Cayin C9

Portable amp with everything but the kitchen sink!

PROS: dual Solid State and Vacuum Tubes timbre, Class A and AB amplification mode, dual LINE and Pre-AMP input modes, 3.5mm SE and 4.4mm BAL for input/output, removable rechargeable 18650 batteries, included interconnect cables.

CONS: price, hissing with sensitive iems (just needs iematch).

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 Musicteck.


Some of you are probably going to find it a bit surprising that I’m reviewing an amplifier.  I had to take a walk down the memory lane, trying to remember the last time I tested portable amps, just to realize it was 6 years ago, and coincidentally one of them was Cayin C5.  Back then DAPs were not as powerful, their internal amp sections were more basic, and battery life was subpar, thus using external amp was beneficial to boost output power and to extend battery life of your portable source.  But you also had to compromise the portability of your setup.

Then, DAPs evolved, becoming more powerful and more advanced, with some of the manufacturers offering modular design solutions with interchangeable amp modules or more advance interchangeable DAC/amp cards like in N6ii.  It all comes down to having more choices and being able to use your favorite source with different sound-shaping options.  And speaking of more options, another example would be N3Pro and N8 from Cayin where you don’t even have to replace the module, just switch from Solid State to Tube.

So, what is next for Cayin after DAPs with Solid State and Tube timbre or DAC/amp cards with Class A/AB amp modes?  The announcement of A02 module for N6ii with Line Out only output was a big clue.  At first some were confused about release of LO only card without headphone output, just to realize later that A02 was a preamble to the upcoming C9 portable amplifier.  I was skeptical at first, thinking why do I need external amp, regardless of its advanced design.  But this skepticism turned into a bit of an obsession in the last few weeks.  Here is more about it.


Unboxing and Accessories.

The unboxing experience of C9 reminded me of the premium IEM packaging.  The giftbox quality packaging box had a magnetic top cover to reveal a non-removable foam insert with a secure cutout for C9 and another magnetic side door for a sliding tray with accessories.  I know, some will say, what is a big deal.  But I found it to be very convenient to access the accessories without digging through and removing layers inside of the storage box.

In addition to the main attraction, C9 with its battery module already mounted inside, other accessories include pure copper single ended (3.5mm to 3.5mm, CS-35C35) and balanced (4.4mm to 4.4mm, CS-44C44) interconnect short cables, usb type-c charging cable, a capsule with 4 spare screws for a battery module and T6 screwdriver.  Plus, you will find a user manual and rear panel glass protector.


The overall dimensions of C9 are 160x80x28mm with a weight of 550g.  It’s a rectangular box, borderline on being portable/transportable due to its weight and considering it has to be stacked with a source (if you go with a DAP).  A big part of its weight and the size is due to internal battery module and 4x included Sony VTC6 18650 batteries (3000mAh, 3.7V).  The battery module tray alone has a weight of 282g and extends 82mm in length.  Thus, half of the length and the weight of C9 is due to its 4x rechargeable 18650 premium batteries inside of a module tray.

The back of C9 has usb type-c connector for charging of batteries, and it supports anything from a standard 5V/2A charger to a higher voltage fast PD or QC3.0 chargers which cut down the charging time by almost a half from 6hrs to 3hrs.  Also, next to usb connector you have 4 battery status LEDs to indicate charging status and remaining battery capacity.  The unit is fully charged when all 4 LEDs are solid and stop blinking.  Both, usb connector and LEDs, are part of the removable charging battery tray which you can use standalone for charging.  Of course, you can buy your own battery charger, but Cayin will be offering spare charging tray for sale soon which should make it very convenient to be able to charge another set of batteries outside of C9 and then just slide in and out a new tray.


The bottom of the C9 has a glass surface with a protective film that was already applied on my review unit.  I would have loved to see included some stick-on rubber feet to make sure the amp doesn’t slide across the surface.  The top of C9 was crafted with two glass oval shaped “eye” openings to reveal a pair of Korg NuTube directly heated triode vacuum tubes when in use.  The right side doesn’t have anything, and the left side has a Pre-Amp activation button, used as a safety measure in addition to Line/Pre-Amp switch.  You will have to press and hold this button for 3sec until the blue led indicator next to it lit up, letting you know that Pre-Amp input mode is activated.

The front of the C9 is where you will find all the ports and switches placed around the volume wheel in the middle.  The volume wheel, which controls 4-channel ALPS potentiometer, is 15mm in diameter and rotates clockwise to raise the volume and counterclockwise to lower it.  The knob of the wheel is flush with the front of the C9 to prevent accidental turning, and easily accessible from the top through a generous cutout to be able to turn its diamond-cut wheel knob.  The rotation of the wheel has a fluid motion and a nice resistance, just enough so you don’t turn the wheel by accident, and still easy to operate with a thumb.

Looking closer at the front of C9, you will find at the top left corner Line (controls output with volume wheel) and Pre-Amp (output is set to fixed level and you control the input to C9 from the source) input mode switch, H/L gain switch (6dB boost), Solid Stage (quad set of Toshiba 25K209 JFETs) or Tube (Korg NuTube 6P1 vacuum tubes) timbre switch, and Class A and AB (dual amplification operation – DAO) mode switch.  In the lower left corner, you have Input ports, 3.5mm SE and 4.4mm BAL, and in the right corner you have Output ports, 3.5mm SE and 4.4mm BAL with a design allowing you to mix SE to SE, BAL to BAL, SE to BAL, and BAL to SE.  In the middle of the front under the volume wheel you will find a power button with a status LED that blinks for a few seconds when you turn C9 on when controller initializes the device, and also when you switch between Solid State and Tube timbre.

