Proper power up and shut off sequence seperates ?

Which should power up first amp, pre-amp,source?Then second and third? When turning your system off what should the sequence be?
Source, pre-amp, amp, then the reverse for turn off.

Agree with TIC. The reason is you don't want your power amp on if any other component happens to send an impulse down the line, even a surge from a power on. Simplest rule is: amp on last and off first.