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
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.