Page 2 – Under the hood.
Page 3 – Sound analysis and Comparison.
Page 4 – Pair up with IEMs and Headphones.
Page 5 – Pair up with DAPs and Conclusion.

31 thoughts on “Cayin C9

  1. Great review Alex! One thing to point out, in my experience, is that using N6ii/A02 paired with the C9 creates a pitch black background for the Odin, seemingly unlike the N8, and is an incredible combo.


    1. If you unplug input to C9 while Odin is connected, do you hear this waterfall type of background hissing? Or when you pause your source? I spoke with a few people who do hear it and others who don’t, such as yourself. So, I’m puzzled now… I can only speak based on the sample in hand, wish I can compare it to another C9. My Odin doesn’t hiss with any daps except N6ii and C9 is quiet with most of the iems, except sensitive Campfire and Odin which is kind of an anomaly. And I tried different daps with C9 and Odin, the same results, even without dap connected.


      1. Doesn’t matter, high or low gain, tube or solid state, Class a or ab. But only with Campfire iems which is expected since they hiss with everything, and Odin which is a bit of a surprise to me.


    1. Been told BX2 was updated to BX2+. BX2 has imbalance at low volume so hard to use for iems. BX2+ fixed that, but I still feel it has way too much power for iems. BX2/+ is better for demanding headphones.


      1. Thank you very much. Your opinion makes my life easier on decision making.
        Do you think EE Odin is not a good pairing with C9 even with iematch?


      2. A more important question, why do you even need such a powerful amplifier to use with a pair of IEMs that sounds great straight out of your smartphone? Perhaps my ears are too sensitive to hissing or maybe something is not 100% right with my C9 review unit since a few people mentioned their C9 is dead quiet with Odin. But I don’t see a reason why anyone would need such a powerful amp for Odin. But if you do want to use it with Odin to color the sound, iematch works great. Iematch is impedance adapter that will change Odin sound slightly, making it warmer, which is what C9 will do anyway. So, if we are talking about C9 + iematch + Odin = great combo indeed that works for my ears 😉


      3. I have tried EE Odin from my daily driver…Lotoo Paw6k. It sounds weird.
        I have tried EE Odin from N6ii E02. It sounds ok.
        Lastly, I have tried EE Odin from Chord Hugo2. It sounds good!!
        So I assume EE Odin need more power to let it sing 😛

        Will demo the pair when C9 is available in my area.

        Appreciate your comments. 🙂


    1. Of course, my personal preference, but I’m not too crazy about this pair up. These earbuds do like power, but they have a thicker warmer fuller body sound to begin with. Coloring it with tubes makes the sound even smoother which takes away some resolution. And even when I switch from tube to ss on C9, I feel the sound is still colored. This is fine with some iems/earbuds/headphones, but not with VE Sun dice/copper. In this pair up I prefer a cleaner and more transparent Romi Audio BX2.

      Liked by 1 person

  2. Hello!

    Wondering how you think the Romi compares with the C9 when paired with the Empyrean?

    Looking to getting the latter and wondering if the Romi at less than half the price is a better match regardless, given how the Empy is warmish to begin with. Would be using the DX300 as the source/DAC.

    Appreciate any thoughts you might have if possible!


    1. For Empy, BX2+ will be a more cost efficient solution. BX2+ is super clear and transparent amp. Now, regarding dx300, wait for amp12, should be soon. It will have a proper dedicated LO, will be better for use with external amp.

      Liked by 1 person

  3. Is the A02 motherboard worth buying for C9+N6II pairing, if i already have the E02 motherboard?
    It’s the A02 better sounding source than E02?


    1. I don’t have A02 thus can’t comment about the improvement of LO between A02 and E02. A02 has just a dedicated clean Line Out to maximized the sound quality when using external amplifier like C9. E02 shares Headphone Out with a Line Out, thus has some other components in the audio path. But that is how with majority of other DAPs where you select PO or LO from the same common jack. But is it worth getting A02 just for LO functionality? If you only planning to use N6ii with A02 and C9, then probably yes. But E02 makes a more practical sense. Tbh, if you want to enhance the sound of N6ii, I would invest into R01 R-2R DAC card, it is really good.


  4. I have the R01, but by this moment it’s not better than E02, maybe with a good long burn in my opinion changes.
    Thanks for your opinion, i’ll try to get an A02 to test it with my C9



  5. Did the WM1Z+C9 combo introduce any distortion? Does the double amping effect the sound quality in anyway? How did it compare to the N6ii+C9 combo? Thanks.


    1. I would recommend LO. Just make sure to get one of those 2.5mm/3.5mm to 4.4mm adapters (like EA AKA or a similar one from PWA). And use 4.4mm to 4.4mm interconnect going to C9.


      1. From your experience, what would be best. Using the EA AKA adapter or getting a 4.4mm to 2.5mm interconnect. Im planning to get an aftermarket interconnect (from Arctic cables).


      2. For A&K daps I would get either AKA or PWA adapters that use ground from 3.5mm jack. A regular adapter should work, but those special ones have a better shielding.


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