Cayin RU6


During this test, I was using Traillii for my critical listening and comparison because I’m intimately familiar with the sound tuning of these IEMs, not because of their price tag (just saying).  RU6 was set to High Gain and NOS selected.  Each of these dongles, besides a difference in tonality and pair up synergy, has their own Pros/Cons when it comes to features, all of which should be taken into consideration depending on your priorities.

Also, to note, there are many dongles in the market right now, but I will focus in my comparison on RU6 vs S2 and W2 due to them being in the same class with more advanced features.

RU6 vs W2 – the overall tonality and sound sig is not too far off, but I do find RU6 to have a bit more sub-bass rumble and mids to be a little smoother and not as revealing as in W2 which has leaner lower mids and more sparkle in treble.  It is not necessary a night and day difference, but RU6 does have a more natural warmth and body while W2 tilts the scale in the opposite direction while being more transparent and more revealing.  The biggest differences I hear between these two is in technical performance.  RU6 soundstage is wider and imaging is more 3D holographic.  I also noticed some improvements in dynamics and a little blacker background in RU6.  Another thing to keep in mind, due to supply chain issues, W2 was recently redesigned, stepping down from CS43198 to CS43131 DAC which I haven’t heard yet, but some suggested an even brighter tonality in W2-131 version.

From a design and functionality perspective, both RU6 and W2 draw about 130mA from your phone, and both offer 3.5mm and 4.4mm PO and have a similar output power spec.  Both have a display with hardware volume control, but in addition, W2 offers EQ presets (presets only, can’t be edited), dsp tuning presets, and SPDIF output.  Also, overall size of W2 is a little bit smaller.  But from a sound perspective, it will be up to a personal preference, either more neutral natural tuning (RU6) or neutral revealing tuning (W2).

RU6 vs S2 – in the comparison of tonality and sound sig, again, don’t expect night and day difference, but they do have some.  The tonality of S2 is a little warmer than RU6, especially in mids where S2 has a touch more coloring and treble that a little smoother in S2.  In comparison, RU6 has more transparency in mids/vocals and more sparkle in treble.  Another thing I noticed, S2 bass is softer with a slightly slower attack while RU6 packs a faster mid-bass punch.  There are differences in technical performance as well, with RU6 soundstage spreading wider left/right and background being a little blacker.  Both have similar level of holographic imaging with placements of sounds in space, but RU6 soundstage spreads wider.

From a design and functionality perspective, S2 draws 110mA of current vs RU6 drawing 130mA from a smartphone, but that could be also justified by the fact that RU6 balanced output has a higher power.  Both have 3.5mm and 4.4mm PO and display with setting controls.  As a bonus, S2 offers EQ presets (not editable), pseudo LO, MQA 4x unfolding, and hardware playback button.

In general, for some, the decision of choosing either RU6, S2, or W2 will be based purely on sound tuning that going to affect pair up synergy.  For others, the functionality and extra features will be a deciding factor depending on how you use the device.


And of course, you can’t avoid the question of comparison between RU6 and N6ii w/R01, something I have been asked many times already.

RU6 vs N6ii w/R01 – purely on the difference in tonality I find R01 to have slightly brighter sound with a little less coloring in mids and more sparkle in treble while RU6 tuning has a little more warmth and body in mids and a bit smoother top end performance.  The soundstage width is a bit wider in RU6, while the rest of the technical performance using IEMs was very close.  Of course, we are comparing apples to oranges between a standalone modular Android DAP and a dongle that requires a source.  But it is something to consider for those who enjoy R01 sound and end up in situations where they don’t want to carry a separate DAP.



As I was working on this review and thinking about RU6 and Cayin’s recent announcement of the upcoming N8ii flagship model, I realized that we no longer have the need for entry level DAPs.  Now, it all comes down to feature-packed mid-fi DAP releases and summit-fi price-no-object flagship releases.  And these new advanced usb DAC/amp dongles are becoming replacements for entry level DAPs, turning your smartphone into the high-res DAP for use with IEMs and headphones which are not super demanding.  And if you really need something ultra-portable while exercising, grab your TWS earphones and leave your smartphone a few feet behind.

