Pros: Plug and play, switchable gain, switchable bass boost.
Cons: no adjustable bass boost (just 3 settings) Distorts with bass boost set high at high volumes. A little pricy for quality next to a CMoy.
The FiiO E11 is my first professional headphone amplifier and I have to say it was rather unexceptional.
First Impression/ measurements:
The first out of the box impression was incredible. Nice matte black plastic leading to a metal like edge with a notch for the volume nob (very intuitive) I accidentally dropped it taking it out of the box but nothing broke and after further inspection it is really very sturdy.
I opened it up and looked inside to see if I could see any hardware. I was greeted by a battery and some concealing plastic unfortunately but I'm certain I could find what they used on their site. I replaced the backing and turned it on.
This is where I expected and issue because FiiO has been known in the past to ship dead batteries (which will decrease their life and maybe even make them unusable out of the box), but, to my surprise, the amp happily turned on and boasted a cute little blue light letting me know it was operational.
I then measured its output for DC offset. For those who don't know, high DC offset (above more than about 50 mV) can cause permanent damage to headphones. The measurements came back as 1 mV on the right channel and 0 mV on the left, which is a very good sign. I then turned on the different levels of bass boost (bass boost also boosts DC offset) and measured. The measurements all came back as 0 mV, meaning some compensation circuitry was most likely implemented here. This is actually quite nice and kudos to FiiO for making sure that this wasn't an issue.
Being excited about its good looks I plugged it in and set it off on a personal favorite mix of mine on soundcloud. It is important to note here that there was no equalization software used here as I wanted to get an impression off the amp on an average laptop with average settings. I will add an equalized test result later for those who wish to see it. I started it playing and noticed it was rather quiet. This was strange because it was set to high gain and the volume was all the way up. I realized that I had stupidly had the inline volume on my headset down so I turned it up....and nearly deafened myself. The FiiO (on 32 ohm high sensitivity headphones) gets LOUD. It started distorting at this volume which was strange because I know my headphones weren't maxed out. I turned the inline volume down again and (As a side note here This lowers dampening factor to the headphones as it adds resistance before the speakers (bad thing) but this shouldn't cause the kind of distortion I noted from the FiiO) It sounded as if the little happy amp was getting rather cranky now turned all the way up with high gain and bass boost all the way up. I just tried to recreate the problem with low gain and was successful. Even at low gain it cannot handle the bass boost all the way up and volume above 6.5 (8 is max). To ensure that this was the amp I turned them all the way down and slowly edged them upward to make sure it wasn't the extra resistance causing issues. As I expected, the distortion stayed the same from lowest to max volume (It sounded like it was running out of current to push because on bass hits it got scratchy) As another side note: It just died and is charging now. If anything changes when the product is fully charged I will be sure to change my review.
Along with this issue of distortion I noticed that the bass boost, even on the highest setting, was rather modest. I've experienced better boost with software equalization on a mobile device. This was a deal breaker for me because I was really looking forward to the extra oomph it would give to bass without equalization.
Bottom Line: It isn't a bad amplifier and looks slick and clean, but it has a few issues here and there that make it a little bit of a bad deal.
I give it a solid 3 stars and would recommend it as entry level equipment to people who want mobility and a little extra volume.