Ever since I've owned an iPod I've wanted a companion headphone amp like the Headroom Total Airhead. Never able to justify the cost and added weight to my already back breaking commuter kit, instead bought nice headphones, Ultimate Ears Super.fi 3, that work well with an iPod's internal amp. Still, my itch for an amp remains.
If I have an itch then this DIY headphone amp mad scientist has a major skin infection. First, he has over 130 different compact headphone amp designs. Second, many of them fit into small mint tins. Third, the Hybrid designs use tubes either hidden in the tin or poking through a die cut and lit with a colored LED light. Lastly, he has circuit designs for all of the amps so the possibility exists that a lowly hobbyist like me could construct an affordable DIY amp with caps, bread boards, headphone jacks and tubes from The Parts Connexion and batteries and Altoids tins from the drug store.