as part of its “high resolution initiative”, sony has launched several exciting new products over 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 turned out to be an exceptional value that has revolutionized the digital audio player market.
the sony pha-2 portable headphone amplifier and dac was created to be a digital “bridge” product, designed to enhance the sound of smartphones, ipods, ipads and computer usb sources. For the on-the-go audiophile who wants to own and take only one DAC/headphone amp on their travels, the Sony PHA-2 might be just what the traveler asked for.
A Tour of Technology The 270-gram (0.6-pound) PHA-2 is housed in an aluminum casing that features a zinc-alloy bumper as well as a unique design rail/rim It has provisions for digital input from a pc via micro-usb, or an ipad/iphone/ipad via standard usb, or a hi-res compatible walkman via sony’s own mini-usb connector. the pha-2 also accepts analog via a stereo mini input that functions as a line level output. outputs include a mini-stereo headphone output plus line level. One side of the pha-2 has a pair of toggle switches for selecting between headphone and line level outputs and for choosing normal or high gain amp output levels.
The pha-2’s controls include a large volume knob, located under one of the alloy bumpers, which also turns the unit on and off. next to the volume knob there are two small leds. The “power” LED lights up green when the unit is running and also tells you the charge level of the internal 3.7-volt 2160mah rechargeable lithium-ion battery through a series of flashes when you turn it on for the first time. three flashes means a full charge, two flashes a partial charge, and one flash means you don’t have much time before you need to recharge. the other led lights up red during recharging.
At the bottom of the pha-2 you’ll find three digital inputs, as well as a small switch 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 a headphone amp, Sony assumes that any device you connect to the PHA-2 will have its own navigation and playback controls. during the review period, i used the pha-2 connected to a variety of devices, including an iphone 5 (via the direct-to-usb digital lightspeed connector), the astell & amp; kern ak100 (via analog input), the astell & amp; 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) through any of its digital inputs. sony’s technical documentation notes that dsd 5.6 is not available for mac, and that audirvana plus 128x footage is automatically converted to 176.24 cfm for playback. the pha-2 employs a usb 2.0 asynchronous transfer mode that uses a proprietary driver for windows; no drivers needed for mac.
setup and use with every portable and desktop playback device I tried with the pha-2 setup it was virtually plug-and-play. the only “tricky” part was selecting the correct position for the pha-2’s digital input toggle switch. From time to time when I was going from dsd to wav material on my mac, I could “trick” the pha-2 into making noise instead of music. resetting audio preferences in audirvana plus quickly resolved this minor glitch.
battery life on the pha-2 is specified from 7 to 15 hours. if used as a dac/headphone amp, the figure will be the lower number; if used solely as a headphone amp, you can expect battery life to be closer to 15 hours. recharging the pha-2 can only occur while music is not playing. This means that if you use the PHA-2 as your PC’s DAC, you must turn the volume 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 off the pha-2, but leave it connected to your computer, it will not automatically recharge overnight.
A clever ergonomic feature on the pha-2 is the “rail” edges. These edges are for attaching two elastic rubber straps that are designed to hold your playback device so that it is securely attached to the PHA-2. I used the bands with the iphone 5 and with the astell&kern ak100. in both cases you end up with a pretty substantial mass that’s too thick to fit in anything except a large cargo pants pocket. Plus, when you add the weight of the PHA-2 to your portable playback device, you’re likely to end up with a package that weighs close to a pound, and in some cases, even more.
If you want to use the pha-2 as a dac in a desktop system, you will discover several minor ergonomic issues. Firstly, with an analog source, such as the Astell&Kern AK100’s analog output, you’ll need to use headphones instead of the analog output to drive your preamp or powered speakers, since the analog output doubles as an analog input. . Also, if you need two outputs, such as when you want to drive a set of speakers and a subwoofer, since the pha-2 only gives you a single analog output, you’ll need to split the signal in two via a jumper or connector and or get feed your amp/monitor-speaker through your subwoofer pass-through.
I used the pha-2 with a variety of headphones, from high-sensitivity models like the westone es5 and ultimate ear ierm to more power-hungry models like the audeze lcd-2, mr. alpha dogs speakers and beyer dynamic dt-990 600 ohm version. With the beyer dynamic dt-990s headphones i was craving a little more gain and volume when listening to my own live concert recordings, even with the high gain setting on. Mr. Alpha Dogs speakers and Audeze LCD-2 headphones had enough gain to deliver satisfactory volume levels with my own source material. With high-sensitivity in-ear headphones such as the westone es5, which make a hissing noise with many headphone amps, the pha-2 was totally silent with plenty of gain, making it portable and highly compatible with the es5s.
