in , , ,

ALO Audio International+ portable amplifier/DAC review

  • If you look at the ALO International+ and see only a headphone amplifier for coupling to an existing digital audio player, look again. It’s much more than that! US$599 gets you a portable 24bit/96kHz-capable DAC coupled to a Class A/B headphone amplifier in a palm-filling robust metal case.

    The upper micro-USB port is for charging from any computer; that’s an improvement on the original International that required a dedicated 12V wall-wart for refills. The Japanese-made 3400 mAh Lithium-ion battery nets up to seven hours playback time when the International+ is used as an amplifier, half that when deploying its in-built Cirrus Logic D/A converter as well. That’s not quite as impressive as the Cypher Labs Theorem 720 (reviewed here) but it would seem ALO have traded in on run time to keep box size down – critical when trying to pocket a portable head-fi rig.

    What sets the International+ apart from its Portland competitor are broader connectivity options and a more even tonal balance.

    In its most basic of applications, the International+ will work as a battery powered DAC/amplifier on the desktop. Connect the lower micro-USB port to a computer and you’ll hear far greater dynamics and detail than your PC or Mac’s onboard soundcard – that much is a given. What comes as a surprise is witnessing the International+’s punchier low end and more caffeinated treble when compared to ALO’s comparatively smoother, slightly veiled ‘The Island’ USB DAC.

    Then there’s smartphone amelioration.

    USB audio is a hit and miss affair with Android devices. An OTG USB cable doesn’t guarantee success – some external DAC/amps only play ball from within the confines of eXtream Software’s USB Audio Player PRO; an app that loads its own USB audio driver and can deal in hi-res audio (HRA).

    On a stock Samsung Galaxy S3, Galaxy S5 and Cyanogen-modded Google Nexus 5 digital audio flowed freely over USB from ALL apps – hello Spotify, Pandora and Qobuz!

    What about Apple devices? The Lightning-to-USB adaptor sees out-of-the-box compatibility with iPhone 5/5c/5s and 5th Generation iPod Touch and its internal battery means the International+ won’t be red-carded by iOS for trying to draw too much power.


    Without the likes Onkyo’s HF Player app, iOS 7 won’t parse anything above 16bit/48kHz. To complain about Cupertino’s current lack of commitment to HRA is to miss the point here. External DAC/amps like this drastically improve what many listeners already use: streaming services and lossless Redbook files. The current run of iPhones and iPods sound good but the International+ sounds great; it adds top to bottom vitality and an uptick in bass heft to strip iDevices’ of their erstwhile thinner, tense sonic signature.

    With an output impedance of below a single Ohm coupled to switchable low, medium and high gain settings the International+ is intended to drive pretty much any headphone you throw at it.

    It provides precisely the kind of amplification diet required to properly nourish the DITA Audio Answer IEMs and thus saving them from occasional treble steeliness heard via the (first generation) Astell&Kern AK120. Icing the IEM cake here is zero evidence of any circuit hiss or noise. Well played.


    The AK120 is no slouch – its output is nice and clean – but its no match for the power served up by the ALO box whose 3.5mm single-ended output pushes 70 mW into 32 Ohms, 100 mW into 50 Ohms, 60 mW into 300 Ohms and 30 mW into 600 Ohms. Need additional power for driving higher impedance ‘phones? The mini-balanced output, untested for this review, gives 240 mW into 300 Ohms and 120 mW into 600 Ohms. That’s good news for Sennheiser HD800 lovers.

    “When we wanted to improve on the International and make the International+ we really did not want to fuck up what was golden about the International, namely the bad ass headphone output stages.”, says ALO mainman Ken Ball.

    I’ve not heard the original but the Plus iteration impresses at every turn.


    I’ve always enjoyed the rockier cuts from R.E.M.’s Monster and New Adventures In Hifi albums but they often stray into skeletally edgy territory without proper handling. The Astell&Kern AK120 driving Audeze’s LCD-X makes a good fist of it but use the supplied straps to secure the International+ to the back of the AK120 and you’ll hear how the piggy-backing amplifier really grabs music by the balls.

    This duo better fleshes out the tonal mass of R.E.M.’s “How The West Was Won And Where It Got Us” for a plumper bottom end, richer midrange and more refinement up top. With the AK120 holding tight to DAC duties and volume set to maximum (via its single-ended headphone socket), the end result is better with the International+ than without it. Strike that – it’s waaay better.

    Nowhere is this improvement more obvious than with headphones that present more of a challenging load. The ALO unit keeps the pin-pricking HD800 treble on a very short leash; that’s a good thing.

    Rewards don’t only spill from higher-end headphones. The KEF M500 really show what they’re capable of in ALO hands, netting some of the finest portable sound quality I’ve heard to date. The International+’s closest rival isn’t the second generation Astell&Kern AK120 but the cradling Glove A1 from CEntrance.


    And similar to the Glove A1, the compromise is size. The AK120 DAP and International+ makes for a bundle that’s only really pocketable in bigger jackets and backpacks; that’s fine for colder climates, less so for Australian summers where even shorts and a t-shirt is sometimes too much!

    It’s also worth noting that ALO have thought about the International+’s in-pocket use. The gain switch and volume pot both require a firm hand to ensure there are no nasty surprises should you bump either whilst removing it from your pocket.

    I see it like this: the Samsung Galaxy S5 sounds OK whilst the iPhone and iPod Touch sound better. The Astell&Kern digital audio players are a step up again. However, the International+ will take each of these portables to a whole new level. And once you’ve heard how it can advance the nebulous but all-encompassing enjoyment factor, it’s really hard to go back.

    Further information: ALO Audio

    Associated equipment: Astell&Kern AK120, Glove A1 DAC/amplifier, Sennheiser HD800, Audeze LCD-X, KEF M500, DITA Audio Truth IEM, Cardas EM5813 ‘Ear Speakers’, Master&Dynamic MH40

    Written by John

    John currently lives in Berlin where he creates videos and podcasts for Darko.Audio. He has previously contributed to 6moons, TONEAudio, AudioStream and Stereophile.

    Darko.Audio is a member of EISA.

    Follow John on YouTube or Instagram

    KEF X300A Wireless powered loudspeaker review