RWAK100 is a RWA modded AK100 like his famous iMod. I was provided a demo unit from him.
As for the details of RWAK100 include order instruction, have a look here.
I am a big fan of his iMod, I have iMod 4G as well as iMod 5.5G. iMod 4G turned the headphone out to line out jack. iMod 5.G is still my favorite work horse of portable gear. I love its smooth and warm musicality even I compared it with iPod classic that I usually use for HP-P1 digital setup. Even if I have iPod classic now, I use iMod 5.5G for almost portable amp setup.
iriver AK100 is a new star of hires DAP world. I use it since I was involved in the pre-production testing audition. AK100 is a little marvelous DAP that delivers a detailed hires sound up to 192kHz. AK100 is a good sounding gear even if I use it as stock condition, some people noticed on high output impedance may harm sound when coupled with low impedance IEMs.
Vinnie probably thought his method of the iMod would be a solution.
Here is the detail of the RWAK100 from his write up.
We bypass the 22-ohm resistors in the output stage, and hard-wire (via Cardas copper litz solid core wire) from the output stage FETs directly to the pins of the headphone output jack. Besides bypassing the 22 output resistors, this also provides the shortest, cleanest path from the output stage to the headphone jack - also bypassing the tiny circuit board traces, and the header that connects the main board to the smaller headphone jack board. It's essentially a direct connection from output stage to the headphone jack. Output impedance is now under 1 ohm...
The point of RWAK100 mod is to improve headphone out quality. Other parts are not modified at all so we can still use optic out and software upgrade. In addition, you can get decent fixed audio output thru headphone out by turn the volume all way up (max - 75). Doing so, you can bypassing the digital volume function. I guess it is an internal function of WM8740 DAC chip. This is same to stock AK100 by the way.
The box package and outlook is exactly the same to stock AK100 expect the base sticker shows RWA mod.
I have upgraded the FW with the latest 1.30 to compare with my stock AK100.
I use UE18 and JH16 mainly that has been combined with Whiplash TWag. Because I think UE18(21 ohm) and JH16(18 ohm) are low-impedance, high-efficiency and best performance to be able to reveal the difference.
The difference between stock AK100 and RWAK100 is obvious than I thought. Off course I hear the sound characteristic of AK100 is inherited but the overall sound impression has changed. The most notable change is the bass region. If you use Pops or Rock with a good bass beats, you will hear the huge difference there. The bass quantity is plenty compared with the stock and the bass is now impactful. I'd say the bass is impactful rather than to say bass is huge. The bass improvement affects on the whole audio spectrum and I feel the overall sound is now richer than the stock.
To feel the sound richer, I think more detail has also been contributed. Yes I found now RWAK100 is even more detailed than the stock. Even if I tried with acoustic instruments track, the difference is there. I can hear a slight guitar fret noise clearer.
With this bass and detail improvement, I enjoyed orchestral sound much better than before. I feel classical tracks more impressive with RWAK100.
I also tried a sample track comes with the iriver microSD. For example "Spanish Harlem", bass impact is a big difference with RWAK100. The bass has more weight and attack. The detail of the hires track has more resolution in RWAK100. I hear more details thee.
Iriver stated Vinnie's mod would "Even it improves the sound power, it reduces smooth and delicate sound detail of AK100".
But I disagree with them. From what I found in the audition, I hear clear detail difference between RWAK100 and stock, that is RWAK100 is better regarding the detail and smoothness. iriver's objection could be theoretically correct I am not sure about it but the actual implementation on the tweak of RWAK100 - like shortest signal path, good cable - would enhance the sonic performance I guess.
As for headphones, I tried with Audio Techinica ESW10JPN(45ohm). Again RWAK100 delivers more bass with deep impact compared to the stock. This is not only for rock or pops, Even in the "Spanish Harlem" I hear the overall sound difference.
I also tried using ultra high impedance Heir Tzar 350(350 ohm). I noticed the bass difference is not huge now but I still found detail difference. When I took a listen with "Spanish Harlem", I hear more transparency in the details.
I was wondering about the bass characteristic of AK100 that is the bass seems inferior in custom IEMs but the bass seems enough with Tzar 350. Now the riddle has solved and the solution is here. Also the details are even better. I'd say RWAK100 would bring out the best of AK100.