Cons: Overly dark sound, bass boost affects lower mids
Got this for a friend off the FS forum, but decided to use it myself for a few days. This was supposed to be the uDAC killer? Really?
My unit (first edition) is presented well and looks to be built all right, though there have already been three revisions and reports of numerous problems with the jack on the forums. So it gets 3 stars there from me.
Clarity is the main issue for the Fiio E10. The upper bass is boosted a little, and the mids around 2500hz are recessed a little. This is enough to create a veil on most of my non-bright headphones. It does tame a Grado very well, however, and the E10 is a nice match for it. It sounds okay until you hear the competition in the same price range.
My HP Touchpad (Beats Audio processing disabled) and NuForce uDAC1 actually sound better than it. This comes as a surprise, since there's at least multiple reviews that state the E10 sounds better than a NuForce uDAC2. Not to my ears, it doesn't. The uDAC1 has significantly more bass impact, percussion impact, soundstage, and airiness. As for the HP Touchpad, it actually has a superior Wolfson DAC compared to the iPad, and it really does give the uDAC1 a run for its money. The HP Touchpad has the best clarity and overall sound quality of the three. It's too bad I can't use it as a dedicated DAC.
(Upon research, the HP Touchpad uses the newer Wolfson WM8958, while the Fiio E10 uses the older WM8740. This may explain the reasoning behind the HP Touchpad's superior sound; it just has a better chip.)
The bass boost is a nice idea, until you realize it boosts the 200hz-500hz range. This is way too much, as most headphones are close to neutral there. Most of the bass help is needed below 100hz. Had the bass boost only affected frequencies below 100hz, it would've been suitable. However, as it stands, it turns the sound into mudville. Sadly, and I hate to admit this, but the Beats Audio processing on the HP Touchpad boosts the bass in a more subtle and ideal way. Guess the Beats brand does something right.
So pair it up with your favorite bright headphone, like a Grado. But if you try pairing this up with a less-bright headphone like a Sennheiser, you might be getting a sound that's just too dark. This isn't much better than integrated sound on your computer, to be quite honest, though it'll boost the volume to levels that integrated sound cannot.
I am astounded as to why this product gets so much praise, but I guess the dark signature just isn't for me. All that negative publicity surrounding the nuForce uDAC really hurt its standing, but I must have been lucky with my uDAC1, since I really do believe it sounds better than the E10. The Headfonia review (http://www.headfonia.com/the-latest-must-have-the-fiio-e10-usb-dacamp/) hinted at the worse soundstage and airiness in its review, but still recommended it over the uDAC2. However, I believe these issues are too significant for the people who prefer a brighter sound signature.
One last thing. The E10 doesn't have the channel imbalance issue that the uDAC1 and uDAC2 have at ultra-low volumes.
(Tested with: Sennheiser HD595, Grado SR225i, Sennheiser CX980, Koss KSC35, Audio-Technica M50)