Cayin N6ii Replaceable Audio Motherboard R01

CAYIN N6II is an old terminator(T800) who fought the audiophilia wars and still hasn’t given up. Given that he has got a new exoskeleton and a better heart, it is back at its game of being the best again. So today we will be looking of how its new heart, fares against its previous models. So here comes the Version 5.0.1 heart (now T800 V2) – “THE R01-24Bit discrete R-2R ladder DAC module”.

DISCLAIMER- THIS UNIT IS BOUGHT BY ME FROM @MusicTeck AND Andrew FROM MusicTeck WAS VERY HELPFUL, TO HELP ME PASS THE SHIPPING AND CUSTOMS HURDLE TO INDIA. I WOULD HIGHLY RECOMMEND TO BUY FROM THEM SINCE, THIS IS THE MOST HELPFUL STORE I HAVE ENCOUNTERED, EVEN MORE THAN MY COUNTRY’S ADUIO STORE. PLUS, THIS GOES WITHOUT SAYING, THE POSTIVES AND NEGATIVES IN THIS REVIEW ARE MINE ONLY, PLEASE DON’T TAKE THEM HAHA! AND I CANNOT BE CONTROLLED BY ANYTHING EXCEPT A DOG/CAT MAYBE
HERE’S THE LINK FOR R01, NOT AFFLIATED OFCOURSE. (spoiler alert-you might want to keep R01 after you try it haha!!! BE WARNED ).

UNBOXING EXPERIENCE-
Now the N6ii I got was from a good friend and it was a real good experience but sadly, it came with T01 module only. So, no unboxing experience for me from there E02 similarly, I missed out since another friend aka @RoXor loaned it to me for an experience and I missed out buying another module again haha!! Well I think my brain and GOD both had same thing in mind for an unboxing experience, so I would let the pictures speak and show how beautifully simple yet elegant it is. (P.S- I like simple yet elegant unboxing)

ACCESSORIES-

• A screwdriver T5X25mm, NO-828.
• Two leaflets for user guide and installation.
• A nice small bean plastic full of extra screws.

TECH SPECS-

SOMETHING MORE ON THE R-2R LADDER DAC’s AND HOW CAYIN MANAGED TO ACHIEVE IT-

“R-2R Digital-to-Analogue Converter, or DAC, is a data converter which use two precision resistors to convert a digital binary number into an analogue output signal proportional to the value of the digital number.



A R-2R resistive ladder network provides a simple means of converting digital voltage signals into an equivalent analogue output. Input voltages are applied to the ladder network at various points along its length and the more input points the better the resolution of the R-2R ladder. The output signal as a result of all these input voltage points is taken from the end of the ladder which is used to drive the inverting input of an operational amplifier. The R-2R resistive ladder network uses just two resistor values, one which is the base value “R” and the other which has twice the value, “2R” of the first resistor no matter how many bits are used to make up the ladder network “quoted from www.electronics-tutorials.ws.

In case of CAYIN, they did research and testing over years to find a good resistance that is – 5.1kΩ and hence adopted this as their Resistor (R). Hence the ‘2R’ is gonna be 10.2kΩ and it’s made to order.

Now they just had to figure out the circuitry and how much of the R-2R can they manage to cram into the small module and yet provide a fully balanced connector and also keeping single ended connection too. Now chips are not everything as implementation also make a good change to the sound. Hence, they went with Oversampling Interpolation Filter – which converts the Digital audio signal to Land R channel of 24bit/768kHz serial audio data signal, further being converted to parallel data signal by Serial to parallel Shift Register and transmitted to DAC circuit. This is then converted to analogue by the 24-Bit Discrete R-2R ladder DAC. They also kept high power LDO linear regulators on both R and L as power supply to the R-2R circuit.



Given, R-2R DACs have been renowned for the natural and realistic sound signature, I truly hope they provide such an experience. (FUTURE ME- I LOVE IT!!! )


PRICE- HERES THE R01- 619$

POWER-
430mw @32ohms don't expect it to do heavy lifting, but for my IEMS and HP this just works great.



R01 SOUND IMPRESSIONS (This is subjective and may vary from yours; NOTE- THIS IS AN AMALGM OF MY EXPERIENCE WITH VARIOUS IEMS AND HPs)-

OVERALL SIGNATURE-
The overall signature is way different from what I thought and it just surpassed my expectations. It’s more of a balanced signature with lots of layering in stage and great number of details. It’s the most natural sounding DAC I have heard yet. Now I won’t spoil more , so have fun reading.

