Skylab did a huge review of 37 portable amps, and htis is what he had to say about the iQube:
"Qables iQube
Info: i-Qube - A new dimension in portable hi-fi » home
The iQube is a very interesting amp. It's a class D amplifier topology. This is the first of its kind as far as I know - a class D portable headphone amp. Class D has at least the potential of being more battery-efficient, and I did get almost 100 hours of play on the first set of AAA alkalines I had in it (which I used up in 100 hours of break in). The iQube will charge rechargeables, but it doesn't come with them, nor does it come with a charger, although it has a fairly wide tolerance for AC adapters it would seem.
Build Quality: A+: Excellent, VERY attractive metal case. I wasn't sure at first about having the jack on the back and the volume control on the front, but I loved it in the end. There is a very slight turn-on tick. But overall, the build quality is among the very, very best, and it's the kind of thing that gives great pride of ownership.
Treble: A+: clean, clear, grain-free, extended and transparent. Great air and extension, and very natural. It wasn't too aggressive ever, but it wasn't at all soft or rolled off. I wouldn't use it with super-bright headphones. But this really isn't the iQube doing anything other than being VERY neutral.
Midrange: A: smooth, clean, and open - with amazing see-through type clarity, while being tonally very neutral. There is perhaps just a touch of reticence, but not enough to worry about.
Bass: A: Ultra-deep and powerful, with excellent definition and speed. VERY tight, but not overly generous. Again, Neutral comes to mind.
Neutrality: A+: The new king of Neutrality. Over and over again that's how I thought of it. Easily shows the difference between headphones in a flash. Only the LISA III is in the same league here. While I still love the Meier Move, it has a "sound" moreso than the iQube.
Soundstaging: A-: The soundstage was great, but it wasn't the WORLD's widest. Still, nothing to sneeze at.
Transparency: A: Nothing to take issue with here either. Try as I might to pick up some kind of issue with transparency related to the use of class D, I couldn't. I just loved it.
I have to say, I was HIGHLY impressed by the iQube. Unfortunately for those in the USA, the current dollar>Euro exchange rate makes the iQube pretty expensive -- as of today, it would cost the American buyer over $460, and January 1 it will cost about $500 (at current exchange rates). And as good as it is, I personally don't think it's enough better than the other top amps to easily justify that price here. I know there is nothing Hans at Qables can do about his costs, or the dollar to euro exchange rate, but it is a pity. If this amp could be had in the US for $335, it would be very easy to recommend as the best buy in high-end headphone amps. But it's $335 EUROS. So for everyone in Europe, this is a great amp to get. For those in the US, I think it requires a little more thought. Nonetheless, it's a superlative headphone amp."
