Making phono resistance plugs

@coachpoconnor,
I think you need to contact Whest to determine the proper resistance value of loading plugs to use with your PS.20. I just looked up the PS.20 Operating Manual, and that is what it advises. Since none of us know the internal resistance of the PS.20, and whether the plugs are in series or parallel to the internal signal path, we can’t help. If you have a multimeter, you could measure the resistance of the plugs used for 100 ohm loading. If we know that we could help you get to 400 ohms.

@lalitk 
My phono pre also has the large step from 100 ohm to 1000 ohm loading. I tried a Y-adapter to add parallel loading plugs, but decided I like the Audioquest “Hard RCA Splitter” better. See https://www.audioquest.com/accessories/splitters-connectors-adaptors/adaptors/hard-rca-splitter-male...
I use a resistor about 1000 ohms in parallel with the 1000 ohm setting to get to about 500 ohms load resistance. I made a bunch of plugs to try various loading between 100 and 1000 ohms, and settled on the 500 ohms loading.