Been away for a while... and now I'm seeking some wiring guidance on a new project.
I'm knee deep in the creation of my third digital music server built into an antique Philco shell.
Here are versions 1.0 and 2.0 for reference:


The third one is going to be built inside a 1948 "Bing Crosby Special", model 46-1201.

(that's not mine, but you get the idea).
I've got 99% of it figured out, but here is where I'm stuck. The Philco will house both a mini-itx based computer and an amplifier. I only want one power cord and one power switch. So I need to know how to wire a relay that routes power to the amp when the computer is turned on.
I have a rotary momentary switch for one of the dials that will fire up the computer. I have a (somewhat) modular power supply that has a separate power input module.
.So I imagine I'll cut the wires between the input module and the PSU, and wire them to a distribution block or something, but everything that comes after that (including the relay) is beyond my English-major engineering "no"-how.
If you're still reading, can you offer some help? Bountiful thanks in advance.
