Snes Console Problem

[AmBrew]

Hello, i just bought a SNES from ebay and im having problems with the sound. Sometimes it plays perfect and then "bam!" this really loud crackly noise starts. It doesnt make the sound all the time, its on and off. Ive tryed tuning into different channels but it still happens. I find if i pause a game and no sound is playing then it wont make the crackle. Im using a RF cable at the moment but i have ordered a n64 RCA AV cable from ebay hoping that will work. Ive searched all over the internet for answers but have failed to find any so this is my last hope. Please help me!

[killsonic]

Never had this problem before, let us know if the stereo cables fix the issue.