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

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

  1. Tachikoma

    Tachikoma Almost "Made"

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  2. purr1n

    purr1n Desire for betterer is endless.

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    I don't think it sounded better at lower volumes using the analog attenuation because this is how I used it with various headphones. I set the volume around 35 for Grados. I didn't use digital volume control at all.

    WIth respect to measurements, here is the -60db attenuation using the analog volume control (instead of digital) compared to using -60dbFS digital attenuation with the volume fully cranked up:

    Cayin RU6
    -60db using analog volume control
    64k FFT, 90kHz bandwidth
    SE output
    upload_2022-9-5_10-41-43.png

    Cayin RU6
    -60dbFS with volume maxxed out to 100
    64k FFT, 90kHz bandwidth
    SE output
    upload_2022-9-5_10-45-17.png

    This result is better, but limited by noise. Note that to achieve -60db, I needed to adjust the volume to 14/100, which is about 20 steps lower than what I would listen to most headphones with.

    Notes:
     
    Last edited: Sep 5, 2022
  3. purr1n

    purr1n Desire for betterer is endless.

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    Here are some linearity measurements. This seems consistent with the -70db, -80db, -90db FFTs earlier. Basically as the signal gets lower, the RU6 outputs a signal lower than it's supposed to. I do wonder if the AP is having trouble locking on to the signal from -60dbFS and up. The 1kHz signal from the RU6 isn't steady and jumps around (massive jitter). It's also possible that the resistor ladder is inaccurate. This would kind of a like "jitter" in the volume domain instead of time domain.

    Cayin RU6
    Linearity (Relative Output Measured vs Intended Output)
    x3 measurements superimposed
    Bandpass Level Sweep (1/24 octave selectivity bandpass)
    Vol set to 100
    upload_2022-9-5_11-3-51.png

    Cayin RU6
    Linearity (Relative Output Measured vs Intended Output)
    x3 measurements superimposed
    Bandpass Level Sweep (1/24 octave selectivity bandpass)
    Vol set to 40 (simulating real world use)
    upload_2022-9-5_11-12-15.png

    For comparison, this what a good linearity measurement should look like.
    [​IMG]
     
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    Last edited: Sep 6, 2022
  4. Cellist88

    Cellist88 Friend

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    Lol I guess that explains why I preferred the apple dongle.
     
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  5. Clemmaster

    Clemmaster Friend

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    What breed is that?
    I want to know exactly what type of shit I seem to like ;)
     
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  6. zach915m

    zach915m MOT: ZMF Headphones

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    I'm actually curious to open the one I have now lol as I bought one since we're a Cayin dealer out of curiosity and just haven't gotten to it yet.

    I actually really like the CS-100 D/S DAC Cayin makes. I don't know if you'll like it or not whatever whatever but if interested @purr1n I'll contact you back channel when you have more time to check random stuff out.
     
  7. purr1n

    purr1n Desire for betterer is endless.

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    This breed is well known and one that I've run into before many years ago when discrete resistor DACs were in their infancy: discrete ladders with cheap resistors. There is a reason why Soekris goes with better than 0.05% resistors in their entry level going up to 0.02% and 0.01%.

    As I've said. The sound is unique and different from every other dongle out there. This in itself will attract a lot of people to it, like a circus sideshow.

    Some possibilities:
    1. This unit is defective or the wrong parts (even more horrible tolerance resistors got fed into the SMT PCB assembly machine). It happens.
    2. I've heard lot of stuff before including discrete ladder DACs with low tolerance resistors which I never liked. I recognize this sound.
    3. The sound is unique and different from every other dongle out there. This in itself will attract a lot of people to it, like a circus sideshow.
    4. One man's shit is another man's treasure. (Hey, I like Grados).
    5. I have a larger burden of responsibility to warning people away from the next FOTM.
     
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    Last edited: Sep 6, 2022
  8. Azimuth

    Azimuth FKA rtaylor76, Friend

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    I suspect seriously a defective unit, but I do not think to manufacturing errors. I think the handling, shipping, and overall abuse this thing has been subjected to as a loaner for about 6 months may be a factor here.

    I agree with @penguins, if this is the case and based on use, it proves to be not a very robust unit and why you should not do stuff like discrete R2R in something like a dongle. If I had one I would use as a desktop setup or baby it if portable. As simple as a device as it is, reverse voltages happen and transistors can go out super quickly. So yeah...kind of a novelty device unfortunately. A new one might sound a bit better and not quite be AS bad as you tested, but I doubt you would like it either.

    I also think it meshes well with the 7Hz Timeless because those are a warmer sounding IEM and might smooth over some of these errors.
     
