Newb qu. re: amps and impedance

[redrich2000]

Can someone explain this to me. I thought the rule was the higher the impedance the harder to drive, hence for unamped portable players 80ohm cans are recommended over 250ohm.

However researching tube amps I keep coming across statements like "The advantages of the EarMax Pro include a slightly higher output level, more robust sound and the ability to drive lower impedance headphones such as Grados."

??? Thanks

 

[EdipisReks]

it works this way, basically. low impedance phones require high current levels and high impedance phones require high voltage levels. tube amps have an easier time producing voltage than current, in general. when unamped (like with an ipod, for instance) low impedance phones tend to be harder to drive well, but they are easier to drive to loud levels.