Pros: Excellent sounding portable amp with USB DAC
Cons: relatively big and expensive compared to its competition
I received a V2 version of the Qables iQube from Moon Audio for review. The V2 adds a USB DAC, and is a little larger than the original iQube. It also how has a standard mini-USB connector for either charging or USB DAC connection, and the V2 comes with rechargable batteries. The amp, however, is identical to the V1, which is a good idea, since I thought the iQube V1 was an outstanding portable headphone amp.
The iQube is a very interesting headphone amp. It's a class D amplifier topology. It was 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 my experience with the iQube was that I did get a very long duty cycle per charge.
Sound quality of the iQube as an amp:
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. While it's pretty big, it's also fairly light for the size.
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 as a headphone amp. As a USB DAC, I thought it was also very good - and shared the same neutrality as the amp. The USB DAC did not quite share the same level of transparency as the amp did overall, but compared to other portable USB DACs, it is competitive with the best I have heard, if not better than them (whereas I think the iQube as an amp is among the very, very best portable amps there are). That said, I was impressed enough with the performance as a USB DAC that I decided to buy a V2 from Drew at Moon after the review was over (and I sold my V1 that I had bought years ago). The V2 is an outstanding product. It's expensive, but it sound excellent and works very well. If you can spend the $$$, and are not put off by the somewhat largish size, the V2 gets my highest recommendation.