airplaymusic
I would like to stream music from my Apple devices to my kitchen.
I've got an old amplifier and passive speakers.
I know that I can simply connect my airport express to the LAN or WiFi and to the ampli as line input, but I would like the ampli to turn on only when there is a line input signal, and then automatically turn off after an idle time, in a way similar to many Subwoofers.
In this way only the AirPort Express will be always powered.
Is there a device or a simple way to do this job?
You just extend the network created by one of the two devices. I.e. you start with the Time Capsule, making it create the WiFi. The AirPort Express then gets configured to just extend this network. If you've setup the Time Capsule to use the 5GHz band then yes, the Express will use that too.
It's effectively just one WiFi network (or two, if you count the 2.4GHz fallback for older/mobile devices) powered by both stations. All devices connected to that network have access to both stations and they will always get connected to the base station which is nearest. Here's this setting in the AirPort Utility:
When setting up a new network with the AirPort Utility you will be asked for this, so it's really easy and happens in two clicks/taps.
Apple also has a good support article on this: Wi-Fi base stations: Setting up and configuring an extended wireless network
sure, this will work. when you extend your wired network, change your airport express to either extend your existing wireless network or setup it up as an access point.
Best Answer
While in terms of the specificity of the desired implementation I agree with @patrix, you could get the desired solution if you're open to reframing how it all gets handled. I'd say the easiest (but somewhat costly) way to get the desired behavior is to get a Logitech Harmony remote.
If the amplifier pre-dates remote controls, you might need to think further outside the box and look into a wifi/BT-enabled power switch (plug the amplifier into said switch and have the hardware power toggle on the amp always set to "On"; give the signal to the power switch to let the power flow through it, the amp then remotely powers on).
Things get very interesting in these days of "Internet of Things"… :-)