Originally Posted by tomwil
Be sure that your older AV receiver can decode Dolby Digital, which is what the optical output on your TV can output depending on program material.
Also, there is a setting on the TV to turn off the internal speakers.
I've got a TC-P46S30, new in September 2011. Though I was surprised that my Bose Cinemate (original with RCA plugs) had nowhere to plug in, some research found that I could bridge the optical audio out on the TV to the RCA inputs on the Bose control box with a Gefen Digital Audio Decoder (GTV-DD-2-AA), which is about $85 (they have a cheaper version, but it will not work for the Panasonic optical audio out). With the TV internal speakers off and the Bose (or similar older setup) on, you will get 2.1 channel stereo (which is all the external setup would deliver to begin with.
HOWEVER, I recently tweaked my comcast remote to fully control my Motorola HD DVR cable box, the Panasonic TV and the Bose Cinemate and have noticed that the sound from the optical audio out is very temperamental. Sometimes, when I turn everything on, Bose sound is fine and other times, there is no Bose sound or it has a delayed start of up to a minute or more or not at all - until I power the TV on/off. Troubleshooting suggests that the Bose system is fine (works ok with separate cd player) and cable box/hdmi connect is fine since there is no problem with the sound when TV speakers are engaged. So possible problems are the Gefen converter (Gefen says that sporadic problems are unusual and if they are bad, they quit working). Panasonic says consistent sound from internal speakers suggest no problem with their audio (which is not necessarily logical). That leaves the optical cable. On one occasion as I was trying things today, I did touch the cable near the TV connector end and the sound cut out. Maybe I do have a bad/dirty cable or a bad/dirty female end on the TV (though it has visible laser light even when there's no Bose sound).
So, I have ordered a new optical cable from amazon and will try a switch on the existing setup as step one. If that doesn't work, next test will be to run the optical cable from the cable box to the Bose via the Gefen (also removing the hdmi from the cable box so as not to overtake the optical signal) to see if there is sporadic sound with the TV out of the mix. If sound is constantly okay that way, there may be a software and/or hardware problem in the TV and I hate the idea of trying to get it fixed only to invite new problems. Perhaps I will also start looking at a home entertainment system which relies on hdmi and has the 5.1 audio and viera link ( I had this setup in my prior equipment and it worked great).
Any ideas from readers would be much appreciated, particularly if you've had and/or solved this problem.