If you have a way to connect by DIN midi, these are much less susceptible to noise than usb midi. I’ve read about this, and it happens with my little phatty, usb connection gives low level buzz (although exeptably low so useable) and when connecting by DIN is silent…
Ground noises are tricky to isolate and are effected by most every connection in the studio. Even though the noise happens when connecting the usb, I’m not sure that means it will be solved with the usb connection? The noise comes up when a device finds a shorter less resistance path to ground and uses that instead of it’s regular ground… Gets tricky with computer, interface, mixer, gear, and various connections in between all…
Anyway try DINs if you can…