Originally Posted by ascherjim
If I recall correctly, the Predator and Pico are portable USB amps that take in the signals they process (converting them from digital to analogue then amplifying to headphones) through their USB ports, the initial signals of which usually come out of the USB ports of their computers. The portable DVD/CD/MP3 player we are talking about here can also function as such a digital-signal source, similar to a computer, but whose digital signal for processing is accessible from its coaxial port, not from its USB port (which is solely use for inputting MP3 from a flash card). In other words, this DVD/CD/MP3 player in this instance is a digital signal source. not a processor. (Of course, it also -- and primarily -- is a source for an already processed -- but inferior -- analogue signal, which you can access directly with your headphones.) If you want to use a Predator or Pico with this, you'd have to get an adapter to plug into the USB ports of the Predator or Pico so as to plug into them a coaxial cable from the DVD coaxial port of the DVD player. Such adapters have been discussed frequently elsewhere in this forum.
Further to my last posting, you might want to consider acquiring an iBasso D1, if you can locate or wait for one. It has inputs for all three digital methods -- coaxial, optic and USB.