As long as you don't hear weird sounds when there is supposed to be silence you need not worry about it.
The easiest way to test for minimal mains leakage (that's basically is what it is all about) is to use a cheap voltage checker with LCD scale.
something like
THIS
It's the same I I used in the past.
Put each component on a table completely disconnected from every thing.
Connect it to a wall socket without safety ground.
Switch it on.
Put the screwdriver point on the RCA outer jacket and hold the special pad on the screwdriver.
There will probably a voltage being displayed.
Remember the reading.
Now rotate the mains plug and repeat the measurement.
See if the reading is lower or higher in voltage.
Lowest value is minimal leakage.
When the readings are about the same it doesn't matter how it is in the wall socket.
Below a picture of me doing this
Mark the mains plug where the lowest value is shown.
Check the wall socket with the screwdrivertester to determine what is phase (has mains voltage on it) and neutral (no to low voltage on it)
The procedure is
shown here as well.
Do this for all devices.
When done connect all devices to each other and you are done.
What does this do ? Now you have the lowest possible mains leakage. I found that when gear is connected this way you aren't bothered by 'ticks' caused by switches of other devices. When leakage currents aren't on its lowest chances are you can hear 'ticks' when something in the house switches on or off.
You don't have to do this to improve sound quality. It will change NOTHING in this aspect. The only benefit I experienced is better imunity for the mentioned 'ticks'.
When you do not experience this leave it as it is and stop worrying.