Disclaimer: MST loaned me two AK240 units, one straight from the offices of Astell&Kern Japan and the other, the modified AK240 R. The stock AK240 went back to Astell&Kern weeks ago.
Now that the AK380 is out and the AK480 is on the horizon, the question on many people's mind is: is it worth upgrading my AK240? After all, the AK380 is defined by Astell&Kern's own maladroit marketing department as the evolution of a masterpiece (and that masterpiece itself being an end-game prodcut). If advertising copy were the measure of performance, the AK240, Be[ing] The Ultimate, couldn't be bested.
But it has been. And that's a laugh.
Fi.Quest father, Ryuzoh, is behind a new AK240 mod, something that snazzes up its innards with parts more ultimate, something which I like to call RZAK240, but which Ryuzoh calls the AK240 R. By the numbers, R spruces up the The Ultimate's output performance by quite a margin, especially when Borging the DAP into outboard pre-amps, amps, or powered speakers.
Ryuzoh's mods and builds under the name Musashi Sound Technologies (MST). His website is in dire need of an update.
AK240 R is part parts-swap, parts circuit reach-around, concentrating on power stability, reduced jitter, better phase performance, and more. As a non-professional, I've been able to test for just a few of those. And the results are good.
Ryuzoh's been at the mod thing for a long time. But his geek cred merely augments his acumen: AK sell. Modding AK DAPs has potential for sales. And as I said above, his mods reap real, measurable rewards. AK owners keen on squeezing the last bit of performance from their devices, should check out MST.
I've been unable to detect whether his upgrades adversely affect battery life. As far as I can tell, you still get 6-8 hours of hot-pocket playback from the AK240, modded or stock. Ryuzoh's mods don't address AK240's nastiest of tendencies: IMD distortion out the wazzoo when the output is set to line out. Every AK device I've borrowed or owned has suffered the same high-frequency whinge whether feeding ALO's excellent CDM (reviewed here; measured here), or straight into the Lynx HILO (reviewed here; measured here) the signal goes to shit. I suggest turning off line-output and backing the volume down to a maximum of 70,5.
But that is a AK problem. No mod I've found yet rectifies it. In most other categories, Ryuzoh's mod measurably improves the AK240. What follows is the list of what Ryuzoh does to your AK240:
“Following is what I did in my AK240R (R represents “Re-Circuit”).
1 - Replacing quartz (20ppm or more tolerance) to 1ppm TCXO.
- It is 12MHz base clock and will be used in multiplied numbers with PLL circuits in WM8804 digital audio interface.
- If the clock’s tolerance would be worse, tolerance will also be multiplied. Then time domain will also unstabilized, and provides huge jitter too.
- Therefore I stick to less tolerance in the clock section.
- The TCXO what I used is also providing less phase noise (about -150dB).
2 - Fortified power supply.
- In recent high performance DAPs, power consumption is huge problem as you know.
- On stock circuits in AK240, most of power supply capacitors are ordinary laminated ceramic capacitors.
- Ceramics has piezo electric effect, and less performance in analog circuit. Thus I added several film capacitors onto each power supply bus (+3.3Vanalog, +5.0Vanalog, -5.0Vanalog, +3.3Vdigital) to reduce influences of ceramic capacitors and to improve sound quality.
3 - Sophisticated analog section.
- This is the most featureable point in this modding service (and takes materials).
- As for $3,000 class tier DAP, resources are strictly cheap.
(1) I replaced WHOLE resistors and capacitors from DAC chip to output amplifying section. Also, transient in filtering section is also getting slightly faster than stock. It’s really tough work for me, but I think worthy to improve sounds from it. Higher resolution, and sublime treble, deeper bass, I had experienced all sound characters are getting improved.
(2) Balanced (BTL) output chips are replaced to OPA1632, which is dedicated to performance audio, and gives higher current output to drive. Also single ended output chips are from OPA1611 to OPA211, they are under same lineup in TI’s audio amplifiers, but this choice was just up to my preference. Signal extracting point to single ended is bypassing balanced amplifier, and will gives more fidelity than stock architecture.
(3) Less output impedance and additional margins.
This is same method to reduce output impedance as like AK100, AK120, etc.. Additionally, I added stabilizer on output section to make margins to drive, also to prevent oscillating.”
That Ryuzoh upgrades AK240s starting at 1000$ (USD) - which works out to the difference between a new AK240 and a new AK380 - is telling: you shouldn't expect your many-thousands $$$ DAP to perform strictly to its price point. Enjoying it for what it is outside of strict dollars-to-performance-discharge is a good idea.
My thoughts:
Honestly, both the stock AK240 and the AK240 R best the ability of my ears to decipher improvements beyond 16 bit audio. Both the stock AK240 and Ryuzoh's mods sound great. And going between them was dizzying as hell. Did I hear the deeper bass Ryuzoh suggested? Was treble more sublime? I don't know. I can only say that I very much like how John Denver and Rob Zombie sounded out of both units.
Measurably, MST's AK240 R is stabler, more dynamic, and has better stereo separation than stock, in some cases almost pornographically so. In fact, so great are the measurable differences between them that I'm tempted to call the stock unit from-Astell&Kern a dog; alternatively, aside from wonderfully low THD and IMD levels, the Ultimate DAP is simply not that ultimate.
I didn't have the stock AK240 long enough to complete a perfect suite of loaded tests. But I did finish a few. In most cases, loaded tests show the AK240 R's prowess less explicitly than do unloaded tests, suggesting to me that this mod is best performed on units whose primary purpose is music server. And in that role, the AK240 R should be staggeringly more capable.
In particular, a reduction of 10dB in noise, a jump of 10dB of both dynamic range and stereo crosstalk performance is almost unbelievable. Again, I'm tempted to say that the stock AK240 I was lent is faulty. Still, it sounded good to me. In some cases, the iPod nano 7G (measured here) bested it.
Each unit was tested under the same conditions, volume set to 70,0 and measured to within 0,3 dB via the Lynx HILO.
On Ryuzoh's tooling:
I've now tested three AK mods:
1. Vinnie Rossie's RWAK100
2. Mezzo HiFi's MSAK100
3. MST's AK240 R
In the first two cases, tooling quality was tip top, though the edge (for not returning the unit to me even the smallest trace of edge scoring) goes to Mezzo HiFi. Then Vinnie Rossie. MST's modifications were performed on his own AK240. Screws from its ass show stress. And the unit itself has been well-loved. I assume that customer units will fare better.
Onto performance metrics
RMAA:
The following Rightmark Audio Analyzer tests were conducted through this equipment.
Source: Astell&Kern AK240 and AK240 R
ADC: Lynx Studio HILO LT-TB
Computer: 2012 27" iMac
Cables: 1,5m Hosa Pro 3,5mm stereo to dual 3-pin XLR (around 8$)
Loads:
NL - no load
SM2 - Earsonics SM2
ES7 - Audio Technica ES7
DT880 - Beyerdynamic DT880/600
NOTE: in the below tests, the AK240 R is called the RZAK240. I took RMAA measurements prior to Mr. Ryuzoh informing me of the exact name of his mods. Besides, RZAK240 kind of has a ring to it.
16-bit & 24-bit TARGETS no load
Square waves (coming)