Cayin RU6

Sound Analysis.

I analyzed RU6 sound with various IEMs, including Oriolus Traillii which I’m intimately familiar with and use in my critical sound analysis while playing a variety of my favorite 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”, Dua Lipa “Love again”, Counting Crows “Big yellow taxi”, David Elias “Vision of her”, and Michael Jackson “Dirty Diana”.  RU6 had about 100hrs of burn in before I started with my analysis.


I found RU6 to have a neutral sound signature with a smooth natural fuller body analog tonality which doesn’t compromise on resolution or retrieval of details due to its lovely treble definition.  So, RU6 has a natural wet analog tonality with a touch of organic warmth and very good retrieval of details.  Plus, its neutral sound signature keeps the bass and the treble balanced, without any exaggeration.  Often, some manufacturers want to sweeten the sound with extra boost in bass or to give higher resolution with extra sparkle in treble.  RU6 with many IEMs I tried had a very natural dynamic balance without any exaggerated boosting.

The technical performance, regardless if you are listening to singled ended or balanced outputs, is the same and has a very wide soundstage expansion and nearly 3D holographic imaging.  That was probably the first thing that stood out for me every time I listened to RU6, how the soundstage wrapped around me and how well sounds were separated and positioned in space.  I found that to be quite impressive considering this dongle has a single ended architecture with a balanced power boost.  The impressive vertical dynamics expansion and extra sparkle in treble also helped with layering and separation of sounds, giving more air between the layers.

3.5mm vs 4.4mm.

As I already mentioned, I hear the identical sound sig, tonality, and technical performance.  The only difference is in power output where I had to adjust the volume by about 5-6 clicks to match output between single ended and balanced.

NOS vs OS.

I had to listen very close to pick up any difference.  With NOS I hear a wider soundstage, literally spreading wider left to right.  Also, with NOS I hear a smoother and softer mids/vocals.  To my ears, with NOS the sound is a little more relaxed, while with OS it is a bit faster (faster transients) and a bit more aggressive.

Source pair up.

Out of curiosity, I decided to compare RU6 connected to my Galaxy S9 vs connected to other DAPs like Cayin N6ii, Hiby RS6, and even a budget $99 Hiby R2.  In my comparison between my Galaxy phone and other two Android DAPs, using HibyMusic app (with Exclusive HQ USB audio access enabled and USB Audio performance mode set), I found the sound to be nearly identical.  And, the same with R2, using it as a digital source for RU6 yielded nearly identical sound performance.


USB-C interconnect cable pair up.

One question I have been asked a lot lately was if other usb-c to usb-c interconnect (IC) cables make any difference in sound with RU6.  I tested and compared stock Cayin usb-c cable vs DDHiFi, OE Audio, and even Lotoo and L&P cables.  In every case I found about 130mA current draw and the same sound in comparison to Cayin stock cable.  If you want a stiffer cable, go with OE Audio.  If you need right angled connector cable, DDHiFi offers that.  Otherwise, no need to upgrade since stock cable does its job.


External AMP pair up.

RU6 doesn’t have a dedicated Line Out.  After all, this is a dongle intended for a portable use where you don’t expect to drag your smartphone and a dongle along with an external amplifier.  But some people asked me how will it pair up with Cayin C9 portable dual NuTube amp, and if I hear any distortion as a result of double-amping.  I assume these audiophiles are looking to use it in their desktop setup with RU6 connected to laptop.  As I already mentioned, for the best audio quality it is recommended to keep the digital volume of the source connected to RU6 at the max level.  Which brings me to the question of C9 setup, either Line Input or Pre-Amp input?

In my testing I was using Galaxy S9 with HibyMusic (USB Audio Performance mode enabled and USB Audio volume locked at max setting) and a few headphones, including ATH-R70x (open back, 470ohm).  For Line Input mode, I set RU6 to its max volume (100) and was controlling the output volume from C9.  For Pre-Amp Input mode, after enabling it on C9, I was using RU6 volume control.

The difference in sound between these two modes is literally night’n’day.  In Pre-Amp mode the resolution was low, literally felt like bit resolution was reduced.  The soundstage was narrower, and changing volume from RU6 was slower and you have to deal with short mutes every 10 steps.  In Line Input, you are dealing with max digital volume (S9), max analog volume (RU6), and adjusting the output using smooth volume control of C9, yielding a dynamic, resolving, layered, fuller body sound without any hint of distortion.  That is a setup I recommend, especially for demanding headphones.


Page 3 – IEMs/Headphones Pair up.
Page 4 – Comparison and Conclusion.

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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