Tv cable and surround sound prob

[Kc_3__]

I have a 780 p magnivox tv and just got a lg surround sound system. The prob I'm having is the tv is not allowing the surround sound to pass through unless I shut off cable box and change input settings on tv for diff HDMI channel then it works just fine how do I get it all to work together

 

[nicolatesla]

Surround sound does not come from a cable box.
It only comes from devices (such as DVD encoded w/ surround sound).

The surround system may have "simulated" surround setting, which allows using a regular stereo audio source to get audio from the surround speakers, etc...
This is used in case the source is not a surround source.
The source for surround...must be encoded with digital surround information. This does not come from Cable TV.

 

[americanaudiophile]

Cable TV does support Dolby Digital surround sound IF the channel has it. You can select that option in the cable box set up menu.
If the TV audio menu won't allow you set the TV to pass the audio in 5.1 then your option would be to use a separate digital audio out from the cable box to the LG. If it doesn't have one you can use an HDMI switch with audio extraction to derive a separate audio feed for the LG. Set the LG surround mode to Dolby if you can. This will give you Dolby Digital if it's present and Dolby Prologic2 when the program is in 2.0. Try any other modes the LG has to see which ones you like.