DAC Review

Cayin RU7

Lucky Number 7.

PROS: 1-bit discrete resistor DSD DAC (the first 1-bit DSD DAC dongle), all-to-DSD upsampling of PCM input (to DSD64/128/256), natural analog tonality with a resolving sound, resistor array volume control, 3.5mm and 4.4mm PO and LO outputs, high output power (BAL), leather case.

CONS: lightning cable is optional, less features in comparison to other similar dongles, higher current draw as you go up to DSD256.

The product was provided to me free of charge for the review purpose in exchange for my honest opinion.

Manufacturer website: Cayin.  Available for sale from various authorized retailers, including Musicteck.

Intro.

Following the footsteps of RU6 release that was based on R01 dac/amp card for their modular N6ii DAP, this year Cayin decided to surprise us with another portable discrete DAC adaptation of their recently released N7 DAP.  Of course, you can’t squeeze in the functionality of a DAP into a dongle, but similar to RU6, Cayin found a way to take the main part of its discrete DAC design, miniaturize it down to a usb-stick size, and give you a chance to upgrade your smartphone or laptop with a discrete 1-bit DSD DAC/amp hi-res audio interface.

As I mentioned in my RU6 review, the deficiency and the 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 discrete DAC solution down to a DAP level.  That’s when we saw a number of DAPs with R-2R designs, featuring dozens of small resistors forming a discrete resistor ladder DAC.  After mastering that, Cayin challenged themselves with yet another discrete DAC solution, 1-bit DSD DAC design.

I think any discrete DAC solution is challenging while trying to pack it into a portable DAP, but getting it inside of a small usb DAC/amp dongle is on a whole different level.  I guess that is one way to stand out in overcrowded “dongle” market which feels saturated already.  Having a volume control, SE and BAL outputs, and a small display is no longer enough.  So, what else do you come up with besides the improvement in sound quality?  After spending the last month testing RU7, here is what I found.

Unboxing and Accessories.

RU7 unboxing experience is very similar to RU6.  This new dongle arrived in a compact black cardboard box with a glossy 3D picture of the device on its cover.  Inside, you will find RU7 sitting securely in a thick foam cutout with accessories underneath.  Included were a short, properly shielded usb-c to usb-c OTG interconnect cable and a quality usb-c to usb-a adapter to use RU7 with devices that have standard usb port.  Also, there was a detailed manual in multiple languages, including English, and a pair of hi-res stickers.

For those with iPhones who require usb-c to lightning cable, Cayin also offers one (CS-L2C model) with same shielded wires and quality connectors, but it is optional and you have to buy it separately.  I’m going to cover other lightning cables later in the review, but one that I highly recommend is by ddHiFi, MFi07S which allowed me to use R70x with RU7 switched to DSD256 in high gain connected to iPhone without a problem.  For IEMs or easier to drive full sizes headphones, Cayin’s own CS-L2C cable is more then enough.  But if you are planning to drive more demanding headphones which need to be pushed harder due to their higher impedance and lower sensitivity, MFi07S is a worthy alternative with a premium look and build quality.

In my RU6 review I recommended the optional leather case, while with RU7 the leather case is already included as part of stock accessories.  That was a nice surprise to find a green leather case with a magnetic back which should work with smartphones that support it (magnetic attachment) or with included matching leather covered small metal plate circles you stick on the back of your mobile device.  The case has a perfect fit, like a glove, has a generous opening for all the ports, and covered volume and function keys.

Page 2 – Design and under the hood.
Page 3 – Sound analysis.
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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