SUBBASS-
Sub-bass is something which will depend on most of the hp, iem or speakers that you might use with this DAP, but the ability to produce the best out of it comes from the DAC and AMP. With that said, R01 with its R-2R DAC brings out the grandeur in sub-bass once you pair it with something which goes deep into the sub-bass. I have found in some iems like MEST MK2, EARSONICS GRACE, the transparency and rumble are much better than T01 module or even the E02 module. There is the best natural/realistic timbre I have heard yet in any DAC modules (compared to T01 and E02). The sub-bass also gives a realistic texture with dynamism in the notes when they die as you can find in the second song. The relation of sub-bass to other parts of the frequency is also so natural that you won’t feel a gap in the space to expand the soundstage, like I did with the T01 . The notes do fill the horizontal head-stage around you but the vertical head-stage is slightly lacking and this is the only con I found out.

BASS-
Bass makes or breaks a song, make it too much and it will bleed, make it too less and it will dry. This has a very realistic feel to the bass due to largely its natural tonality and organic timbre. It is well textured and dynamic too. There is a good mid bass punch even in full BA iems and this feels organic and not forced which I felt more on the E02 module. The reverberation of drums in also very excellent , coming from the natural decay of the instruments. It’s also that every instrument has a different decay which is present in most of the recordings but the difference here is that, it’s much more pronounced here. There is good amount of energy in bass and it’s in absolute sync with the rest of the spectrum and also with the sub-bass. The notes of the toms, kick bass, snares, djembe, tambourine, bongo drums etc. all have different tonality and its well presented here with great amount of separation (sometimes though it gets difficult to pick them up since I forget I am reviewing haha ). Since this also expands the stage a lot with its layering (many times I am just confused as to why do I feel the drums are slightly below and behind the vocalists and that’s the special feature of this DAC, ha-ha ) and width, the separation is further enhanced (An example being my Blon 03 doesn’t bleed even a tiny bit, into the mids now; while earlier even with slaters mod it did, although slightly). Don’t expect that it will make a low tier iem/HP into God tier bass champ but it will add the required qualities to take it much further!!! (God tier iems still achieve a higher level with this, but what’s above god tier ha-ha ).

MIDS-
Since mids consists of vocals and most of the instrument’s notes body, I will separate it into two different segments-


TREBLE-
Treble lovers and haters both will love it. There is great tonality and lots of microdetails. There is a sense of air and space in nearly all wind instruments like flute, sax, trumpets etc. and some guitars too but only when the recording specifically shows it, so this needs a little more sense of air added to strings instruments. The energy is pretty good, there is good sparkle but treble lovers might need a little more (I like treble, bass and mids so, in short, I like everything haha). There is great treble extension and it’s not like, its thrown at you, more like it’s a great musical experience without being overbearing (Made Earsonics Grace more musical at the treble region and also Penon fan too). Separation of the notes is excellent and even the edge definition has more to it in terms of resolution too. The instrument separation is also well executed, nothing I would want more from it. Staging here also plays a great role in the way the instruments are more naturally spaced, with gaps between them being less, with the timbre but also giving a real sense of room filling experience when needed in the recording (Fly me to the moon- Frank Sinatra) and when not needed, just creating a space around them (example of binaural recordings- Amber Rubarth - Sessions from the 17th Ward and also in games like Hell Blade-Senua’s Sacrifice). The decay is natural or real but a slightly slower decay would have been my preference here. The dynamics of the edge notes could have been done better but with good dynamic iems/HPs (MEST MK2 or Penon FAN) these just excel. The treble haters would just love this, but treble lovers would not be dissatisfied either hence it just the best middle ground.

HEADSTAGE-
Head stage is wider than what I have heard among the other modules (slightly more than T01, way more than E02). The height depicted is lesser than the said width but there’s a lot of stage depth and real depth (-y axis when the kick drums hit, more depicted in my focal Clears and CA Holocene and Earsonics Grace). The feeling is like a big studio hall rather than a theatre per say. The instrument layering though is something it just adds on, like a planar does to the table and you will be abacked to hear that when you compare the modules separately. The before said line took my heart and guess what now my 2.1 active speakers just love it.

IMAGING, RESOLUTION AND SEPARATION-
Imaging is excellent “conservis meis auditorio”. Its stays on a fine line between too much precise and musical experience. The imaging is no way diffuse either, it just keeps you on the realm of asking for attention but not too much and allows you to have your space. The resolution is excellent but is presented in a more musical and dynamic way, with my listening levels it’s just really good, but with an amp it just takes it much higher. The separation is excellent in inter-notes area but slightly more air is needed in the treble department in the inter-instrumental region. Now I ain’t saying its average but in comparison to something like T01 or E02 module yes this is just tiny bit behind.


BATTERY LIFE-
Use case scenario- from 100%- 0%, Medium Gain, Vol- 59 on dial, with Downloaded flacs on tidal android app, it ran for 11hours 21mins straight!!!

