Cayin RU6 R2R Dongle Review (and Measurements: shit happens)

Discussion in 'IEMs and Portable Gear' started by purr1n, Sep 4, 2022.

  1. purr1n

    purr1n Burned out

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    When members of SBAF mentioned the RU6, it did pique my interest. Wow, a portable R2R DAC dongle. Knowing the complexities of R2R design, particularly those that use discrete resistors, and the need to develop suitable oversampling filters (this isn't the 90s anymore where chips were available to do this, and even back then, they took up significant space), I had my doubts.

    PXL_20220904_171111701.jpg

    Those doubts were not unfounded: the RU6 sounds like shit. Take a worn-out 12AX7 and have it try to push something it shouldn't. This is the sound of the RU6. I would describe the sound as kind of a weaksauce, dirty, even strident at times. NOS mode sounds better than OS. This I presume is properly because the oversampling algorithm is garbage. I guess at times the R2R NOS sounds shines through in the form of syrupy lows, rolled highs. In this respect, I feel the RU6 will have its adherents. The RU6's sound is unique and different enough that there will be people who will like how it sounds.

    However, for me, I'd easily take a iFi GO Blu over Bluetooth than the RU6 over USB. I get what the RU6 is trying to do, but the sound isn't even remotely similar to a Sonnet Pasithea or Abbas Special. While the latter two desktop DACs are in the different price range, the law of diminishing returns suggested that a miniaturized version should be 70% as good no? The RU6 isn't even remotely close because its sound is so utterly incompetent. Heck, the Wolfson (Cirrus) based iFi GO Blu sounds closer to these desktop DACs with respect to lushness than the RU6.

    Note: my use case was using the RU6 as an AIO into easily powered cans: Grados and ETA Minis from the SE output.

    P.S. I grabbed this unit from someone who was "curious" about the RU-6.
     
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    Last edited: Sep 4, 2022
  2. k4rstar

    k4rstar Britney fan club president

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    I must say this is the worst DAC I have ever heard and I have heard a lot of DACs. it is slightly disturbing to me that people like it, because what it does is kill both the recording and musical aesthetic. clarity: gone. detail: gone. intonation: gone. all that's left is a poopy chi-fi diaper sound which is great if you want Rammstein to sound like Rihanna (I suspect this is the secret wish of most audiophiles).
     
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  3. purr1n

    purr1n Burned out

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    I can't disagree with this statement. It's been a long long time since I've heard anything so bad. I think even the infamous Audio-GD Singularity was worse. In that case, AGD had a target, but just missed it really badly. As for the RU6, I have no idea WTF this is supposed to be. Did anyone at Cayin even decide to listen to it? Or did they just push it through because it was "R2R NOS". While I don't always love NOS, I get what it's trying to do. The RU6 should have been left in the prototype stage. What's wrong with audio designers today? Sometimes certain things do not deserve to make it into production.

    I'd have to go back at least ten years to remember anything that sounded so bad.
     
  4. purr1n

    purr1n Burned out

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    Cayin RU6
    1kHz into 100k-ohms (simulated as a DAC input into an amp with 100k-ohm input impedance)
    upload_2022-9-4_12-52-11.png

    Cayin RU6
    SINAD (90kHz bandwidth)
    upload_2022-9-4_12-50-23.png

    Cayin RU6
    1kHz waveform from 24-bit input (90kHz bandwidth - since no anti-aliasing and jaggies)
    upload_2022-9-4_12-53-5.png
    Note: strange behavior - one channel slightly lags behind the other.
     
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  5. Lyander

    Lyander Official SBAF Equitable Empathizer

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    This reminds me I've been meaning to make a thread on an amplifier that was FotM around that time period. Would be fun to compare to modern budget offerings, but perhaps a waste of server space? :D

    Less derailment: how does it fare with single DD IEMs or multi armature makes vis a vis the Go Blu/Bar/I swear iFi has way too many SKUs that it's confusing?
     
  6. purr1n

    purr1n Burned out

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    You guys remember back in the day when I did the triangle wave measurements with a limited number of bits. The reason for this was to look at the accuracy of the R2R ladder. This is a -42db signal, in other words, a crawl for the 9 least-significantly bits at 220.5Hz.

    Cayin RU6
    Triangle Wave 220.5Hz, 9LSB crawl up and down
    upload_2022-9-4_13-10-54.png

    Did they use 5% resistors at the local Radio Shack for the ladder? WTF?

    I have a DD somewhere, but same sonic results with the CFA Solaris. The DDs like the Drop Etys are more difficult to drive and I will report back. The problem isn't necessarily with the amp (although I will see how this performs into more difficult loads). The DAC is garbage. Garbage in, garbage out.

    The iFi Go Blu is the diminutive version that only works will with Grados, Minis, BA IEMs. I believe the Go Bar is more balls and can power full sized headphones better. There is dongle loaner out right now.
     
