Sometimes it's the little things: the audio out jack on the AirPort Express glows red when you start playing music and there are no speakers plugged in : r/apple
Apple Airport Express USB Audio Output Mod | H i F i D U I N O
How to Turn USB Printer into a Wireless Printer using Airport Express - Appuals.com
Apple AirPort Express Base Station (Summer 2012) review: Apple AirPort Express Base Station (Summer 2012) - CNET