I'm also in a 1960s Manhattan condo with about 600 units (Kips Bay Towers) Wiring aside, I did some other things that helped greatly with electrical noise:
(1) Power conditioner -- One of the best things I ever did was to get a Shunyata Hydra 8 power conditioner (w. Shunyata power cords.) Amazing improvement, like doing a major upgrade in one of the main components such as an amp. I also plug the amp into it -- no adverse effects, just better sound.
(2) Upgrade the wall outlet -- I had one of the staff remove the old outlet and install a PS Audio outlet (and make sure the outlet was grounded since some of the ones in the building weren't.) Big improvement, everything "snapped to attention" when plugged in, unlike the old outlet.
(3) Add Quietline filters. I added 14 Quietline filters to the various outlets, esp. near the refrigerator. Seemed to reduce the electrical noise.
(1) Power conditioner -- One of the best things I ever did was to get a Shunyata Hydra 8 power conditioner (w. Shunyata power cords.) Amazing improvement, like doing a major upgrade in one of the main components such as an amp. I also plug the amp into it -- no adverse effects, just better sound.
(2) Upgrade the wall outlet -- I had one of the staff remove the old outlet and install a PS Audio outlet (and make sure the outlet was grounded since some of the ones in the building weren't.) Big improvement, everything "snapped to attention" when plugged in, unlike the old outlet.
(3) Add Quietline filters. I added 14 Quietline filters to the various outlets, esp. near the refrigerator. Seemed to reduce the electrical noise.