KAB RF-1 subsonic filter

KAB recommend install the RF-1 between the phono stage and preamp

I've tried the filter installed here as well as between the preamp and main amp (which is where it currently is), no difference I have been able to discern with vinyl and digital sources sound no different as well. 

That said, just to appease my OCD, I likely will put it back in the phono to pre line as to not have one more variable in the line with other sources. 

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. 

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.

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.

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

They do. 

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

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. 

It should go between your preamplifier or linestage and the amplifier(s).  I took a quick look at a photo on-line.  Looks like you have a pair of female RCA inputs at one end and another pair of RCA jacks for output, at the other end.  Unfortunately, you will need a second pair of ICs to use on on side or the other of the RF-1, as opposed to the single pair needed to connect a preamp to an amp.  Got it?  I would have thought these very simple instructions would have come with the RF-1 from KAB.