Cayin RU7

Cayin RU7 Review​

Last year Cayin announced their new N7 player, the first on the market to utilise a 1bit DSD DAC. Rather than employ an off-the-shelf DAC chip from AKM, Cirrus Logic or ESS, the N7 uses 128 precision resistors to convert PCM data into DSD format, in a manner reminiscent of, yet distinct from R2R players.

I’ve yet to try the N7 but have read positive reports of its’ tonality in particular, so when Cayin announced their new RU7 dongle would also feature the same 1bit approach I was intrigued.

The problem with dongles is there’s so little available space to innovate that most of them use lower-end DAC chips and end up sounding fairly similar. Whereas the RU7 takes a different approach, and even uses two PCB’s sandwiched together to facilitate a more complex circuit.

My expectations for RU7 were fairly high, and as you’ll discover they’ve not been let down!

Packaging​

The USD $289 Cayin RU7 arrives in a small cardboard box which contains a manual, USB-C to USB-C cable, and a USB-A to USB-C adapter.

Cayin have also included a leather case which does a great job of protecting the RU7 during use. The leather is surprisingly supple though green wouldn’t be my preferred colour of choice, but it’s nice having a case right out of the box.

Features & Ergonomics​

The RU7 is the first dongle on the market to utilise a 1bit DAC, which essentially uses precision-matched resistors rather than a DAC chip to process sound. It features two gain levels, a small screen that displays the current volume level & sample rate, and lets you to automatically convert PCM content into your choice of DSD64, 128 or 256. It supports PCM to 384 kHz and DSD up to DSD256, with 400mW of output power to its’ 4.4mm jack.

At 24.1 grams the RU7 is extremely light but feels very well-finished, with two physical buttons to control volume and another to activate & scroll through the menu system.

It’s worth mentioning the RU7 is the only dongle in this shootout to include a fully-fledged Line Out which functions from both the 4.4mm & 3.5mm jacks, bypassing the internal amplifier for when you choose to pair it with an external amp.

Sound Performance​

I tested the RU7 with a USB-C iPhone 15 Pro & M1 Macbook Air, using Noble Audio Spartacus IEMs.

The RU7 sports a terrific balance of tonality & technicality, and there’s something particularly special about the flavour of its’ 1bit DAC which no other dongle I’ve tried has captured.

This is best demonstrated in the midrange, where vocals on the RU7 are very forward – really grabbing your attention with rich sense of warm fullness and effortless resolution that’s at least on par with any other dongle out there.

Bass is biased more towards midbass and is impressive by dongle standards, though kept in check to avoid overshadowing the midrange. Treble is similarly impressive but again not so forward as to take any spotlight away from the midrange.

The RU7’s soundstage is wide and deep, dynamics are superb and imaging is very solid but this is not a dongle in which more treble-energy has been added purely to increase technical performance – instead my attention drifts back to the midrange thanks its’ superb tonality & resolution.

Dongle Comparisons​

iFi Go Bar 10th Anniversary (USD $499)

After you notice the 10th Anniversary’s much higher noise floor, what jumps out is its’ bottom-up presentation with greater bass thump & more midbass quantity. Surprisingly the RU7’s bass feels a little more dynamic however, and despite its’ warmer tonality the RU7 retrieves more detail.

The RU7 midrange is undoubtedly richer and more resolving, leaving the 10th Anniversary sounding flatter & less dynamic by comparison.



Luxury & Precision W4 (USD $449)

The W4’s tonality is cooler and more neutral but this can come across as less organic & more “hi-fi” at times. The advantage of that approach is W4’s higher level of technical performance across the board, with a slightly deeper & taller soundstage, more precise imaging and more prominent treble that resolves details slightly better.

By contrast the RU7’s midrange is richer and more impressive, and it may be more dynamic overall. W4’s bass is tighter & better textured, though the RU7 has a little more bass quantity to compensate.

I find these two dongles complement one another, with the W4 pulling ahead on technical performance but the RU7 delivering a more special tonality especially in the midrange.



Penon Tail (USD $74)

The Tail has been tuned with a more bottom-up approach with greater bass quantity, and tends to sound more musical & groovy though this could be partly due to greater note-smearing.

Where the RU7 pulls ahead is with its’ larger & more spacious soundtage, improved dynamics, treble that feels a bit more sophisticated in its’ articulation, and midrange richness & resolution.

Conclusion​

The easiest way to explain my feelings toward the Cayin RU7 is to reveal that I purchased one.

Does that mean it’s the best-sounding USB-C dongle to date? I think it sits alongside the L&P W4 which occupies a slightly higher rung of technical performance, but what the W4 lacks is the RU7’s amazing midrange tonality which is really something special.

Nor is the RU7 so far behind the W4 in terms of soundstage, resolution & imaging that these areas feel deficient, and the RU7’s 4.4mm Line Out is invaluable if you ever want to use an external amp.

As always in audio things are rarely clear-cut so I strongly recommend demoing both dongles to see which fits your preferences, but suspect you won’t be disappointed with either if they fit your budget.

In the meantime the RU7 has convinced me 1bit DAC technology has merit, so I can’t wait to try Cayin’s next 1bit DAP or dongle release.

Introduction: RU7 is the latest flagship dongle released by Cayin as a successor to their previous flagship, the Cayin RU6. While the RU6 features a 24-bit Discrete R-2R Resistor Ladder DAC, the RU7 uses 1-Bit Discrete Resistor Network DAC, a different type of technology trickle down from their flagship N7 DAP, instead. This dongle has a MSRP of 290$.

Disclaimer: I bought the Cayin RU7 with my own money. Everything i said in this review is my subjective opinion only.

Unboxing:

The box was quite smaller than i thought. It’s only as big as my Poco F3 phone.

Inside the box, we have a few things: The C-C OTG cable, C-A adapter, a green leather case, a user manual and 2 magnets (sadly i lost it)

The green case itself fit the RU7 very snuggly. I won’t need to worry about the case coming loose anytime soon, unlike some previously known cases of the RU6.

Design

The RU7 has a small rectangular form factor. Its chasis is made out of aluminum with a matte black finish and glass panel with a built-in OLED screen on top.


On the side is the 3 buttons, 2 of which let you controlled the volume and the “mode” button to control the settings of the RU7. Click the “mode” button once to turn the screen on/off. By holding it in a few seconds, it let me go into a setting menu. I can change between Low gain and high gain, switch between the 3 DSD modes and the output of the RU7 (Phoneout or Lineout).



User experience:

The Cayin RU7 is small, light weight, has a protective case so i dont have to worry about scratching. The setup was relatively smooth when i wanted to use my RU7 with Window 10 laptop. I just need to plug and play and that’s done.

With 2 levels of gain, 3DSD mode and 2 output types, the RU7 gives me a lot of flexibility on how i’d want to use it on a daily basis.

Overall, my time with the Cayin RU7 was quite enjoyable. However, it’s not without its quirks.

First thing i’d like to note is how much the Cayin RU7 battery consumption. It drains my Poco F3 faster compared to every dongle that i’ve own. It only took me more than 4 hours to drop my battery percentage from 100% to 0%. Not to mention that even without playing music, the RU7 keeps draining the battery of the phone.

