Sorry to disappoint you but the DX50 does have DC coupling caps on both the HO and LO for a total of 4 caps, one on each channel. You can use 200 uF cap replacement (that is the electrolytic value on those caps), may I suggest some of film variety? You may be able to find supercaps rated at or a higher level, that would work even wonder. Just remember that hand soldering is a must and they are really tightly placed close to each other so the space is rather limited. Don't bother calling iBasso if you DX50 dies after the caps have been replaced unless you are skillful enough to move the older caps back with shorter leads in place.
Thank you, I just saw the PCB photos now. 4x 220 uF / 10V electrolytic THT capacitors. On the bottom side are even two more (golden color). It looks like the silver ones are 2x 2 pcs in parallel for L/R headphone out, and the golden ones could be for the line out.
I think these 440uF per channel are big enough for the Headphone out and the bass extension won't be much better with bigger caps (sorry, i'm too lazy to do the calculations). Foil caps you won't find with a high capacitance that fit inside the case. You could shorten the caps and build an extra adapter cable outside, but never ever forget this adapter (and maybe the relay will not even switch on if it is part of a DC-Protection circuit).
This soldering work is not a problem for a experienced solderer.
good luck IceOgre
Edited by cholero - 5/26/14 at 5:03am