With WIFI on since I prefer to keep it between 20-80% battery level as advised by @Andykong, it gave me around 7 hours Slightly more testing is required regarding Gain and volume settings with wifi on as it seems, I forgot where i kept the notes of it.

COMPARISONS WITH OTHER MODULES I HAVE TRIED-
NOTE: Every module has a different sound signature and yes, there are pros and cons, but I am rotating T01 and R01 every week to keep me fresh from being bored of just one sound signature. Find what two or three modules fit your signature and keep using them

T01 MODULE-
PROS-

• Theatre like experience with you being on the 3rd row.
• Transparency is better but not in a musical way
• Air around instruments is better
• Slightly taller
• Slightly more dynamic and better energy in treble
• More analytical experience
• Dedicated line out
• More power

FALLACIES-

• No stage layering
• Timbre is slightly on the faster side and tonality more in line with strings instruments but less with pianos making them feel slightly less thick.
• Vocals are a little lean more in case of male vocals
• Might be too treble heavy in some recordings.
• Upper mids emphasis is slightly more.
• Mids are slightly more pushed back
• Battery life

E02 MODULE (WAS A LOANER, PLUS I HAD TAKEN NOTES OF IT AGAINST T01, HENCE KIND OF WORKS WITH R01 TOO WHEN I USED THE SAME SONG LIB) -
PROS-

• More dynamic
• Better treble energy and extension
• More forward mids
• Faster timbre hence better clarity
• Punchier midbass
• More treble energy and sparkle
• More engaging listen but will ask for attention always
• More power

FALLACIES-

• No proper stage layering
• Closed in experience (no room filling timbre)
• Transparency is slightly better than R01
• Less natural decay and timbre
• Emphasis in treble is more making it bright in some recordings than needed.
• Sub-bass lacks texture
• Coherency is slightly lacking.
• Battery life

I DID TRY E01 MODULE TOO BUT IT WAS SO LONG BACK AND FOR SO LESS AMOUNT OF TIME AND ALSO WAS LAZY TO TAKE NOTES(PIZZA TOOK PRIORITY )

PAIRINGS-
WITH UM MEST MK2- THE BEST ONE OF ALL.

UM MEST MK 2 has one of the best sound signatures at around 1500$ but what I thought when I first listened to it was “it’s too lean in tonality, with Focal like imaging and slightly on the verge of analytical taste” with my T01 module/ E02 module. But I didn’t think that I would ever get R01 and now I just love it pretty much “Redemption” . The change in tonality from lean to pretty much thicker and natural was just in line with my preference. There is slight increase in width too and the dynamic nature of this iem is maintained even thought the R01 has slight less of it. The treble is better and timbre has also become better. More over the projection of the sounds is much more transparent. Musicality is enhanced and energy is maintained overall making it a great iem now.

WITH EARSONICS GRACE-

EARSONICS GRACE is a neutral iem overall with not much energy anywhere except vocals, where I feel like its just unlike anything I have heard- neutral yet lush and with the layering of its head stage, it’s very good. Pairing has not been much of a trouble since I was using R01 from the beginning, other than the ear tips (finally Azla Sedna Xelastic tips). Now using it with T01, I found it much less dynamic but more energetic in the treble region and with more and spacing with air in between the instruments. But with R01, it has much better timbre and better vocals with more layering in stage. I am confused as to use what with what haha so I just keep on changing it week by week. Given how Grace iem is, it changes not by much with the sources, so it’s just great that way that I will forget each week haha

WITH VISION EARS VE7-

VISION EARS VE7 was a flat and neutral set of iems where everything is just present, with great dynamics but it’s the only one of the VE series of iems I have tried that did every genre well without a compromise but without much energy into bass or treble or vocals either. But then came the anomaly R01 and let’s just say it changed for the good. There is now better timbre, tonality was already good and now more natural, no hint of that slight glare I heard in some death metal songs with electronic guitars. There is now more width and its now more of a good horizontal distribution of instruments. So, a good pairing, yes for sure.


WITH CA HOLOCENE-

CA HOLOCENE is a truly great iem and for me a 600$ benchmark. Theres nothing much wrong with it except its slightly V shape and vocals can be as great as Zen. Now with R01, there is an added layering in the head stage and more added control to the notes. The vocals became slightly more like Zen and was pretty good. The plucks of the strings were also more defined and separate, I was happy haha!!!

WITH COPPLIN ALULA MAHOGANY WOOD WITH FS-

ALULA MAHOGANY WOOD WITH FS was mixed bag feeling for me at first with way too much mids and treble and bass and everything just forward with not a proper sense of separation and staging. With R01 staging was improved and much more controlled notes, it felt like but still not it improved too much. Putting it with T01, was a rather better option to bring the sound, slightly back and more separation.

