Woody wrote:
A mistake that many people make with lo-Z headphones is to run an amp
straight into them and then wonder why there is so much residual noise.

The easiest method is to use a small power amp such as a LM386 or
TDA2003, then put a resistor in series with it - something in the range
330-470R will usually suit. You will probably end up with a far more
acceptable result as the amp is specifically designed to drive audio
rather than just a general purpose amp.

That's an impressive damping factor.
I wonder how the frequency response of headphones changes when
current-driven
rather than voltage-driven.

--
Eiron.