Cayin RU6 USB DAC Headphone Amplifier

Product Information

In this post, we review the Cayin RU6 which is the first-ever 24BIT discreet R-2R implemented dongle-type portable DAC and headphone amplifier. To be honest, it is quite difficult to tell the two settings apart and it requires attentive listening and good headphones. In fact when paired with my ER4SR and Shure KSE1500 I am hearing every micro details that are available in the recordings. The R-2R DAC circuit in the RU6 is quite demanding on incoming data integrity and the digital volume control on mobile phones will inhibit the overall sound quality. RU-6 value is its naturalism of replay and presenting the flavor of R2R w/o dropping technicalities.

The RU6 from Cayin is a portable USB DAC and headphone amplifier, allowing you to connect to your devices for high-quality, audiophile-grade sound wherever you are. The RU6 answers energy spikes well with good control, and again the oversampling mode enhances separation and helps the vocal cut through the mix more clearly.

If you've heard M15, how do they compare to the Cayin RU6, especially with the Viento (or any Moondrop IEM)? While owing to the analog tonality of all R2R tech devices - this may not be the most resolving one but the Oversampling mode somehow takes care of it quite well and the resolution is just great. I find the tonality very much similar to the Chord Mojo, with a warm and intimate presentation, and overall smoothness that sounds mature and inviting. The elaborated decay sounds punchy with piano and drums, breathing in more air and bounciness while not coloring the output boomy.

Another thing to note, RU6 doesn’t have a fully balanced design since there is no room for all the components. Natural is the word to use again, not only to define the timbre but also for expressing the decay, the notes are born and then fade away with the perfect timing. While the design principle behind it has been around for a long time, the deficiency and discontinuation of various Delta Sigma DACs triggered by AKM factory fire and chip shortage during challenging pandemic times pushed some manufacturers to be more creative and to bring this discrete solution down to a portable DAP level.

I don’t have iPhone but measured current from lightning connector of ipod touch with RU6 connected, and it was drawing 130mA as well. R-2R DAC circuit is very demanding on incoming data integrity, the digital volume of mobile phones will damage sound quality badly.

The tuning is very easy to the ear but it cannot be said that the RU6 is not resolving, missing in clarity and agility or lacking in energy as to sound dull or slow. I use it exclusively with conventional home stereo systems - feeding the signal into a preamp - with a Jitterbug between the PC source and the DAC. I have found using the Ru6 with older CD flac files such as Deep Purples greatest hits brings out the old analog sound I used to get while listening from my home stereo. The appearance is quite modern and minimalist while finish and build quality are excellent with the only negative being that the glass surface is a fingerprint magnet but if you ask me, I wouldn't care a lot. However if I am going to be nitpicking, I would say that I would have preferred RU6 to exhibit just a tiny bit more of smoothness.The RU6 doesn’t kick deep or respond speedily but it is more elaborated in the upper bass with a typical retro coloring that leans musical and engaging rather than analytical or neutral. It's impressive how Fiio has considered the upgrade path for E7 DAC owners by integrating an iPod-style dock connector into the E9. vs Hidizs DH80s - the DH80s is having good musicality but favors analytics vs naturalism of RU-6; these two are really a good pair if you like musicality, power and want a good value performance.