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

I still like how the RU6 sounds. I suspect part of this is synergy. I haven’t and wouldn’t try to drive full size headphones with it. It seems to me that a lot of people like the RU6 with ortho iem’s which is all I’ve ever used it for. Sounds great with my modded S12. :shrug:

Do I think it’s a good reference? No
Do I tune my iem’s with it? No
But I think it sounds good for a little dongle with ortho iems specifically.

That being said, if these technical shortcomings are true I would love to see a well designed R2R dongle. Not that I even use mine much. I prefer desktop tube amps fed by my Yggdrasil with my S12.

 

I’m currently on holiday and listening a lot using my RU6 and Roon ARC. I noticed that there is material where I really like what the RU6 does while there is other stuff where I get meh sound at best.

I think I may have found the culprit: Bit depth. The RU6 seems to produce great output for everything that is 24bit, while most 16bit input sounds like shit. Which is bad, of course, because most content is 16bit, and there’s no chance to upsample on the go.

Or maybe … in this case, Android phones that output 48/24 no matter what might be a godsend. And what about Spotify? The same song streamed via Spotify or 44.1/16 via Roon ARC actually sounds a bit better from Spotify to my ears. This made me wonder at which bit depth the decoded content from Spotify is sent to the DAC. Will that be 24bit? That would explain why it could sound better from the RU6, if it’s not just some sound processing done by Spotify.

This would also be at least a part of an explanation why I liked the RU6 so much better upsampled—that will always be 24bit, after all. And maybe people who listen to lossy streaming will have no qualms, either, because their phones produce 24bit audio?

 

Adding 0's to 16 bit material shouldn't really help anything. Upsampling the frequency can help with filtering. I personally find original bit depth more important than original sample frequency.

 

Sure. It just seems to me as if this particular DAC did strange things with 16bit material. It doesn’t help with a DAC where that works correctly, of course.

But you’re right, adding zeros is all that is required, and one would expect that this shouldn’t be a problem in the internal upsampling process. Plus, there are 16bit songs where I’m not sure if I hear any problems at all. Maybe my theory isn’t that perfect.

I’ll have to do more listening before I can actually say if this is really a lead or just a random impression.

 

Well... the nightmare triangle earlier in this thread was charted for the 9 least significant bits. For 24-bit material, you could probably wipe out the last few bits and it'd be hard to notice (A/B testing with 24-bit files where one is normal and the other has the last 8 bits replaced with random noise would be funny). So if this is doing that with 24-bit material, and maybe not all 9 of those bits are wrong, and everything -else- is mostly fine... then maybe you wouldn't notice anything.

But then if 16-bit stuff is decoded the same way, errors in the least significant bits there would way more noticeable. And I suppose there could be some engineering choices where this happens.

If it were like that, maybe stapling a bunch of zeroes to the end of the 16-bit codewords actually would help, by pushing all the fucked decoding below where anyone hears it.

 

I just got the RU6 and I enjoy it very much in my main speaker/headphone system. I would like to remind anyone who has the RU6 to read the manual and follow this advice:

"Most USB dongle DAC will rely on the volume control of your mobile phone to control the volume of the headphone output. Unfortunately, this is not a viable solution for Cayin RU6. R-2R DAC circuit is very demanding on incoming data integrity, the digital volume of mobile phones will damage sound quality badly, so the more effective solution with R-2R design is to keep the incoming bit-stream at full volume and then implement a high-quality analog volume control after the R-2R DAC circuit. For these reasons, the Music player app. supports bit-perfect USB is recommended. If we use HiBy Music App as an example, you need to turn on Exclusive HQ USB Audio Access and USB Output setting > Lock USB Audio Vol in your App setting (as illustrated below), this will safeguard the quality of USB Audio output. For applications that don't provide a similar feature, you'll need to turn the volume to 100 manually. This is inconvenient to users for sure, but fortunately, most, if not all, current mobile phones will "remember" the volume setting of the different plug-in devices. So as soon as you unplug the RU6 from your mobile phone, the volume will fall back to the setting BEFORE you plug in RU6, and when you plug in RU6 again, your phone will raise the volume to 100 automatically."

https://www.head-fi.org/threads/cayin-ru6-r-2r-usb-dongle-dac-with-head-amp.960113/

I did not follow this advice when I first got the RU6 and it sounded totally broken.

 

Time to move on to the RU7

I think the RU7 is better than the RU6. but that probably isn't a high bar for some here.

Compared to the Gryphon, I didn't hear any notable loss of technical performance, and the RU7 also sounded (maybe) slightly more engaging.

 

I got the RU7 to somewhat make up for never hearing or getting the RU6, and while I don't know how the RU6 sounds, the RU7 doesn't sound like it has any serious deficiencies to me. It's a very dense but somewhat glassy sound that seems to pick up little details in decays and timbre clearly while it nicely controls sibilance and other sharp transients to keep things enjoyable. I also say dense because the bass is very present with convincing weight, even stuff the center channel can slam and rumble, but it's not boosted or out of control, it's got great articulation and detail that makes for easy positioning and layering. I think the most impressive part is the stage and imaging, because with my Andromedas/Ara, it projects a very large, wide, and deep sound that pockets everything in a mix tightly with a center image that's as strong as the left and right, and it really gives a stage/band around your head feeling that's super entertaining and hard to take out, very much like the ZX2. The 1-bit DAC is also interesting, everything gets converted to DSD then converted to analog, and you can even choose the sample rate from DSD64, 128, or 256. I don't really hear any significant difference between the three using 16 bit 44.1 or even up to 24 bit 192khz in apple music, headstage doesn't magically get bigger/wider and doesn't seem tighten anything either. In fact I think DSD64 performs best from iphone, 128/256 seems to fatigue me easier, and it's also more prone to skipping/errors in playback, so I think there's some funky stuff going on where iphone just can't provide enough power from its choked as hell lightning port. I'm skeptical as well there's any real benefit to increasing the rate to 128/256 when the highest I listen to is 24/192, but I'm not about to try to wrap my head around the numbers on whether shit is being up or downscaled, it sounds good and I'm leaving it at that. So yeah, I'm enjoying the RU7 and can't believe the RU6 is that bad, especially when this sounds pretty decent, but I'll still just take people's word for it lol