Low frequency problem while playing vinyl

Dirty bearings? Warped records? London recording of Tales of Czar Saltan?

Rumble or not, it's still feedback. The primary issue is not on what, but where the tt is placed in relation to the speakers.

Thanks for your responses. I did some more testing to locate the problem. The low frequency signal seems to be generated by the phono pre amp (VALVET soulphono MM/MC tube phono amp‏). With the phono pre amp hooked up to the pre-amplifier (Krell Evolution 202), without the turntable connected the woofers go crazy when I turn up the pre amp volume.

I suggest getting rid of the problem rather then covering it up with a filter. Linns do best on very lightweight small tables ( probably the Dual too). The next thing to think about is the cartridge/arm compatibility..you don't mention the arm or cart. A major mismatch here would actually make the cartridge mistrack you don't mention that. These large subsonic excursions are caused by waves...many times the front of your supporting table will move differently than the back. If your table that supports the turntables are close to the wall, either anchor the table to the wall, or put a prop between the table and the wall to prevent the table from moving inappropriately....I would try these things first before clamping down your system with a filter.