Late to the party here, but I would also like to know if this is standard behaviour? I use mine as an external effects unit for synths etc in my studio. The hum isn’t super-loud but is a bit annoying, to the point where I bought a second unit second-hand (as I thought the first unit was damaged). But I have a similar hum from the second unit. Is there a quiet transformer that could replace the one it ships with? If there’s a way to fix this I would love to know, thanks!