KAB RF-1 subsonic filter

If your amp/preamp has a tape loop, you can attach directly - that is the best option.  Otherwise as Lewm suggested, you will need an extra set of RCA's. 

Thanks guys. Hooked it up between pre and power amp and it is working. No more woofer pumping.

 I would have thought these very simple instructions would have come with the RF-1 from KAB.

They do. 

I thought KAB recommend install the RF-1 between the phono stage and preamp, so the RF-1 will be out of the chain when playback other sources.

https://www.kabusa.com/frameset.htm?/rf1.htm

The KAB RF-1 is easy to install. Place it in between the phono preamp and control amp or in a process loop.

Thank you for doing the necessary research, imhififan. I don’t doubt that you’re correct. What you write makes perfect sense in the case where one owns a separate phono and linestage, especially since it comes from KAB. I hope the OP reads your comment.