Cayin C9, TOTL Tube/Solid-State Portable Amplifier

General Information

C9-01 .jpg

Cayin C9: TOTL Portable Headphone Amplifier

Cayin was founded in 1993 and is one of the largest audio tube amplifier development and manufacturing facilities in the world. We have developed over 400 products to date, ranging from CD players to speakers, all of which provide the same high-quality benchmark, but our amplifiers have been particularly well-received within the audio community. That's why when we venture into Personal Audio back in 2013, we started with C5, a portable headphone amplifier, because amplifier is always our purest achievement.

The N8 DAP marked our milestone in Personal Audio and laid down the foundation for a flagship portable headphone amplifier. The 2018 N8 was Cayin’s first cost-no-objective product in Personal Audio, but that does not mean we can ignore the scientific (physic and electronic engineering) constraints, so by the end of the N8 R&D, we pondered: what if we can find a way to relax the physical constraints? What if when we have more space, more battery power, more room for heat dispersion, …., we know we need to apply the law of subtraction and take away some features in order to stay focused. There were several ideas on the table: C8, C8DAC, ….etc, eventually we started off with C8 and today we delivered the C9.

As the model number has implied, C9 is the top model in Cayin product lineup. When we develop N8, we decided to use “8” because that is a lucky number to Chinese and we also visualized that there might be technology advancement to DAP down the road. For C9, we didn’t need to reserve that leeway because we know the analogue engineering inside out, it’s very mature and as far as Cayin’s concern, this is our ultimate.

The C9 will be available by 20 January 2021 and the suggested retail price is US$1999. Price and date might vary because of logistic and tax consideration. Please consult your Cayin dealer for local availability and price.


Highlights of Cayin C9 Portable Headphone Amplifier

1. Choice of Timber: select between Vacuum Tube and Solid State timber on the faceplate. This is no doubt the most attractive, most discussed, and most sought after feature of C9.
  • There are several portable tube headphone amplifier in the market, most of them are low power and with limited portability (microphonic effect from shock and vibration). C9 is a truly portable headphone amplifier, you can put it your backpack or hold it in your hand and walking around while listen to it.
  • C9 is designed around the KORG Nutube. This is a new generation vacuum tube developed by KORG in Japan. It is a Direct Heated Triode (DHT) but KORG replaced the traditional filament by LED technologies. It offers some advantaged that makes it a very good candidate for portable audio applications (flat form factor, low power drain, generated very little heat, …), but it maintain the microphonic problem of DHT vacuum tube, so the Nutube was not widely adopted in portable application.
  • Cayin N8 DAP is the first successful implementation of the Nutube in portable music player. We have developed a custom silicon housing and a spring-loaded suspension system to resolve the vibration, shock and impact, C9 has incurred the technologies from N8 (with modification). On the other hand, Cayin N8 used only one piece of Nutube so you can only listen to the Nutube with 3.5mm single-ended headphone, this is an inevitable limitation of N8 given we need to operate it as a DAP, but C9 has use a pair of Nutube so the Timber selection function is available to both single-end and balanced circuit, making C9 the first fully balanced portable tube headphone amplifier, to the best of our knowledge.
  • We didn’t overlook the important of Solid State option. We designed a discrete audio circuit around two matched pair Toshiba 2SK209 JFET as the alternative to Nutube in the Timber Circuit.

