I have struggled with this type of issue for ages.
I got really close to getting it handled. Every time I readjust my instrument set up, it’s the same troubleshooting procedure each time.
I’ve solved for ground loops, spent more than a grand on a solution. Still sent it all back.
I had a lot of success with a groundless power supply. In fact, the results from adding DI’s, stage bug, ground lifters, an isolation transformer, and even isolated psu’s, didn’t come anywhere close to achieving the same thing a 13 dollar PSU did.
I changed my set up again, reconfigured everything, threw in a massive power conditioner, and the noise is back.
I know there is something in my setup causing an issue. However, if I don’t use a mod device, the issue goes away.
I haven’t figured out what’s going on, why it changes during my gear refresh (even after accounting for the new variables), or if it is actually MOD related.
The noise seems to be hit or miss for people. I know I get noise from my dwarf far more than from my MDX, I even use the same power supply.
The noise gate stuff can be useful, but the ground loop compensator did absolutely nothing for the issue.
Looking at my dwarf unit, I have the kickstarter branding on the underside, even though I paid full price through reverb. So my dwarf is probably refurb, and the noise issue may be related to that.
I took a B-stock MDX at “full” price (aka accepted a plugin coupon) and the unit is far cleaner audiowise than my dwarf is, but seems to be sensitive to my other powered gear.
I’m a synth person if that helps, my gear is already powered and produces Line Level audio, and I’ve come to terms with the fact that my gain staging needs special attention.
You aren’t the only person with the issue you are facing, but mine is non critical because I am no longer recording or posting online for a while.
For others, like yourself, this is a far more critical thing to address imo