I purchased this a couple of months back with a "Firestone Supplier" which is basically just a power supply, so I dont get what the fuss is about... something with clean power... whatever... I got it for free so why the heck not? This is part of Firestones "Cute" series, so this amp/dac combo is very small, though the Supplier takes up just as much space as the amp itself (made with the same enhousement)
 
- I've switched out the standart op-amp (OPA2604) with 2x OPA627, but (this could just be my ears...) didn't really notice the difference (this could also be due to me not listening to them side-by-side).
However the sound... what can i say?... MASSIVE step up from the normal on-board sound on my motherboard (ALC889), the sound's so clean and neutral, pair this with a nice (high impedance... explanation later) headphone and you got yourself some nice equipment!
 
- Now to the low impedance "problems", I've tried this amp with multiple low impedance headphones (Sennheiser Momentum, and a bunch of IEM's) just to conclude that it's not the headphones, but the amp creating the slight hiss in the background. When listening to music I dont notice it, however when there's no audio playing I can clearly hear a hissing sound (though when I'm not listening to any audio I usually take of my headphones any way, because I have some tinnitus which is pissing me off.
 
But if you have some higher impedance cans (100+ ohm) I'd definetly recommend this amp, however at the "stock" prising (of the updated versions) there's some tough competition out there, ex: the O2/ODAC
 
Enjoy your music

Ok so, this was my first ever "hi-fi" headphone, and my first thoughts were "Why haven't I cared about audio before now?" I was literally blown away, coming from the cheap "gaming" headsets (Gamecom 780, Corsair 1400 etc.) these just sounded so much more clear and "clean". The bass reaches down quite low, without being emphasized, the mids are just perfect, and the highs are high without being harsh.Not only is the sound great, these things are also built like a tank, not only are the ear cups made of genuine leather, the headband is also made of one piece of stainless steel, so I don't see these breaking any time soon
 
I started using it just straight of of my pc (Realtek ALC 889) and HTC ONE (m7), and I really enjoyed the sound. But then I got a little more "into" the whole head-fi world, so I bought myself a Firestone Fubar IV, and that little thing just increased the sound quality one bit. So if you're purchasing this for "on-the-go" I'd definetly look into at small portable amp/dac combo.
 
Just to quote Tyle from Innerfidelity: "I dont think I've ever heard a headphone that does so much, so very well"
 
- Now for the comfort issue I was talking about: If you have big ears (or just a little above average) the earcups could easily get to small for your ears to fit nicely, I personally don't find this to be a problem for short listening sessions (1hour) but for a long flight (or whatever these do get uncomfortable, and my ears start to hurt.
 
- Enjoy your music

Just bought this amp (actually bought two, because of the pricetag!) and at first, when i powered it on, i was a little worried, as it wouldn't light up in the front, but i just left it their lying on my floor, and when i came back to my room it worked... *easy problemsolving*
 
This little mini amp sure have an amazing sound/price ratio, and with a little modifications, it actually sounds really great! the bass and clarity are a little boosted, while the mid sounds a little muddy, but overall it's definetly worth the 20£ i payed for it (with upgraded powersupple) I'm not an audiofile by any means, but i do own some headphones (ex: Sennheiser Momentum) and my uncle have some 10.000$ speakers, so I do know a little about sound... so back to the modifications i was talking about, recapping the whole thing makes it sound quite a lot better, but the biggest difference (I believe) was upgrading the powersupply; from the stock 12v 2a to a 12v 5a, as the stock one simply doesn't deliver enough power.
 
So overall this mini amp is definetly worth its pricetag, but probably not worth the "Hi-Fi" label. as one of the other reviews said: "You will not find anything remotely close to this amp's sound quality at this price range. But if you do have the budget to afford something better, that might be a better route to go."