The Superdongles: Cayin RU7 and L&P W4

Sound comparison


While it’s difficult to describe the ‘sound’ of a dongle (or DAP) without some reference to the IEMs or headphones they’re driving, I’ve found it’s possible to zero in on certain tonal traits. It’s important to understand that these traits are often very subtle – so where I’m describing a slight lift in midbass or a hint of treble roll-off, the actual degree of difference is usually quite small. 

Depending on the IEMs or headphones used, however, these subtle differences can sometimes be amplified by the transducer’s tonality, which results in a much bigger difference than it would with other, less sensitive or tonally different drivers. 

All that said, I hear RU7 and W4 to each have their distinct tonal personality, so to speak. 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 first thing I have to make abundantly clear is that 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.    

Continue to track notes…



Picture of Guy Lerner

Guy Lerner

An avid photographer and writer 'in real life', Guy's passion for music and technology created the perfect storm for his love of portable audio. When he's not playing with the latest and greatest head-fi gear, he prefers to spend time away from the hobby with his two (almost) grown kids and wife in the breathtaking city of Cape Town, and traveling around his native South Africa.


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