Cayin C9

Cayin C9 is a flagship transportable fully balanced portable tube amp that can output up to a whopping 4.1W at 16 ohms. It'll cost you just shy of $1999.


Cayin C9 is a flagship transportable fully balanced portable tube amp that can output up to a whopping 4.1W at 16 ohms. It’ll cost you just shy of $1999.


Cayin is a manufacturer that probably I don’t have to introduce anyone. They’ve been in this market for quite a while delivering a stellar price to performance audio equipment as well as unique designs such as tube DAPs or R2R DAC modules. However, this time what we’re getting is basically a transportable powerhouse. Portable Class A battery-powered amplifier that also has tubes and it can deliver almost 3W of power at 32 ohms… Ladies and gentlemen introducing, Cayin C9.

Packaging & Build Quality

Don’t let this picture fool you. This amp isn’t THAT small.

Cayin C9 comes in a rather large box and to open it you have to slide out a smaller box from one side and open side doors from the other. Inside apart from C9 itself we also will find plenty of additional stuff, such as a nice braided USB-C cable, a screwdriver, a set of screws, and two very well-built interconnect cables. 3.5mm for single-ended, and 4.4mm for balanced.

Let’s proceed to the device itself because we have a significant amount of things to cover. Starting with the build quality, it’s just top-notch. Beautifully machined metal brick that you certainly can kill a man with. On the top, we can find the Cayin logo, top of the potentiometer and small windows where you can see your Korg Nutubes glowing green when working. At the back all you’ll find is a single USB C port as well as a battery indicator with tiny orange LEDs. The front is where all that fun stuff happens.

Here we have numerous amount of different options. Starting with Line/Pre switch. It changes the device between being able to control the volume by potentiometer or being fixed at a max volume all the time. However, Cayin was clever while implementing this. If you want to switch to Pre you have to put the switch to Pre mode and then click the button on the side. Such double step procedure in my opinion is very clever, because you don’t want to accidentally blast 3 Watts of power into your IEMs. They will be destroyed, as well as your hearing. Next up we have Low and High Gain switch which is pretty self-explanatory. On the right side though we are getting Timbre and Class switches. Timbre changes what source we are listening at the moment. Solid State or Tube. They do have their own pros and cons and none of them work well in every single case scenario. The class switch is pretty simple. It changes between Class A and Class AB amplification. If you do care about power then you should stay with A. If you’d like to preserve slightly more battery, AB is the way to go.

Look at these connectors. And they come with an amp!

Last but not least all inputs and outputs. Cayin C9 has 3.5mm single-ended and 4.4mm input on the left side and output on the right side. We also do have a small power button with tiny white LED that indicates if the amp is ready to listen to. Last is going to be that potentiometer. It works smoothly and even. It does have a moderate amount of friction so it’s not that easy to accidentally bump it which is a huge plus.

I also have to mention the battery. Inside we have 4x Sony VTC6 18650 batteries that will give you in total 3000 mAh and can work up to 15 hours while using Class AB Solid State and Single Ended. The most power hungry-setting which is Class A Vacuum Tube Balanced mode will decrease playtime to about 6 hours. It also takes about 6 hours to charge the C9 with your standard charger. However, if you have a Quick Charge 3.0 charger then the charging time will be decreased to about 3 hours.

Oh, do you still remember about that screwdriver and set of screws? Well, it turns out that those batteries are swappable. If they’ll start to give up you can simply open your C9 and swap them for something else. This is a great feature that’ll make this device last literally for years, maybe even decades. Cayin, you’re getting a huge thumbs up for that.

Trip companion.


The Cayin C9 packs a lot of very unique tech. Let’s start with the star of the show, the so-called Timbre circuits. For Solid State, we have 4 Toshiba 2SK209 JFET’s and for Tube – 2 Korg Nutube 6P1’s.

THD+N measures at around 0.003% on SS and 0.03% on Tube. In terms of Dynamic Range, we’re getting 123 dB on SS and 114 dB on Tube. And last which is Signal To Noise Ratio:
125 dB on Solid State and 114 dB in Tube mode. I have to point out that for a circuit mainly based on tubes these are some stellar measurements.

