I have Bose AE2i headphones which were designed to fit into Apple products which support TRRS. But I would like to use these headphones with my new Desktop which has 2 x 3.5mm ports, one for mic and one for headphones in TRS form. So is it safe to plug in my TRRS 3.5mm Jack into the headphone port? I accept that the mic won't work though.
any time that you have a break in a line (a splice or connection of any sort) there is always some quality loss.
for example if you had a cable running from device to a wall plate then a cable from the wall plate to another wall plate then from the second wall plate to a device thats 3 different cables and many connection points. the chaces that you have signal degradation, static or distortion is quite a bit higher. a single wire would only have two connections (one at source one at end destination) so wouldnt have the distortion.
with that said... generally you only notice degradation when you have quite a large number of splices or connections. with only a single splitter cable being used there is still degradation (there is ALWAYS some degradation of some sort) but its not going to be noticible at all. especially not if you have a decent cable with decent connectors.