Cayin C9 Portable Headphone Amp Review

Cayin Side

We last checked out a product from Cayin when I reviewed the N3Pro around last year. Now. I’ve had the chance to check out one of their more premium items, the C9 portable amp. There are many special features included on this amp that set it apart for other portables, and it’s easily one of the more high-end models with a $1999 price point. Is it worth such a pretty penny?

Cayin contents

What You Get

  • C9 headphone amp
  • SE 3.5mm to 3.5mm short cable
  • Balanced 4.4mm to 4.4mm short cable
  • Type C charging cable
  • 4 screws
  • T6 screwdriver
  • Glass protector
  • Manual

Cayin glass


There are a few interesting facets to construction of the C9. Of course, the main chasis is made up of andonized CNC aluminum but the bottom of the amp features a glass plate. It’s not something you see often, and thanfully glass protectors are provided to defend against scratching, which you can easily do since the amp lays completley flat on every surface. Holding the amp in my hand, I was suprised to see that the C9 was roughly the size of my iphone, which compleltey sheltered the top of the amp. Although portable, the C9 still posseses some considerable weight at 550g. The most defnied features of the build are its oval shaped slits sported on the top of the amp, sporting mirrored glass revealing the tube.

The face of the C9 will show you most of what this amplifier has to offer. Starting with the top-left is a swtich for “Line” and “Pre” modes. This dual input mode will benifit those who wish to select between different sources, which also affects output volume. I mainly used the C9 on line mode with a DAP through the amp’s 3.5mm input jack located jsut below this switch. A 4.4mm input option is also available, as well as output variations of the same terminations as the inputs. Next to the input mode is another switch for high and low gain, which will mainly help depending on your perfered input method. For my testing I kept the C9 in high mode, as low mode just didn’t provide ample enough gain to suppliment my device, but this will definitley change from each source. Cayin claims 6dB of headroom for most headphones and IEMs.

To the right hand side of the device there are two more pairs of switches. The first one labeled “timbre” will operate the solid-state or vaccum tube funtions of the amplifier. This Korg nutube is bears the foundation of the C9’s main design, as this specific tube aims to offer more advantages for a portable device with its Direct Heated Triode (DHT). Then you have the choice between class A and AB, which also have an effect on sound signature and battery consumption. Finally, the last main features on the C9 are its completley removable battery, and volume knob. The dial is a little stiff but is placed nicely and feels natural to operate.

Cayin ins and outs

Sound Quality

Testing the Cayin C9, I wanted to choose a few IEMs and at least one over-ear headphone to get a good sense of what the overall sound signature was like. With the many different modes featured on the C9, sound quality is a bit more complex, so each section here will be about how each headphone/IEM responded. With the C9 I used the Focal Celestee, JH Audio Jimi Aion, and the Legend X from Empire Ears.

Focal Celestee

One of the most immediate shifts in tone for me was when I tried the C9 with the Focal Celestee. This headphone had the clearest chance in response when toggling between the amps many features. I believe the Celestee to have a natural warmth to its sound signature, and when in class-A mode, the headphones feel closest to its natural timbre, along with a significant amount of improvements. The mid-bass features a lot more clean tones, with more easily identifiable details. You still get that sense of warmth while limiting the resonance of those frequencies to be more consistently clear. There’s, even more, treble definition here, giving the Celestee a more lively timbre. High-frequency detail is given a bit more accentuation, properly defining more sound elements across its signature.

Using AB mode, more warmth is added without falling into excess. The Celestee felt more pronounced in this range, making the timbre appear with a lot more body. Switching on the tube, all of that fullness smoothes out considerably but doesn’t recess any frequency information. Instead, it made the Celestee a bit more textured in its response, with a more laid-back tonality than you get with the solid-state.


The JIMI AION with the C9 gave me a less significant change in response than I had expected. It’s a complicated piece to test on its own, with its many filters and bass boost options. I was excited to hear just how much more I could get out of the AION with the C9, but the changes weren’t as varied. Tube mode on class A brought out the most engaging tone between warmth and hard bass impact, but the midrange didn’t receive as much definition.

Mid-bass is still prominent, fulfilling the AION’s crunchy tonality perfect for hard rock and metal, but it still remains picky in its frequency response. Switching to class AB gave the midrange a bit more life in certain areas, but fail to impress with its lack of articulation. However, changing to solid-state fixed this issue a bit with its improved soundstage, offering better separation and intricate laying to most tracks.

Empire Ears Legend X

Looking to the Legend X I was interested to find if further improvements were even possible, and thankfully I stood corrected. I started in tube mode on class AB where I felt like I got the evenest level of detail across all frequencies. The warmth of the mid-bass contrasted with the sparkly treble and unrivaled vocal clarity made the C9 an excellent companion to the Legend X. This was definitely the most easily digestible sound signature for this device, and the C9 built upon it with heightened resolution and coloration.

Class A with the tube keeps this tone while exaggerating that upper midrange timbre just enough to make vocals even richer. With the solid-state option, the biggest advantage for the Legend X is its soundstage, which the C9 brings out even more. I definitely felt more width here, but class AB provided the Legend with a bit more depth, adding more height to vocals, and more rounded instrumentals that add more space to the stereo field.


With its many modes and featueres, there’s a lot to admire about the C9. Cayin has crafted a unique amplifier that contains a complex design, with its vaccum tube and class options that can help personalize the timbre of your headphones, and bring them out with a significant amount of drive. Even with its great build and sound quality, it’s hard to reccomend considering its price range. For this price you can get some of the best desktop amps in the market, and since I can’t see taking the C9 out and about, it becomes harder to justify. All in all, the C9 works great as an amplifier on its own, and I’m looking foward to see how it responds with more headphones and IEMs.

ProsĀ  Cons
  • Varriety of operations
  • Warm sound
  • Removable battery
  • Durable build
  • Balanced ins and outs
  • Price

The Cayin C9 is available at Audio46.

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Alex S. is a sound designer and voice-over artist who has worked in film, commercials, and podcasts. He loves horror movies and emo music.