Emotiva XDA-2 USB DAC/Digital Preamp/Headphone Amp
Jam-packed! Emotiva XDA-2 ($399)
The machined front panel and control layout is a near clone of the discontinued XDA-1, but internals are mostly all-new, the Analog Devices AD1955 multi-bit delta-sigma DAC is the only carry over from the XDA-1. The Analog Devices AD1896 asynchronous sample rate converter and current-to-voltage stages are new; likewise the analog resistor ladder volume control that maintains resolution even at low volumes; the internal power supply (no wall wart) is more elaborate and uses separate regulators for the analog and each digital stage; the OPA2134 precision op amps; and there's a new fully-discrete high current headphone amp that can deliver 2 watts! The amps' output impedance is rated at an unusually low 0.1 ohms (there's a 1 ohm series resistor that protects the amp from faults, but the feedback point is after the resistor which effectively nulls the impedance of the resistor).
You get 24/192 support for all inputs, including the two RCA coaxials, two Toslinks, one USB, and one XLR AES/EBU. The all-metal remote feels a lot more luxurious than the typical plastic units you get with DACs in the Emotiva's price range. The XDA 2 has RCA and XLR line-level outputs. Emotiva's five-year warranty provides more coverage than most of the competitors, and the XDA-2 is sold with a 30 day home trial.
Gripes: I'm not crazy about up/down volume control buttons, I much prefer volume control knobs. It's nice that the XDA-2's control works in 1/4 dB increments, but ramp up/down speeds are sluggish, and take about 5 seconds to make a 10 dB change. When switching between sources I frequently need to make even larger volume adjustments, so I found the XDA-2's slow-poke control mildly annoying. I can zero-in on the exact volume over a much larger range with a quick twist of a volume knob---up/down buttons can never be that fast, you'd overshoot the mark every time. On the upside the volume control "remembers" the last volume setting for the headphones and line outputs, and automatically reverts to the last setting when switching between headphone and main outputs. Also, the resistor ladder volume control doesn't pop or click as the volume ramps up or down.
My estimation of the XDA-2 went up again when I plugged in my Audio Technica ATH M-50 full-size headphones. There, the amp's power advantages were immediately obvious with Amon Tobin's bass heavy Bricolage album. The tunes' low-end antics are downright subterranean, the XDA-2 delivered the goods, and the bass remained focused and tight. Watching YouTube videos with a pair of Koss Porta Pros on my noggin was a blast, those cheap and cheerful on-ears never sounded better. My Ultimate Ears UE 900 IEMs dazzled with the XDA-2, and the amp is dead quiet. My old Sennheiser HD-580s were glorious, their smooth midrange was impossible to fault, but the Hifiman HE-400 was the one I kept coming back to for its transparency, wide open soundstage, potent bass, and delicate highs. Stepping up to high-resolution 192/24 files, the XDA-2's transparency and low-level detailing were absolutely superb!