Remove Radio Station Background Noise

What is the best way to remove radio station sound from the TT feed to the pre amp? 

When I turn the volume up to about 50% I can hear radio station noise if my ear is next to the speaker.

I started using clamp-on ferrite chokes that clip around the cables from the TT to the phono preamp to eliminate the noise.  I wanted to know if there is a better solution or if the ferrite chokes compromise the sound.

The TT is a VPI Classic 3. The phono preamp is a Sutherland PhonoBlock and the pre amp (DMC-30SV) and amps (DMA-400) are Spectral Audio.  All cables are MIT Oracle MA-X.