The Superdongles: Cayin RU7 and L&P W4

RU7 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. 

Continue to sound comparison…



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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