The biggest thing that I’m missing with the O2 is bass impact and punch. It’s funny because if you build a Cmoy with two 9V batteries you’d get a far better bass impact than you do with the O2, and a much sweeter midrange that is always the character of Cmoys like the JDSLabs CmoyBB. Another area that I question is the detail level. If we gonna promote the O2 as a technical amp (due to the superior black background), another thing that technical amps are usually good at is micro detail level. But with the O2, I would say that the detail level is not that superior from a Cmoy.
The question I have with the O2′s superior black background is if it’s indeed the result of superior circuit design or mostly just a function of a lower gain setting. I had both the Epiphany and the JDSLabs with me at one point in time (The JDSLabs later I sent to Lieven for his evaluation), and the two O2 builds differ in the application of gain levels. The Epiphany build applied an overall lower gain level on both its low and high gain setting than the JDSLabs (1X and 2.5X on the Epiphany, 2.5X and 6.5X on the JDSLabs). This leads to an even blacker background in the Epiphany amp. Of course you can ask JDSLabs to build you an O2 with the same low gain levels so that’s not really an issue, but the point that I’m making is that with a lower gain, the sound is cleaner and the background blacker (as is the case with almost all other amplifiers). However, the opposite is also true. At the high gain setting (6.5X), which is closer to the gain of a typical Cmoy build, I really don’t hear the technical advantage anymore. The noise levels are up, the black background is gone, and comparing it with the JDSLabs Cmoy I even discovered that the Cmoy has a better midrange clarity, though more rolled off in the bass (boost OFF).
NwAvGuy seems to have a very strong belief in his measurements, but one thing about amp measurements is that even the biggest names in audio amplifier designs have confessed that good/bad measurements doesn’t always relate to good/bad sonics. Of course the premise that good measurements equals good sonics in itself is largely an assumption, and a statement from Nelson Pass actually casts a strong doubt on the validity on the premise:
“It is nevertheless possible to have a product that measures well but doesn’t sound so good. It is still a mystery as to how this could be, but there it is.”
I am not saying that you don’t need to do measurements and good design practices, but relying on them alone is not enough. A good feedback from a pair of good ears to further improve the design and the tuning would definitely help.
If you’ve had the chance to listen to the AMBLabs Mini3 and the Cmoy amps, you know that both amps are very good sounding. I certainly won’t go around the web blasting both the Mini3 and the Cmoy just because it measures bad, if the fact is these two amps in fact sound very2 good. I personally have yet to hear one guy who’s heard the Mini3 and gave a negative listening impression. When I did the sub $100 portable amp shootout, I noted that while I’m not such a big fan of the Mini3′s sound signature, it was clearly the most competent technical amp of the bunch. And comparing its technicalities to the O2, I think that both amps have their advantages and disadvantages in terms of technicalities (i.e better articulation, speed, detail level on the Mini3). The Cmoy is actually, in my opinion, the most musical sounding of the three here and despite the cheap association we have with the Cmoy name, what matter is that a lot of people do enjoy the sound of it. Likewise the Mini3 also has a huge fan base, and I don’t think that they’ll start abandoning their amp simply because NwAvGuy wrote so convincingly about how his amp is superior to the AMBLabs’. Of course both the Cmoy and the Mini3 can be build in an enclosure small enough to match the iPod’s footprint, making them real portable amps. As for the O2, it’s a good amp, but not really the total knockout NwAvGuy would have us to believe.
Edit 05/04/12: John Seaber from JDSLabs’s confirmed in the comment section that all O2′s now ship with a set of stick-on bumpers (feet), so the O2 can’t slide around. “Headfonia’s O2 sample shipped before we spotted this inconvenience…”