Optical you need a miniToslink to Toslink cable bypass the analog output completely.
https://www.amazon.com/Toslink-Fosmon-Digital-Optical-Chromecast/dp/B01MY2DJUM/ref=sr_1_4
https://www.amazon.com/Toslink-Fosmon-Digital-Optical-Chromecast/dp/B01MY2DJUM