Thanks AnyDave, and the idea of using a adjustable resistor set to 78ohms would then perhaps convert the ER4PT's to ER4S sounds okay?

Hi AnyDave and thanks for the quick response! So the closest I think I can find is this which is 22 ohm resistance, but appears to be "2.5mm TRRS Balanced Plug" but then says also they can do 3.5mm. I can contact them to confirm that but otherwise would you say this is appropriate...

Hello, So I'm 100% noob when it comes to the technical side of thing. However I know that I love the sound of my ER4PT's in my Sony NWZ-A15 on the go and at home with on my stereo when converted to ER4S with the "ER38-24" P to S converter cable. However, I've had these a just under a decade...