Many power distributors overlay the basic 50 or 60Hz mains frequency with control signals of higher frequency. Power supplies in equipment normally filter these out but, given it is a location based issue, have you checked whether it could be affecting you? It can cause transformer buzzing as well as other things. You might need to borrow a mains conditioning unit to help eliminate this factor.

Cinema/Music: Trinnov Altitude32 8-16,218,Cloud 4 channel, Marantz UD5007,DSP5200SE(2+C),DSP3300(4),DSW(2),271,MShort Ceilings,AppleTV 4K
TV: Marantz SR7013 Wharfedale Diamond 9x4+Celestion(C)
Music: Roon,i7NUC8gen,QNAP TS253A, Sony Scala, MS200, Garrard DDQ650,Wharfedale Diamond 12.3
Kitchen: AD88 (bluetooth via i80).