You’d need to get the USB C line in adapter from Sonos, and then put that between the CD player and the Era 100. Then you could play CDs on that speaker, or any other Sonos speaker ( or groups of speakers) in your system. 
 

See this FAQ: 

https://support.sonos.com/en-us/article/play-line-in-on-your-era-100

Your profile says you have a Play:5. If it’s not in use as a surrounds speaker, you could use its line-in, and select that as the “source” to play to the Era. That might make cabling a bit easier?

Good day/evening! After doing more research, it seems that the Line-In solution will only work if the old (and I mean 20+ yo) CD player is directly connected to the Era 100. That won’t happen. The ERA’s sitting on our porch, the bulky 5-CD player is in our living room. All this sounds like we need to buy the Port, hook that up to our CD (or our receiver/amp??) and then…??

Sorry to be kinda dense about this architecture, but I want to get it right first time around.

Thanks.

Why will the cd player only work if it’s directly connected to the Era? Sonos lets any input stream to any speaker. 

I don’t see why you don’t just use the ‘existing’ Play:5 line-in, connected directly, or indirectly, to your CD player? You just need the RCA analogue line-out cable, from your CD or Amp, going to that speakers line-in and then in the Sonos App, select the Sonos Room(s) you wish to play to and select the Play:5’s line-in as the chosen playing music source. With an Era-100 you could connect it directly, with the line-in adapter, but personally I would save your money and use the hardware that you have already.

Sonos has zero knowledge about what device is at the other end, feeding the line in. All it is looking for is a line level input, anything could be feeding that. 

Sonos led the way in making all CD players obsolete by allowing the music on CDs, ripped to a local hard disc that is connected to the home WiFi to be played wirelessly over it, giving you in effect much more than just 5 CDs that can be played without touching the “changer”.

Streaming services that play almost all the music in the world, then made this Sonos solution obsolete, making a local NAS unnecessary.

But there is still a way to use the 5 CD changer if you absolutely must. Wire its outputs to the line in on the Port and then set up the Port to autoplay as soon as it gets signals from the changer, to the Era, wirelessly. Expensive, given the cost of a Port, but can be done.

Or, if you have any other Sonos kit that has a line in and can be kept in the vicinity of the changer, that can be used in place of a new Port.

I think this was meant as a reply to @Airgetlam ‘ advice to connect the CD player to the Era. In this case that won’t work because the Era is to far from the player. So either a Port, the existing Play 5 or a new Era (a 100 will do) with adapter is needed.

Olliedawg348,

Regardless of where the physical connection is made, any Line-In can play in any combination of SONOS Rooms. Line-In is simply a resource on the network. Unlike old world Hi-Fi gear, there is no physical connection between a jack on the input “box” and output from that box. By this I mean that an input analog device does not automatically play through the box where the device is physically connected. 

Here is a general Line-In discussion:

https://support.sonos.com/en-us/article/use-line-in-on-sonos