Sony PHA-1 Portable Headphone Amplifier REVIEW

March 31, 2013
8 mins read


5 Stars

Embracing a niche within a niche market, Sony has come up with a very cool way to boost earphone sound quality on the hoof, and make a quirky style statement to boot.

IT’S NOT OFTEN that we encounter review gear that can best be described as bizarre, but Sony’s PHA-1 portable headphone amplifier falls into that category.

WDF-Sony-PHA-1This compact battery-powered device is designed to offer go-anywhere high-quality headphone sound, and while it’s not unique, it’s also not something anyone would expect to see from a mainstream manufacturer like Sony. Oh sure, Sony has ventured into some strange territory over the years, but this is out way there, mostly because it’s aimed at such a small target market.

Admittedly, portable audio is a huge category, and there’s a ready market for high-quality in-ear monitors and stylish headphone, but few consumers value audio fidelity enough to incorporate something like the PHA-1 into their lives. That’s a pity, because it means that not many people will get to experience what has to be one of the most charismatic audio products I’ve yet reviewed.

Features & Construction

Charismatic? Yes indeed, the PHA-1 made an impression on me from the moment it was liberated from its packaging. To start with, it’s a gorgeous little thing, the diminutive proportions seeming strangely at odds with its purposeful exterior design. The angular aluminium chassis is anodised in military brown, which is perfectly complemented by the exposed screw heads, rubber protectors and the silver cast zinc alloy bars surrounding the front panel, and lining the rear panel.  Dimensions are 67 x 26 x 130mm, with a weight of 220 grams, so the PHA-1 is light enough to actually be useful.

WD-Sony-PHA-1There’s a tiny rotary volume control up front, along with two 3.5mm audio jacks – one for input and one for the ‘phones. A two-way gain switch is located on the side, while the back panel gets a three-way selector switch, a full sized USB input (for Apple devices) and a Micro-USB input (for computer audio and recharging purposes).

The PHA-1 is supplied with most of the cables the user will need – there’s a cable to digitally connect Sony’s range of Walkman products, a 3.5mm to 3.5mm cable, a Micro-USB to USB cable and a 30-pin to USB cable to connect Apple devices. Users of the latest generation of Apple products will need to supply their own Lightning to USB cable for the PHA-1 (Lightning is verified to work with the PHA-1, according to online commentary) but good luck getting a short one. All of the cables bar the Micro-USB to USB cable are exceedingly short, because they don’t need to reach very far thanks to the four “Silicone belts” that Sony supplies. The theory is that you take your iPod, iPhone or Walkman and lock it to the PHA-1 with a couple of the stretchy belts, link a short cable between the two and bung the lot in your pocket or backpack.

Once joined like this, you end up with a portable audio solution that makes a statement, and to some that statement may well be “I’m crazy!” Hey, but that’s just part of the charm of the PHA-1. Of course, you don’t have to use it like this, it could just be lugged to work in a laptop bag or mooched around the house as a movable headamp, but it’s just too damn cool as a portable unit to be limited like that.

Obviously with all those supplied digital cables the PHA-1 is more than just a headamp, it’s also a DAC; a 96 kHz/24 bit DAC to be precise, based on a Wolfson WM8740 chip that supports asynchronous data transfer mode without the requirement for additional drivers in either MAC or PC environments. Only the Micro-USB input offers high-res audio support.

The amplifier section is built around a Texas Instrument TPA6120 headphone amplifier, which is described as a “high fidelity audio amplifier built on a current-feedback architecture”. The TPA6120 incorporates high slew-rate, current on demand and gain independent frequency response technologies, and it supports headphone impedances from 8 ohms to 600 ohms, so it should drive just about any headphones known to man. The digital and analogue circuits are isolated from each other to prevent internal interference, while the aluminium housing acts as a shield to keep out interference from external sources.

WD-Sony-PHA-1-2Power is supplied by a rechargeable 3.7V 1200mAh Lithium-Ion battery life that offers 10 hours of life from the analogue input and five hours when connected to an Apple device. The charge time is 4.5 hours. In practice, the PHA-1 delivered at least this amount of running time with headphones and slightly more with in-ear monitors.

Sound Quality

The PHA-1 was first put to service with a set of Sony’s XBA-4 in-ear monitors (reviewed here) running straight from the 3.5mm output on an iPod Classic. Physically, this configuration looks and feels clunky because the short 3.5mm to 3.5mm cable follows an awkward route from the iPod to the PHA-1’s input, and gets in the way of the XBA-4’s own 3.5mm jack.

From an audio perspective, however, there’s nothing clunky about it at all because the PHA-1 really does lift the iPod’s game. Simply put, it sounds marvellous, opening up the sound of a 320kbps rip of Eddie Vedder’s ‘Society’ from the Into The Wild Soundtrack by providing more transparency and detail right through the frequency range. Pushing the volume levels up on ‘Hard Sun’ from the same album showed that the PHA-1 was allowing the balanced armature tweeters to highlight the top end in a way that the iPod’s weedy output stage couldn’t match. The big drums also carried additional weight and impact, as did every other element of the recording. The differences weren’t light and dark but they were noticeable, and the more I listened to the PHA-1, the more I appreciated its contribution, especially with CD quality files.

