My Shure SRH440 has a very low, poor sound when I'm using my MP3 player (Ipod nano). Since the sound gets much better when I connect it to my Receiver (a Sony one) or even to the computer, I think that using a headphone amp could be good.
So, what characteristics should I look for in a headphone amplifier? I'm not sure if suggesting specific brands / models is allowed in this site, but if it is, does someone have some recomendation ???