Do I need to buy another receiver to use the 4k media player?
I already have a receiver to watch 3d.
No, you do not need another receiver to use the media player. Just use a second hdmi cable in the audio out port of the media player. The main hdmi port on the media player requires a receiver that supports HDCP 2.2 encryption. There are only a handful of receivers that currently support HDCP 2.2 pass through. Onkyo is The only manufacturer that I have found that currently makes them. But..... Sony was smart with this media player by offering a audio only hdmi port to bypass the new encryption standards.