I have a google home mini which I'm casting music to a set of legacy bookshelf speakers. These speakers have a standard 3.5mm male connector. The speakers do not have bluetooth. Instead, I plug them into a chrome cast audio device. I'm now adding a amazon echo dot to my environment. I'd like to connect the dot up to the same set of speakers. I can't use bluetooth, as the speakers don't have bluetooth. I'd like to use the audio output of the dot to connect to the same speakers. But right now those speakers are already plugged into my chromecast device, for playing from the google home mini.
My question is, is there a way to have two wired inputs to the same set of speakers? (Something like a headphone jack splitter, but in reverse?). While theoretically there could be sound coming from both the dot and the chrome cast device at the same time, in practice it would only be one used at a time. If such a device exists (a switch, some kind of mixer?), I would like it to automatically switch (if necessary) between the input sources, depending on what has active sound. (Or, if it were always combining the sounds from the two inputs, that'd be fine too). And I'd like to maintain stereo sound, from whatever the active source is. And of course the cheaper the solution the better (although if a more expensive option has certain benefits, I'd appreciate hearing about it).