For the last year, I've been streaming music from the interwebz via a Google Chromecast Audio (optical out) into a Cambridge Audio DAC (optical in). Works and sounds great. Then a few days ago, I removed the DAC and connected the Chromecast straight to the RCA inputs on the amp, i.e. using the Chromecast's internal DAC. One word: MUD! Muffled, murky, veiled sound coming out of my Elac bookshelf speakers. The Cambridge Audio DAC (DacMagic Upscaling DAC) is more than ten years old, but still works fine. Just goes to show: crap in crap out.