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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

    John Darko

    Written by John Darko

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

    Darko.Audio is a member of EISA.

    Follow John on YouTube or Instagram


    1. Since the ALO International now has a + in it’s name, I have to ask the most relevant question of all. Does it bend? =P

      Going off on a slight tangent here, so bear with me, JD.

      Unless I’m mistaken, you seem to use (or have used in the past for an extended period) a Nexus 5 as your daily driver smartphone. How does Android compare to iOS with regards to streaming services (Spotify, Mixcloud, Pulselocker, etc) app interface and useability?

      Also, how has the “pure Google” Nexus experience been for you in general? My contract’s up next month and my personal choices are between upgrading my iPhone 5 to a 6 (non +), or going contract-less and having an acquaintance in the US get a Nexus 6 for me.

      • I really like the Nexus 5, not least because Android allows for background processes to run when the phone is in ‘standby’ – a must for when downloading offline content from streaming services. Android also makes it easier to download mp3 files direct from websites and play them immediately using one’s audio player of choice (of which there are many). I’m now rocking a Samsung Galaxy S5 with similar satisfaction.

    2. I purchased the International+ and love the way it improves the sound coming out of my iPhone 5. Still thinking about returning it because, while it’s great the International+ has a battery, streaming music via Spotify or Tidal drains my phone battery in about 1 1/2 hours. Is there a way to get around this? The International+ plugs right into the charger slot as you know.

      • Jason, this doesn’t sound right. I have an iPhone 6+ and an iPad Air and use both Spotify at high res and Qobuz (lossless) running off their internal batteries both with a red wine audio isabellina and an iQube 1 and in all situations my battery lasts many hours. After 1.5 hours streaming lossless off internal battery to either the dac/amp or amp I’d expect to my battery to be down maybe 10-15%.

    3. Hello John – I’m looking at the International+ to use in combo with my iPhone & Alpha Dogs. Any opinion on if it will be able to drive them well enough? The specs look a little borderline. Thank you for your time.

      • The International+ is a little powerhouse and should have no issues getting the Alphas up to speed. 🙂

    4. Hey John,

      I’ve had the original International since mid 2013, and love it. It drives the Alessandro MS2s I use in quieter environments beautifully on the mid gain setting, and the Shure SE425s that I use when traveling love it too. Just drop the gain to low and the earbuds are well looked after.

      What’s the crucial point of difference with the +? You say you’ve not heard the original, but on paper does it look like it’s worth springing for the upgrade?



      • Hey Dave – I went straight to the horse’s mouth (Ken Ball) with your enquiry.

        Ball’s reply: “The main difference is we cleaned up the output impedance, so now the + is less than one ohm output impedance. Also better battery and component quality also works with most Androids platforms. Switched from mini to micro USB. Did not change a huge amount.”

        Hope this helps. 🙂

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