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. 

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Hum should only be audible when you put your head about 6" or so from a speaker cone with volume set to your "normal" listening level.

If it's audible from normal listening distance with your volume pot set to where you usually like to listen, something is way wrong.  

Could be grounding issue among your components in the chain, or some problem with the internal electronics of the amp.

I've had two tube power amps with KT150 tubes in my system the last few days and neither had any hum whatsover.