Here's the thing - I've been playing around with FiiO E11s power output switch (under the battery), and with the headphones I use, I don't really hear any difference between low/high power (maybe a slight one, but I'm thinking it's just my brain telling that it should work better on high). I use MBP -> FiiO E11 -> Koss Pro DJ100.
So the question is - are the DJ100s easy enough to power so that there might not be any difference? And what parameters should I be looking at for heaphones to get the idea, when they would benefit from a high output power (e.g. impedance, or something else)?
 
Thanks!

bump

not sure i understood what you're talking about... if you're talking about high vs low gain, you should always use the lowest gain that can still give you sufficient volume and still leaves some headroom. if your talking about messing about with the inside of the amp, i cant help.

It's a power and not gain switch. I believe it lowers the rail voltages to conserve run time. I heard a slight difference when I had mine and preferred the low power setting on my IEMs. The setting doesn't change anything else. Whichever you prefer sonically at your highest listening requirement will be the right one.  I used mine at High gain and low power for the short time I had it.

I used low power and high gain for some time and i quite liked it, but I ended up switching to high power and low gain, since I thought the it sounded more 'powerful' that way. Although I still think it's just my brain reasoning that it should sound better at higher power.
Anyway, thanks! Will do some more testing then.