That was impressive enough, considering that the PHA-1’s DAC hadn’t yet entered the equation. With the short 30-pin cable pressed into service and the rear selector set to the USB input, the sound quality took another step upwards. Again, the differences were incremental rather than dramatic but they were there, most notably in terms of clarity and detail rendition through the midrange and into the very top of the treble. There was extra air and atmosphere to the recordings, while vocals and instruments had more body and presence.

Heavy Loads

That the PHA-1 is capable of improving the sound of a set of high-quality in-ear monitors came as no surprise. Like most good ‘phones, the XBA-4’s will benefit from any signal path improvements from amplifier to source to recording. In this case, the PHA-1’s digital to analogue converter, amplification and its noise suppression and interference rejection would be substantially ahead of the humble iPod’s.

What did surprise me was just how well this headamp coped with my Sennheiser HD650 headphones, which are known to be something of a tough load. The output stage in an iPod doesn’t like them at all, and they sound distinctly average when driven that way: more like a set of $100 ‘phones than what were Sennheiser’s flagship reference product before the HD800’s were released a few years ago.

With the PHA-1 in charge, however, the HD650’s are transformed. The detail levels go through the roof, and the dynamics move from flat and compressed to outstanding, with masses of headroom. There’s heaps of grunt in this amp, and the gain switch allows the volume pot to be used in the centre of its range for maximum linearity.

There may well be no sillier sight than an ostensibly sane man walking around with the three meter cable of a set of Sennheiser HD650’s draped around his body like a skeletal Roman toga, leading to a strange bulge in the pocket of his shorts. Then again, I can assure you that I don’t give a hoot about looks when a portable headphone rig sounds this good.

Desktop & High Resolution Playback

More normal people might find the PHA-1 to be more useful in its compact desktop headamp/DAC role, which is another area where it excels. Much like the Arcam rPac (reviewed here), the PHA-1 brings high-quality headphone audio to any place you care to take it. It’s obviously light and compact enough to be a viable addition to a traveling workers gear, and once ensconced on a desk, it’s in its element.

The PHA-1 totally refused to get along with a MacBook Pro at first. As expected, the DAC was picked up by the Mac every time sans drivers, but there seemed to be no way to get music to emanate from the headphones. In the absence of a user manual, Google provided the answer, and once the Mac’s Audio Midi settings had been changed from 16/44 to 24/96, harmony was restored and playback started. This is a strange anomaly because online feedback indicates that the PHA-1 should still work when set to 16/44, but there’ll be loads of noise and interference. After that first instance of non-co-operation, this proved to be the case with noise aplenty, but as long as it was set to 24/96, all was well for the duration of the review.

Sonically, the PHA-1 was well ahead of the headphone jack on the Mac, which gets loud enough but sounds unrefined and even harsh through the HD650’s. The PHA-1 offered a smoother sound that was more energetic, deeper and tighter through the bass and much more spacious overall, not to mention richer and more full-bodied. There was also an increase in headroom, and far higher volume levels were available when desired. High-resolution files sounded fabulous through this setup – textures were more apparent, timbre  more accurate and the air and space improved. However, it would be really nice to have 24/192 support in a device that’s capable of working so well with some of the most revealing transducers available today – reference headphones.

The PHA-1 adds to the enjoyment of low-resolution files, too, with feeds from Pandora and Spotify sounding better than they do via the Mac’s headphone jack.

In Use

It was secure with the iPod locked onto the headamp with the Silicone belts, and the combined package was easy to carry around. The belts do get in the way of an iPod’s controls or an iPhone’s screen, but this can be worked around. You wouldn’t go for a run with this ensemble, or even a walk for that matter unless you stashed it in a backpack or god-forbid, a fanny pack. It would, however, work beautifully on a train or bus or in a café, if you don’t mind looking as non-mainstream as a hipster typing love notes on a typewriter in public.

There’s a real sense of pleasure to be had from using the PHA-1, from its great sound quality to the sheer joys of its tactile interactions; for example, being able to control the PHA-1’s levels with that knurled volume knob. It feels as silky smooth as any you’ll find on a piece of high-end hi-fi gear, and it’s capable of minuscule changes – if small things amuse small minds, then mine must be small indeed, because I never tired of using this simplest of all interfaces.


There are a number of choices for small headphone amp/DAC combinations, mostly available online but few of them are both portable and mobile. Of those that are, some are substantially cheaper than the PHA-1, but the Sony is just so well engineered in comparison.

Arcam’s locally available rPac is cheaper, but the PHA-1’s battery-powered functionality adds to its cost, and admittedly, this unit is going to appeal to a very specific niche buyer within a niche market. Most headphone fans won’t care about going mobile, but for those who find the PHA-1 to be as wonderfully charming (not to mention eccentric) as I do, it’s going to be hard to resist, even at the not-inconsiderable price.

I’m seriously thinking about buying the review unit. It’s allowed me to use my HD650 ‘phones on an almost daily basis, where they’re normally only brought out occasionally when my Perreaux headphone amplifier is set up. That alone is worth most of the price of admission. Throw in the splendid sound quality and the ability to boggle the brains of workmates or random strangers in cafes, and the rest of the cost is covered. ASHLEY KRAMER

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