First, the issue is very common with older HiFi systems. I won't dive into all the prior discussions and skip to something that may help. Also I never discuss having the TV and the HiFi speakers enabled at the same time (again, well discussed!)
Try this -> Disable any video smoothing and processing in the HDTV.
Sorry but how to do that is up to you or Sony to reveal. It's a common thing I try and it has helped.
Help, I can't get the KDL55HX853 to work with my NAD HiFi speakers.
At the moment I have to run the red and white sound cables from Sky box to the Hifi. The result, the sound from the hifi speakers and TV is out of sync.
Also I cannot use my HiFi speakers with my PS3 as it does not take any sound cables. My old TV I just had to run the sound cables from TV to the HIFI and connect my PS3 to the TV. it would do all sound via HiFi speakers in sync perfectly without having to change the channel on the HiFi.
I want to connect my SONY BRAVIA KDL55HX853 to my HIFI and use the speakers, please help. Do I need a certain kind of cable ?