I bought one of these Comsol 3.5mm Splitters from Officeworks recently. Hoped it would duplicate an audio output to use on two devices, but it turned out to approximately halve the output level and muddied it up considerably (bass in particular sounded terrible). My fault for not researching first, but it is a little annoying that the advertisement or specs contain nothing to suggest how limited the device is.
In the scale of audiophile-ness, I'm a long way down the ladder, so if I can tell it's bad then it's must be really bad. (Maybe I was expecting too much?)
Do not recommend one of these at all.