If we are talking about the amplification section already I also have to mention that this amp requires a little bit of warm-up especially if you are turning it on for the first time during the day. If you’ll start to listen to C9 right after switching it on, you’ll experience a massive channel imbalance, but don’t worry. About a minute and it will balance itself out. Also, I do not recommend carrying the C9 in a pocket or especially trying to sandwich it and then carry that in a pocket. It’s a small powerhouse that also has tubes inside. It is normal that it gets a little warm at times.

And speaking about being a powerhouse… it can deliver up to 4.100 mW of power through Balanced output at 16 ohms. For a portable amp that is… A lot.


Lots of I/O and different switches on the front.

There’s one thing that I need to clarify first. The Cayin C9 offers a true stationary level of audio quality on the go, which is a great thing. With so many options, including two timbre modes and A/AB class sound, it is a true powerhouse. It’s not too easy to review such a unit, having in mind that it basically has many sound signatures. That’s why I’d be focusing more on the actual quality of the frequencies, instead of telling you about its timbre, as it really, really depends.

Starting with the bass, it’s not really surprising. It’s big, bold, powerful, and well-controlled, with great textures. The main thing worth mentioning is that it’ll be able to power almost every single pair of headphones in the world (with very few exceptions, like the Susvara by Hifiman). Thanks to that, you’ll be getting a big, saturated, and dynamic sound from top to bottom.
It offers a very high quality of the low frequencies, which are filled with details and different textures. There’s absolutely no sign of any sloppiness, lack of definition, or being overpowered.
It works exceptional with my HEDDphones (review here), providing them enough juice to really shine, without sacrificing their beautiful timbre. Class A and Solid State is the way to go here in my opinion, as it keeps that thick, fun, and saturated performance, without really changing their type of performance.
What’s the most important here is that the HEDDphone isn’t really that easy to drive, and the C9 handles them better than both Cayin N3Pro and iBasso DX220. As I said, you’re basically getting a stationary-level quality on the go. Not really portable, but transportable, and that’s fair enough for many hard-to-drive headphones on the market. You won’t be taking them for a walk in a park anyway.

One of the nicest battery indicators I’ve ever seen. And it’s orange!

The midrange is probably the most impressive thing about the C9, together with the bass. Even while using it in A/B + SS mode you’re getting that slightly warmish, highly natural sound that is basically Cayin’s trademark.
While using it with the Hifiman HE1000se, I actually prefer to switch to the tube mode. It gives them that additional warmth in the midrange, that could help with their non-forgiving sound performance.
No matter which mode you’ll use though, you’re always getting a highly resolving, textured, and rich midrange performance, that’ll suit basically anything that you’ll plug into it.
The star of the show is the vocals here, as the C9 really grasps you by its superbly natural voice timbre. It’s not a device that’ll dictate the way of recreating the sound to your headphones, as all it does is making sure that you’re getting a properly tuned and superbly-layered midrange performance. Because of that, you still need to rely on your headphone’s type of sound, as it won’t really change much while using the C9. Don’t treat it as some magical tube amp that’ll make your dry-sounding pair of headphones into a lush and warm one, as it’s not the case here. It’s not a 300B tube AMP at the end of the day, and its goal is quite different – to give you vast flexibility when it comes to the pairing, and giving you the possibility to use your power-hungry headphones on the go.

This thing is kinda a weapon.

The treble is very clean, coherent, and shiny sounding, and depending on the choice of timbre and class switch, you’ll be getting different results. Switching to the tube output, you’re getting a more delicate, smooth, and more forgiving type of experience with high frequencies, ideal to some harsh sounding pair of headphones. You can also use it with poorly mastered music, as it tends to hide some slight details that you don’t really want to hear.
If you want a more romantic and lush sound performance though, Class A and Tube is the way to go here. It gives the upper mid/lower treble a slight creaminess and warmth, that’ll suit some pairings perfectly.
Have in mind though, that the C9 is never a slow-sounding or overly warm type of amplifier. The changes you’re getting with all those options are noticeable, but it’s not a night and day difference. Thanks to that, every single switch setup gives you a saturated, detailed and crisp treble performance, which you can simply tune to your liking or current mood.
One thing that sounds exceptionally great on the C9 is an acoustic guitar. No matter which sound preset you’ll choose, it’s able to give you that insightful, shiny and physical treble response on the strings, that is pretty necessary for the acoustic guitar to sound the most natural. The whole album “Acoustic Live” by Nils Lofgren is a perfect example here, as it sounds natural and aggressive in the upper frequencies, no matter what headphones you’ll use. It’s well controlled and highly-textured though, and you don’t have to worry about any harshness or unpleasant spikes.


