I have a seemingly simple problem that I can't figure out how to resolve. I've repurposed a few bakelite radio cabinets with upgraded internals. I'm attempting to build one with a little class D amp with a volume knob and a Bluetooth module. Both devices are powered independently by the same 12v source (a 26650 5-battery bank). In order to use it, I have to turn both the amp and the Bluetooth module on. When done, I need to turn both off. I'd like to be able to trigger the Bluetooth module on and off when the amp is turned on. Is there a relay of some sort I could use to accomplish this? The amp has a 12v input, line level input and stereo speaker output, and the Bluetooth module has 12v input and stereo line level out. I was hoping I could solder a lead wire onto one of the exposed posts for a trigger (like a remote amp turn on for a car stereo) that goes through some sort of logic board for 12v to send a signal to the Bluetooth module to power up. I just don't know where to start with this, other than asking here.