No reason you should be getting feedback unless something is defective. In any case, I use Nordost under the carpet.
Do you meaqn feedback like a high piutched howl? Cables can't cuae this. Are you using any tubed equipment? If you put a tube very close to a speaker, you can get feedback, just move the thing away from the speaker. I had this problem when I had a tube effects pedal in froint of my bass guitar amp (right in front of the port). Just had to move the pedal a couple feet away, no mopre howl. A turntable close to a speakier could probably also do the same thing