KORG Nutube.jpg



2. State-of-the-Art analogue amplification: C9 is probably the most sophisticated portable headphone amplifier for both earphones and headphones in the market. Cayin firmly believe that when the amplifier excels in control and equipped with appropriate volume management, there is no such thing as over-powered. Even IEMs will perform at a different level when we have ample power. Unfortunately, from what we observed, most, if not all, high-end headphone amplifiers are designed with full size headphone in mind, portable amplifiers are mostly DAC/Amp with emphasis on the digital audio technologies. Given the rapid development of high-end IEMs in recent years, Cayin believes there is a market for ultimate portable headphone amplifier that can bring out the best of these high-end IEMs, especially when they are equipped with demanding dynamic, planar magnetic and/or EST drivers, and yet versatile enough to cover a lot of full-size headphones in portable scenarios.
  • One of the very few fully Balanced portable headphone amplifier in the market
  • Dual Amplification Operation (DAO): allow users to switch between Pure Class A and Class AB
  • In-house developed Amplification circuit with discrete components, not IC or Op-Amp based
  • Selectable High/Low gain that is widely applicable to both input modes (LINE and PRE) and all amplification operation (Class A or Class AB), offer extra 6dB headroom when needed and enhance paring with different earphones and headphones.
  • High-precision and highly linear 130 steps volume control system that composes of a 4-channels ALPS potentiometer with a pair of MUSES72320 low noise, low distortion resistance ladder based stereo electronic volume.
  • High Power portable headphone amplifier (4,100mW to 2,600mW per channel at 16-32 Ohm loading, and same rating for both Class A or Class AB)
  • Special attention to make sure C9 can work with most, if not all, IEMs in the market satisfactory. Design a premium high power amplifier requires engineering and experience, but is attainable in general, make it enjoyable with both IEM and headphones are way more challenging.



3. Dual input mode: on top of regular LINE input mode, C9 can also operate in PRE-amp input mode (or known as pure power amplifier mode), with volume control disabled and all stages operate at full capacity.
• When operate in LINE input mode, which we presume will be the primary input mode of C9, it will receive audio signal from the line level output of DAP, DAC, or from any reliable audio source.
• The PRE-amp input mode is designed to work with variable level inputs (e.g PRE-amp or DAC with variable-level line out).
• Alternatively, if you have a DAP with high quality low distortion phone out but no line out, you can use the phone out as PRE-amp output. Switching between Line input and PRE-amp input is an unique feature, the first of its kind to the best of our knowledge.

4. Versatile input and output options: C9 supports 3.5mm single-ended and 4.4mm balanced for both input and output, the amplifier will also optimize balanced inputs to single-ended headphones, and from single-end input to balanced headphones. The following interconnects are bundled in the C9 package:
  • Single-ended Portable Interconnect CS-35C35 (3.5mm to 3.5mm)
  • Balanced Portable Interconnect CS-44C44 (4.4mm to 4.4mm with GND)



5. Replaceable battery: the removable battery module houses 4 x Sony US18650VTC6 (3000mAh 3.7V) lithium batteries. You can charge the 18650 batteries while the battery module is attached to C9 or after you detached it from the amplifier. The battery module supports standard, PD and QC3.0 battery charging through USB-C connector.
  • Users can acquire and replace the batteries conveniently to extend the battery duration when needed.
  • User can acquire extra set of battery module.
  • In case the original battery are run down after extensive used, user can replace the battery conveniently, making sure the C9 can serve a very long time without worrying the 500 charge cycle of lithium battery.
  • Changing to different make and specification of 18650 battery might introduce small changes to the sound signature, audiophile can enjoy battery rolling as an additional tweak to their system.


C9 Faceplate Temp.jpg

C9 Functional Framework.jpg

C9 Specification.jpg

FAQ and Resources
Charging and Protection Circuit
Burn in Setting
Gain Control, Volume Control and Input Sensitivity
Dual input mode: LINE input vs PRE-amp input

Latest reviews


500+ Head-Fier
Cayin C9 - TOTL IEM/Headphone Portable Tube/Solid-State (SS) Amplifier Review (1/2)
Pros: World-class Sound Performance. Variety in Sound Signatures: Tube/Solid-State, Class A/AB. Replaceable Batteries for Future Upgrade. Solid Build.
Cons: Price and size could be a concern.
This is going to be a long review so I will break it into two parts: The first for C9's functionality and general performance (this post), and the second for its specific pairing with my various gears.

