Good question!
To be 100% sure that the right polarity is guaranteed from the wall outlet over the power strip to the device, you need one of these phase tester:
You call a technician who checks the polarity of the wall outlet with the phase tester.

Insert phase tester into the wall outlet and press the red button. Where the light of phase tester goes on, this is your L phase (Live Wire).
Mark the L phase with a dot.
Do the same with the power strip.
Some power strips have already markings for the L phase.
Nevertheless, you must check again the polarity of the power strip if it coincides with the markings.
If polarity is reversed, then unplug the strip from the wall and twist the Shucko plug by 180 degree. Now polarity should coincides with markings.
Now the power strip has the right polarity.
Go to the wall outlet where the power strip is plugged in, and assign/transfer the marking from the wall outlet to the schucko plug of power strip. So the next time you unplug and plug again, you have the right polarity.
Do the same procedure with the power cords from the power strip to your devices.
By having the right polarity from the wall outlet to your devices you can increase sound quality.
If you have a fuse with direction
Insert the fuse into the fuse holder with the right direction