I get lost in all these posts, but here's what works for me

I have an LG HDTV with a optical digital output for sound and an older external analog speaker system which uses RCA plugs for input. It sounds like your setup may be different from mine, but in case it's similar, here's what I use to convert the digital audio to analog for my speakers:
http://www.amazon.com/Gefen-GTV-DD-2-AA-Digital-Audio-Decoder/dp/B0021QBIBQ/ref=sr_1_2?s=electronics&ie=UTF8&qid=1370140257&sr=1-2&keywords=gefen .
It's a Gefen box with input from the TV and two RCA plug outputs for the speakers. It's expensive, but it has been working flawlessly for me for the last 2.5 years.
By the way I tried using the audio output from the cable box using RCA plugs. It gets the sound to the speakers, but totally out of sync with the video on the TV, so I had to use the only audio output from the TV which was the optical digital one.
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Good luck.