I think it will also be useful that I open this review by giving my conclusion of C9. It is a truly TOTL amplifier for IEMs and headphones. It has the ability to bring any DAPs one or two levels up in their performance. This is true not just for mid-tier DAPs, but even for TOTL DAPs like Lotoo PAW Gold and AK SP2000. The improvement is comprehensive. With it, the sound opens up, the veil is lifted, and the performance of both the DAP and the IEM is brought to their full potentials.

In general, I consider the combo of a decent DAP + C9 to be at least at the level of Hugo 2, which I considered as the king in driving IEMs.

Some Background Info of Portable Amps

If you are quite familiar with portable amplifiers, please feel free to skip this section.

So what is a portable amp, and why do I need it? A portable amp is something that can be connected with your DAP (or any source component) to further enhance its performance. In a super general level, you can consider any DAP as doing two jobs simultaneous: (1) it has the DAC portion that helps to decode the music; (2) it has the Amp portion that takes the input from the DAC portion, amplifiers the input, and then delivers it as the output from the DAP.

Most modern DAPs have the line-out function which, if it works as intended, will bypass the Amp portion of the DAP and only outputs the signals from its DAC. With this function, the DAP can be connected with a dedicated amplifier to achieve a performance upgrade. C9 is such a dedicated amplifier. In principle, an additional, dedicated Amp should do a much better job in taking up the Amp job: It has an independent power supply, better components/circuit design, and potentially better functionalities.

General Introduction of C9

I want to start with a simple personal experience in my journey of DAPs. Back in the days, I got my first DAP from Lotoo: LP6K. I really like its functionality and sound signature. However, I find that it could not really drive my LCD-i4 or IER-Z1R very well. So I thought, OK, let me upgrade the DAP to get better performance out of the two IEMs. I then sold the LP6K and got the LPGT. LPGT did have better performance and I was quite happy with it for a while, but I still have the feeling that there is still room for improvement. I then continue my journal of searching, go through a couple of other DAPs, and eventually come to Hugo 2 which I am finally happy with its performance in driving virtually any IEMs I have.

Does this experience sound familiar to some of you? I think a lot of people have had similar experiences. When C9 came out, I in fact don't really need it as I am quite satisfied with Hugo 2. But I keep thinking this: If C9 were available back in the days when I wanted to upgrade LP6K, maybe all I needed was to buy a C9. No more need for DAPs exploring, and I get to keep my favorite Lotoo sound signature. So, I bought the C9, and I am happy to report that it not only does such a job, but it accomplishes it extremely well.


C9 is a tube/solid-state dual-mode portable amplifier. Besides these two modes, it has two classes as well: A and AB. Just from this, you can see that C9 gives you a lot of different sound signatures to explore. It takes both 3.5mm and 4.4mm input and outputs in both 3.5mm and 4.4mm - so again very flexible in how you want to connect your DAPs and IEMs/headphones to it.

An additional interesting point is that, unlike many portable amps that only take line-in signals, C9 can also take pre-amp signals. Its pre-amp mode is designed when your DAP does not really have a line-out function. In that case, you can simply use the regular headphone output and connect that with C9. C9 will then serve as a "power amp" that dramatically increases the power of the signals from your DAP. Unlike the regular line-in mode, where C9 takes up most of the job of delivering the sound signature of the output, in pre-mode the signature of the DAP is mostly preserved. This is ideal for DAPs like WM1Z, which has an excellent sound signature but has been known for its relatively weak output (in today's view). Then, the pre mode of C9 allows you to preserve the sound signature of the 1Z, but gives it a lot of power.

When I say C9 has a lot of power, don't worry, it works very well with sensitive IEMs. In fact, C9 is designed with such a goal in mind. In its low gain mode, C9 works well with virtually any IEMs. In its high gain mode, you get huge power that is enough to drive planars like Abyss Diana V2.


Here I am going to give an overview of C9's sound performance. Its pairing with my specific gears will be covered in the second part of the review (in a later, separate post). My source gears for this review include Cayin N6ii (E02/A02, both in line-out), Lotoo PAW Gold (line-out), and Hugo 2. My IEMs are Fir M5, UM Mest (with Iliad), and 64 U18t (with Socrates).

