DAC Review

Cayin RU7

Sound Analysis.

I analyzed RU7 sound with various IEMs 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”.  RU7 had about 100hrs of burn in time before I started my analysis.

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I found RU7 to have a neutral sound signature with a bit of a revealing natural analog tonality that was dependent on DSD output format selection.  It went from a smoother laidback presentation (DSD64) to a more revealing where you can hear a different level of treble sparkle and mids transparency (going from DSD128 to DSD256).  The tonality does have a natural analog flavor, but not necessarily too warm or smooth.  The treble had less sparkle than RU6, but the sound was still quite resolving and detailed.

The technical performance, regardless if you are listening from singled ended or balanced outputs, is the same and has a very wide soundstage expansion and nearly 3D holographic imaging.  This always stood out for me every time I hit the play, the width of the soundstage and the separation and the position of instruments and vocals in space.  I found that to be quite impressive considering RU7 architecture of going from balanced discrete DAC to single ended volume controller and then adding a parallel amplification for a higher rated balanced output.

DSD format selection.

This testing was done using Jewel w/FT cable and RU7 set to High Gain.  I found changing of DSD format between 64, 128, and 256 to have the effect on sound tuning, more noticeable from 64 to 128, and more subtle from 128 to 256.  Of course, everything will depend on pair up synergy with your IEMs/headphones.

  • DSD64 – has a more intimate laidback presentation of the sound with a smoother warmer tonality, and average separation and layering of the sounds.
  • DSD128 – the sound has more depth and I hear some improvement in imaging; tonality is a little more revealing, less coloring in mids, with improvement in retrieval of details and more airiness in treble.
  • DSD256 – I hear a touch more width in soundstage expansion; tonality is a bit brighter and more revealing, including crisper treble.  I also hear some improvements in layering and separation of the sounds.

I personally preferred DSD128 which showed a noticeable improvement over DSD64 in terms of retrieval of details, improvement in resolution, more depth in sound, yet still remaining natural in tonality.  DSD256 improvement was good as well, but in some pair ups it lost a bit of that natural organic flavor.  In a way, DSD format selection gives you a choice to figure out what works better with your favorite IEMs/headphones.

Also, I found the sound difference while switching between DSD64/128/256 in RU7 to be more noticeable than in N7.

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3.5mm vs 4.4mm.

Similar to RU6, with RU7 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 5-6 clicks to match output between single ended and balanced.

Source pair up.

I compared RU7 connected to Galaxy S22 smartphone vs other Android DAPs.  For consistency, in my comparison I was using HibyMusic app (with Exclusive HQ USB audio access enabled and USB Audio performance mode set), and I found the sound to be nearly identical as RU7 was processing the incoming digital PCM data and upsampling it to a specific DSD format.

USB-C interconnect cable pair up.

I often being asked a question if various usb-c to usb-c interconnect (IC) cables make a difference in sound quality of usb DAC dongles.  I tested and compared stock Cayin usb-c cable vs ddHiFi, OE Audio, and even Lotoo and L&P stock cables.  Other manufacturers stock cables didn’t make as much difference, but aftermarket cables did have some.  Plus, when dealing with iPhone, MFi07S was a lifesaver where it stopped the sound stuttering due to current limitation.

RU7 (HG, DSD128) w/Jewel (just sharing what I’m hearing):

  • stock vs OE Audio – the only difference I hear is a bit wider soundstage with an interesting effect of some of the sounds wrapping around my head.  This cable is a bit stiff.
  • stock vs ddHiFi TC07S – also hearing a bit wider soundstage with sounds wrapping around my head; and noticed a bit more rumble in the sub-bass.
  • stock vs ddHiFi TC09S – very similar changes to TC07S.  The main difference here is TC09S being stiffer in comparison to a softer TC07S which is better for a portable use.

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External AMP pair up.

As I already mentioned, RU7 added Line Out (LO) functionality, allowing a better connection to the external amplifier.  In theory, RU7 is intended mostly for a portable use on the go with a smartphone and IEMs or average headphones.  But you also have the option to use more demanding headphones by adding a powerful amp like, for example, Cayin’s own C9.  With RU6, you had to worry about double-amping, which btw wasn’t bad at all.  Here with RU7 you have a choice of selecting LO for either SE or BAL with a fixed voltage output.

