Will the Karma (or the empeg, for that matter) drive full-size "studio-style" headphones, or is it only powerful enough to drive the little earbuds? In particular, will it drive noise-canceling headphones?

For that matter, do the studio-style headphones even require more power than the earbuds?

tanstaafl.

All the noise-canceling headphones I've seen require batteries.

Larger drivers do like more power, but I doubt there are any devices that would fail to drive even the largest headphones; they just won't sound as good as they could.

There are a number of places that sell headphone amplifiers, even battery-powered ones. (for example)

Depends a bit on the impedance. High impedance (>100 ohm) headphones will be quieter - eg some really high end ones are 600 ohm and require a lot more voltage swing to drive them well.

The Karma has about a 3v p-p swing on the output. I use it with Sennheiser 691's without a problem, loud enough for me... I think these are 64 ohm.

Hugo

Doesn't the Karma use the same Wolfson WM8731 headphone/DAC (CODEC) combo IC that most of the recent iPods had been using? I believe these provided 50mw at 16 ohms impedance which works great for Grados but not so well for 300 ohm Sennheisers like my HD-600. If mated to my iPod, I get fair volume and bass, but nothing spectacular.

Stu