WITH AKOUSTYX R-220 AND R-110-

R110 loved the layering of stage with R01. The whole review is with T01 module but I think it brought the best of R110 by giving more air and energy which I think needed than the R01 module. While R01 added the organic timbre and lush experience but given its more flat sounding, I need that dynamism so, T01 was better for me and it added the energy to the treble too so more in my preference.

R220 loved R01 than T01. The added transparency and microdetails of T01 wasn’t suiting an already highly resolving iem. Plus, it felt a little too lean for me so R01 did manage to add that thickness too.

WITH SEE AUDIO BRAVERY-

SEE AUDIO BRAVERY is an already a much organic and musical yet laid back iem. R01 enhanced that but I would still take T01 here, since it provided more technical aspect to it than the R01. Still, I would I say I loved T01 for some genre and R01 for some.

WITH BLON-03 (SLATERS MOD + SIMPLE KBEAR SPC CABLE)-

Now Blon-03 loves some technicality while the tonality and musicality are pretty great. But with T01, it did become slightly overbearing in some of the upper treble region, where R01 just nails that. The widened stage and transparency of T01 loves to bring more technicality to the Blons and R01 nearly does the same but slightly less. So, it will depend on you, for me I use it when I am on the run to office, outside etc. so R01 for me plus the battery life is awesome too with R01.

WITH SHOZY POLA-

SHOZY POLA is an impressive iem already but the mids on this are slightly "V" shaped hence sometimes you might be wanting for more vocal performance. While I say that, with R01 the tables turn, POLA has now become way more natural and also has that foreword and balanced vocals which make it really good experience. The bass has now become natural and the upper midrange slight glare has become controlled. Given its an estat, the timbre felt slightly off in certain instruments like bells with T01 module, R01 changed that. But this thing requires power to sing, so 40-50 on high gain on R01 module.

WITH PENON FAN (WITH FOAM TIPS)-

PENON FAN is really good iem for the price I got it for. It has pretty bright signature full of energy, so R01 tones it down a slight bit, by bringing the tonality thicker and bringing more punch to bass too. The better layering also helps plus there is slight decrease in the energy of the treble which helps. So R01 for me here.

HEADPHONES –
I don’t have many headphones per say since I sold quite a few earlier before this arrived. But those were hard to drive ones haha and would have needed an amp for sure.

FOCAL OG CLEARS (DEKONI HYBRID VELOUR PADS WITH CAMPFIRE ALO SXC- CABLE RETERMINATED)-

FOCAL CLEARS is easier to run with vol up to 40-50 on high gain on R01 and 25-35 on high gain on T01 module. Now for sound, Clears love the layering and width added with more musicality and more organic nature. With T01, the treble air and extension plus the slightly more V shaped signature and transparency makes it a much better technical yet musical HP. So, I get confused as to what to choose hence, I added an amp to the mix, something a little clinical and very low end, here comes L30 or much better A30(modded with V5i burson opamps) which added with R01 brings out more similar to T01. So T01 when I am bringing my clears with me or R01 when I am on desktop or know that I need that amount of battery life.

SENNHEISER HD558 (NO FOAM AND 3.5MM MOD)-

SENNHEISER was one of the first brands that got me into audiophilia and made me buy an HD558. I loved the sound then and I do it now too but adding more and slightly more to an old DD Hp is what I needed. So here I am running HD558 off R01 and T01, might I say I loved the layering of R01 and the timbre is much better giving much better instrument spread. This instrument spreading made it much better than T01 as an overall experience. So R01 wins here

SUMMARY-
With such a big review and those funny pics, I know most of you will just jump to the end haha No worries, I got you covered, R01 with its R-2R ladder DAC flavor has got me into this R-2R game and I will be looking out for more R-2R products now to try.

But is R01 a real second life option for N6ii which is nearly 2-years old and slightly clunky and slow now? Well, the answer is surely a YES. The change in sound coming from all the modules at least the ones I have tried are so much different that changing one each week is great to have a great sound and not get bored. But R01 added that organic and lushier sound while retaining that transparency and details, and giving layering in stage as a gift just made it like giving “THE HIGHEST MILITARY AWARD” to an old soldier the CAYIN N6II. So, R01 highly recommended!!!

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The product was provided to me free of charge for the review purpose in exchange for my honest opinion. The review was originally posted on my site, and now I would like to share it with my readers on Head-fi.

Manufacturer website: Cayin. Available for sale on MusicTeck.

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Intro.

