Low freq. rumble????

Recently I have returned to analog. I purchased a Music Hall MMF-7 with the HO Goldring cartridge. Everything sound great, until I try to turn up the level to around 90-95db. At that point, I get a low frequency rumble (I don't think it's feedback, as it only occurs when the cartridge is tracking a record).
I've tried TTWeights ISO feet under the table, and have now added a Ginko platform. Nothing seems to help. It occurs not only during the track, but is really evident during the lead in tracks.
The table is on top of the Ginko, and the Ginko is on top of a Mapleshade Samson rack.
Any ideas what coyuld be going on, and what to do to get rid of it?
In advance, thanks for any suggestions you may have.
..sounds like the wrong cartridge for that player..

KAB Rumble Filter is your answer.

I had major, major problems with woofer pumping until I got one.

This completely neutralizes rumble, and it won't affect the sound.