I know exactly what you mean. The Superego is such an odd and interesting pedal, but that is such a hang up for me. My blues junior already has the expected amount of hum going on and this added noise is such a headache. Wasn’t sure if it was just me so I’m glad I saw your post! I tried powering it off a daisy chain and by itself with a boss psa adapter (same as the 9.6v power supply that comes with the superego). It seems like it’s going to produce that noise no matter what. I don’t have an isolated power supply around so I’m glad your post helped me to rule that out as a possible fix.