Audio hum when monitor connected via Core X is active

Mac mini 2018, Core -x, Radeon Vega 64, any connected monitor. Any activity on that monitor, or on any other monitor I connect via the core-x will cause an audio hum on my power speakers when connected via copper ... analogue or USB. There is no hum if I connect my speakers via bluetooth (but that his not how I wish to connect for the quality of audio implemented. Activity ... paint a window, move a window, resize a window ... all case a hum on my speakers.