Hum is one of the most annoying things to eliminate. Going through the PS Audio process is definitely recommended to establish if there is a ground loop issue and if so how to cure it.
Sometimes I've found that hum is caused by EMI interference where the shielding on interconnects is not sufficient to eliminate such interference. If EMI is the cause then usually (i.e. not always) moving interconnect cables marginally (for example away from amp transformers or from power lines or not running parallel to power lines) can eliminate hum.
On your TT are you running a grounding wire back to your preamp/amp?
Current: [P20] Roon/Tidal > Custom PC> Chevron Paradox NDF16 > Phast Pre > Neuro. 686 > Tannoy Berkley (RFC tweaks)