I can crank the volume on 97db sensitivity speakers, with no signal running through them, and can't hear anything plugging the charger in or out in the first stage or pulse mod that it has.
And I have to crank it for a long time to get it out of that stage (all day long and then some).
Then if I were to have it unplugged, and I did leave the buffer on, then it might take a week to run it down to 11 volts. Batteries are cheap. My two 100 amp hour batteries cost about the same as one good power cable.