Different systems playing same music simultaneously

Thank you for the suggestions. I see some interesting solutions...
What I have right now is a bunch of old style amplifiers. Some solid state, some tubes. No streamers, no modern receivers/amplifiers with network connectivity.
So I'd like to try something like a dongle that I can connect to each of the amplifiers to receive the signal (coming from a computer or a phone). I think there are already some receiver devices that can be synchronized in order to receive the same signal at the same time. Am I right?

Meanwhile I did a short research and it seems the most effective devices for what I need (at a reduced price) are the Chromecast Audio, the Dayton Audio Wave Link and similar products.

@migueca yes, that’s the systems I have. My Fisher 400 and console are vintage tube receivers. My Arcam is a modern receiver. The Google Chromecast Audio units are individual “dongle” devices. They connect on their own to your WiFi through minimal setup. So your receiver or amps do NOT need to have any sort of connectivity. They simply need an analog RCA input.

I have Sonos speakers in several rooms and three complete systems, Media room, shop and garage. You put a small Sonos "Connect" on each system and everything talks to everything via your wireless network. You run the whole thing with an app on your phone. Very cool to have the whole house going at once. Great way to get your wife to commit suicide:)

One imagines nobody has heard of the problems associated with multiple speaker rooms or, if they have, assume just because the speakers/systems are in separate rooms they don’t affect each other. Even if they don’t act acoustically. It’s similar to the concept that cell phones in the room degrade the sound. Is that too advanced?