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In my testing I was using Galaxy S22 with HibyMusic (USB Audio Performance mode enabled and USB Audio volume locked at max setting) and a few iems and headphones, though mostly focusing on ATH-R70x (open back, 470ohm impedance, 99dB sensitivity).  The testing was done with RU7 PO volume set at max 100 versus switching to LO, balanced output connected to C9.  Here is what I found.

RU7 PO (volume at 100) vs LO – with Line Out I found the sound to be more transparent while at volume 100 (PO output, not LO) mids sounds a bit warmer, smoother, maybe even a tad congested.  I probably wouldn’t even notice that by itself, but I can definitely hear it in A/B comparison.  Btw, while monitoring usb-c port, I noticed the current draw being the same with either LO (at fixed voltage) or PO at max volume of 100.

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Page 4 – IEMs/Headphones Pair up.
Page 5 – Comparison and Conclusion.

Pages: Page 1, Page 2, Page 3, Page 4, Page 5

21 thoughts on “Cayin RU7”

    1. In general, C9 is a very powerful amp that will color the sound. RU7 by itself has plenty of power for most of the iems and even some harder to drive headphones. Adding C9 will enhance it (more output current, even higher power, choice of solid state and dual NuTube “coloring”) which adds more body to the sound and changes pair up synergy depending on what you are trying to drive. Keep in mind, C9 will hiss with as sensitive iems. So for more sensitive or average iems to keep the sound more transparent and with deeper blacker background, perhaps stick with RU7. But at the end of the day, it is up to you and how you want to refine the sound.

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  2. Hi Twister6, Great review, thank you!

    With ddHiFi TC28i Pro and mFI07S, were you able to use the iPhone to drive the Cayin RU7 to at least Vol:50, High gain, DSD256?

    I am currently using iPhone 11 Max Pro with Cayin RU6 and ddHifi mFI09S. I get stuttering / music cutting out at Vol:55, High gain. With the TC28i Pro, I wonder if it is the phone being charged or the Cayin RU7. Thanks!

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    1. Which iems or headphones? Actually, just tried iPhone XS MAX with TC28i Pro, RU7, and Meze Empyrean headphones, RU7 DSD256, volume up to 65, high gain, no stuttering.

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      1. Thanks – I was using Fatfreq Maestro Mini on EA CODE23 on the iPhone 11 Max Pro and Cayin RU-6, vol.: 55-65 and high gain. The music would stutter or cut out when the bass kicks in. I reckon its due to the iPhone limitation. I’ll give this a try then.

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  3. Thank you for the excellent review of RU 7. Here’s what I wanted to ask you : I have sennheiser i 900 headphones and they are constantly plugging, even in DSD 64 mode after volume level 45. I have already ordered the ddHIFi adapters you mentioned, but I am not sure about the success of the future design. Are the sennheiser such a big load for the iPhone? Perhaps the purchase of a cheap android phone is necessary? I listen to the Qobuz streaming service.

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    1. I don’t have IE900 to try it, thus hard to tell. DSD64 at volume 45 shouldn’t give you a problem. Have you tried using RU7 with your laptop, just a sanity check with IE900 without iPhone current limitation problem.

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      1. Thanks for the quick response. Yes, I used on windows 11, via Ruun, no problems with either Sennheiser or Audeze LCD 2 in any modes. I also noticed that when streaming higher resolutions the plugging comes faster. Nevertheless, as a person with a long experience of listening to classic high end systems, I recognize the baby RU 7 as an excellent result. But the situation with the iPhone is extremely frustrating, and there are no reviews about it except yours.

