If the manufacturer does not offer to eliminate the issue - and it IS an issue - or if they refuse to replace the defective amp, then return it immediately. You should hear no hum from the transformers of a new amp. I have (reluctantly) discarded products that over time have developed a pervasive and musical enjoyment-destructive hum in the transformers. As I understand it this is not something you can fix other than replace with brand new transformers. If you hear it now with brand new transformers, imagine what it will be like as those transformers age.
How much hum is normal from a new tube amp
I just bought a great sounding Lab12 Suara KT120 tube amp. The issue I am having is a hum that is coming from the transformers. I can hear it with no music playing faintly from my listening position 12 ft. away. The question is, should I return it, or is this normal acceptable.