[Sardonyx]

This might be a silly question, but here goes:
There is a common theme that bus powered amps lack power for high impedance headphones, battery is usually better, even though not as good as an AC powered desktop amp.  So I am wondering if the limitation is USB's voltage or current?  What if you used a Y-cable like this:
http://www.amazon.com/Cables-Go-28108-Y-Cable-Black/dp/B0013LSFJI
to supply more mA? 

 

[Nebby]

5V 500mA is the standard and normally it's the voltage that's the issue. For all the effort it would take to maybe-kinda-sorta get something workable, you might as well get a normally powered amp.