popping noise

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

This happen quite often with Integrated amp.
I think the sequence go like this :

ON: Cd player 1st, Preamp and then Amp.
Off : Amp 1st, preamp and then CD player.