The second thing i’d like to note is the clicky, zappy sounds while using the RU7. This sound is very different from the usual humming noise floor when i use my Ibasso DC04 Pro and 7hz 71 with a powered laptop. These audible noises appear when i’m switching songs, when fast forwarding music and worst of all, it’s even appeared during some quiet session of the songs or videos. This is due to the resistor working inside. Andy from Cayin has already commented about this on the Cayin RU7 thread, so this behaviour is normal to the RU7. Some can live with it, but honestly after i noticed this sounds, the existence of it is quite...annoying.

Last thing i want to talk it how much heat the RU7 generated during use, especially in DSD256 and LO mode. I don’t know the exact temperature, but i’m pretty sure it’s over 50 degree Celsius after 30 minutes of listening.

Sound impression:

I’d describe the sound of Cayin RU7 as neutral and analog sounding.

Bass has this more rounded and fullbody sound to it with very light midbass emphasize. You can say the RU7 sounds a bit warm to it due to this discription, but i’d still say the RU7 is on a neutral side of things.

Midrange wise, the RU7 just do it just right. Neither too forward nor backward. The midrange of RU7 just sounds natural as is.

Treble is detailed smooth with no digital glare. There’s a subtle lower treble boost in the RU7, in a way that it makes the percussion instruments’s attack just sound a bit more crisp.

Technicalities wise, RU7 is the most technical sounding i’ve heard. Only after 10s of using RU7 that i know this dongle is quite something else. The soundstage is really wide with clear imaging and layering.

For a more relative context of how RU7 performs compared to others, please continue reading for the comparison parts.

Synergy: RU7 can synergize with a lot of gears, but i don’t think it’s suitable for the overly colored or warm sounding sounds tranducer.

For people that want most fast sounding bass, highest detail, clearest, more hi-fi sound rather than analog sound, the RU7 would not be for them.

RU7 in LO mode: I want to test how the RU7 would sound in LO mode without having to use an additional amplifier, so i tested the LO mode directly with the TGXear Totem, since i think having an ỉmpedance of 700ohms would somewhat keep it safe and not making it too loud. After thorough testing, i think the the sound from LO mode is slightly better than PO mode. Compared to the PO mode, LO mode sounds like it has a better impact subbass and a bit more transparent.

Word of caution if people want to test LO mode with other more sensitive gear: If you’re using a laptop or PC, please lower the volume of the software you’re using to listen to music, not the OS themself. For some reason, even if i turn my laptop vol from 100 to 1, the loudness of LO mode remains the same. Only when i turn down the volume of foobar2000 app or youtube’s video that the volume did come down. Also, it seems like the RU7 does not let you change between the modes rapidly, where you’d need to wait around 10 secs for the mode to be changed again. (the screen may show that you’ve already changed the output mode, but you’d need to wait for 10 secs for it to take effect)

Differences between DSD64, DSD128, DSD256

Truth be told, it was really hard for me to do comparison for these 3, as i feel like the differences was too small between them. Switching between the modes for every 10-15 seconds of the same songs did not really help me. So in order to make this comparison, i have to listen to each mode for around a few days then switch to another. After thorough testing, here’s what i think about the 3 DSD modes.

DSD64: Slightly more warmth and full. More analog sounding

DSD128 Jack of all trade. Most balance sounding, loose a bit of detail for naturalness

DSD256: Highest detail and clarity. A bit more digital sounding

Driving power: The Cayin RU7 is no doubt a very powerful dongle. At high gain and 100/100 level, it can drive my Shuoer S12 to a deafening level of 90db. It can also drive my 700ohms of impedance TGXear Totem earbuds to a comfortably loud level (around 80-85db) without sacrificing much, if any, bass texture and overall dynamic, so power is definitely not an issue here

Sound comparison:

1/ Ibasso DC04 Pro

I know i know, the DC04 Pro is not really in the same realm as the Cayin RU7. Its price is not even half of the RU7. However, the DC04 Pro was one of the most famous dongle in 2023, ranking 1st in the Best bang for buck category by DongleMadness. Many people were able to afford this. It was also my previously EDC dongle, so comparing these 2 against each other is something i should do.
Both dongle in my opinion has a neutral and analog-ish tonality, but right of the bat, there’re 3 differences that i noticed: the bass, the treble and the imaging.

The bass has more thump and better texture to it, compared to the DC04 Pro. Using Penon Serial to test, the bass on the DC04 Pro feels like it got cut of at the end of the notes. Those “strings plucking” moments in some of my jazz tracks just feels a bit incompleted, whereas it sounds more completed on the RU7. The bass there feels more lifelike, i can virtually imagine the instruments being played

As for treble, i feel like the treble of the RU7 is crisper than the DC04 Pro. However, due to this right here, the synergy of the RU7 would be a little different from the DC04 Pro. Some iem that has too much treble would not be able to synergize well with the RU7, whereas the DC04 Pro would be a better option between the 2, cue the TGXears Serratus and Hifri’s Barcelona. The treble there just feel a bit more pronounce with shaper, crisper transient.

Imaging. Coming from the DC04 Pro to the RU7, my first thought was “man, has the layering always been this crisp and distinct?”. I thought i was being paranoid due to “new toy syndrome”, so i listen to RU7 for a while longer then switching back to the DC04 Pro, the sentiment was still the same. The Cayin RU7 sounds wider, with better instruments separation and a more distinct layering between the instruments compared to the DC04 Pro

That being said, the RU7 did not completely kill the DC04 Pro. The DC04 Pro has a better battery consumption rate, it drained my phone’s battery way less. Even without listening to music, RU7 drains the battery of my phone. The DC04 Pro also generate less heat. It doesn’t have that usual clicky, zappy sounds from the resistor of the RU7. On Android phones, there's an app from Ibasso that let you adjust some settings of the DC04 Pro. Another thing i’d like to note is the noise floor when using the RU7 with my plugged in laptop is virtually zero, compared to a small amount of noise when using with the DC04 Pro. Although in my opinion, that would just like changing from another devil to another: The humming noise (due to the plugged in laptop) of the DC04 Pro vs the clicky sound of RU7 in those silent moments like during songs transition.

Is the Cayin RU7 an upgrade to the Ibasso DC04 Pro? In a sense, yes. It improves upon many things of the Ibasso DC04 Pro like the overall tone and the technicalites, despite it already is a good dongle in and of itself. If you’re looking for a do-it-all, only-keep-one dongle, then yes, buy the RU7 as an upgrade to the DC04 Pro. Is it worth it? Depend on your wallet. But if you already have the DC04 Pro and you’re looking for a dongle to diversify your dac/amp collection, i’d advise you to look for something else like the Cayin RU6 or the Hiby FC6 and keep the DC04 Pro. Despite me describing the differenes of these 2 for this long, the DC04 Pro is more similar to the Cayin RU7 than they are different. Both have i’d call a neutral and analog sounding.

2/ Chord Mojo.

Now i’ll reverse the scenario. Here i’ll compare the the Cayin RU7 against something that has more than double the msrp of it: The Chord Mojo. It was sold for 599$ the moment of its release. The reason why i’m picking the Mojo is that the Mojo are being sold in a very competitive pricing in the 2nd hand market (around 150$-160$ in Vietnam and Chinese), so good sound is very affordable there. The Mojo was arguably one of, if not the best sounding dac/amp during its time.

