I haven’t had any issues with hum, but I’ve used one of the original red label adapters mostly. I don’t know of a way to ground it. The original doesn’t have a ground either. It is falling apart and so far what I can see on the insides is a cap and a transformer. I have 5 of the red label. I think I have an obsession with these little portable amp from the 70s and 80s! I snagged a non working Dwarf amp, traced the circuit, then figured out it had a bad IC. Was able to find the IC, amazingly enough, and get the little amp back up and rockin! I think it’s 8 watts and can be powered by battery and it also has an AC cord(no ground).
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