Floating ground ?

[Username1]

If the home has knob and tube wiring .................

I would worry more about this little bit of funky wiring, and the possibility of
FIRE and less about your electronics.....

And looking at my own house, and some of the stories on VK about house wiring
It does not matter what the code is, what matters is WTF they actually did....
And if the stuff made back then has any surprises yet to show themselves
because you may put a greater demand on them than what previous owners
may have......

.