So here, we’d have a battle between the top of the dongle world in 2023, against the previous top of the portable dac/amp world in 2015. New vs old, how would they fair against another?

Both of these are wildly different. The Mojo has a battery and the RU7 does not. The Mojo has a custom FPGA DAC technology, whereas the RU7 has a 1-bit DAC technology. The Mojo has 2 3.5 phoneout ports rather than a 3.5mm SE and a 4.4mm balance of the RU7. Despite being SE only, Chord Mojo has more power to tap into compared to the RU7.

The differences in sound reproduction between the 2 were immediately perceiveable. Compared to the more neutral sounding RU7, the Mojo definitely has a more colored sounding. It’s more “romantic” in a sense. It’s warm, but also analytical.

Using the Penon Serial to listen to these 2, i definitely like the sound of the Mojo more. The Serial has a better bass texture, with more depth to its sound. The treble is also softer, yet the detail was around the same level. Imaging, i would hand it to the crisper imaging of the RU7. The Cayin RU7 has a touch wider soundstage compared to the Mojo. Synergy wise, i like to use the Serial on the Mojo more despite the Serial already warm sounding. The Serial just sounds more musical to my ear in this combo. Part of it was also due to me being a mild basshead.

Using the TGXear buds, the story was still the same. The Chord Mojo also colored the whole sound of the earbuds. The Serratus has a more natural bass tone with a better treble decay. The Totem was sort of brought to life more when pairing with the Chord Mojo. The Totem has a 700ohms Berylium driver which just screams for power, which the Mojo has. The neutral, reference-ness of Totem just synergize well with a more colorful and romantic sounding Mojo.

The Sunniva on the other hand. Sunniva is the one that the RU7 synergize well with due to the Sunniva already warm and thick sounding. The Sunniva sounds more balance, the treble becomes crisper with better imaging and layering when using with the RU7.

All in all, it’s all depends on taste. Personally, since i’d rather my music to be more musical and colorful and because i have many more colored sounding iem and earbuds (as opposed to a more neutral set like the Etymotic’s), i’d pick the Chord Mojo over the Cayin RU7 in many cases, despite its cons like the using of micro usb, 3.5mm port only and i have to charge it to use it.

3/ Cayin RU6

Brother from the same mother, the Cayin RU6. The Cayin RU6 uses an R-2R DAC technology inside its body. It’s been a while since i last used it, but judging from memory, the RU6 also has an analog type of sounding, however it feels warmer compared to the RU7. The bass on the RU7 has more authority compared to a more soft sounding bass on the RU6. Midrange and vocal wise, the RU6 is better than the RU7 in my opinion. I’d describe the RU6’s midrange and vocal as romantic, emotional and velvety. The RU6 used to be my go to dongle when ever i want to listen to some lyrical music or when i just want to vibe with the music, not analyzed it. Treble sounds crisper and shaper on the RU7. Techinicalities wise, especially the soundstage, the RU7 is definitely better than the RU6. The RU7 has more details, wider sense of stage and a more distinct imaging. Synergy wise, i’d say the RU7 is easier to synergize with a lot of stuff more than the RU6.

Conclusion:
With the price of 290$, is Cayin RU7 worthy of its price? Yes
The Cayin RU7 is one heck of a beast. It has become a benchmark in the dongle world, where future to-be-released flagship dongle would surely be compared against this. The RU7 gives people to have a chance to try what a 1-bit DAC would sounds like without hurting their wallet too much. The form factor maybe small, but what it brings to the table is not. Despite some of it quirks, being a neutral, analog sounding dongle with an impressive technicality, i’m confident that many people will like this powerful dongle if they can get their hands on it.

That’s it for my review and thank you for reading.

Hi there, at this opportunity I would like to make review for the Cayin RU7 dongle.
The RU7 is purchased with my own money and all of this are 100% my opinion.
Unboxing
Inside the box you get :

• Dongle
• Leather Case
• Manual
• Hi-Res Stickers
• 2 Steel plate
• C to C Cable
• C to A Adapter

Build Quality
I had some problem with my samples of the RU7.

My first sample had a tilted screen that looks really ugly and triggered my OCD for real.
It also has a rattly 3.5mm port.

While my 2nd sample screen is pretty much perfect, it still also has a rattly 3.5mm port.

There are some people that has this rattle on the port, but some are perfect without rattle at all.
Andy from Cayin has explain it to me it is rather normal to have some rattle on the RU7 because of how the 3.5mm made and used on the RU7.

but be warned, do not ever shake your dongle, I have been warned very strictly that It is counted as an abuse to the dongle and it can void and jeopardized your warranty.

Power Consumption
It consumed around 12 - 15% / hour of my Xiaomi 13T phone and is super hot during use using all to dsd 256.

Sound
The RU7 to my ears is sounding a bit warm, musical and analogue, with very good technicalities.
well.. it depends on the all to dsd configuration, the all to dsd 64 is the most warm, 128 in between, 256 is the most neutral of all, also the technicality is better with larger number.

I will mostly do my review on the all to dsd 256 configuration.

RU7 has one of the nicest timbre I've ever heard in a dongle dac.
Especially the bass, ooft it has a superb impact and slam with very good control and bass sounds grand if that makes any sense to you.

I really love how the RU7 presents bass with very good control and authority and bold presentation and also sounds very natural and has proper lingering decays.

While for the midrange, it has a very natural and organic and analogue-ish timbre that makes vocal and instruments sounds very realistic and "wet" or I should say it has a correct decay that makes things sounds really natural.

The midrange presentation I found it to be a bit pushed back a little, not the most forward and intimate, but thanks to that, it creates a very good soundstage and separation for all instruments and vocal.

Treble here I found it to be smooth but VERY EXTENDED, it has superb extension and airy representation that I can describe it again as "wet" sounding because of the rather long decay.

Technicality wise, the RU7 is one of the most technically capable dongle that I ever heard, and is pretty much a steal for its price.

For context, previously myself use the Luxury Precision W2-131, and the RU7 absolutely destroys the W2-131 in terms of tonal, timbre, and technicality.

It has one of the largest stage that I've ever heard from a dongle, very open sounding and has a lot of space between all instruments and vocal.

Imaging is also top notch, I try to plug the RU7 with Moondrop CHU2, and it has holographical presentation that makes me wondering how is that even possible.

Separation and positioning is top notch, thanks to its very large soundstage and very spacious presentation of how the sound is rendered.

3.5mm SE vs 4.4mm
Has a minimal different, the 4.4mm has more power and a bit more separated or room between sounds.

HISS?
With Hidizs MS3 and MS5, I got a slight white noise from the 4.4mm balanced output but the MS3 and MS5 is known to be very sensitive to the source.
All of my other IEM have no hiss at all on both 3.5mm and 4.4mm balanced output.

Comparation

Hiby FC6
The FC6 is also one of the most pleasing timbre dongle that I've ever heard, for timbre wise I pick the FC6 all day, it suits my taste more than the RU7, the FC6 has less output power but more efficient battery consumption (8-10% / hour compared to the 12-15% / hour of the RU7)
Sound wise, the FC6 has more intimate stage, a bit more warmer than RU7, but still wide and open.
It depends on what you're searching for in sound representation really...

