Vindanpar, I don't think that you should conclude the situation is hopeless. Are the two units plugged into the same electrical output or into different outlets? Make sure they are plugged into the same outlet. Also, try using a cheater plug to remove the HA3000 from AC ground, if the H3000 is correctly grounded itself using a 3-prong plug. The HA3000 will still see AC ground but only via the IC that goes to the H3000, and this is safe. Finally, try flipping the polarity of the cheater plug. All of these tricks will affect ground loops, if that is the problem.
If the tonearm is grounded to either unit, try grounding it to both and then try un-grounding it entirely from either unit. Same goes for the turntable.
Somewhere, somehow, there is a specific combination of grounding and un-grounding that will be the cure. But I say this on the assumption that you are hearing typical hum that arises from grounding problems, not white noise or hash or buzz, and that the problem is audible in both channels.
If the tonearm is grounded to either unit, try grounding it to both and then try un-grounding it entirely from either unit. Same goes for the turntable.
Somewhere, somehow, there is a specific combination of grounding and un-grounding that will be the cure. But I say this on the assumption that you are hearing typical hum that arises from grounding problems, not white noise or hash or buzz, and that the problem is audible in both channels.