Long story:\n\nI bought these R1900TIII in 2015.\n\n\n\nhttp:\/\/specsan.com\/computer-speakers-edifier\/edifier-r1900tiii\/\n\nImportant note: My city has 220v power outlets and the speakers are 110v, so I've used a simple voltage converter (100VA) since always with them. The speakers do not have a ground pin.\nThey worked fine for a year in Apartment A. They are active 2.0 speakers that connect to each other using one of these:\n\n\n\n\n\nI connect them to a TV through an RCA cable, since I use them for listening to music and watching movies \/ playing games:\n\n\n\nIn 2016, I moved to a house. Let's call it House A. No problems here either.\n\nIn 2017, I moved to House B. Again, no problems with interference whatsoever.\n\nIn 2018, I moved to Apartment B. The apartment is right next to an radio station antenna the size of the building itself (a 13-story building). There were extremely high levels of RFI (I could literally listen to the radio station). I mitigated the problem by using ferrite beads around the cables.\n\nNow, in 2020, I moved to Apartment C. Here, there seems to be 2 different kinds of interference messing with the speakers.\n\n- The first one is a high frequency interference that happens on both the active and the passive speakers, but ONLY when I connect them together. If I connect the active speaker alone, even if I connect the RCA cable to the TV, it doesn't hiss. If I roll the active-passive cable with ferrite beads, I can almost eliminate the hissing in the active speaker, but it only mitigates the problem in the passive speaker. Is there any kind of shielded active-passive cables?\n\n- The second one - which bothers me the most - is a low frequency hum that happens occasionally. It sound like when you disconnect the RCA cables with the speakers on. I suspect this is a problem with the electricity of the apartment, but I can't confirm that. That low frequency hum happens even if I connect only the active speaker in the outlet (no TV, no passive speaker, no computers).\n\nI haven't got any clues as to what to do. I'll ask a electrician to take a look, but my hopes are low about that. I'm considering to get a isolation transformer too, but I guess that could only potentially solve the low hum. I'm also considering to take the speakers to a technician.