If you like more intimate and more mid focused stage like the vocal is the main spotlight on your music, then maybe,, maybe the FC6 is the one for you.
But if you like your sound to be more separated and, OR use OR need to drive headphones, well, the RU7 is the one more suitable for you.

Luxury Precision W2-131
The W2-131 is using your traditional DAC / delta sigma DAC, it has more neutral presentation compared to the RU7.
for technicality wise, the RU7 pretty much superior in all categories, that I don't even need to explain.

Conclusion
Is the RU7 worth it?
well yes of course despites I had bad luck with my RU7 sample, myself as a reviewer try to be objective all the time for the review.

so what's up with only 4*?
well... -1/2* for the super hot dongle during usage like my 4.4mm steel jack is piping hot to touch, and -1/2* for the power consumption on all to dsd256.

It is easily has the best timbre and technicality for $300USD and probably you can compare it to more expensive DAC / AMP and the RU7 will not embarrassed itself.

It just needs more tighter QC tolerance, that's all and it would be the perfect $300 USD dongle at least for now.


Thanks for reading this far !

Just in case you're Indonesian or you understand Bahasa Indonesia, you can watch this review here


-littlenezt

This is a brief summary of the Cayin RU7 review that is available in my website.



Executive summary

The Cayin RU7 is a portable USB DAC dongle that uses a fully balanced discrete 1-Bit DSD DAC to convert digital signals to analogue through a fully differential 4-ch DAC architecture. All incoming signals are converted to DSD before they get to the conversion circuit that is composed of 128 (4x32), high precision, thin film resistors. The RU7 supports PCM up to 32-Bit/384kHz and native DSD256 decoding.

The Cayin RU7 features a shared line output. This function will configure the 3.5mm or 4.4mm phone outputs into fixed voltage outputs, bypassing the volume control. The output voltage is 1.2Vrms for the 3.5mm output and 2.4Vrms for the 4.4mm, carefully selected to retain as much details and dynamics of the 1-Bit DAC with minimum noise and distortion.

The Cayin RU7 is very powerful, it can provide 400mW/32Ω of undistorted power from the balanced output when most USB DAC dongles will max at about 260mW/32Ω with a couple of exceptions like the iFi Go.

The Cayin RU7 is very well shielded against EMI and host internal noise. It offers a pitch black background that helps a lot with detail retrieval and lets you enjoy your music without noise.

The Cayin RU7 offers a class leading audio performance that combines timbre realism and musicality with great transparency and technicalities. The sound signature is very organic and analogue-like with complete absence of digital glare and treble artificiality. Smooth and musical yet extended and crystal clear, the Cayin RU7 will move your heart and connect you with your favorite tunes into a pure listening experience.

The Cayin RU7 is something special and one of the best USB DAC dongles you can buy right now. The audio performance is flawless and similar to that of high quality mid-range DAPs or even desktop DAC/amps. The Cayin RU7 is leading the USB DAC dongles race and competition will have a hard time to catch up with it.

I would like to thank @Andykong for providing a review sample of the RU7 and additional technical information as required. This review is an extract from the The Superdongles feature in The Headphone List.


I have a real soft spot for Cayin, even though I haven’t owned a Cayin music player since my very first DAP, the Cayin N3, several years ago now. I briefly flirted with Cayin’s RU6, given my preference for ‘analogue’ R2R DACs, but found it redundant alongside the more powerful R2R DAPs I used at the time (and still do), nor the most resolving dongle I’d heard with my IEMs.

When Cayin first introduced its N7 DAP earlier this year, I was intrigued by the inclusion of a discrete 1-bit (DSD) DAC in a portable player, a first of its kind. Well, Cayin has done it again, only this time shrinking its 1-bit DAC design even further for the dongle format.

Cayin’s RU7 ($290 at Musicteck) features the world’s first discrete 1-bit DAC in dongle format, following closely on the company first 1-bit DAC-in-a-DAP in the N7. It’s a sign of the times that you can now get native DSD audio up-sampling from a low-power portable dongle the size of a matchbox – a feature that was previously the preserve of some serious desktop computing hardware. Not only that, the RU7 isn’t far behind the N7 when it comes to driving power, especially with IEMs, despite the $1,700 price difference between the two.

It has other interesting features too, like a dedicated, albeit basic, line out mode, and an All-To-DSD engine that I’ve only seen in seriously expensive players before now.


Packaging and accessories

RU7 ships in an small, understated box with a matte black satin finish and a glossy silkscreened image of the dongle from two different angles. Inside the box you’ll find the dongle in a custom foam tray, and separate tray with a USB-C to C cable and USB-C to A adapter.

There is no USB-C to Lightning adapter or cable included, Cayin opting to sell its $20 CS-L2C cable separately for some reason. Cayin does include a protective green leather case as standard, however, along with two matching leather stick-on magnetic patches to connect the dongle to a smart device in case you want to stack them.

Design and use

RU7 has a ‘conventionally’ rectangular design, coated in a silky-smooth matte-black aluminium finish with a glossy glass top. A small OLED screen is built into the glass panel, offset to the left of the player rather than centred in the frame.

There are three slightly raised buttons on the topmost long side of the dongle, two volume toggles and a menu/function button. Outputs include 3.5mm single-ended and 4.4mm balanced headphone ports, which double as true line-out ports for connecting RU7 to external amps without double amping.

One usability issue I have with the input buttons is that they’re flush with the case, and although the case is slightly indented around the buttons, I often end up lowering o raising the volume when I want to do the opposite, or accidentally changing the volume when I want to change settings.



Specs

• DAC: 1-bit discrete resistor fully-balanced 4-channel DAC
• Volume control: discrete resistor 100-step linear volume control
• FPGA: No
• SNR: 114dB (3.5mm) 112dB (4.4mm)
• Power output: 160mW (3.5mm) 400mW (4.4mm)
• THD+N (32-ohm): 0.006% (3.5mm) 0.008% (4.4mm)
• Dynamic range: 115dB
• Screen: 0.91-inch OLED
• Audio formats (PCM): 16/24/32-bit 44.1-384KHz
• Audio formats (DSD): DSD64-256
• Dimensions: 66mm x 24mm x 12mm
• Weight: 25g

Settings

• Gain: choose between low and high gain, for sensitive to less sensitive loads.
• All to DSD: choose between up-sampling PCM audio to DSD64, 128 and 256.
• Output: choose between PO (headphones out) and LO (line out).
• Backlight: choose between permanently on, to auto off in 10-second increments between 10 and 60 seconds.

Notable features

World’s first dongle-based 1-bit discrete resistor DAC. Made up of 128 pieces of 0.1% 25ppm high precision thin film resistors, the custom-made 1-bit DSD DAC features an All-To-DSD engine that up-samples incoming PCM signals to DSD64, DSD128 or DSD256. The higher the setting, the more precise the conversion with higher resolution. The up-sampling level also has a perceptible effect on tonality.

Parallel dual phone amplifiers. Cayin has implemented dual parallel amplifiers in the RU7, boosting amplification current by as much as 80% from the RU6. They’ve done this without significantly increasing the noise floor of the amplifiers, resulting in a near-silent noise floor with all but the most sensitive IEMs.

