Cayin C9, TOTL Tube/Solid-State Portable Amplifier


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.
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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.