[Darryl Ramm]

So far you've isolated it to the Eleven Rack or the environment. Have you tested with a different high-gain guitar amp in the same environment? Sounds like standard run of the mill pickup noise to me. That happens when you palm mute because you (the player) is behaving as an antenna. proper grounding of the guitar cable and grounding inside the guitar is important (e.g. on a Stat type guitar make sure folks have not broken off the bridge ground cable when messing around with changing trem springs). If you've tried multiple guitars this should hopefully not be the problem. What pickups are in the guitars?

So while just suspect this is really just environment/input noise, but just in case...

What revision is the Eleven Rack? (earlier revisions had a grounding issue on the front panel output to amp jack-only an issue if you use that jack). You can search for those old threads on this forum.

What amp are you driving? (via main outs or output to amp). Describe exactly what is connected to the Eleven rack over what connections. If you unplug all external amps, computers, just have a guitar connected and turn off all nearby computers and florescent lights (or any that are not "nearby" but on the same circuit. Make sure nothing is connected to the FX loop and the FX Loop block is disabled. Do you heat this noise in a pair of headphones attached to the Eleven Rack? Do you hear it when the guitar is unplugged? In extreme cases of tracking down pickup noise I've turned off every except one power circuit to a house and made sure that the guitar amp (Eleven Rack in this case) was the only thing on that circuit and then went turning on other circuits to find the culprit (A CFD light hidden in a closet in one case). Guitars can also hate odd things like refrigerators. You have to just play around.

Darryl