Pop sound when switching on / off Pass Aleph 30?

I'm running an Anthem Pre 1L with Aleph 30 power amp. Speaker is ProAc Tablettle 50 Sig. I notice that when I turn off or on the Aleph 30, there will be a audible "pop" sound from the speakers. I wonder if this is normal else will this damage the speakers in any way?

Advice needed. Thanks.