp over your power cord. Radio Shack carries these.

Finally, make sure all your equipment is grounded.

Well I'm confused....

I asked this question because somebody on another forum said NBS cables were all about EMI and RFI rejection....I use NBS and like them....

After seeing the responses so far....I found this on the NBS website...

"Noise, in a cable, can and will affect the audio frequency range and interfere with an audio signal. The most common noise, Radio Frequency Interference (RFI), affects a cable directly in the audio range. RFI presents itself as hiss, commercial radio broadcasts, intercom broadcasts, or any other radio signal broadcast in the audible range.

Another source of noise is Electromagnetic Interference (EMI). Whenever electricity, i.e., an audio signal, passes through a wire, it produces inductance that creates an electromagnetic field. Because EMI manifests itself at a high frequency, it is commonly believed not to interfere with the audible range of frequencies. However, all frequencies demonstrate harmonic structures. Even if the cause of EMI is outside the audible range, the upper and lower harmonics of a given frequency often present themselves within the audible range. At the very least, EMI causes degradation of audio frequencies."

http://www.nbscables.com/info/why.html

So I guess it still open....