re: Connecting a soundbar to TV using a digital audio optical cable

Can you explain a little more what you're trying to do? You were using outputs on your TV (composite - red/white) out to your soundbar and could control the volume that way with your cable remote (control the soundbar sound, not TV sound) but now you are trying to do the same thing with the optical out on your TV?

If that's the case, the optical out on your TV is likely meant only for if you hook up an antenna to your TV and that's the digital out for only antenna audio, and won't work for any other audio that would normally come through your TV screen like a cable/sat/dvd/blu-ray/etc.

If that's the case I don't think the optical cable will work for going cable audio to TV and then to soundbar. You could do Cable audio straight to soundbar via optical and then either not use TV speakers at all or also connect r/w to the TV along with a video cable (or HDMI or whatever you use).