Do you mean output impedance? If so, I haven't seen the specs output impedance, but I suspect it would be no higher than 10 ohms and most likely 0.5 ohms like the E11. In general, I'm not concerned because I've read opinions by people who have used many amps are still fine with 10 ohm output impedance, for example Mad Lust Envy was happy with his 32 ohm Beyerdynamic DT990 out of his E9k's 10 ohm output, even vs straight out of his E17 (with a fractional output impedance). Then, there are posts like this one: http://www.head-fi.org/t/402067/a-super-simple-6dj8-headphone-amp/435#post_8779560
Originally Posted by nikongod
The 10ohm resistor wont do anything to protect your hearing, and probably wont do much to protect the headphones either. The 10ohm resistor is just there for the amp.
The objectively correct way to drive headphones implies that there is an objectively corect headphone. Ask the objectivists to identify the objectively correct headphone some time, its amusing if you like making fun of people.
The fact of the matter is that the largest difference between any 2 amps with any aspiration of "quality" is smaller than the difference between almost any 2 headphones... So until there is an objectively correct headphone (there will never be - measures flat VS sounds flat VS diffuse field) building an objectively correct amplifier is an interesting academic exercise but ultimately an exercise in futility.
Where does the damping factor rule come from? Certainly not from the IEC standard for driving headphones that specifies a 120ohm output impedance - which gives only a damping factor of ~3 with HD650 or 2 with any 250ohm beyer headphone... The damping factor rule comes from multi-way speakers where it only makes any sense because there NEEDS to be a standard so that things work across brands. When multi-way speakers started to become the norm in the 60/70s the companies that explained it best happened to be the ones that were very good at building ~0ohm output impedance amps. The companies that built VERY nice systems with everything designed as a system got left in the dust.
In headphone land where there are no crossovers (except in multi-way IEM's, which realllllllly need 0ohms, which just proves the need for 0ohm amps for things with crossovers...) the importance of achieving an arbitrary damping factor could even be counter productive. Quite a few headphones sound subjectively better with a decent bit of output impedance...
In the end the only way you will find the right answer is to experiment. Well, at least until the objectivists can identify an objectively correct headphone*. Heh, considering that there are half a dozen ways to measure a headphone (In onter words they cant even agree how to measure) you still have plenty of time on your own.
*How ironic would it be if the objectively correct headphone only measured correctly if it was driven by a 120ohm source impedance?
Also, I noticed that FiiO still hasn't quoted the output power of the Mont Blanc. >700 mW @... What Ohm load? I assume 32 ohms, that's pretty standard, and would put the Mont Blanc E12 at over twice the output power of the E11. Still, it would be nice to know for certain.Edited by Evshrug - 12/29/12 at 11:48am