This thing is good, really. Is better than the amp of Fiio E10K, if anyone heard that, which is well rated for the price. So, for the price, is really good, probably not bette than let's say an aune B1, which worths 5x more, but it does the job of better defining your sound on the go.
Though, as a hint....replace the provided cable with a better one as it's bottleneck. Get something better, not just another, there are worse. It really makes a big difference, as I did some tests with different cables. I use it now with some hama 10-15$ cable, plated and everything, so get something at least like that.... don't jump over $20 with it as that turns stupid fast from there on.
The better cable improved the signal from phone to it and everything got better, more hifi, the level of details increased.
Also, use it with a proper phone, probably that's a good thing to do, ever if you're a freak of this sort. I play it with a LGV20, so it looks like a good match. Get a decent phone with a proper DAC in it and a good cable... forget dongles or other junk :)..like bluetooth, beats, so on. I tried it with some Meze 11 Neo and 12, DT770 250 and 32ohm, 990, K240, yamaha hph200's and 4xx. It makes them all clearer. I didn't thought it will have any impact on the Mezes but it made them sound even clearer too plus more sound stage, though they are 16 ohm iem's.
So, in short, I recommend this, not that I'm some authority but it worth the investment :). Don't forget to get a better cable.