how to hook up sound bar and apple tv?

I had connected my sound bar via RCA -red and white cables to my cable box and i was able to get sound from my sound bar, except when watching Netflix movies. And then it just stopped working even for ordinary tv shows, no sound from sound bar. Someone suggested i use an optical cable from apple tv to sound bar instead. Si I connected my 46 inch smart tv ( no optical audio cable output) , via hdmi cable to my ATV2 and an optical audio cable between my ATV2 and my sound bar. I put settings for ATV2 to PCM as instructed in sound bar booklet BUT still no sound coming out of my sound bar. Can someone please help. I hear a click when i push the input button on sound bar but no sound. What is wrong? I have read many posts and there seems to be an issue with Apple tv and sound bars??? any ideas??? sound from my smart tv is awful

thanks

pauline