Shared line out ports. It’s rare to find a line out function in a dongle because of the limitations on the hardware needed to provide a separate line out circuit. Cayin circumvented this limitation by folding line out functionality with the headphone ports.

This does limit line out quality and output levels – 1.2V for single-ended and 2.4V for balanced (compared to typical 2V and 4V outputs in dedicated DAP line outs), but it’s apparently a user-requested feature and so Cayin made it happen.

Be warned – selecting line out is not automated, and the dongle won’t switch back to headphone mode after a line out session, so be careful when you use this feature to switch back to PO, especially when using sensitive IEMs.

Discrete digital volume array. RU7 uses three banks of resistors and switching relays to provide 100 steps of precise volume increments.

Separate digital and analogue circuits. The digital and analogue sections of the RU7 are split into two separate PCBs, shielding the analogue amplification signal from digital clock and DSP noise.



Sound impressions
Tonally, RU7 has a rich, slightly warm, and subtly coloured tonality that emphasises some frequencies over others. Bass gets a moderate bump, more midbass than sub, which makes certain instruments and lower midrange vocals sound fuller and warmer than they would from a neutral source.

Midrange is fairly linear, though lower mids ‘benefit’ from the thicker bass density, if that’s your preference. That’s not to say any part of the midrange is veiled; on the contrary, I find RU7 to have an excellent degree of clarity through the mids, without any veil whatsoever, but the midrange notes are sweeter and sound quite organic, especially when up-sampling to DSD64.

Treble also gains a subtle boost to my ears. It’s not peaky, and I definitely wouldn’t call RU7 a ‘bright sounding’ dongle, but there’s plenty of energy here when the music calls for it. Overall, I find RU7’s tonality to be quite ‘musical’, which is to say warm of neutral with a natural, organic and full sound through the midrange, and enough shine in the highs to sparkle even when the bass is pumping.


Despite its obvious musicality, RU7 delivers excellent and occasionally outstanding technical performance. I’m hearing a decently wide stage with most IEMs, not quite as wide as I do with more powerful and expensive sources, but I don’t feel staging is compromised in any way either.

Other staging elements, like imaging, separation and layering, are all very good, and consistent with the highly technical levels achieved by the higher-end IEMs I used for testing. I did come across the odd track the sounds a touch more congested than I’d like during very complex passages, but that’s to be expected given the limitations of the format, and it’s only apparent in comparison to larger sources.

I thought for sure that noise would be a bigger problem than it is; I’m yet to hit any significant noise floor with any of my IEMs, even when turned up loud, and even with super sensitive IEMs where noise would sometimes be an issue. This is even more impressive given RU7’s powerful and very dynamic sound, that would normally show up any issues with signal noise, but to my ears, there is none.

Overall, I feel RU7’s ‘superpower’ is its ability to deliver such a rich, coherent and lively sound with a high degree of technical polish. From memory (and copious notes) this alone sets it apart from its predecessor, the RU6, and is possibly reflective of the technical advantage of its 1-bit DAC compared to the latter’s R2R derivative.



Select pairings

FiR Audio Rn6. RU7 warms up this already warm-of-neutral ‘reference’ IEM a touch, making it sound fuller, wetter, more cohesive but slightly less resolving. It’s musical but not muddy, with a punchy bass and vocals I can usually describe as earthy. Stage can is wide on some tracks, but with busier music it can get a little congested. An excellent pairing, and easily driven, with low-thirds volume in low gain.

FatFreq Maestro SE. With RU7, MSE comes into its own, offering up a warm, pleasantly even tonality with standout bass when called for. RU7’s slight midbass bump works well with MSE’s rather linear midbass tuning. It also works nicely with MSE’s neutral midrange, adding a touch of warmth and weight to vocals, though female vocals are still quite airy and occasionally wispy. Treble is nicely extended, and not too elevated, but sparkles and shines where it needs to without getting in the way or taking over the performance. Another excellent pairing, with a comfortable listening volume at 55/100 in high gain – not bad considering how difficult MSE is to drive.



HiBy Zeta. With RU7, Zeta takes full advantage of the slight bass lift to deliver a bold presentation that somehow doesn’t bloom or spill over into the lower midrange. While vocals (and the midrange in general) isn’t as resolving as it is with MSE or Rn6, it holds its own with just enough detail to satisfy and never too much to fatigue. I like how RU7 controls Zeta’s occasional upper midrange peak, and so is never shouty or sibilant, even with poorly recorded material. Easily driven at low volume in low gain, this is another excellent pairing, and shows off RU7’s versatility with different IEM tonalities and sensitivity.

Sony IER-Z1R. With RU7, Z1R has more midbass heft, and more bass in general. Vocals are well separated, and treble is clean and distinct, giving the sound a deeper U tonality. If you like your Z1R warmed up, RU7 will do that, though the famous Z1R stage will sound slightly more compressed and not quite as deep. Another IEM that loves power, and RU7 delivers impressively at 45/100 in high gain.



Compared to L&P W4

RU7 is notably warmer-sounding than the more neutral W4. RU7 bumps the midbass region ever so slightly, thickening the note weight of the lower frequencies. W4, by comparison, is more sub-bass focused, with a tighter bass punch and not quite as much weight or decay in the midbass notes.



Increasing the DSD rate on RU7 has the effect of stretching out the lower frequencies, or at least relative to the increase in midrange and treble detail, but the bass never becomes a tight as with W4. Even though bass is still nicely controlled on RU7, it’s also ‘bigger sounding’ than W4, mostly due to this subtle bass lift.

I hear similar differences in the midrange of these two dongles. W4 shoots for clarity and transparency, with a neutral and fairly linear midrange that’s more revealing, while RU7 mids are a touch denser and more euphonic. The lower the DSD sampling rate, the ‘wetter’ the RU7 mids become, although at no point do they get as warm and full as the midrange of a typical R2R DAC like RU6 or HiBy’s RS6.

RU7’s lower midrange sounds slightly fuller to me, but also a touch more recessed compared to W4, whereas the upper mids are mostly on par between the two. That’s not to say W4’s mids are thin. Both dongles dig deep into the musical information in the midrange, and neither come close to sounding overly analytical. RU7 leans slightly more musical than W4 in the midrange, however, but W4 in turn sounds more accurate, with a lifelike, natural timbre to instruments and vocals.

The upper frequencies of both dongles are also quite linear, without any notable peaks or dips, and excellent extension. I’d hazard a guess that RU7’s treble is ever so slightly lifted compared to W4’s crisp and neutral treble response, but it would be just that, a guess.

Combined with the bass lift, slight lower midrange recession and subsequent treble rise, you’d be forgiven for thinking RU7 has a V-shaped tonality, but it’s much closer to a gentle U. W4, in contrast, is even flatter by comparison, about as close to true neutral without ever crossing into stale, cool or analytical territory. Both dongles are naturally musical, but RU7 is musical with a warmer, fuller tilt.



The technical level of both these dongles is nothing short of impressive. I’d be hard pressed to pick out the difference between either dongle and a really good mid-to-upper tier DAP based on technical performance alone.

That said, and since I won’t be comparing these dongles directly to actual DAPs other than in passing subjective comments, there is a limit to how technically-accomplished and refined you’ll hear them yourself, especially if your weapon of choice is a higher-end DAP or desktop system.

