Touch & Turn noise when adjusting analog gain

Hi everyone

I happened to be comparing microphones and noticed as I adjust the analog gain there is a slight noise as I turn the rotary. The noise level is consistent regardless of turning up or down and is there even if a microphone is not connected. I tested this on the surface and mixrack inputs and I get the same result. There is no noise with Trim.

Has anyone encountered this and a solution?

Regards
Brian

this is how it works, it is a stepped gain, and each step makes a little bit of noise
in normal situations it is not audible