Is the noted sound with all front end devices? Is it more pronounced with digital or vinyl? The reason I am asking is, I use to have a Technics SL-1700 w/Denon DL-160 cartridge and in that configuration with my related gear, I had a lot of rumble. I searched rumble and found out it was low frequency noise originating from the TT. What happened to me more than likely is not your issue but it is a shot in the dark.
Good luck
Good luck