> I have a raspberry pi set up with an infrared LED to control my old NAD amplifier.

Interesting - could you share a little about how you have done this?

I have a Raspberry Pi that I use as a jukebox, connected to a NAD C320BEE amplifier, and I would like the jukebox to turn the amplifier and (active) loudspeakers on, using a usb-controlled relay, when I unpause mpd and off when I pause it, but unfortunately when the amplifier is powered on, it is humming until a source is physically selected!