Any loose bolts on the power transformer?
That's the low hanging fruit. If you press on the transformer, does the hum stop?
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.