Overall, while the C9 has many options when it comes to the sound reproduction, they all share a refined, rich, and natural tone that’ll suit the vast majority of headphones on the market. The flexibility lets you tune the sound a little bit, which is a great thing when you’re in the mood for a specific type of playstyle, while only having one pair of headphones at your disposal. That’s why it’s the perfect companion for any trip, as it’s a 4-in-1 type of experience, giving you the choice that is often lacking in its competitors.


Hifiman HE1000se

Even though the 1000se isn’t a demanding pair of headphones when it comes to the power, it sounds so transparent and detailed, that you don’t really want to plug it into the first amplifier you’ll see and call it a day. The C9 is a brilliant choice with the 1000se though, as it easily outputs a very high-quality signal, and all the sound presets are there to tune it to your liking or to the music you’re currently listening to.

While the A/B / Tube setup made the 1000se more forgiving and lush sounding, it is a great choice for some older recordings or some late-night, chill listening sessions. Fair, you’re losing a bit of that crispiness and detail, but remember that the 1000se is a very unforgiving and neutral-sounding pair of headphones, that often doesn’t sound that great with poorly mastered records. With the options to tune the sound on the go, you’ll be able to comfortably use the 1000se as your only pair of headphones, and you won’t have to worry about the poorly mastered stuff as much.

On the other side, if you’re in the mood for a very detailed sound, or you’re simply listening to some really well-recorded albums, you can easily switch to the AB/SS setup and enjoy every single detail and spark in the music.

Keep in mind that it’ll never sound dry or harsh, as the C9 is a natural and rich-sounding amplifier no matter the type of sound you’ll choose. That makes it a fantastic companion for the 1000se, as it’s able to unleash their full potential, while giving you a choice to slightly adjust the tune.


The HEDDphone is more demanding when it comes to the power than the Hifiman HE1000se. While you can plug the latter into any modern DAP and get a really good result, the HEDDphone really improves when it’s used with a powerful amplifier.

I’m not gonna lie, taking such heavy-duty equipment on a trip is nowhere close to what I’ll ever do, but I know there are some hardcore audiophiles that want to have an ultimate experience everywhere, and they don’t really like IEMs. For all of those people, the C9 could be a life-changer. It definitely has enough juice to run the HEDD in a great fashion, giving you a very juicy, natural, and extremely fun sound performance.

The setup I actually like the most is Tube/AB with this specific pairing. It gives as that slight tube-ish timbre with superb layering and detail retrieval of the AB class. That setup sounds refined and technical at the same time, providing you with gorgeous vocals and an outstanding soundstage wherever you are. The amount of textures and dynamics you’re getting with this setup is spectacular, and it’s definitely one of the best pairings with the HEDDphone that I’ve heard.



The Cayin C9 is a very flexible and functional powerhouse. It has enough power to run most headphones on the market, and it has this classic Cayin sound, which is natural, rich, and very dynamic. It’s big and heavy, making it a more “transportable” device, but if you’re a regular hotel visitor, it could actually be the best audio companion in your arsenal. Also, thanks to having four different sound outputs to choose from, you’ve got plenty of choices when it comes to the music and headphones you’ll be using. Brilliant device.

Absolutely recommended.


The Cayin C9 reviewed above is a loan unit and it has been returned to the sender.
Thanks cayin for sending us this device. all of the above is my honest and unbiased opinion.


Gear used during this review for the sake of comparison and as an accompanying equipment:

  • Headphones – Beyerdynamic DT770 Pro, DT1990 Pro, Campfire Audio Solaris 2020 LE, Audeze LCD-3, Hifiman HE1000se, HEDDphone
  • Sources – Sony ZX300, SMSL M100 Mk II, Schiit Modi 3+, SMSL SU-9, Cayin N3Pro