MODS: Three M.S.T. mods, sitting in a tree

Disclaimer: I paid for materials for each of these mods and nothing for the labour. You can get ahold of Mr. Ryuzoh via his website:

Relevant links:

Report – A case for the Cowon Plenue D
Mezzo Hifi MS-AK100 And MS-AK120 – Perfect Nipples
Review: Chord Mojo – The Chosen One
Review: Balancing Mojo with MST Audio’s Mojo-Kai
RMAA: MST Audio Chord Mojo-Kai (balanced) 24-bit

From the mundane, to the sublime, M.S.T. have something for everyone. In my possession are three mods, one of which marks a market revolution and another of which soups up Cowon’s entry-level DAP. The most mundane of Ryuzoh’s mods is a straight parts swap, that, while offering audible and measurable improvements to the now-classic AK100, you’d be forgiven for passing over. And yet, that is only where Ryuzoh’s mods begin. 

The thing with his mods is that they come with choices for almost every price point.


The AK100 unit MST-modded for me outputs similar amounts of hiss noise vis-a-vis stock, but pushes a mean stereo separation of -95dB under load, while stock makes it to -73dB. Both THD and IMD measure 10x less than stock under load. In this respect, it is like an RWAK100. Different to it is that you can also add a bunch of stuff. I paid for the most intrusive mod, and which tips the scales at 74.000¥. Ryuzoh added coaxial to the AK100’s digital outputs.

It is a brilliantly conceived mod, and one I wish Ryuzoh would pursue even further.

MST three mods 03-1


It pairs beautifully with Mojo-Kai, the revolutionary Mojo modification about which I wrote this article: Review: Balancing Mojo with M.S.T. Audio’s Mojo-Kai. While Mojo-Kai delivers few single-ended measurable performance gains vs. stock, its high-performance balanced output returns performance far and away better than any high-end balanced DAP I’ve tested. And, because it’s a Mojo, its USB input can turn any any computer into a lightweight, balanced powerhouse. Mojo-Kai is one of a kind.

Plenue D-Kai

Then there is what I will call Plenue D-Kai, a mod that due to space constraints in the compact DAP, and comparatively prohibitive costs, Ryuzoh deems unmarketable. And I understand why. Spending $300 to modify a player costing less, on first blush seems silly. But then again, a full Mojo-Kai goes for 74.000¥, or about what you pay for a new unit. And used AK100ii’s go for 35.000¥, which is roughly what Ryuzoh’s high-end mods of it cost. In other words, it’s not out of the question. And, given that there are notable improvements in THD in both %s and sweeps, it is an interesting mod. The only downside I’ve found that stereo crosstalk may be lower than stock. I don’t hear a difference. It is the stealthiest, and least externally intrusive of Ryuzoh’s mods. But perhaps Ryuzoh is right: stock, the Plenue D is so good that pipeline improvements reveal themselves with less pomp against the AK100’s mods. 

MST three mods 02-1

Back in the late 1990s in suburban Toronto, souped-up and lowered Honda Civics and Pontiac Sunfires pooted around every street corner. At the time, I held nothing but contempt for them. But their market was real. Their owners were enthusiasts. So are many of us. Paying for an expert to drive the last performance out of our products is a tangible improvement many are willing to pay for. 

A souped up Plenue D is, in its own market, every bit the equivalent of a Honda Civic with a new exhaust system and firmed-up chassis. Mojo-Kai? A 2×2 Audi modded into a Quattro. The AK100-Kai? I’ve not found a car analogue to the addition of another SPDIF output and firming up of its general output. But, for fans of the AK100, it is a real boon, although nowhere near as much an overhaul as the MZAK100. 

Which makes me wonder: when will Mr. Ryuzoh do to the AK100 what Mezzo Hifi did? 

I am confident that buyers intent on the long view realize that mod expertise so applied could breath new life into players and DACs both hi and low-end, and could transform out-of-circulation gear. 

5/5 - (4 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 June 28, 2016

    Barun C

    Nice article Nathan. Was waiting for this since the last Ryuzoh mod article. Mezzo is still better then the Ryuzoh mod eeigh? Seems okay since the mezzo mod costed something like $500 I guess?

    Anyway, any vanilla DAPs you’ve found which sound good straight out of box when lining them up against the Ryuzoh or RWA or Mezzo mods? (Excluding the iPod Shuffle and Nano)

  • Reply June 28, 2016


    Short but hopefully semi-sweet. The Mezzo has a few things in its favour:

    1. very low levels of hiss
    2. higher measurable performance across the board

    But it runs hotter, gets worse battery life, and while it adds an unamped balanced line out, doesn’t add coaxial, which is (at least to me) the preferred SPDIF method, especially since you can use any old cable for digital output. (The caveat of course, is that you get best performance with a 75Ω coaxial cable.)

    At the ear (normal listening volume levels), most players equalise quite a bit; still the AK Jr. is really good (despite some loss in current when under load), and even the AK100 mkii is very good (similar loss of current). I don’t have as wildly extensive experience with many players though.

  • Reply June 28, 2016

    Barun C

    Mezzo mod seems like more of an “audiophile” choice among both audiophile mods. Battery life is really critical in today’s world even with the availability of chunky portable battery packs. People want to carry something light and convenient, hence the term portable audio player. The earlier AKs may have been small, but the current one’s are not small by any stretch of the imagination.

    Even the cheap pen-drive based Chinese audio players I used to use in the mid 2000s with small displays were great despite not being perfect in SQ and memory size as they lasted for days and costed not more then $20-30 max.

  • Reply December 12, 2016

    Alex Alanis

    Excellent article as always. In your opinion, what would you choose? Modding AK100 to RWAK100 or just buying a Plenue D?

    Thanks btw are you going to review PSB M4U4 or iBasso TI03? I’m looking forward to seeing those iems reviews

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