That's one of the downsides of having a quite sophisticated TT with air bearings, vacuum pumps etc. etc.I have reported to my dealer & he is seeking advice. No tech available in my small city. I am the tech
My investigation revealed that the power / pump unit is vibrating. Drive motor is vibrating / some noise. Mostly as a result of this, the vibration has been transmitted to the main platter unit and the less welled damped arm in the GM3 it manifests as an undulating hum.
Started with the thinking that it is the PP2000 but ended up realising it's the AF3P![]()
One of the main reasons I bought the Kuzma XL DC (as well as it's looks and performance) is for it's ultra simplicity, solid engineering and less to go wrong.