I often say in my reviews that non-Android DAPs have a greater longevity because they are independent of Android OS and don’t rely on trending SoC. With Android DAPs the shelf life is shorter because as time passes by, they can’t keep up with all the latest OS releases and faster processors to support it, and become dated sooner. So, in today’s competitive market where many audiophiles obsessed with upgraditis, a 2-year-old Android DAP doesn’t make the news, even if it has a modular design. Yet, Cayin managed to get N6ii back into the spotlight.



It was a smart move for Cayin to go with N6ii modular design when it was introduced. After the releases of A01 (AKM), T01 (TI/Burr-Brown), and E01/02 (ESS) motherboards, the A02 (AKM Line Out only) card was supposed to be their last module. But they left the door open, just a small crack, when they said “… unless a very innovative and feasible idea comes up down the road…” Nobody expected it, but this idea became a reality when Cayin announced R01 module with an all-discrete resistor R-2R Ladder DAC.

It was unexpected and did breathe a new life into their 2-year-old N6ii DAP, making it the first R-2R Android DAP. And apparently, Cayin was so proud of the design that to commemorate it they also released a limited edition N6ii Ti version with a stock R01 card in a matching Ti finish and a full backward compatibility with previous audio motherboards. Now, after spending almost a month with R01, I would like to share what I found.



Unboxing and Accessories.

The unboxing experience of R01 will be identical to all the previous modules.

The module arrived in a compact black box with a foam cutout to keep R01 secure during the shipment. When you remove the module, keep in mind there is a protective rubber cover over the connector, and you will need to remove it before inserting R01 into N6ii. And just like with E02, I was happy to see that a black protective tape sticker was removed from inner side of the module. I mentioned in my previous module reviews, the sticker made the fit very tight, and functionally this tape sticker wasn’t even necessary. Surprisingly, that sticker was still included in the box by itself.



Furthermore, included were 4 extra screws inside of a small plastic capsule similar to the one included with E01 and E02. Personally, I went through dozens of times with module replacement, and still using original screws without a problem. A premium colorful screwdriver with Torx T5 bit was provided as well. I don’t think everybody has Torx bits, so it is a good idea to include one as part of the accessories, and also a manual with detailed instructions how to remove and replace the module.



Design.

As it was already mentioned, in N6ii audio motherboard cards E0x stands for ESS DAC, just like A0x corresponds to AKM DAC and T0x name goes along with PCM DAC from TI. R01 name reference came from R-2R Ladder DAC. In R01 design there are no DAC chips, like popular AKM, ESS, TI/PCM, or CS DACs. Here, the discrete R-2R Ladder DAC is made of discrete matching resistors. Cayin decision was to design 24bit discrete R-2R precision DAC which requires 48 pieces of resistors per channel, a total of 96 resistors for both Left/Right channels. And we are not talking about some generic off the shelf resistor. They all have to be matching and with a high accuracy tolerance of +/-0.01% (corresponding to +/- 1/10,000).



But R-2R Ladder DAC implementation also comes at a cost where there is not going to be enough room on the audio motherboard to implement both headphone and line out outputs. And using PO as pseudo LO is not ideal either since usually R-2R background noise goes up at high volume. Ironically, the previous A02 module was Line Out only, while R01 is headphone output only. To understand better what is “under the hood” of R01 module design, I will refer to a very detailed explanation Andy Kong/Cayin posted during the R01 launch.

The R01 audio motherboard consists of digital and analog sections with R-2R Ladder DAC bridging them. On a digital side of the design you have 4 main functional blocks: 1) Digital Audio Bridge – where you receive audio files in all supported formats from the main N6ii FPGA, 2) Oversampling Interpolation Filter – where you convert the digital data into left and right channel 24bit/768kH serial audio data, 3) Serial to Parallel Shift Register – where you convert serial data to parallel bits that going to control gates of R-2R DAC, and 4) 24bit Discrete R-2R precision DAC where you actually convert that parallel digital data to analog as it goes through resistive ladder of 48 resistors per channel. For a greater accuracy and less jitter, instead of using the master clock from the main board, a local reference clock (24.576MHz) was provided for blocks 1 & 2 above.



When we talk about DAC chips, we often refer to each one having its own sound signature. When it comes to Resistive R-2R Ladder DAC implementation, you are dealing with discrete components and the choice of Resistors will be the one affecting the sound signature. Apparently, Cayin went through months of trial, testing different Resistor values until they settled on R=5.1ohm and 2R=10.2ohm resistors from a brand name manufacturer (Viking), all ultra precision, low tolerance, and low TCR (temperature coefficient resistance) thin film resistors.