The stage size of both dongles is very similar; neither dongle projects the largest stage I’ve ever heard, but neither is staging too intimate. Width, height and depth are just about even, with W4 maybe edging RU7 in depth and RU7 sounding a hair wider. Both are what I consider natural, projecting sound ever so slightly out of head with my largest-stage IEMs, but not quite as holographically as I know them to be capable of.

Where W4 does take the lead is in separation and layering, aided perhaps by its mildly leaner tonality. Sounds emanate more distinctly from the blackness of the background with the W4, and are also more spaced out from each other. Imaging is excellent with both, neither coming off as too diffused, especially in light of their average stage size.



Speaking of background, both dongles are essentially noise-free. RU7’s thicker notes and closer spacing might give the impression of a less inky backdrop, but I don’t think that has anything to do with noise. Regardless, W4 does sound cleaner. It also sounds more detailed, and while RU7 is at least as resolving as some higher-end DAPs and desktops with the same IEMs, W4 is even more so.

Dynamically, RU7 is the more exciting of the two. That said, depending on the setting, RU7 can also lean more relaxed (DSD64), and switching W4 to Tone 01 has a similar effect on the sound.

Overall, both RU7 and W4 have set a new benchmark for technical performance for dongles, at least of the many dongles I’ve heard. Both outclass their predecessors, for example, sounding cleaner, more precise, less noisy, and more resolving. Where they differ more is tonally, which in turn affects the perception of the subtle intangible technical differences I’m hearing.

The only cap on performance is the cap imposed by the physical size of these devices. Sadly, not even the most ingenious DAC designs or amplification circuits can defy the laws of physics, and as such expecting dongles – even these Superdongles – to match and exceed the performance of larger, more complex, and more computationally-powerful devices is fanciful. It’s not about price, it’s about size.

But, on their own terms, the sound quality they have already attained is about as good as we’re going to get in this format with current technology.



Closing thoughts

Cayin’s RU7 continues the company’s hot streak of breaking new ground in DAC design for the dongle format, and I won’t be the first to say the all-new 1-bit DAC in the RU7 is even more impressive than the R2R DAC in its predecessor. Not only that, the new parallel amp design has proven itself with some of the hardest-to-drive IEMs I’ve ever used, and in doing so, RU7 is no longer hamstrung by piddly power output, the usual Achille’s Heel of most dongles.

With a smooth, rich and musical tonality, RU7 is also the most versatile dongle I've used with the selection of high-end IEMs in my collection, and is probably my pick of the new crop of 'superdongles' if I could only choose one. Highly recommended.

Overview:

Up for review today is the Cayin RU7 1-Bit Resistor DAC/Amp USB-C Dongle – which from now on will simply be referred to as the RU7. This little guy is Cayin’s attempt at bringing the excellent Cayin N7 sound to a smaller form factor at a significantly cheaper price. The Ru7 retails for $289.99 and mine was provided to me by Musicteck (shop.musicteck.com) with a discount in exchange for a review. You can buy one here: Cayin RU7.



Build Quality / Design / Specs (20/20):

The build quality on the RU7 is excellent with CNC a milled aluminum chassis that only weighs 25g. That’s a LOT lighter than a normal DAP would be and the RU7 even comes with a tiny screen that tells you the volume and sample rate. The green leather case that comes with it is a nice touch as well (and not yellow). Of course, the main thing that the RU7 is missing is a power supply since it’s driven directly from your phone or computer. Battery and a built-in power supply/screen/all-in-one design are the obvious benefits of a DAP. So, while the RU7 manages to capture the spirit of the $2k N7 by using a 1-bit resistor ladder DAC, it could never truly capture the insane amount of performance the N7 does with far more space at 9x the cost. While some people were likely hoping for that result, and Cayin themselves directly compares the RU7 to the N7, I want to negate that idea early on in the review – these are two very different products.

What you do get is an excellent dongle that doesn’t have the issues that a lot of dongles have. You also get DSD256 and PCM 384kHz, but no MQA decoding (which may not matter soon anyway based on MQA’s bankruptcy). On top of that, there’s a resistor array volume control that works fantastically and channels the feel of a DAP’s volume control. You also get 160mW of power from the 3./5mm jack @32ohms. There is also a 4.4mm balanced output (there had better be at this price level) that provides 400mW @32 ohms. That’s a lot of power from a little dongle (that’s not really all that small compared to the HiBy FC3 – which is about 1/3rd the size if you’re looking for smol). You can also switch to line out if you want to use it as a mini-DAC, but then you end up with a silly 3-piece chain and I can’t imagine doing that with a phone – computer maybe if you really need extra amp power. There’s a lot of power and sound quality in a small, light, well-designed package – I have no reason to pull any points off here – 20/20.



Accessories (18/20):

What accessories do you expect with a USB dongle? Likely a USB-C to USB-C cable to connect to your phone – and that’s probably about it. The RU7 comes with that, and it’s a little longer than I’d like at 4” – but it’s useable and the RU7 mostly just sticks out of my pocket, making the volume controls easily accessible. However, the RU7 also comes with a USB-A to USB-C adapter included as well – likely for laptops, etc. So that’s a nice touch, although it’s missing a Lightning to USB-C converter so add an extra $10 to your purchase price if you have an iPhone as you’ll have to buy an adapter (I used this one: https://amzn.to/441d10A). The RU7 also includes that leather case though which is just awesome because if you’ve looked at a lot of dongles, you already know that almost no one includes a case with a dongle. Heck, L&P charges $33 extra for their leather case for the W4 (also available on Musicteck) – on a player that already costs $450 and provides the same output power. The W4 does come with a lightning adapter at least, so that’s…cool…

The RU7 earns 18/20 points for accessories and if it had included a Lightning adapter, it would have been the full 20 – a slight, and relatively cheap oversight on Cayin’s part.



Software / Setup / Ease of Use (20/20):

This section is going to very short as there is no setup and only 3 buttons on the player. I do want to mention though that when I plug in most dongles, Tidal pops up a message asking if I can allow the dongle. For some reason, the RU7 doesn’t have that message – it is just ready to go. All I have to do is hit play and adjust the volume. You can also go to the menu and adjust the quality to DSD 256 since it starts at 64 for some reason. There’s really nothing else to add here – it’s easy to use and the volume controls are excellent with tons of stepping and gain to really dial in your volume – an issue a lot of dongles have. 20/20 points here.

Performance / Sound (18/20):

The battery usage is excellent – I get more battery life from my Samsung Galaxy S23 Ultra using the RU7 than from the HiBy R6ProII with its large internal battery ($750 retail). I’d say that the RU7 averages around 6-7% of my phone battery an hour vs the R6PII which used almost 15% of its battery an hour. That was my biggest complaint with the R6PII (other than some weird software bugs) and the RU7 sounds trumps the R6PII in that category. The R6PII does, however, sound better than the RU7. The Cayin N7 sounds better than both, but again, we’re getting into massive levels of price difference with the R6PII costing around 2-3x as much as the RU7 and 2.5x cheaper than the N7. The RU7 sounds better than the Shanling M3U, but just slightly and that one STILL costs more. Dedicated DAPs are excellent and very hard to beat, but I would say that the RU7 gets pretty close to the excellent sound of the R6PII, while sounding slightly flatter and less full-bodied than the R6PII. It’s easily the best-sounding dongle I’ve ever heard, but that is a really low bar since most dongles just sound OK – this one at least sounds very good.