In its solid-state mode, I think the best term I can use to describe C9's performance is that it helps to reveal the music. With it, the sound is cleaner, the imaging and placing improve dramatically; you hear ALL the details of the music but in a nice and not "all in your face" manner. I think this is what impresses me the most. Different DAPs/sources I currently own could have different weaknesses in their sound. What C9 does (in line-in mode) is that it "reorganizes" the music and produces a well-rounded, comprehensive presentation of the music. I generally feel like the music coming out of C9 is what the music producers want it to be, and it is no longer limited by my DAPs.

In terms of general IEM pairing, it works really well with the three IEMs I own. I am happy to report that C9 does not work like Hugo 2 in giving a dominant sound signature such that different IEMs sound more or less the same (although in a good way). Instead, it helps to preserve the signature of the IEM rather well but pushes them to their full potential.

Meanwhile, I would say C9 does add some coloring to the music. I would say its signature is between LPG (which is extremely neutral IMO) and Hugo 2 (which adds color to the music and in a very pleasing way). In SS mode it gets closer to the neutral end, and with tube mode, it gets closer to the lush/coloring end. I haven't had the time to compare Class A and Class AB. I mostly just go with Class A because it is my favorite, and it sounds fantastic. I did briefly try Class AB and it sounds almost as good, but it seems a bit softer to my ears than Class A.

Detailed Pairing with DAPs and IEM/Headphone

To be continued in a follow-up review post.

Short Conclusion

In my own experience, C9 is the single biggest improvement I have brought to my system. Before getting C9 I have been listening under the assumption that TOTL DAPs should most likely have competent Amps, at least for IEMs. It was after getting C9 that I realized how much these DAPs are limited by their Amp section. I also want to quote the feedback from @KickAssChewGum which I totally agree with.

"I’m in total agreement with this. I couldn’t believe the improvement with my SP2000 plugged into the C9 and absolutely wasn’t expecting it to be anywhere near as drastic as it is. I’d go as far to say that the C9 is actually the one component that I’ve ever bought that has the most significant effect on sound (for the better). I’m massively impressed by what Cayin have achieved here. The C9 has made me a Cayin devotee for life and it’s literally the first Cayin product I’ve ever bought. I cannot recommend the C9 enough!"

To me, if you are quite happy with your current DAP, but want to upgrade your listening experience, C9 is an excellent choice. You get to keep what you enjoy with your existing DAP, such as its functionality and sound signature; meanwhile, C9 helps you to transform it into a world-class listening system. You also benefit from the great versatility of C9 for its various modes and sound signatures - You can always find one that suits your need, and you will never get bored,

Finally, I am really pleased that Cayin builds C9 with the goal that it is built to last. The VP of Cayin said that Cayin wants C9 to last for 5-10 years. In this process, the technology, especially the functionality of DAPs, will likely evolve quite dramatically. Think about what we had 3 years ago for the Andriod DAPs and the DAPs we have today like DX300, R8 that are at the same level in system functionality as flagship smartphones. So, when you are upgrading your DAPs in the future, with C9 you don't have to go from one flagship to another flagship. You can simply focus on getting the one that has the best functionality and suits your daily needs, and be confident with the fact that when paired with C9, it will always bring you a world-class music experience. C9 has really solid built, removable batteries for easy replacement and future upgrades, and TOTL sound performance. If you have the chance in the coming months, I will strongly recommend to reach out to your local dealers and request a demo unit to try it out yourself. I am sure that a lot of you will be pleasantly surprised by how the C9 can help you bring your current favorite DAPs to the next level.

Edit: For further questions and discussions, please join us in C9's discussion thread.
Last edited:
Seems like overpriced one!
Did you notice any hiss when using iems with tubes?
No I did not. Meanwhile, none of my IEMs are as sensitive as something like the CFA andromeda.


There are no comments to display.