The Chromecast Audio comes with a 3.5mm cable to connect to your speakers, but some speakers require an RCA or an optical cable. The Chromecast Audio doesn’t come with such connections, but universal adapters are available to make it work. In fact, those adapters are quite cheap.
Google decided to release official cables for the Chromecast audio so you can use the device with RCA and optical speaker systems. This is great, as first party cables are often quite nice. Unfortunately, the problem is in price. These short adapter cables run $15 a piece, which is quite pricey considering you can find the RCA adapter for as little as $5. Not to mention the yellow color, which doesn’t matter if it’s hidden away.
If you’re intent on using first party cables, hit the source links to buy the cables from the Google Store. Otherwise, I’m sure most of you can find a far better deal.