Some TVs let you keep the speakers on when the headphone jack is used. Some let you change the jack volume with the TV remote. But no model numbers mean no one can check the manual.
But here's a thing. Are you reporting Sony and the dealer are not answering questions or supplying user manuals?
The other solution. Get the headphone jack and run it to a soundbar or such and a splitter (too many to note any one in particular) to both headphones and the soundbar or receiver.
So here's the problem. My Grandparents just got a Sanyo 4k TV but it doesn't have an RCA audio output. On their old TV, the RCA audio out was wired to wireless headphones so that audio was coming through the TV's speakers and headphones at the same time.
It seems to me that the only sort of audio out is a 3.5mm aux out. I thought about getting a 3.5mm to RCA adapter, but then the TV speakers would stop playing and the headphones would be the onl y ouput. The inputs that are going into the TV are, a DVD player that uses a red/yellow/white RCA, a Roku that uses HDMI or RCA. And a cable input (the kind that screws in).
If you need any more info, please let me know. I really appreciate any help anyone gives me. Thanks.

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