How to hook up headphone amp?

Hi,  I am hoping someone can advise how to hook up a headphone Amp to my Jadis integrated please.  My Jadis has not been very reliable ( very expensive) and I'm terrified to cause a problem.
Basically my Lehmann headphone Amp has two rca inputs and a volume knob.  My Jadis has a tape loop, preamp CONNECTIONS AND A tape / source switch on front panel.  Switch on rear I think goes to preamp inputs.  I can't figure out how to attach the schematic and photo of inputs to this post which I know is needed.   Many thanks.  Andrew.