Interconnect between h-phone amp and integrated

It depends on the output impedance of the integrated amp output that you are connecting to (the lower the better), on the capacitance of the interconnect cable (the lower the better), on the susceptibility of the two components to ground loop effects (which is unpredictable), and on several other variables. In other words, it's not possible to give a general answer. The most likely symptoms, if there is a problem, would be upper treble rolloff, sluggish transients, and/or hiss and noise.

Regards,
-- Al

My experience (if you can do it that way) is to keep the headphone amp near your integrated, and then use a longer high quality headphone (extension) cord for your phones.