Shure A15RF RF Filter
The Shure A15RF reduces interference from AM radio stations that may bleed into microphone lines when using long cables in microphone installations such as suspending choir microphones. The A15RF passes phantom power, and can be used with condenser microphones.For best results, the A15RF should be installed at the end of the cable nearest to the microphone. In situations where this is not practical, the A15RF can also be installed at the mixer input, although RF attenuation may be somewhat reduced.
In cases of extreme RF interference, two or more A15RF's can be placed in series in the same microphone line, preferably with one at each end of the microphone cable. In cases where interference is present but not audible, the A15RF can improve perceived sound quality by removing low-level interference components from the audio signal path.