Originally Posted by Ian
I've got a feeling that I may be hyper sensitive to low frequency hum.
Me too. One the reasons why I got rid of my Naim amps - 4 of them hum quite loudly. I did find that the hum level varied from day to day which may reflect differences in the quality of the mains supply. A Bryston amp which has a DC filter built in was silent even with its substantial toroidal PSU.

Main system - Sources (Kodi-HTPC, Vero 4k, FireTV, Sat) into Trinnov Altitude 32 (8-16) (+Roon), Trinnov Amplitude 8 amp & Vivid Audio (Giya G3, V1.5) and REL Stentor III speakers. Others: F80 + Raspberry Pi and other Pi systems.