I use a subsonic filter, -3dB at 8 Hz., 24dB/octave. I use it when I listen at loud volumes. It can be switched in or out through a tape monitor type circuit.
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I do not use one or needed one. Haven't had that problem in about 40 years. As the quality of my turntable went up. Typically it is a resonance problem with your turntable or compliance mismatch between tone arm and cartridge. Perhaps there are some other possibilities. But look at your turntable and setup to find the problem. |
+1 best to chase down to eliminate the feedback than to try to filter it out
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Most "audiophile" phono pres don’t make this a switchable option, or really even make clear what they’re doing. The original RIAA spec is flat to 0Hz. Some stages probably use this. RIAA IEC modified this to add a high pass at 20Hz. Other stages probably use this. The IEC spec is not a very steep filter - definitely helps a bit, but it’s not going to save a bad configurations on its own (bouncy floors, crappy racks, subwoofers nearby etc). The KAB Rumble filter is a different beast and much much steeper than IEC or anything I’ve had built-in to a phono stage - it can in fact save bad configurations. The question is whether you find it sonically transparent or not for audible frequencies. That said if your woofers are flapping wildly, no question it’s better to use a KAB until you get the mechanical issues under control - which ideally you would do anyways. Electronic fixes are more of a band-aid. |
My Boulder 1108 does have a button. It's described as a 3-pole (18db/octave) low cut filter, with response of -3db at 10 Hz. When I asked a former Boulder tech person about it at my dealer they told me I shouldn't need it under normal listening circumstances. I have yet to find a use case where I feel I even need it. Record warps are inconsequential to me since I use a 750 gr record weight and 1500 gr peripheral ring. That's enough weight to make Dolly Parton flat. |
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