My current phono preamp (MoFi Studiophono) has a subsonic filter button. I’ve always had it activated. I know what the button is supposed to do, but I don’t know if I’ve ever heard problems with rumble or whatnot on my system. Are subsonic filters meant to address problems experienced more often on more advanced systems? I currently have a Pioneer Elite SX-N30 stereo receiver running KEF Q100 speakers, hooked up to a Pro-Ject Debut Carbon DC, so nothing fancy. I’m looking at a few new phono preamps, but none of them have a subsonic filter button. Do I need that thing? I live in an apartment building, so I rarely play my music loud without headphones.