I experienced this as well. It sounds great hooked up to a speaker, but I tried going to an external amplifier and there is an audible click or pop at the beginning and end of each file played. I also noticed a little buzzing while playing, but maybe I only heard it because it comes out much louder.
Did you ever get this fixed? Has anyone else had luck hooking this up to an external amp? (Lepai mini amp, which sounds great when I hook my phone up to it)
BTW, all I did was hook up the SPK+ and SPK- pins to some RCA cables which go into the amplifier. Is that correct or should they be hooked up another way?