K4040 with iPod, iPad, iPhone, etc as input

Please can you advise if the K4040 can accept the headphone output of an iPod, iPad, iPhone, etc directly. If not what would be the best kit (or module) to use as the interface. The objective is to achieve the highest possible quality sound output.

It is possible but you can’t use the K4040 at full volume because the output voltage of the i-things is too low. You need a preamplifier like the K8084 or similar.
By the way: achieving good sound quality starts with a good sound source and i-things are not good sound sources, neither are songs downloaded from iTunes and so on.