Oh, yeah, and I can power my Sennheiser HD700s and my Sendy Aivas from the 4.4mm jack at about 60/100 volume on high gain from my PC. I don’t even own a dedicated DAC or Amp anymore – it cost me about $18 for a high-definition USB-C cable (https://amzn.to/441r8TC). I ran that cable from my PC to the top of my desk and I plug in a dongle there which provides me with excellent sound quality as long as I’m not using super power-hungry headphones like the $6k Susvara (if you have a Susvara, buy a better source). Even crazier, I can power my speakers using this combo with the HiBy DAP dock. So yes, the RU7 gives me a balanced mobile and a desktop solution all in one – wicked. 18/20 points here for the excellent battery life and great sound quality.

Comparisons / Price (18/20):

I’ve covered a lot of the comparisons in other sections of this review since that’s kind of the most important part of this dongle. It has sound quality close to a $750 DAP, but without the battery issues that has, and without the dedicated platform that improves the sound quality. It’s not as small and cheap as the OK HiBy FC3 but it sounds and works significantly better. I’ve never heard the L&P W4, but the RU7 is 35% cheaper and includes a case, so more like 40% cheaper – I kind of doubt that the L&P W4 sounds 40% better (if someone wants to send me one to compare, I’ll update this section). The elephant in the room here is really the $60 Truthear SHIO (https://amzn.to/3Pd1tDj) – easily the best budget dongle out there. The SHIO doesn’t have the build quality or the OLED screen or fancy modes, etc. of the RU7, but it does have the 3.5mm and 4.4mm outputs and very good sound quality for a lot less $$$ - they’re even similar size.

This leaves the RU7 in sort of an interesting middle ground. If you just want a cheap, good dongle, the SHIO is the best cheap option. If you want better sound, a premium feel, an OLED screen, better volume control, and a 1-bit resistor DAC – the RU7 is the obvious choice. If you’re a massive L&P fan (or just love blue more than green), the 40% increase in price won’t deter you from just getting that dongle, even though the RU7 likely does everything just as well (or close) for less. If you want a separate device that doesn’t need your phone, there are a ton of small, portable options with good battery life. Where the RU7 really excels though is providing great sound quality at a reasonable price with good battery life that doesn’t require you to have a second unit in your pocket. It also gives you a really nice computer solution – you can hook this little guy up to your computer and use it as an output for music with far better quality than any soundcard is likely to give you – and it’s WAY cheaper than a full-size dedicated DAC/AMP (as long as your headphones don’t require a TON of power. 18/20 points here since the SHIO exists at 1/5th the price.

Side Note: I hated the Dragonfly Cobalt due to weird software issues where it tried to blow out my ears multiple times - this is better than that - and cheaper.



Conclusion:

My wife kidnapped my Truthear SHIO for her computer, so I have been looking for the next step up for a while and finally found it with the RU7. No, it’s not an N7 in dongle form, but at 15% the price of an N7 – it shouldn’t be. The leather case is a great touch and the sound quality and size likely can’t be beat in this price range. Also, the RU7 just works with everything I’ve plugged it into, and that in itself is worth the price of entry.

Wolfhawk’s Rating: 96/100

DISCLAIMER
The RU7 is a personally purchased unit.
Burn in was done for 100+ hours.




SPECIFICATIONS/INTERNALS

• Fully balanced 1-bit discrete resistor network DAC
  • 1/1000 ultra-high precision TCR25 low-temperature coefficient thin film resistors
  • Native decoding of DSD64/128/256, supports PCM up to 384 kHz
  • Different DSD output settings might sound slightly different and drain more power when a higher-resolution output format is selected
• Display: 0.96 inch OLED, 128 x 64 pixels
• Size: 66 x 24 x 12 mm
• Weight: 25 g
• Has gain options and line out functions
• Source jack: 3.5 mm and 4.4 mm
• Power output: 160 mW @ 32 ohm (3.5 mm), 400 mw @ 32 ohm (4.4 mm)
• THD+N: 0.006% (1 kHz)
• S/N Ratio: 114 dB A-weighted (3.5 mm), 112 dB A-weighted (4.4 mm)
• Dynamic range: 115 dB A-weighted
• Frequency response: 20 Hz - 42 kHz
• Channel separation: 76 dB (1 kHz) (3.5 mm), 92 dB (1 kHz) (3.5 mm)
• Output impedance: 0.5 ohm (3.5 mm), 1.0 ohm (4.4 mm)
• 100 steps 3-segment high precision resistor array volume control
• Hardware volume +/- button
• Two 6-layer PCB, digital and analog circuits on separate boards
• Compatible with Android, iOS, macOS, Windows 7/8/8,1/10, and DAPs with USB Audio output
• Tested at $289.99 USD

At face value, the RU7 does not have class-leading measurements that will make measurebators salivate; however, the RU7 operates via a discrete 1-bit architecture instead of the dime-a-dozen delta sigma dongles. Thus, the specs here are not a true apple to oranges comparison due to the different technologies employed. Indeed, the RU7 sounds different from these "sterile" delta sigma sets. Additionally, some measurements are just a plain overkill, and may not be audible to the human ear; in fact, some devices that don't measure well actually sound superb (the RU7 is a case in point, as we will read below!)

The following data in the spoiler tab below will delve into the finer minutiae of the 1-bit architecture and the internals of the RU7. If you ain't a fan of technical jargon, feel free to skip to the rest of the review.



ACCESSORIES

These are included:
- RU7 Dongle DAC/amp
- USB-C to USB-C cable
- USB-A to USB-C adapter
- Leatherette case
- 2 x circular metal plates with adhesive tape pads




Other than the absence of a lightning adapter for our Apple friends, the other accessories are quite serviceable. Unlike some other dongles that do not come with a detachable cable (cough cough looking at you Moondrop Dawn), one can easily pair aftermarket cables with the RU7 should you wish to do so.

The green leatherette protective case is quite elegant yet functional, it fits the RU7 dongle snuggly and allows one to press the buttons easily. The case is actually magnetic, and one can stick metal objects such as the above USB-A adapter to the case on-the-go, which is a really cool feature!


DESIGN

Fashioned from CNC aluminum, the entire fuselage of the RU7 is seamless. Weighing in at 25 g and measuring 66 x 24 x 12 mm, this dongle is light and small in profile. It is smooth with no overtly sharp edges.




A gorgeous 0.96 inch OLED screen is found on the front, which boasts 128 x 64 pixels.

One side of the chassis has the volume buttons and a mode button. The volume is divided into 100 steps, and these are finely tuned, permitting users to control the volume accurately.




Holding down the mode button brings us to the settings menu, where one can scroll through gain options, DSD sampling rate, line out and the backlight timer.




On one end, we have the USB-C ports, and the opposite end has the 3.5 mm and 4.4 mm ports. All the ports are reinforced with gold-plating, which is an excellent touch.






