Mezzo Hifi MS-AK100 And MS-AK120 – Perfect Nipples

Disclaimer: The prototype Mezzo Soprano AK100 and AK120 mods I received from Sean Chan were well beat-up. Neither did they run perfectly stably. Mezzo Hifi modded my AK100 free of charge for the purposes of this review. The MZAK120 mod I used for the same month-or-so trail period before deciding that the MZAK100 was THE ONE TO HAVE. In perfectly stable shape, both prototypes reflect the performance of production units. And that is awesome.

Here’s to sanity. Here’s to patience. Here’s to sticking with it. Here’s to the once-Ultimate. Yep, here’s to not throwing out your first-gen iRiver AK100 and 120 players. While not a fan of the original AK100, nor its stick-it-to-the-customer mkii version, I’ve managed to purchase two. I bought them late last year, right before they turned one year old. I’m a sucker like that.

But I tend to hang with the performance crowd, and since I’m not keen on high amounts of background noise, I rarely used either player. I was this close (holds up a tweezer between baby thumbs) to selling both.

Enter my personal saint, Headfi’s muscular Sean Chan.

The dude prepared a paper bag stuffed to the brim with various electronic devices while I queued for a meatball sub. The bag changed my life. I divested myself of the sub the following morning.

In the bag were two glue-stained prototypes from Mezzo Hifi. Though dubbed mezzo soprano, they were ugly, unrefined, and inelegant hardware modifications of the original AK100 and AK120. Out of their asses jutted a lit-up plastic switch. They were scratched up and sported glue traces along their flanks.

Evidently, they went for 500$ for the AK100 mod, and 700$ for the AK120 mod. If you ain’t got either of the players, you can send 1100$ for a brand-new MS-AK100 mod, or 1950 MS-AK120 mod.

Here in Japan, AK100’s go for 220-400$, and with iRiver’s penchant for obsoleting its own devices, I’d scour the web for something used. The great news is that the final hardware revisions are nearly immaculate. Gone are the glue traces, gone are the scratches. Other than the hardware switch for the soft knee, the players look and act, as good, or better than their original versions.

“Care to review ‘em?” asked the saint.

I’ve seen production models worse off; unperturbed I nodded, brushed off a metal chair, and sat down to a bright afternoon in Tennouzu square. Sean opted for white bread; I went for honeyed oats. Subway grit snowed from our finger tips. Pigeons bobbed and dodged around our feet.

After waving goodbye, I set off home, enjoying Sean’s famously eclectic music. My earphones of choice were the Ultrasone IQ. From that moment on, the MS-AK100 became my DAP of absolute awe.


What I heard is why. This is what I heard:

1. noiseless output
2. perfect left/right balance
3. incredible resolution
4. power
5. control

I ran that battery down as fast as ever I have a DAP. The official party line is that Mezzo’s mods drain batteries about 20% faster than usual. BS. I get roughly 20 hours on the original AK100, sometimes more. The Mezzo mod gets me 12 hours, give or take.

But it is the sort of twelve hours of spastic enjoyment that the original AK100 simply hasn’t a chance in hell of affecting. In fact, I will argue that the mighty AK240 shows as poorly next to it.

Stock, the AK100 it is as noisy as early iPod nanos. It also suffers as much as they do with supplying the right amount of current to low-Ω earphones. The result is stifled bass output, intense swings in frequency response, and notable signal instability at higher volumes. The AK120 suffers similar problems, albeit to a lesser degree.

Both the MS-AK100 and MS-AK120 fix all of that, though the MS-AK120 to a lesser degree. Namely, MS-AK mods boast headphone outputs with the cleanest signals I have ever heard, in any portable device, ever. That means absolutely noiseless music even paired with hyper-sensitive earphones favorites like the Noble Audio K10 and the Grado GR10. Hiss=zilch. Likewise, it supplies perfect current to every headphone I’ve thrown at it, resulting in distortion-free playback of demanding music at all volume levels.

By the numbers, its loaded output runs ahead of the AK240, supplying both wider stereo separation and lower distortion number. But numbers only tell how a device performs.

At the ear, the result is absolutely tidy. The MS-AK100’s superbly clean, superbly dynamic, superbly reference-level output opens up your music like never before. It’s trite to say that you will hear things you previously didn’t. But even very low levels of hiss can mask small details. And the MS-AK100 and MS-AK120 are absolutely free of hiss and background noise.

