This is a copy/paste of a question I have asked on What HiFi, in case someone here has any ideas. It's a problem I have no experience of dealing with because I've not had it before. 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?
Whilst I can't tell you how to sort it, I can offer some diagnostic steps. - Try the optical input on the BT100 - Try the headphone out direct from the PC onboard - If you're powering the BT100 from a wall wart, try from the PC - If from the PC, try a wall wart - In either case, try a USB power pack I'd suggest the optical route anyway if you can - the DAC -> ADC -> DAC signal path across three separate devices as it stands now makes me twitch.
Thanks Tad, I hadn't thought about all the processing going on there. Optical seems like an excellent suggestion, guaranteed no hum. Toslink cable ordered. So much easier with wired headphones...
A friend has it with a macbook years ago, its something to do with the USB grounding I think, he isolated it and it went away.
My old flat was bloody terrible. https://www.amazon.co.uk/Smof-Groun...96063538&sprefix=ground+loop+i,aps,252&sr=8-7
