crackling issue has been solved by the software update.

  update to the latest ..BMEA firmware , no more cracking sound on the sgs4 (i9505).

i can confirm that the issue of the sgs4(i9505) has been solved by the ..BMEA firmware update on the s4. I used to hear that crackling sound with my senn cx400(16ohms) on full volume. upon updating, no more crackling sound:)