I had the same symptoms. My problem was low frequency feedback. The final solution for me was using 30 foot long interconnects between the phono pre-amp & pre-amp, which allowed me to move the turn table well away from my speakers. Playing with arm setup & platform weighting & floor mass loading etc. would effect the problem & may be good enough to fix the problem in your case. Others have had great luck with wall mounts for the table. If you think you are getting feedback through the floor you should be able to verify this by pushing down on the table with your thumbs, this should reduce the rumble (but it ain't a comfortable way to enjoy the listening experience). Good luck!