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    Last edited: Sep 4, 2022
  7. purr1n

    purr1n Burned out

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    Cayin RU6
    1kHz -90db into 100k-ohms
    upload_2022-9-4_13-15-6.png
    Note: more noise than signal!

    -80db
    upload_2022-9-4_13-18-32.png

    -70db
    upload_2022-9-4_13-17-29.png
     
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  8. purr1n

    purr1n Burned out

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    Cayin RU6
    1kHz 0db into 1MHz (44.1kHz sampling rate)
    100kohm load
    upload_2022-9-4_13-21-0.png

    Cayin RU6
    1kHz -100db into 1MHz (44.1kHz sampling rate)
    100kohm load
    upload_2022-9-4_13-24-55.png
     
  9. Ksaurav402

    Ksaurav402 Friend

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    I like R2R DAC for the dense vocals and mids and my biggest issue with RU6 was the mids out of it. Well it was not good. I felt there was not enough energy till 2 KHz and then I felt there was some bump in presence region making all singers sound like they are using lot of throat but not enough chest, not sure if it makes sense and as far as warm sound goes- Mojo 1 is warmer then RU6. I don’t have IEMs except FDX01 so I gave it benefit of doubt and gave it to my younger brother as a gift but looks like I killed his passion right then and there.
    Have to say it didn’t sound smooth but bright to me and I feel Cayin M3X is better choice between 2
     
  10. purr1n

    purr1n Burned out

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    And this is what really killed the RU6 for me, and why I specifically said that the likes of something like the delta-sigma based iFi Go Blu pulled off the "lush" (NOS-like) mids better than the RU6. The RU6 was just all over the place with the mids. Yes, the default or what it tried to be was the romantic, syrupy, gooey deal. But more more often than not, it sounded like this distorted weaksauce. Not to mention scratchy highs that ruined the mids. There's nothing worse than defective R2R.

    The Cayin RU6 in a nutshell, and I can say this with a straight face that SBAF is being fair.
    poop.jpg
     
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    Last edited: Sep 4, 2022
  11. zottel

    zottel Almost "Made"

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    .oO( Must. Not. Listen. Don’t let reviews ruin my experience … )

    Ok, more seriously, it disturbs me a bit that the review is that negative. I like my RU6. I didn’t use it as a dongle a lot, only on vacation now, and I must admit that I didn’t use it much during the last week as it didn’t really make me want to use it, so to say. The sound is ok to me, but I can’t say I have much experience yet in the hifi world.

    But I absolutely love it at home in NOS mode with external upsampling. Did you try that?

    Defeats the purpose of a dongle, of course, there’s no such thing as external upsampling in the Qobuz app.
     
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    Last edited: Sep 4, 2022
  12. YMO

    YMO Chewbacca's hairy brother

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    No regrets on my end. I still love my RU6. Brb, I’m on a boat.
     
  13. Gazny

    Gazny Friend

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    Any chance this is at 100%output ? I believe it has clipping issues at full output noted by Cayin.

    I don’t own one but I considered it as a desktop source but the above put me off it.
     
  14. Beefy

    Beefy Almost "Made"

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    Might be a contributing factor for the 0 dB tests. But the awful triangle waves are at -42 dB, and all the -70 to -90 dB tests are similarly nasty.
     
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  15. purr1n

    purr1n Burned out

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    The measurements in the third post above were actually at -1dbFS. Yes, I was hiding stuff, giving Cayin the benefit of the doubt. Here is how it looks like at 0dbFS:

    Cayin RU6
    1kHz into 100k-ohms
    0dbFS
    upload_2022-9-4_16-40-0.png
     
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  16. Beefy

    Beefy Almost "Made"

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    Eeeek. Not just harmonics, but distinct sidebands at seemingly ±100 Hz. Spectacularly crappy digital processing.
     
  17. Merrick

    Merrick A lidless ear

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    Guess I kinda like the sound of shit sometimes.
     
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  18. Azimuth

    Azimuth FKA rtaylor76, Friend

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    You know…when I had it first it was fine. When I got it again it was acting weird and glitchy. Unless a brand spanking new one acts the same, then I doubt know.

    I also know that it sounded WAY more harsh the second time around. I thought it was just I’m comparison to the iFi devices, but it is odd that at some point it started to sound harsh.
     
  19. limesoft

    limesoft Friend

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    I noted something was off in the highs, smooth but dirty at times. Its volume sensitive too, I only use it with sensitive IEMs otherwise when pushing the volume it just gets dirtier sounding.

    I still don't think it's absolute thrash, there definitely something very pleasing in the way it delivers mids - like gentle waves pulsing and washing over. I can't correlate the thrash measurements with this, not sure what's going on.
     
  20. penguins

    penguins Friend, formerly known as fp627

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    Wonder if something unique to the R-2R architecture isn't robust enough inside and gets damaged during what some may consider normal use or possibly via shock, etc? Regardless, if that is the case, I would still consider this a design flaw considering that a dongle is going to be "handled" regularly.
     

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