Hello,
 
	I recently set up my X5 64. Everything is good except for this issue. I am getting no Sound when my resolution is set to 3840x2160. I am hoping someone can help. 
 
	If I select the Auto Switch to best select resolution, the system sets the resolution to 1920x1080p 59.9hz and the sound is working. I tried switching to another HDMI port but no change.
 
	Here is my setup:
 
	TV:  Vizio M658-G1, 4k 120hz refresh rate
 
	Audio: optical digital cable to Bose 550 sound bar
 
	I have most the current firmware update.
 
	Thanks for your time.