Do I need a new sound system

[Bryan_90]

I'm gonna buy the Sony xbr850D and don't know if I absolutely have to buy a new sound system with 4k passthrough. Or an alternate way I can do audio to my current system without ruining the 4k resolution

 

[kango69]

If your TV has either HDMI (arc) or Optical out then you are covered for sound.
If you have a 4K TV then I recommend connecting all external devices directly to the TV with HDMI then output the Audio from the TV with either of the above sockets.
This method lets you keep your older amp and there will be no problems with hdcp protection or worrying about 4K passthrough issuses

 

[jsmithepa]

When you changeover to 4K, that means ALL of your HDMI ports should also become 4K capable, including the ones in the AV receiver. You can "hold over" by using TV to switch video, and leave the older Receiver to switch audio only.

Or go "hybrid." Leave everything as-is, and today, February 2017, most likely you have a SINGLE PLAYBACK SOURCE that is 4K capable, your HTPC? hook that up directly to the TV them, and everything as said, through the AV receiver.

AV stuff, ask the question, WHO is doing the switching?