Recently, I’ve fallen in love with DACs and sources whose sound rifles through aggressive to semi-aggressive low-pass filters. The TENTO PortaDAC 1866 is one. The Linenberg Vivace is another. The MS-AK100, switched to either phase position, is a third. With an output so clean, so highly resolved, and accurate, it approaches, if not surpasses, the limits of the typical human ear. I would argue that a low-pass filter is important. It softens aggressive highs. It mollifies sibilance

Which, considering that my favourite full size open headphone is the DT880/600, is a blessing. Speaking of which, I’m enjoying Armin Van Buuren’s A State of Trance, Episode 467 through the DT880/600 and MS-AK100 combo now. While not optimal, the MS-AK100 supplies enough voltage to make a turn to 100% of the volume pot too much to handle for these ears. And, even at that setting, signal quality remains high, with only the barest hints of IMD- a feat at which most players would balk. The signal remains full, dynamic, and punchy.

Sure, some DAPs get louder than the MS-AK100 with voltage-hungry cans, but not a one boasts the same signal quality.

That includes the MS-AK120. Mezzo Hifi transplants the same WM8741 from the AK120 into the AK100. The AK120 gets similar treatment: 3,5mm balanced output, hard-stopped volume pot, minimum apodisizing filter, minimum phase soft knee, and the removal of background noise. But, it doesn’t offer the same audible returns.

High-current, low-Ω earphones will suffer inexplicable (although minimal) frequency dropouts and lifts, though not as bad as the stock AK120. Apart from that, performance really is exemplary, but if you’re really into the bang-for-buck experience, the MS-AK100 is your best bet.

Follow the jump for features, meh, and more:

3.7/5 - (3 votes)

Back before he became the main photographer for bunches of audio magazines and stuff, Nathan was fiddling with pretty cool audio gear all day long at TouchMyApps. He loves Depeche Mode, trance, colonial hip-hop, and raisins. Sometimes, he gets to listening. Sometimes, he gets to shooting. Usually he's got a smile on his face. Always, he's got a whisky in his prehensile grip.


  • Reply November 14, 2014



  • Reply November 14, 2014


    I was offered a lend of an early prototype after the Tokyo Show to try out, but i was too busy to do it justice and pointed the way to other Tokyo head-fiers. I have regrets….. 🙂

    • Reply November 14, 2014

      ohm image

      Really this thing is awesome. I didn’t expect much at all. Considering I’m not a fan of the AK100 or AK120, my surprise, and later, praise, for the MSA mods is big.

  • Reply November 15, 2014

    Ronen Weiss

    intrested to know how do these two compaire to the dx90 you recently reviewed?

    • Reply November 15, 2014


      I reviewed them, not Nathan. But he does have or knows the DX90 so he should be able to reply

      • Reply November 19, 2014

        ohm image

        I own both. Both are awesome, but the MSAK100 is the more impressive sounding device. That said, stock, the AK100 is poor by comparison to the DX90.

    • Reply November 15, 2014


      +1 – especially given the significantly higher price of admission.

    • Reply November 16, 2014

      ohm image

      The MSAK100 and 120 both have LESS background noise even than the DX90, both have balanced 3,5 TRRS outputs, and longer battery life. You cannot rockbox the MSAK100 or 120, but apart from that, there is no real competition. THat said, the MSAK100 is the better performing part for low-Ω / high-current earphones than the MSAK120.

      I have never, ever, been as impressed by a portable DAP or MD, or anything – soundwise. The problems inherent with iRiver’s navigation, etc., can’t be fixed, but soundwise, there is no equal.

      • Reply November 16, 2014


        how does the msak100 line out compare to the dx90 line out sonically?

        • Reply November 17, 2014

          ohm image

          Both are excellent. The LO on the MSAK100 has the low-pass filter, but apart from that, there’s nothing between them.

          The balanced output on the MSAK100 of course is something which only the MSAK mod has.

      • Reply November 17, 2014


        Damn… maybe I should have waited a couple more weeks before buying my DX90… not that I regret my DX90 though. Far from it.

        • Reply November 17, 2014

          ohm image

          Like I said, stock, the DX90 is unrivalled. Between them, the differences I expound upon are, when enjoyed back to back, minimal. But if you listen FOR something, say, like hiss, you will notice the difference.

          I’m the dude known to headfi as “the hiss king”. I hate it. And I do what I can to eliminate it. Until the Mezzo mod, the DX90 was about as good as I’d heard.

          • Reply November 18, 2014


            I wasn’t expecting it to sell in my country but it appeared less than two weeks after my DX90 purchase. Part of the appeal was due to the balanced line-out as I have a CL Duet. Then again, I bought the DX90 so I wouldn’t have to lug around a separate amplifier when going portable.

            I’ve asked before on the HP-V1 review if you’ve gotten the chance to compare the HP-V1 with the A2P TUR-06 but haven’t gotten a reply. I’m assuming you haven’t seen it? Although not the place for it, may I ask for a comparison in terms of bass quantity, level of warmth, and soundstage? Thanks oh and I love the podcasts. They’re quite… comical.

            • Reply November 18, 2014

              ohm image

              Hello Marc, I may not have gotten back to you, or I may have, but indirectly. Either way, I’m sorry. I do not own the HP-V1. It was loaned to me for 2 or 3 weeks. I can no longer compare it to anything. It was awesome though.

