is usually not necessary to adjust these settings. If you connect a device such as an AV amplifier for a home theater to the PS4™ system’s DIGITAL OUT (OPTICAL) port, you can manually change the audio output setting. To adjust settings, select [Sound and Screen] > [Audio Output Settings] > [Primary Output Port] > [DIGITAL OUT (OPTICAL)].
情報源: KC Article: PS4: Change Audio Output
で、これがデジタル出力(OPTICAL PORT)の場所。