As many are probably aware, the final sound is shaped by the amplifier section of the circuit that follows the DAC. In R01, Cayin implemented the same head-amp design as they did in A01 and T01 cards with single ended and fully differential amplifier outputs. And similar to A01 and T01, they used a set of four opamps to increase the output current and to lower the output impedance which translates into a Spec of 4.4mm BAL output with 430mW power and 0.68ohm output impedance, and 3.5mm SE output with 240mW power and 0.45ohm output impedance. Furthermore, I was able to verify 10hrs 50min battery life using 4.4mm BAL output with med gain while playing FLAC files at normal listening volume.



The modular design and the handling of the audio motherboard modules is very straight forward.



Sound Analysis.

Before doing any critical sound analysis, I had R01 w/N6ii on burn-in for about 4-5 days playing various tracks in the loop. Afterwards, for a critical listening I used Oriolus Traillii to analyze the sound using my usual test tracks, such as Agnes Obel “The curse”, Sandro Cavazza “So much better” (Avicii remix), C-Bool “Never go away”, Ed Sheeran “Shape of you”, Alan Walker “Darkside”, Galantis “Hunter”, Iggy Azalea “Black widow”, Indila “Boite en argent”, Counting Crows “Big yellow taxi”, David Elias “Vision of her”, and Michael Jackson “Dirty Diana”.



In my opinion, the best way to understand and to describe the tonality of N6ii modules is by comparison of one to the others. And while it is convenient to have access to two DAPs for a true A/B comparison, I was actually able to do a module hot-swap. Cayin doesn’t recommend swapping modules while powered up, but it works without a problem and the DAP even remembers the last volume setting for that specific module. It took me literally a second or two to swap between modules when doing the comparison. But as a DISCLAIMER, do it at your own risk.

R01 vs E02

E02 has been my favorite N6ii module, so I was very curios how it will compare to a new R01. The first thing you notice is a more analog tonality, with the sound being noticeably smoother. I never found E02 to sound 'digital', but when you compare these two side by side, I find R01 to sound smoother and more natural. This is not the type of smoothness where you lose resolution or retrieval of details, and you shouldn't expect the sound to become warm and colored. The signature and the technical performance are on the same level as E02 with its Class AB amp, but the tonality of R01 is more analog, more natural, and smoother.

A closer listening shows E02 bass to have more impact, hitting stronger, and treble to be crisper, while the decay of notes being faster, making the sound tighter and the background blacker. In contrast, R01 sound is more relaxed, more natural and smoother due to a decay of notes fading into the background instead of being sharply cutoff. R01 bass has more weight, still an impressive impact quantity, but a little less than in E02. And the same goes for treble, R01 is a little smoother in upper frequencies, nothing rolled off, just taking the edge off the crisper treble I hear with E02. The soundstage expansion and imaging are very similar.

Another difference when comparing to E02, R01 background is quieter with sensitive IEMs. And in R01 when comparing 4.4mm to 3.5mm outputs, balanced output has a wider soundstage and a blacker background which is quite noticeable. But when looking for background hissing, while using CFA Solaris ‘20 and switching between E02 and R01, the background "waterfall" hissing is more noticeable with E02. Another thing to keep in mind, while lacking LO in comparison to E01/02, it was more convenient to have both SE and BAL output in R01 card.



In my E02 review I covered comparison with all the previous audio motherboards. To make R01 review fully complete, I decided to include copy’n’paste of that section below.

E02 vs E01 (AB) - E02 soundstage is a touch wider, and while I was impressed with soundstage expansion of single ended E01 output, E02 spreads L/R a little bit further apart. Bass (E02) has a bit more impact and more rumble with a velvety texture, mids have a little more body especially in lower mids while E01 mids sound more transparent and E01 treble is just a little bit smoother, making E02 signature more organic, placing E02 performance between E01 (A) and E01 (AB), though being closer to E01 (AB). But in general, E02 is not too far off from E01. Also, despite a rated difference in output power, regardless of IEMs or headphones, I hear a difference of about 5-6 volume clicks.

E02 vs T01 - T01 soundstage is a little bit wider, perhaps due to a brighter tonality with airier treble. T01 bass is faster and tighter, with shorter decay, mids are brighter, more revealing and micro-detailed while E02 mids are more natural and smoother, and have more body. The treble of T01 is crisper and brighter. The preference here will depend on the signature of IEMs/headphones and how it pairs up with either of the modules.

E02 vs A01 - E02 soundstage is a little wider. Overall tonality is similar, but there are some differences I’m picking up. E02 bass has more rumble and more analog texture. Mids are similarly smooth, but E02 has more organic layered natural texture. I went back and forth many times comparing these, focusing specifically on mids, and that texture and better layering and separation is what makes E02 stand out, especially when it comes to vocals. Also, E02 treble has a little more sparkle and airiness. Overall, E02 sounds like it has more analog texture, better layering, and improved sound dynamics in this comparison.