  • Reply November 16, 2014


    Er…why couldn’t iRiver have done all that in the first place? They make enough noise about their players.

    • Reply November 17, 2014

      ohm image

      Noise is one of the major things the Mezzo Hifi mods fixes. RWA’s modification fixes the impedance problem of the AK series. The Mezzo adds bells and whistles that audiophiles really dig.

      It is a serious hardware mod, so not something iRiver would have done. That said, at its current used prices (in Japan), it would have been awesome had iRiver done it right in the first place.

      My players were got for 350$ and less. Today, you can sometimes find them for 250$ here.

  • Reply November 18, 2014

    Michael Amouyal

    So how do they perform vs. AK240 and 901?

    • Reply November 19, 2014

      ohm image

      Lower noise than the AK240, and by the numbers, better all-around performance. Ditto the 901, but a somewhat similar high frequency roll off. Not as aggressive, though. Imagine the HM901 with a perfectly performing output but with the same great signature. Then make it smaller, with better battery life.

      This mod isn’t as powerful but it makes the AK100 by far, the most impressive portable hi-end DAP out there. It is worth the 1000$ or so investment.

  • Reply November 19, 2014


    does the MSAK100 still have the high output impedance that the original AK100 has? (just wondering in relation to lower impedance CIEMs – Thanks

    • Reply November 20, 2014

      ohm image

      No, it does not. It spits a lot of current into low Ω loads, and is able to sustain incredible signal quality even with the hardest to drive low-Ω earphones. Excellent. No noise. Perfection.

  • Reply November 23, 2014

    Calvin Xin Ci

    I was looking to get the DX90 soon and this came up. Nathan oh Nathan, such poison. My wallet is dying..

    • Reply November 25, 2014

      ohm image

      It’s very very hard to keep up, but I suggest this: decide what you NEED. Decide what you want. SQ is great on both units, though I argue very strongly that it is better on the MSAK100 than the DX90.

      That said, the differences are probably not as large to the ear as they are to the reviewer and the benchmarks. I favour size over everything. Then good interfaces and format support. Next up is battery life. Finally, the other stuff.

      And the MSAK100 delivers on ALL fronts. It’s noiseless output is a dream. Once you experience it… trust me, there is no going back.

      • Reply November 26, 2014

        Calvin Xin Ci

        Now there is a product that came to play, the Glove Audio A1. Seems to have very good reviews. I’m planning to get an used AK120 from Japan, then send to mezzo audio.

        • Reply November 27, 2014

          ohm image

          The AK120 MSA mod isn’t as good. The AK100 has better all-around performance. But if you prefer the sound style of the AK120, it may be a better investment.

          Also, the MSAK100 gets its DAC replaced with the one (just not dual) in the AK120.

  • Reply November 27, 2014


    Nice review Nathan, especially the pockets for the dacs are lovely, would definitely get one if you can share the info 🙂 Greetz P.

    • Reply December 11, 2014

      ohm image

      The pockets come with the modifications.

      • Reply December 11, 2014


        Sadly to hear, the spread a nice atmosphere, probably because of my memories in the alps. Maybe I will sew a pair, shouldn’t be that difficult – I hope.

  • Reply December 26, 2014

    Nick P

    Hey Nathan – I have the AK100mk2 and have a chance to upgrade to either the MS-AK100 or MS-AK120. Can you confirm that the MS-AK100 actually sounds better than the MS-AK120? I was wondering whether the MS-AK120 is better overall but there is a bigger improvement in SQ between MS-AK100 vs AK100 compared to MS-AK120 vs AK120? Thanks!

    • Reply December 27, 2014

      ohm image

      I prefer the MSAK100 to the MSAK120. That is personal, but measurements bear out that the MSAK100 may perform better. The difference is minimal, but present.

  • Reply May 3, 2015


    Hi Nathan,
    after a few months, what is your thought, do the good impressions last? i’m having the chance to get a second hand unit of the msak100, but curious if, unamped, this unit is a long time keeper or if it dies of AK’s in my opinion horribly slow interface screen…
    thx for any opinion

    • Reply August 4, 2015

      ohm image

      Hello whatever. I’m sorry I’m late.

      The unit I originally tried performed wildly better than the unit Mezzo later modified for me. I hope it was an anomaly. If not, I will have to update this review with serious provisos.

      • Reply August 9, 2015

        Shoghi Sadeghi Afshar

        hope you give us an update soon, I nearly went and bought a AK100 for this mod.

  • Reply January 2, 2016

    Lee ZH Edgar

    Hi Nathan,

    Could you comment on the improvements between the MS-AK120/MS-AK100 and their stock versions when using the line out to a portable amp?


    • Reply May 15, 2016

      ohm image

      They measure better. There is some voltage instability, but it is inaudible.

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