Power Station PS-2A hum

[stephensawall]

Maybe it is this ?

Audible vibrations from transformer to case cover?

Yes, that’s normal. This is the big transformer in a small box syndrome. All transformers make noise. The box they are housed in determines how noticeable that noise is to the user. A big box made of wood will absorb a lot of this noise. A small steel box will vibrate in sympathy with the magnetic field generated by the transformer. The bigger the transformer, the more it will “excite” the steel enclosure. The PS-100 has an unusually large transformer relative to the physical size of the unit…