I've read in several places that you can't just swap between the S4 and S5 headrest speaker amps- at least partially in part because the S4s took a speaker-level input and the S5s a line level. Besides that though, are the connections (and connectors) otherwise the same? I'm curious because I'm hoping to keep the functionality of the center console switches when I upgrade my S4's stereo system, but it should like trying to make the speaker-level input work would be much more involved than the S5's line level, so if there's a reasonably easy way to get the S5 amp to work in the S4 it sounds like it would be an ideal solution. Thanks!

 

I get everything you're saying, and I will add that the S5 system sends a stronger signal to the headrests than the S4 system.

I recommend you download a S4 and S5 Factory Manual and check out the wiring diagrams. The pin design of the plugs are illustrated as well as what is wired to what. You should find all the answers to your questions there.

And, before you ask, there are links in the "FAQS" to download the manuals. Icemark will be very happy if you do.