Sony PHA-2 DAC/ Headphone Amplifier

Capable, Quiet, and Portable

Equipment report
Digital-to-analog converters,
Headphone amps and amp/DACs
Sony PHA-2
Sony PHA-2 DAC/ Headphone Amplifier

As part of its “high-resolution initiative” Sony has rolled out several exciting new products during the past year including the HAP-Z1ES and HAP-S1 digital players, the NW-F887 portable player (Asia only), and the PHA-2 portable DAC and headphone amplifier. I reviewed the HAP-Z1ES in Issue 241. It proved to be an outstanding value that has shaken up the digital-audio-player marketplace.

The Sony PHA-2 portable headphone amplifier and DAC was created to be a digital “bridge” product, designed to improve the sound from smartphones, iPods, iPads, and computer USB sources. For the on-the-go audiophile who wants to own and carry only one DAC/headphone amplifier on his travels, the Sony PHA-2 could be just what the traveler ordered.

A Tech Tour
The 270-gram (.6-pound) PHA-2 is housed in an aluminum enclosure that features a zinc alloy bumper as well as a unique rail/edge design. It has provisions for digital inputs from a PC via a micro-USB, or an iPad/iPhone/iPad via a standard USB, or a high-resolution-supported Walkman via Sony’s own proprietary mini-USB connector. The PHA-2 also accepts analog via a mini-stereo input that doubles as a line-level output. Outputs include one mini-stereo headphone output plus the line-level. One side of the PHA-2 has a pair of toggle switches to select between the line-level and headphone outputs and to choose the normal or high-gain amplifier-output levels.

Controls on the PHA-2 include a large volume knob, nestled underneath one of the alloy bumpers, that also turns the unit on and off. Next to the volume knob are two small LEDs. The “power” LED glows green when the unit is playing and also tells you the charge level of the internal rechargeable 3.7-volt 2160mAh Li-ion battery via a series of blinks when you initially turn it on. Three blinks signify a full charge, two a partial charge, and one blink means you don’t have much time before recharging will be needed. The other LED glows red during recharging.

On the bottom of the PHA-2 you’ll find three digital inputs as well as a small toggle to select which one is currently active. If you’re looking for a mute button or any way to navigate through a music library, you won’t find it on the PHA-2. Whether you’re using the PHA-2 as a DAC or as a headphone amplifier, Sony assumes that any device you hook up to the PHA-2 will have its own navigation and playback controls. During the review period I used the PHA-2 tethered to a variety of devices including an iPhone 5 (via direct-digital lightspeed-to-USB connector), the Astell&Kern AK100 (via the analog input), the Astell&Kern AK240 (via analog), and several of my Macs via micro-USB.

The PHA-2 DAC section supports a wide variety of digital formats including PCM up to 192/24, and DSD 2.8 (64x), and DSD 5.6 (128x) via any of its digital inputs. Sony’s technical literature notes that DSD 5.6 is not available for the Mac, and using Audirvana Plus 128x material is automatically converted to 176.24 PCM for playback. The PHA-2 employs an asynchronous USB 2.0 transfer mode that uses a proprietary driver for Windows; no drivers are needed for Mac.

Setup and Use
With all the portable and computer playback devices I tried with the PHA-2 setup was virtually plug-and-play. The only “tricky” part was selecting the right position for the PHA-2’s digital-input toggle switch. Occasionally, when going from DSD material to WAV on my Mac, I could “trick” the PHA-2 into spitting out noise instead of music. Resetting the audio preferences in Audirvana Plus quickly solved this minor glitch.

Battery life on the PHA-2 is spec’d from 7 to 15 hours. If used as a DAC/headphone amplifier the figure will be the lower number; if used solely as a headphone amplifier you can expect battery life to be closer to the 15-hour figure. Recharging the PHA-2 can only occur while it is not playing music. This means that if you use the PHA-2 as your PC’s DAC you need to turn the volume to “off” at the end of the day if you want to have a full charge for the next day’s playback. If you forget to turn the PHA-2 off, yet leave it attached to your PC, it will not automatically recharge overnight.