If you’re looking for a headphone amp to drive particularly inefficient headphones, you should give the pha-2 a try to see if it provides adequate power. Some would-be owners will no doubt be disappointed that the PHA-2 can’t control everything in their headphone arsenal, but in my experience it’s nearly impossible to find a headphone amp that works equally well with all types of headphones. a more reasonable goal is to find a headphone and headphone amp that synergize together. For my uses, the Pha-2 proved ideal with highly efficient hearing aids like the Westone ES-5 and Ultimate Ear Ierm, and certainly suitable with most medium-sensitivity cans. the new oppo pm-1 headphones were an especially good match for the sony pha-2.
sound since the main reason for choosing the pha-2 over other dac/headphone amps like the adl x1 is the pha-2’s dsd capabilities, i spent most of my critical time on listen playing my own dsd recordings live on location through the pha-2. one of my most recent recordings was made at a house concert in boulder, co, using a pair of alesis/groove tube gt am30 fet microphones with cardioid capsules to capture a performance by mandolinist/clarinettist andy statman accompanied by jim whitney on bass acoustic. The microphones were set up approximately five feet from Statman and Whitney in a matching pattern. Statman’s energetic playing provided material with an extremely wide dynamic range, as well as a rich harmonic palette. listening with the pha-2 plugged into my ultimate ear irems headphones, which were the in-ear monitors I used while originally making the recording, I was instantly transported back to the moment the recording was made. it was as if I was listening to the live microphone feed. even during statman’s most frenetic and dynamic clarinet solos, the pha-2 never felt the slightest bit of stress or dynamic constriction.
In the applause from the audience between numbers, the pha-2 did an excellent job of preserving all the subtle location cues, as well as the not-so-subtle transients that clapping hands create. Frequency extension and tonal accuracy through the PHA-2 were especially good on Whitney’s acoustic bass. he could hear not only the transient pulse of his plucked notes, but also the way the acoustic bass flourished as the notes spread across the room.
when i switched to using the pha-2 as a dac/preamp connected directly to an april music eximus s-1 power amp driving a pair of clair audient 1+1 audience speakers in a near field setup, once I was most impressed by the sonic abilities of the pha-2. all dimensional and location cues were accurately preserved by the pha-2. I even noticed when Statman pointed his instrument in a slightly different direction, by the way he changed the reverb and flourish in the room. When Statman switched to the mandolin, all of his characteristic contrapuntal humming could be clearly heard and located in space, several inches above his mandolin. the pha-2 also preserved the differences in room reverb and bloom between statman’s voice and his mandolin.
Since many prospective owners will be using the pha-2 with smartphones, I spent some time near the end of the review period with the pha-2 connected to my iphone 5 via its lightning digital connector. using several high definition internet radio stations as primary sources, I was impressed with how immersive and musical the results were. Using the “Hidef Radio” app I listened to Italy’s 128 kbps Classical Venice Radio.eu, and heard reasonable depth and dimensionality of a recording of Brahms’s Piano Sonata No. 2, as well as an excellent sense of weight and power from the piano’s lower registers. switching to boston’s wgbh 160kbps on the tunemark radio app i was greeted by a series of sonically spacious recordings that brought back fond memories of my time living in boston and regularly attending the thursday night concert series.
As far as I could, I also compared the sound quality of the 160 kbps wgbh internet radio stream of the hyperion trio playing mendelsohn’s op piano trio. 49 routed from the iphone 5 to the pha-2 and then to an analog input on a wyred4sound mpre with the same internet radio stream also coming through my macpro’s itunes to the wyred4sound mpre dac via its usb 2.0 connection. after matching the output levels, I found that it was virtually impossible to tell the difference between the two radio transmissions. both were equally spacious, dynamic, full-range, and detailed. when the program material changed to the soundtrack conducted by james levine playing symphony no. 14, I immediately noticed on both sources the slightly astringent sound of the string section and the overly reverberant recording technique.
Conclusion Some prospective owners may find that my main ergonomic issues with the pha-2 are its greatest strengths: its sturdiness and weight. the pha-2 isn’t even close to being in the running as the most “travel-friendly” portable dac/headphone amp I’ve ever used, weight-wise. Compared to the resonessence herus or the audioengine a3, the pha-2 is huge. when i recently attended axpona in chicago, i chose to bring the astell & kern ak100 as my primary portable audio device due to its much lighter weight and much smaller size. facing the same levels of travel-induced trauma, the pha-2 would certainly survive better than the ak100, but at the cost of additional weight and bulk.
As consumers demand more comprehensive solutions for portable and computer audio playback, we’re starting to see a steady stream of new headphone amp/dac products designed for home and travel use. the sony pha-2 offers many capabilities and great sound for less than $600. But since no one device can do it all, prospective owners should take a close look at the pha-2’s feature set to make sure it does what you need it to do. if you plan on using it with particularly unwieldy headphones, you should definitely listen to it with those headphones before making a final purchase decision. while the pha-2 drives higher impedance headphones, like the 600 ohm version of the beyer dynamic dt-990 with more authority than the astell & kern ak100, most users are unlikely to carry this type of headphone while traveling. For those audiophiles who prefer hard-to-drive headphones, the PHA-2 will be a better choice than the headphone amps built into most portable devices. also for owners of highly sensitive custom in-ear monitors, who are tired of hearing the low-level background hiss that emanates from many headphone amps, the pha-2’s lack of noise and hiss might make it an ideal match for the westone es5, as well as many other custom high-sensitivity in-ear headphones.
specifications & prices
digital inputs: usb micro-b input (for charging and pc), usb mini-b input (for walkman), standard usb type a (for ipod/iphone/ipad) recharge time: approx. 7 hoursoutputs: phones (stereo mini-jack, only 3-pole compatible), audio input/output (stereo mini-jack, only 3-pole compatible)analog input: oneoutput power: approx. 165mw+165mw (8 ohms, 10% distortion); approx. 90mw+90mw (32 ohms, 1% distortion); approx. 25mw+25mw (300-ohm, 10% distortion)input voltage: maximum: 1v rmsdimensions: 2.67″ x 1.14″ x 5.5″price: $595