Pros - Tons of power, cheapish price, seriously well built,
Cons - A personal con- could be the sound card I use but I think it is the amp, needs to be turned up a tad louder then I would like when listening to VOIP
I have been using a E09K to power my DT990 600ohm cans for over two years now, long enough that I don't really remember exactly when I got it but for sure over two years. I use this thing every single day for hours each day because it is part of what I use for my work. It literally could blow my 600ohm cans if I pushed it loud enough I'm pretty sure, I never ever go above half volume because it literally hurts my ears and probably is causing hearing damage when over half ''so I just don't''.
Two years and not a problem at all except last night a box weighing about half a pound fell on the power adapter and knocked something inside of it loose, I now have to use a 12volt adapter until I have the time to either fix the 15 volt adapter or buy a new one.
I run this in tandom with a Asus Xonar DG, it sounds amazing compared to anything else I have heard for under 1000$ Canadian. A friend has a Biforst amp and dac and some 1400$ cans I forget the name of to be honest and its the only thing that comes close to what I have on my head and am listening to rite now, for being a 100$ amps combo with 400$ cans and a 40$ sound card this stuff cant be beaten.
On a side note, thanks to everyone here on Head-Fi that told me about this stuff and all the great reviews, everything I have ever read on this site has been correct or at least personally correct for the person writing a review, because of that I now have had amazing audio for two years and still love it.
I will keep this review short as there are lots of other well done in depth reviews out there. I have had this unit for a while now ( about 4-5 months) and I love it. I have had no issues with it and I pair it with the e17. The amp alone is well made, relatively neutral (slightly warm). It has plenty of juice which should power most headphones and stubborn hard to drive ones. In general it tightens and extends the base a bit giving it a more polished feel. Additionally it will open of the sound stage a decent amount (depends on specific headphones). Overall it is a great value, begs the question of why you may need a 1000 dollar amp. My only complaint is that there is not a third gain switch that is lower. I wish there was a gain of 6 as well, just to add more versatility to it but not a huge issue.
Pros - Tons of power, not much coloration, works well with the E17, looks great
Cons - Distortion at higher gains
I have used this amp for about a year now, and I must say it has served me well.
Through many different headphones, the FiiO E09K hasn't skipped a beat, and has driven everything from high power, low impedance to high sensitivity to 250ohm headphones. It really is a great amp to start with, or to buy if you're on a budget, simply because it can handle everything you throw at it.
This amp is probably one of the best I've had the pleasure of owning in terms of overall build quality. It has a very sturdy feel to it, with its solid enclosure and steady dial. Never once did I have to worry about breaking it, or someone else breaking it. It also takes up very little space on my desk, which is certainly a plus if you're working in a smaller area. It also looks fantastic!
The E09K seems to simply give you pure, unaltered sound. It doesn't color much, and you'll probably end up hearing more of the traits of your headphones than that of your amp. Now, this might be a pro or a con for you. It was a con for me, since I'm not mixing, and I like my audio smoothed down a bit. Also, there is some audible distortion at higher gains, which was a bit of a pain, but not too much of a problem most of the time. It was really only in select situations when I ran into problems.
The ability to dock a portable FiiO DAC is very neat. I do own a E17, however, I didn't often use it with the FiiO. It actually seemed to degrade the audio quality, especially if you're using its equalizer. I can't say I'm a big fan of the combo, however, it was very easy to set up, and the two units worked flawlessly together. If you need a portable amp, I would highly recommend it just because it's nice to have the option of using optical.
This is a really good amp for the price. I'm actually going to be selling it soon to get a tube (but seriously FiiO, it's not you, it's me). If you want low amounts of coloration and an amp that will serve you well even as you buy better headphones, this amp is amazing.