The old Audiocontrol C-101 equalizer has a Rumble reducer button(Low frequency summing) and a subsonic filter. They regularly show up on ebay and sometimes here.
Anyone wish they had a rumble subsonic filter?
I sort of do. I see my woofers moving due to ultra low frequency signal when I play certain LPs. Doesn't affect the sound, but I don't like it. Anyone have a solution for rumble, since modern preamps no longer seem to have subsonic filters? Scoutmaster on a Gingko Cloud 10 on a solid rack on a cement floor, is what I have.