Inputs, outputs, and controls are simple and straightforward. On the rear panel, one finds a USB 3.0 (2.0 compatible) jack that is used for file transfers and battery charging, a coaxial S/PDIF digital output, and a standard/minimum phase digital filter selector switch (iFi recommends minimum phase settings for listening, but standard settings for test measurements). Out front, the Nano iDSD provides a stereo RCA analogue output, a 3.5mm headphone jack, and a control knob that doubles as a volume control and power switch.
The top panel of the Nano iDSD sports a tiny, multi-function, multi-colour LED that indicates formats and sample rates for files being played, connectivity status, and battery charging status. Unlike inscrutable DACs that refuse to tell you what they are doing, the Nano iDSD’s status LED tells you exactly what’s going on (once you learn its colour code, of course).
Unlike competing compact DAC/amps such as the Audioengine D1, Audioquest Dragonfly II, Resonessence Labs Herus, or the upcoming Light Harmonic Geek Out, the Nano iDSD incorporates a 1400mAh Lithium-polymer battery and thus can be USB or battery powered. Users select their preferred power mode by following specific start-up sequences. By switching on the DAC before connecting a USB cable, the Nano iDSD will run on battery power, but by plugging in the USB cable first and then powering up the DAC, the Nano iDSD will run on USB power. This feature means listeners can use the iFi with devices (tablets, etc.) that might not be capable of supplying USB power. iFi also offers this important tip: “For Apple iPhone/iPad/iPod Touch, (or) Android devices, please use Battery Power; otherwise you may receive error messages from your device.”
According to the manufacturer, “MAC OSX (10.6 or later) has built-in native support for the iDSD.” However, Windows users (XP or later) will need to download and install driver software from the iFi website: www.ifi-audio.com. Note that iFi makes periodic improvements to its driver software and iDSD firmware to expand the unit’s capabilities and improve sound quality over time. For example, planned firmware upgrades for the Nano iDSD will soon add support for ASIO 2.2 Extensions for DSD, plus support for DSD256 (11.2Mhz/12.4MHz). Plainly it pays to keep your iDSD driver and firmware up to date.
How does the Nano iDSD sound? The answer depends, in no small part, upon the transducers you choose to use—a point I make because the Nano iDSD’s potentially excellent-sounding but relatively low-output amplifier handles certain loads far more gracefully than others. As a general rule, the iDSD responds well to earphones and headphones that offer a combination of high sensitivity, high resolution, and neutral tonal balance. On the other hand, if you choose ‘phones that are low in sensitivity or known to be ‘current-hungry,’ you may overtax the iFi and get less than ideal results (in such cases, you might need an auxiliary amp such as iFi’s Nano iCAN or the more powerful Micro iCAN). While I tried the Nano iDSD with 17 different earphones and headphones, I did the bulk of my listening through two models that yielded spectacularly good results with the iFi: namely, NuForce’s phase-coherent, quad-driver, Primo 8 earphones and Oppo’s very high sensitivity PM-1 planar magnetic headphones.
At its best, the Nano iDSD delivers a refined and decidedly musical sound that exhibits natural (not artificial) warmth, a beautifully rounded and full-bodied presentation, excellent bass, suave yet articulate mids, and smooth, well-detailed highs. I also found the Nano iDSD did a good job of conveying the three-dimensional qualities found in better recordings—even though, unlike some other iFi models, the Nano iDSD does not incorporate specialised ‘3D’ circuitry.
I was particularly impressed by the Nano iDSD’s ability to leverage the top-to-bottom phase coherency and all-around timing accuracy of ‘phones such as the NuForce Primo 8s and Oppo PM-1s. Personally, I judge qualities of coherency and timing accuracy by asking two straightforward questions. First, do the upper harmonics and overtones of instrumental and human voices sound like a natural and well-integrated extension of the fundamentals of those voices, or do they sound disembodied or ‘disconnected’? Second, do transient events have a naturally quick, clear, and incisive attack with realistic decays, or do they sound overwrought, as if artificial ‘edge-enhancements’ have been applied? The iFi answers both questions in a clear, sharply-focused, yet appropriately musical way that fosters long-term listener satisfaction.
Consider, for example, the Nano iDSD’s performance as it drives the NuForce Primo 8s on Keith Greeninger, Chris Kee & Brain’s song “Close to the Soul T2” (Blue Coast Special Event 21, DSD128). On this track Greeninger’s vocals range from a whisper on up to full song and back down again, depending upon the requirements of the lyrics, and the iFi helps the NuForce ‘phones capture every subtle shift in emphasis and inflection along the way. What is more, the iFi helps the ‘phones tap deep reservoirs of low-level sonic information, giving the harmonics of Greeninger’s voice and of his gently strummed acoustic guitar their due, while also retrieving reverberant and spatial cues as the voice and guitar interact with the acoustics of the recording space. Finally, the accompaniment from an acoustic bass is heard with appropriate weight, warmth, and a soaring, richly-textured growl. Throughout, the iFi enables the NuForce to deliver a finely focused and simply masterful rendition of the recording, in the process giving a great example of a high-end audio system that could fit easily in a listener’s pocket or handbag.