Kondo Overture PM2i - buzzing noise from transformer

Hi to all, 

could anybody please share their experience with Kondo amplifiers concerning noise from transformer.

I experience a little (but disturbing) buzzing sound coming directly from the left transformer of my Kondo Overture amplifier (no noise through the speakers, but directly from the transformer itself).

In a quiet room and when listening at very low volume, you can hear the buzzing noise at the seating position 2-3 meters away from the amp...

Thanks in advance for sharing any experience with Kondo amplifiers.

Best
Robert