Chromecast Audio uses an optical connection because of space constraints any technical reason. The Chromecast Audio uses the mini-Toslink variant which fits inside a 3.5mm analog jack.

The XtremeHD Toslink optical audio cable includes a 3.5-mm optical audio jack adapter, which enables users to connect any Apple product with a 3.5-mm optical digital audio output jack or Toslink ...

The new Chromecast Audio is neat. But the box only comes with a 1/8th inch aux cable (AKA a headphone cable), so if you want to use that handy little streaming gadget with anything that doesn't ...

The basics Both HDMI and optical pass digital audio from one device to another. Both are better than analog (the red and white cables). Both can pass multi-channel audio, like Dolby Digital.

Mini-Stereo-to-RCA Audio Cable The most common solution used to stream iTunes to an audio receiver is to connect the "Audio Out" or "Headphone" jack from the computer's sound card to the receiver.

In the 2015, and earlier, MacBook Pro, and every other Mac model with optical audio out on the 3.5mm jack, the listing is amplified with a statement like "support for audio line out (digital/analog)." ...

Optical audio output is used to link Macs to home theater setups and A/V systems capable of multi-channel surround sound, by way of a mini TOSlink adapter connected to the 3.5mm jack.