First, some background: I am a mechanical engineer who has some experience with electronics, circuits, etc so I can understand basics but simple things like this elude me. What causes the hiss you hear from audio outs? The source is circuitry because as soon as the component is powered it...

I'm a bit of a newbie but looking to get into things more. Most of my music is flac or ogg 320 kbps avg with some mp3's mixed in and I have some decent headphones but I lack anything good at the portable level. I'll be on a 9 week bike tour across Europe this summer and want something portable...