Xpantastic!

Oh, sorry, did you say that your Xpander is humming even though you don't have any loadspeakers connected and all other gear then the Xpander off?!

I think it is then only the power unit that is able to hum like this and it would require to be replaced. (Can be a fire risk, if you don't.)

Have you tried to connect it in a provenly correctly grounded (three wires) wall plug? And, also, tried in the both orientations of the plug?

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