KAB RF-1 subsonic filter

The reason you want to do this is, whatever noise the filter makes will be attenuated along with the signal if the filter comes before the volume control. But after the volume control, the signal will be attenuated but not the noise! The signal to noise ratio will decrease along with the volume.

Yes, exactly. If you have a separate phono stage put it between the phono stage and preamp. The KAB then will have a consistent input and it will be less likely to be overdriven into distortion. You could also place it in a tape loop if you have one.