are any of the LEDs blinking in your setup? like a button set to tap tempo or something? i found that turning the LED brightness down to minimum pretty much eliminated this sort of noise. also, you may want to experiment with different screen brightnesses… this can also help a lot with background noise, not related to power or groundloop issues.
see…
https://forum.mod.audio/t/noise-rendering-mod-duo-x-unusable/6018/28?u=plutek
…and…
https://forum.mod.audio/t/duox-noise-and-screen-brightness/6281