  9. rlow

    rlow A happy woofer

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  10. Gazny

    Gazny MOT: ETA Audio

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    Thanks Rlow,
    Yea it measures about the same from other people.
    might rule out the "broken" theory.
    Part of the "charm"
    Maybe the higher end module is better.
     
  11. purr1n

    purr1n Desire for betterer is endless.

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    This wasn't the loaner unit. It was more or less brand new unit purchased by a member, used for no more than a day, and is now sitting on my desk. Now we do have the loaner, which I am sure will make it to me eventually.

    I'll take as an AIO measurements at 0, -10, and -20dBU at various loads.
     
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  12. Clemmaster

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    Now I’m curious about how mine measures.
    I’m pretty sure it will have the same weird non-linearity because I thought I noticed the sound kinda jumping in volume, actually.
    The volume implementation was always bothering me with this thing, actually. Looking at your measurements, the whole engineering seems bothersome :poop:
     
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  13. purr1n

    purr1n Desire for betterer is endless.

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    The jumpiness could also be the L and R signals being multiplexed into a single R2R ladder. This explains the lag between the L and R signals and jitter.

    upload_2022-9-7_9-25-50.png

    I can't get a stable frequency reading. LOL, this is visible jitter - gross errors.
    upload_2022-9-7_9-31-17.png
    upload_2022-9-7_9-32-8.png
     
    Last edited: Sep 7, 2022
  14. purr1n

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    Use as a AIO driving headphones/IEMS.

    Cayin RU6
    0dbu into 300-ohms
    Adjust via volume
    DAC output set to -1dbFS (benefit of the doubt to avoid anomalous behavior at -0dFS)
    upload_2022-9-7_9-34-50.png

    Cayin RU6
    -10dbu into 300-ohms
    Adjust via volume
    DAC output set to -1dbFS (benefit of the doubt to avoid anomalous behavior at -0dFS)
    upload_2022-9-7_9-36-57.png

    Cayin RU6
    -10dbu into 32-ohms
    Adjust via volume
    DAC output set to -1dbFS (benefit of the doubt to avoid anomalous behavior at -0dFS)
    upload_2022-9-7_9-37-35.png

    Cayin RU6
    -20dbu into 32-ohms
    Adjust via volume
    DAC output set to -1dbFS (benefit of the doubt to avoid anomalous behavior at -0dFS)
    upload_2022-9-7_9-38-11.png

    Finally, I noted the channel disparity increases at lower impedance loads.
    upload_2022-9-7_9-39-41.png
     
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  15. SoupRKnowva

    SoupRKnowva Official SBAF South Korean Ambassador

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    That was my first thought when you showed that weird lag before. And it only gets better in OS mode cause the sample rate is so much higher
     
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  16. purr1n

    purr1n Desire for betterer is endless.

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    Here is OS mode. I literally have no clue what the oversampling rate is supposed to be. 10x?

    Cayin RU6
    1kHz -100db
    44.1kHz sampling rate
    90kHz bandwidth linear scale
    upload_2022-9-7_10-0-5.png

    500kHz bandwidth linear scale
    upload_2022-9-7_10-0-48.png

    1MHz bandwidth
    upload_2022-9-7_10-1-9.png
     
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    Last edited: Sep 7, 2022
  17. Biodegraded

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    Looks like the unit Archimago tested has much better channel balance (edit: in terms of distortion behavior) than this one. Could that be resistor differences, even within tolerance?

    He found the same L-R signal lag in NOS mode, which he attributed to an interchannel delay evident in the impulse response. Do you see the same in this one?

    Edit: flaky links. To get to the spot referenced in the first, find "IV. 1kHz THD+N"; in the second, "Something else I found interesting".
     
    Last edited: Sep 7, 2022
  18. purr1n

    purr1n Desire for betterer is endless.

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    There could be something wrong with this. One channel seems to struggle under load. The more difficult to load, the worse it gets.

    Cayin RU7
    OS 44.1kHz
    37Hz into 300-ohms, -10dBU output
    -1dbFS, output set by volume
    upload_2022-9-7_11-6-1.png
    upload_2022-9-7_11-6-13.png

    Cayin RU7
    OS 44.1kHz
    37Hz into 32-ohms, -10dBU output
    -1dbFS, output set by volume
    upload_2022-9-7_11-7-27.png
    upload_2022-9-7_11-7-39.png
     
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  19. purr1n

    purr1n Desire for betterer is endless.

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    Here is the lag in NOS
    1kHz square wave
    upload_2022-9-7_11-21-12.png
     
  20. purr1n

    purr1n Desire for betterer is endless.

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    Cayin RU6
    Frequency Response (NOS)
    -1dbFS, volume set to 68
    300-ohm load
    upload_2022-9-7_11-24-8.png
     

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