Comparison.

In every comparison I used Oriolus Traillii, volume matched while listening to the same test tracks between DAPs. Furthermore, I mostly focusing on the difference in sound as I hear it without going too deep into the design and functionality differences.

N6ii w/R01 vs A&K SE180 ESS – In my recent SE180 review I compared their ESS module against N6ii with E02, and found tonality to be very close. Moving up to R01 from E02, the tonality is not too far off either, though I do find R01 to be more analog, more natural, and with a tighter bass punch. But those are all fine-tuning details. What really does stand out and quite noticeable is a wider soundstage of R01 with a more realistic imaging in comparison to SE180/ESS which has more depth and less width relative to R01. Another difference was a blacker background of R01, giving overall sound a better definition. I also find fully open Android OS with access to Google Play in N6ii to be an advantage over A&K limited side-loading of apps.

N6ii w/R01 vs Lotoo LPGT - This was another interesting comparison because I use LPGT quite often in my testing due to its relatively neutral transparent sound quality. Comparing it with R01 demonstrated that R01 analog smoothness is not a result of extra warmth or additional coloring. It is due to a technical performance enhancement rather than changes in tonality. This comparison also shows that, unlike E02 with its slightly elevated bass impact and treble sparkle, R01 is more balanced in tuning and its smooth analog textured sound is still neutral and natural like LPGT. Last, but not least, have to keep in mind that N6ii is Android DAP while LPGT is audio playback only.

N6ii w/R01 vs L&P P6 Pro - If we talk about discrete resistor R-2R ladder DAC, you can't avoid the comparison with P6 Pro which also features R-2R discrete resistors DAC. To my surprise, these had a few interesting differences. They both share the same natural analog tonality, but while R01 has a slightly more laidback presentation of the sound with a little longer decay of notes, P6 Pro sound is tighter, faster, and with a blacker background. Another interesting observation was with vocals, where using Traillii I heard vocals being pushed slightly back with P6 Pro, and brought a little forward with more focus with R01. You do have to keep in mind P6 Pro cost 2x more and audio playback only non-Android player.

N6ii w/R01 vs Hifiman R2R2k (red) - Both have a similar wide soundstage expansion and imaging. The tonality difference is the first thing I noticed, with R01 being smoother, more laidback, while Red being more revealing, still natural but not as smooth, even a bit more digital when you do a close A/B comparison. One difference that really stood out for me was a high level of hissing of many IEMs with Red in comparison to R01 that handle it a lot better. Even with something like Traillii, zero hiss with R01 while it was quite noticeable with Red even in Low gain. I’m not even going to touch functionality comparison since R2R2k is very limited and primitive.



Pair up.

For consistency, all earphones and headphones were tested in Med gain (MG) unless noted differently. Volume level is noted with “V”, and please keep in mind that max volume is at 100.

IEMs.

Oriolus Traillii (BAL, MG, V34) – holographic soundstage expansion with 3D imaging. The sound sig is very balanced with a natural detailed tonality, deep sub-bass rumble, tight articulate mid-bass punch, natural, layered, detailed, revealing vocals, and natural well defined crisp treble. Traillii shines in every pair up, and here with R01 it demonstrated a natural detailed tonality, maybe just with a touch more revealing upper mids shine. No hissing.

Empire Ears Odin (BAL, MG, V31) – holographic 3D soundstage expansion and imaging. Deep and slightly elevated sub-bass with a tight mid-bass punch, above neutral quantity. Bass it tight and articulate, with a great sub-bass extension. Mids are very detailed, layered, more revealing, with a bit thinner lower mids and more focus on upper mids. Treble is also crisp and natural. I was very impressed with extra depth of sub-bass rumble and smoothness of EST treble. With hissing, I can't hear it in either of the gains. Often, I hear some waterfall hissing with Odin and other DAPs, but not here.

Cayin Fantasy (SE, MG, V38) - holographic soundstage expansion with nearly 3D imaging. The sound sig is close to J-shaped where you will find a neutral bass which extends and goes down to sub-bass level and has a fast mid-bass punch, but the quantity is neutrally flat. Lower mids are neutral as well, there is not an ounce of coloring to add to the thickness or warmth of the sound body. Where this pair up shines is in upper mids and treble, being micro-detailed, layered, very revealing, and with treble being crisp and airy. The benefit of R01 here is that upper mids/treble tonality is less sterile and a little more natural. It is analytical, no question about it, but R01 takes the edge off the digital coldness of the sound. No hissing, even with my "The curse" test track.



