No audio, so I can't hear what voltage(s) are being applied.
With that being said, I have used a bench supply set at five volts DC through a homemade adapter that tells the Galaxy devices that it is a 2 amp power source to charge with. This works with GS4, GTab2, GTab4, and GS7E. Obviously, I don't get quick charge this way, but it's still faster than plugging into my computer...