SUMMARY: You can buy an Echo and a 3.5mm cable to connect to your stereo and play Amazon music throughout your house. You can go a step further and buy a smart plug to turn your stereo on and off.
The Fletcher’s put in a “whole house stereo system” when they built the place. We normally play music via an Amazon Echo as they are scattered throughout the house, but on occasion it is fun to use the existing sound system.
I have an Echo Dot in our stereo cabinet.
The only current device that has a microphone port is the 4th Gen Echo:
https://www.amazon.com/Echo-4th-Gen/dp/B07XKF5RM3/
It is connected to the stereo via a 3.5mm microphone cable, like this one:
Amazon Basics 3.5mm Aux to 2 RCA Adapter Audio Cable
https://www.amazon.com/Amazon-Basics-Adapter-Subwoofer-Gold-Plated/dp/B01D5H8JW0
The stereo/receiver itself is plugged into a smart plug, like this one:
Kasa Smart Plug Ultra Mini 15A, Smart Home Wi-Fi Outlet Works with Alexa
https://www.amazon.com/gp/product/B091FXQQMQ
So I say, “Alexa, turn on stereo” (the name of my smart plug), and the smart plug turns on the stereo.
Then I say something like, “Alexa, play my favorite songs”, and it will play music throughout the house.
It looks like Amazon is doing away with microphone ports to save a few cents:
https://decortweaks.com/does-amazon-echo-have-an-aux-input/