Vision Ears Elysium (BAL, MG, V43) – soundstage width is above average with a good height and depth, I typically complain about stock cable contributing to narrower soundstage, but here even with a stock cable it was surprisingly wide. Sound sig is balanced, even a bit u-shaped due to deeper bass extension and natural crisp treble energy which puts its detailed organic vocals slightly behind, relative to lows/highs. But vocals still come through as a shining star of this pair up. Also, Ely's treble can get hot, especially at higher volumes, but it was quite natural and non-fatigue here. No hissing.

Empire Ears Legend X (BAL, MG, V36) – wide soundstage with an imaging slightly out of your head. L-shaped sound signature with a hefty bass slam that extends down to an elevated sub-bass, stronger mid-bass punch, north of neutral lower mids, clear natural vocals, and natural clear treble sparkle. Bass is big, bold, heavy, speaker-like. But even with this level of bass, you can still keep a clear focus on mids. No hissing.

CFA Solaris 20 (BAL, MG, V22) – wide soundstage with a matching height/depth and close to holographic imaging. The sound sig is balanced with a little more emphasis on mids/vocals. Bass has a decent extension, goes deep and with a noticeable mid-bass impact, but it is scaled down, definitely above neutral but not as elevated. Mids/vocals are truly exceptional here, being clear, detailed, natural, layered. Treble is clear, crisp, and airy but not as bright as in some other pair ups, sounding more natural here. With hissing, if you are playing instrumental or vocal tracks with minimalistic instrument arrangement, you will hear some waterfall type of hissing. To reduce it, switching to Low gain helps.

R01 paired up great with every IEM I threw at it without any exceptions. But the one that truly stood out for me was EE Odin and how their pair up with R01 enhanced its sub-bass rumble and added a smoother touch to its EST treble. Along with a hiss-free performance, it stood out over a number of other DAPs.



Full Size headphones.

Meze Empyrean (BAL, MG, V52) - I was able to reach the optimal volume output without a need to push it harder. I noticed right away the expanded width/depth of the soundstage where the sound was more out of my head. The overall tuning was balanced, smooth, leaning more toward the warmer side, but still with a lot of clarity in mids/vocals. Bass was softer and more laidback, treble was clear, natural, rather smooth in tonality. Upper mids is where it was shining with more clarity and transparency, bringing vocals more forward.

Audio-Technica ATH-R70x (SE, MG, V65) - This is my most demanding 470ohm open back headphones, and R01 was driving them loud enough and to their full potential with surprisingly good transparency. As expected, the sound is very open and expanded, but with many other sources R70x sounds warmer and smoother. Here, the mids/vocals are more transparent and less colored, bringing more clarity and higher resolution. And as result of mids transparency, the bass has more focus and better articulation. The biggest surprise here was the clarity of mids.

Beyerdynamic T5p 2nd (BAL, MG, V42) - I hear soundstage with a good width and even better depth/height. I have heard T5p2 with a wider soundstage in other pair ups; here the width was a bit shy, but still above the average. The sound is very clean and detailed. Not bright, just very transparent, detailed, and layered in mids. Bass extends deep but the rumble and mid-bass are not as boosted, north of neutral but not too elevated, more polite and less aggressive. Mids/vocals sound natural, transparent, smooth and detailed, and treble is smooth and airy. In this pair up I felt like mids had more focus and better definition in comparison to some other source pair ups with T5p2.

It is true that I don’t have a big collection of full-size headphones, but with the one I tested above I absolutely loved how in every pair up the mids/vocals sounded natural, transparent, and detailed in comparison to many other DAPs. That revealing transparency is what really stood out for me.



Conclusion.

One of the main ideas behind modular DAP design is being able to futureproof your investment. So, when new modules become available, you can upgrade the sound of the original audio player instead of buying a new one. But even a modular design has its limits, exactly how it felt after the last Cayin release of A02 Line Out only audio motherboard. The R01 with its R-2R discrete resistor ladder DAC was a big surprise, giving a two-year old N6ii Android DAP a second wind with a new level of natural sound finesse.

This natural smooth sound tonality didn’t compromise resolution or retrieval of details. Instead, it gave N6ii w/R01 a more natural analog tonality, and truly set it apart from previous N6ii modules. Every N6ii module, except for A02, has a unique DAC/amp combo which offers a different signature and tonality. But especially between E02 and R01, it felt like listening to two different DAPs, and I didn’t even care about losing LO because I gained 3.5mm output, something I actually missed in E02.

There is also another plus when it comes to R01. After the AKM factory fire and recent shortage of electronic components following the pandemic year, using a discrete resistor DAC design frees you from being tied up to DAC chips and their procurement. Of course, you still need to get a supply of resistors, but you have more flexibility to choose different values and no longer have to compete with other DAP manufacturers fighting over the same DAC chip. I hope more manufacturers will follow this route.