My first experience with iFi Audio was their iFi - Nano iDSD DAC; a delightful sounding unit that works equally well on the go driving IEMs and at my desk driving Audio-Technica ATH-M50x Professional Studio Monitor Headphones. The big draw for this DAC, especially at the time, was its support for an incredible range of digital audio formats: PCM from 16-bit, 44.1kHz to 32-bit 384kHz, plus DSD64 though DSD256 and DXD--really unheard of at the time for less than $200, and still pretty uncommon. Of course, ninety-something-high percent of my music collection is CD resolution, so while the capability has been a nice-to-have, it's the sound quality playing 16-bit, 44.1kHz that really matters. And the iFi DACs do that incredibly well. Music emerges from a deep black background with delightful separation, pace, and rhythm. Lows and highs are nicely extended with no sign of digital grain or harshness.
Finally, on to iFi's latest micro iDAC2. Unlike the two iDSD models which are powered by internal batteries, the iDAC2 seems to be more intended for use at your desk or in your home audio system. There's no on/off switch, and the analog RCA outputs completely bypass the volume control, which is what you want for best sound quality. The iDAC2's feature set is more similar to the nano than the micro iDSD. While its headphone amp does not have the crazy power of the micro iDSD, it is significantly more robust than the nano iDSD and able to drive even my Sennheisers to more than satisfying levels. However, where the micro iDAC2 really shines is in my home playback system. With the Class-A output stage, it excels at micro and macro dynamics. It shares the iFi house sound with the iDSD models but is slightly more forward and alive in the mids without ever sounding harsh. Soundstage is huge, extending far outside the left and right loudspeakers. Quality is really surprising for a $349 DAC, and in my opinion, is slightly better in my home system than the more expensive and feature rich micro iDSD.
Because the iDAC2 lacks battery power, I do recommend that it be coupled with the iFi - Nano iUSB 3.0 Power Supply to ensure that it's being fed with the cleanest possible power and data signals. I'm using iFi's Gemini USB cable (mentioned above) between the DAC and iUSB3.0 power supply and their Mercury cable feeding the assembly from my PC transport. Although the combined cost of these four parts from iFi is nearly $900, the performance is favorably comparable to other DACs costing twice as much or more, several of which I have either owned or auditioned in the same playback system. Highly recommended.