Thanks, Good to rule out transformer.
FYI, there are no audio cables attached during my testing, it's just the speaker connected to mains.
See vid attached in link (you may need headphones to hear the"hum").
https://1drv.ms/v/s!AmC_jh877FTgkQcBxq7zgj-LnO0U
Am I being too precious/unrealistic...