Question Annoying mains hum problem.

[Friesiansam]

My wife has an Asus Xonar Essence STX feeding a Sennheiser BT100 via a headphone extension cable, this sends to a pair of Sony WH1000-XM3s. I believe the cable is picking up a mains hum. We have tried to route it away from power cables but, with only limited success. The cable is the one supplied with the headphones, would a better cable, or a clip-on ferrite suppressor be likely to help?

 

[Friesiansam]

Received a suggestion elsewhere, going to get an optical cable. should be problem solved.