Isolation transformer for laptop charger?

I assume the MacBook charger is a SMPS which are known to be very noisy.

Unplug the charger, use the internal battery of the MacBook Pro play some music and see if you can hear a different.
Maybe a LPS?
https://www.computeraudiophile.com/forums/topic/17840-linear-power-supply-for-a-macbookpro/

@imhififan,Thanks for the link and the suggestion.  The MBP should run quietest from its battery I would think.  if it makes a difference then all I need to do is remember to disconnect the charger when listening to digital files, and more importantly, remember to reconnect it when I'm done!  I own several isolation transformers but use only one to isolate my preamp.  I found that it works best in this location.  Adding additional ISO trannies to other components was detrimental to the sound.  Nevertheless I am fascinated by these devices. 

detrimental?  when used on the amp?

maybe they aren't sized correctly?

If this means that the "hot" slot is consistently the shorter one (across all outlets used for my audio system) then I can get a "polarity tester" and check it.