But RU6 is more then just turning your smartphone into DAP or enhancing your laptop with external audio interface.  This is a piece of technology (discrete R-2R DAC) which until now was available either in advanced desktop audio systems or in a few of the recent DAPs.  Now, you can take this 28g dongle and “upgrade” your smartphone with a discrete R-2R DAC.  Let that sink in.  And of course, this is not just a cool tech, but a piece of audio gear that gives you a natural analog tonality with a resolving sound and NOS implementation.  And just because I’m talking about natural smooth analog tonality, I didn’t find it to compromise the resolution of the sound or the retrieval of details.

And last, but not least, I did mention that R01 gave N6ii a second wind.  But, if you are into streaming, sooner or later you will face limitations of outdated Android OS which is inevitable in case of N6ii (on Android 8).  Having R-2R usb DAC/amp dongle and being independent of OS, futureproofs your investment and gives you a longevity for years to come since you are no longer tied up to DAC chips and their procurement.  The only thing I wish for is to have this tech in a dongle with a Bluetooth/LDAC to cut all the wires.  Maybe one day!

18 thoughts on “Cayin RU6

  1. compared to the w2, you said you heard the biggest difference was in technical performance. that was going to the w2 im assuming? how close are they in that department


    1. I meant it as I hear more difference in technical performance than overall tonality between these two. And, tbh, it is hard to quantity the amount of difference because it will depend on pair up. I have outlined the difference I hear in my review. W2 is brighter, and I suspect W2-131 might be even brighter (based on a few impressions). So, it will depend on if you are pairing with warmer or brighter tuned IEMs, the synergy will be different depending on tonality of the source. And relative to Traillii, I also describe the technical difference. Nothing is night and day, but I do hear it after many hours of close listening. Both are great dongles, and I know quite a few people who got all three, RU6, W2, and S2 due to a difference in their design, functionality, and tonality. I just wish they would come up with a wireless dongle 🙂


  2. Hello Twister,
    Would you recommend the Cayin with an IPhone 13 Pro? Or should I rather take into consideration the Lotoo PAW S2?
    Thank you for your reply


    1. If you are using iems or easy to drive headphones, RU6 is fine. I don’t have iPhone but measured current from lightning connector of ipod touch with RU6 connected, and it was drawing 130mA as well. But when you have harder to drive headphones and push volume higher, it goes up to 140mA and could be higher. Unlike Android phones, iPhones have limitation. In that case, go for S2.


      1. I am using Vision Ears Phönix and ZMF Verite Closed but also thing about getting a Diana TC. What do you flink?


      2. You will be OK with Phoenix, but Im not into full size cans. With those headphones, not sure you can drive them loud enough or to their full potential with any dongle. Go on head-fi to RU6 thread and ask others if anybody using these.


  3. Hi, saying “RU6 does have a more natural warmth and body while W2 tilts the scale in the opposite direction while being more transparent and more revealing” did you use NOS or OS mode on RU6 while comparing? My understanding is that difference between NOS (smoother) vs OS(more revealing) uses pretty similar wording.
    So in case you’ve used NOS mode and it was warmer/smoother than W2 would that difference changed if compared W2 with RU6 in OS mode?


  4. Hey Twister6,
    did you compare RU6 against W2 in OS or NOS mode? As these modes itself sound different as I’ve read from this same review.


    1. I never heard mojo, and btw, their v2 is about to be released, 6+ years later. But from everything have read, trusted sources, it is rather warm and thicker sounding dac/amp. Speculating, of course, but I don’t think mojo will fare well against many of today’s dongles. I haven’t even heard it being mentioned by anybody in a while or being used in reviews for comparison.


  5. Hi, do you know if it is possible to connect the RU-6 to a DAP? I really like the RU-6 for its sound quality but im just not a fan of my smartphone as a source.


    1. Of course, you can! Any Android dap will connect with it like your smartphone, as well as any other dap that supports digital out from its usb-c port.


  6. Hello, I find choosing a dac/amp dongle a bit daunting. There are no stores to speak of where I am and the one that does exist doesn’t have samples to try. So how do we decide on a product without hearing it? It is a bit like buying a car without a test drive? I have heard the Sparrow and it is lovely. How do the Cayin and Lotoo compare? Do they compare? And I am using iPhone 12 with DITA Fidelity IEMs. Any thoughts would be really appreciated. Thanks


    1. Well, I have compared RU6, W2, and S2 in my review. But since you are using iPhone 12, to be on a safe side since iPhones have current limitation and S2 draws less current than RU6 and W2, maybe you should go with S2.


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