The RU7 is a plug-and-play device, and it is compatible with Android, iOS, macOS, Windows 7/8/8,1/10, and DAPs with USB Audio output. I am not an Apple user, but the RU7 was easily recognized on various Android smartphones and PCs/laptops, in addition to my DAPs from Shanling and Hiby.

This dongle natively decodes DSD64/128/256, and supports PCM up to 384 kHz. The RU7 does not support MQA, but this may be seen as a boon to some, as MQA is in its death-throes (https://www.whathifi.com/news/mqa-is-going-into-administration), and MQA is a controversial format for a solution to a problem that does not exist (for some).


SOUND

The RU7 is tuned warm neutral, it is extremely musical yet retaining wonderful technical chops. Think of something with a whiff of an analogue signature, yet holding its own in imaging, soundstage and layering. Essentially, the RU7 is a smooth dongle with minimal harshness even with shouty transducers or "banshee" tracks.

Soundstage (depth, height and width) is expansive and dare-I-say, "holographic". Instrument separation is a standout. Music is spaciously layered on a dark background, with instruments easily pinpointed in their own space. Notes edges are rounded and not piercing. Note weight is hefty with organic timbre for acoustic instruments and vocals. The RU7 is not the most analytical or micro-detail focused dongle, but it also does not lack in these areas. "Euphonic" is a good descriptor of the RU7's house sound.

As the RU7 is a warm dongle, it may not synergize the best with overly warm gear, as warm + warm may give a veiled signature, though perhaps some that like a tube-like or vinyl sound may actually desire this. Nevertheless, slightly warm gear still sounds natural with the RU7, and the RU7 does extremely well with transducers that are thin in note weight or are bright. Hell, even neutral gear is a splendid pairing with the RU7! However, if you are a purist who wants a dead neutral dongle that is incredibly analytical, please look elsewhere, as that is not the RU7's signature.

The RU7 sounds better on the 4.4 mm port, with the 3.5 mm port giving less dynamics and sporting less power. This is not unexpected considering the published specs.

The RU7 has high and low gain options, and the RU7 is one of the more powerful dongles, pushing out 400 mW @ 32 ohms on the 4.4 mm jack, which some DAPs can't even provide. This dongle can drive most gear out there, perhaps other than planar headphone behemoths or extreme outliers.

These are my usual crucibles when trying out a new source:
- Final Audio E5000 (low sensitivity at 93dB/mW)
- Sennheiser HD650 (high impedance at 300ohm)
- Yinman 600 ohm (600ohm impedance and 87db/mW sensitivity!)

If the Final E5000 is not powered well, it sounds bloated and muddy in the bass, with one-noted boomy basslines heard. Thankfully, the RU7 powers the E5000 well on 4.4mm (high gain), even with complex bass tracks.


Test passed with the Final E5000.

The HD650 can sound boring and undynamic if not juiced well. The RU7 passes this test too on 4.4mm (high gain). While writing this review, I was stuck listening to the HD650-RU7 pairing for a few hours. By the time I realized it, dang one afternoon had passed. Vocals are quite magical with this setup!


Test also passed with the Senheisser HD650.

The final boss, the Yinman 600 ohm earbuds, has very low sensitivity with a high 600 ohm impedance. The bass can be very nebulous and fuzzy when it is not juiced well, and the RU7 does a decent job powering it on 4.4mm (high gain), though perhaps desktop amps with larger power on tap may do a better job with regards to bass tightness and dynamics.



The Yinman 600 ohm needs a nuclear reactor to drive em!


The RU7 has 0.5 ohm and 1.0 ohm output impedance respectively on the 3.5 mm and 4.4 mm ports, allowing it to be paired with fussy sensitive IEMs (based on audiophile rule of eights). Thus, the RU7 doesn't skew the frequency response of fastidious IEMs like the Campfire Andromeda, unlike some higher OI rivals.

There's no hiss with sensitive IEMs too, and no EMI heard, which was an issue on the predecessor Cayin RU6. There's occasional minute soft clicking in between tracks or when switching songs - this is the DSD conversion in play - though this is usually not too noticeable and is a minor issue in the big scheme of things.

The RU7 gets warm especially on high gain/4.4mm, but nothing scalding. The RU7 is quite a power hog when paired with smartphones, which is not unexpected - huge power output has to come from somewhere - so if you wanna pair it with smartphones, it is best to bring a power bank along. That's something I can live with considering the marvelous sound the RU7 provides.


COMPARISONS




The RU6, the predecessor R2R DAC dongle from Cayin, is warmer and more analogue sounding, with weaker technicalities. The RU7 is more refined and is superior in driving power especially on the 4.4 mm port. The RU6 also suffers from EMI/hiss, which isn't the case with the RU7. Both dongles consume battery quite fast when paired with smartphones, but I appreciate the RU7's larger power output for almost the same amount of battery drainage. Indeed, the RU7 is a true upgrade.

Doing A/B comparisons, the Questyle M15 (ES9281AC DAC) has a markedly more intimate soundstage, with weaker instrument separation. The M15 is a bit more neutralish with slightly better imaging/micro-detailing and more edge definition to notes. The RU7 can power more demanding gear compared to the M15, which is a bit limited in this department (though the M15 has better battery consumption). The M15 also has slight hiss with sensitive IEMs, unlike the RU7.


CONCLUSIONS

It was a big risk to import the 1-bit technology into a dongle instead of utilizing the tried-and-tested hackneyed delta sigma DACs, but this has paid off for Cayin. The RU7 is a technological marvel, and I will stick out my neck and say that this will be one of the benchmark dongles; audiophiles will be comparing the RU7 to new releases, asking, "how does XX dongle compare with the Cayin RU7?"

The RU7 is built like a tank, with a good accessory spread. It is easily pocketable with a light frame and small profile. The RU7 has gain options and single-ended and balanced ports, increasing compatibility with various transducers. It melds musicality and technicalities into a fatigue-free and pleasant soundscape. The RU7 is CRIMINALLY SMOOTH, and this SMOOTH CRIMINAL tames even harsh gear or sibilant tracks to let one chill to music.



One of the highlights of the RU7 is its cavernous soundstage, with excellent imaging and layering on a dark background. Cayin has fixed the hiss and EMI issues of the predecessor RU6, which is something much appreciated too.

Most dongles fall short when it comes to juicing demanding behemoths, and the RU7's power output is admirable; for such a pint-sized device, the RU7 can power most stuff out there other than some extreme outliers. Additionally, the low output impedance allows it to be paired with fussy low impedance/high sensitivity IEMs, so the RU7 is quite a versatile dongle that can drive sensitive IEMs all the way to 600 ohm monsters.

There are some nitpicks though. The RU7 gets warm, especially on the high gain/4.4 mm output, and the huge power it brings to the table comes with a compromise of some battery drain in phones. The RU7 is perhaps not as micro-detailed or analytical as other delta sigma competitors like the M15, but the RU7 trumps the M15 in other departments such as soundstage, power and providing a hiss free environment.

In a nutshell, this little powerhouse will let listeners enjoy smooth tunes for hours on end. In the past week after buying the RU7, I've been using it almost exclusively over my other DAPs and dongles, bringing it everywhere I go. Even at home, the RU7 even gets more eartime than my dedicated desktop amps, which is the best compliment I can give to a portable source! The RU7 is a keeper in my book!