True! And that applies for every case. Even if you have 100% isolated mains with solar or battery, you'll get 50hz from neighbours (especially apartments) and p

True! And that applies for every case. Even if you have 100% isolated mains with solar or battery, you'll get 50hz from neighbours (especially apartments) and power lines close by. I remember having this issue when working in a recording studio during college, even when we switched to battery and turn the mains off, we'd still get hum in some guitars. Funny enough I was recently reading an interview with producer Michael Beinhorn and he mentioned having some "mystery EMF/RFI event" happening in New York around 1997, coming from a specific block, and he had to relocate a recording session to Los Angeles because of how strong it was interfering with the guitar amps and other equipment [1]. [1] https://gearspace.com/board/interviews/1385579-interview-michael-beinhorn.html#vw-head-80 https://gearspace.com/board/interviews/1385579-interview-mic...