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    2. Hi, thanks for the nice review ☺️
      I read the short comparison with the ru6 (which I own)!
      I wonder if switching to ru7 is a valid update, I read that the treble is less brilliant in 7, do you mean that it can be less “”””ringing “”””? I find it hard neither in the instruments nor in the voices with “s” and “c” (like rammstein and ghost) in ru6, although it is quite sharp and it seems to me that ru6 has the voices quite close up too! is ru 7 smoother?
      thanks (sorry for the mistakes I use google translate)

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  4. Thanks for the extensive review. I just got mine this week and am currently testing it with my various earphones and headphones. While I like what the dac can do, I want to know if during your testing, you encountered occasional short delay/pause during playback, i.e. similar pause to the one would encounter when increasing volume passing the volume segment. For each playback, I would experience 2-3 delays. Just for reference, my files are mostly flac with 24/44.1 or higher resolution and DSD64, and I’m testing the dac using my Mi9. I wonder if this phenomenon would change later on after further burn-in. Your input would be very much appreciated.

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    1. Mi9, is that a phone, Android? I assume? What payback app are you using? Does it happen with every app? Have you tried using RU7 with another source, maybe your laptop to see if it happening in there as well?

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      1. Yeah, running it from android phones (LG v50 and Xiaomi Mi9) using HiByMusic and UAPP with USB exclusive mode. There are some differences in the audio output, but the pause is there. It may have to do with the USB audio setting. I will play more with them. However, on LG V50 music player, there was no pause, but it is not outputting bit-perfect when it comes to certain files. So, I thought I’d give it more burn-in time since I didn’t do it in the beginning at all. Reading reviews here and there, it seems others have given 70+ burn-in time. On windows, currently it gives pops and clicks sounds like what you’d encounter when playing an LP back in the days (don’t know if turntable still doing that these days since I haven’t used one in aeons) truly analog sound. 😀

        Thanks again for your reply. I take it you didn’t experience the pause based on your response.

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      2. Okay, I figured out why this happened: DSD mode has to be set to DoP for this device. Though the specs say there’s support for DSD64, 128, and 256, it does not offer native dsd decoding support. Changing the DSD mode in my app to DoP solved this.

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  5. Hello, nice review there. Planning to upgrade from dap to dongle. I said upgrade because it seems like it on the ru7. But of course I’m not sure, just an assumption. I’m currently using my old dx160. And the dap is no longer performing well with so many issues, planning to go phone dongle setup. My question would be does my plan make any sense? Or dx160 will still stand superior against ru7 phone setup. Thanks! Appreciate the review and your response if ever.

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    1. Well, considering you will be using RU7 with your smartphone, this probably does qualify it as an upgrade over DX160, in both the sound and “system” performance since your smartphone will be faster and more robust running the latest apps.

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  6. Hi Twister,
    Went to most of your publications here and want to say CONGRATS. Great info with details and comprehensively presented.
    Now, regarding the RU7 – I am having the RU6 and love it, also I have the Hiby RS2 and Mojo2. Is it worth getting the RU7 or I’d better save more and got to N7 or DX320?
    The dilemma b/n N7 and DX320 is also quite big for me.
    Please, advice! I listen mainly rock & metal (Deep Purple, White Snake, WASP, OZZY, Metallica) but I am also a big fan of Pink Floyd, Santana and Moby, Robert Miles. Not too much fan of female vocals like Adele, Agillera, … I value extremely big soundstage replay and balance (fair neutrality) – I hate too much (sub)bass or too much treble, and too forward (in the face) vocals but like clear nuances and details. My favorite ‘modern’ IEMS are Z1R, MMK2, Helios.
    Thank you in advance!

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  7. Hi,Thanks for the great review. I was wondering if you know if the current iPhones that have a USB-C instead of Lightning connector still have the iPhone current limitation problem. Was that a Lightening-specific issue or is that an Apple issue in general?Thanks in advance!

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    2. I have an iPhone 15 with USB-C and haven’t run into the current limitation problem. The problem I do have is rapid battery drain. I’ve ordered a DDHiFi TC28C Pro from AliExpress to solve the problem.

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      1. Hi,
        Thanks for the reply. Glad to hear you’re not having the current limitation problem with your iPhone 15, but the rapid battery drain is definitely a bummer. Good to know the DDHiFi TC28C Pro offers a solution, but it kind of affects the portability for on-the-go use if you also have to carry around a power bank.

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      2. Hi,Thanks for your reply. Glad to hear you’re not having the current limitation problem with your iPhone 15, but the rapid battery drain is a bummer. Good to know the DDHiFI TC28C Pro is a solution, but it kind of affects the portability if you also have to carry around a power bank.

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