popping noise

Your On sequence is OK but when turning Off the sources will often send a pop or spike. Since your preamp and amp are still On you may here a spike from that. However if you are getting the same pop during your On procedure I would have the amp checked out. There is usually a small cap across the power switch inside the amp that keeps the momentary voltage arc at the power switch from causing a pop at turn on.

tube gear - could be a tube going bad or older capacitors going bad.

Reasonable probability that you are hearing noises from your sources as they shut down. General rule of thumb would be source-pre-amp for turn on and amp-pre-source for shut down.

To add to the above responses.
On startup allow a minute before turning on the amp. This will allow equipment upstream to settle down.

On system shutdown turn volume down on preamp,
turn off amp,
wait at least a minute for power supply caps to bleed off,
then turn off preamp and input source/s.

You could also check to make the amp is not causing a pop by turning on the amp only, wait about 10 minutes and then turn off the amp. You should not hear a pop.

Thanks to all I will check it out
pete