Cayin C9

Under the hood.

You can already get a good idea of what to expect under the hood from the Design section of the review.  Cayin been in business of audio electronics for almost 3 decades, especially with a focus on personal audio products in the last 7+ years.  C9 amplifier looks like a combination of their best design elements combined together in one package.  And speaking of the design in general, some already asked on Head-fi “why amplifier only?” and if “Cayin planning to release DAC/amp version of C9?”  The response from Cayin was clear, due to DAC and sw/fw dependency, DAC/amps get outdated faster than a pure amplifier that can stay relevant for a much longer time and be used with many different sources.  And here is what you will find under the hood of C9.

First of all, you have a dual Input mode where you either select Line Input with the incoming signal from the source being fixed and you vary the amplifier output using C9 volume wheel, a more traditional headphone amplifier operation.  Or you switch to Pre-Amp Input where C9 functions as a power amp with a fixed max gain level and you adjust its output by varying the input from the source.  Some DAPs offer LO with an adjustable output controlled by a volume wheel, thus a name of “Pre-Amp” since you are adjusting the amp volume in pre-amplifier input stage.  And because Pre-Amp output will set C9 to max gain level, as a safety precaution in addition to a switch you also have to press and hold pre-amp activator button on the side of C9.


After the initial input stage, signal gets timbre treatment depending on a selection of either Solid State (2SK209 JFETs) or Vacuum Tube (Korg NuTube 6P1).  Yes, C9 is Solid State/Tube amplifier, but that part of the circuit is responsible for “coloring” of the sound prior to the actual headphone amplifier section.  And as I already mentioned, this sound “coloring” will be applied to either SE or BAL inputs and C9 has a clever design to process audio directly through single ended or balanced path, as well as being able to switch from BAL to SE and SE to BA, considering amplifier offers both of these inputs and outputs.


The amplifier gain control is done in two stages.  Primary Gain control is between Low (0dB) and High (6dB boost) gain selectable from the front panel switch.  Secondary Gain control uses 4-channel ALPs potentiometer (volume wheel) with a pair of MUSES Series low noise, low distortion resistance ladder electronic volume (MUSES72320).  Especially when using sensitive IEMs while keeping the volume low, I never experienced L/R imbalance with C9 volume control.


And last, but not least, the fully discrete headphone amplifier section with a selectable (by a switch) Class A or Class AB dual amp operation (DAO) mode.  Many are probably going to remember that Cayin featured Class A and Class AB in their E01 card for N6ii.  With E02 there was not enough room to have fully balanced circuit and both A/AB, thus E02 only featured Class AB.  Here, C9 will give you both Class A and Class AB.


So, how does C9 amplification translate into the actual output power?  C9 is rated at 700mW (@ 32ohm) from 3.5mm SE and 2,600mW (@ 32ohm) from 4.4mm BAL output jack.  Of course, depending on headphones, with higher impedance the rated output power will scale down accordingly since it is inversely proportional.  Considering this is a portable battery-operated amplifier, the power output parameters are quite impressive.  And speaking of battery, the rating it from 5.5hrs to 15hrs and will depend on a mode of operation.  Vacuum Tubes consume more current and will drain battery faster in comparison to Solid State.  And you should expect to drain more battery in power hungry Class A or when using Balanced connection.


Thus, you can expect to go from Balanced Tubes and Class A with 5.5hrs to Single Ended and Solid State Class AB with 15hrs of battery life.  And don’t forget, we are talking about components that generate a lot of heat, especially combination of discrete Class A and Tubes that make C9 feel quite warm.  That is a reason why Cayin paid close attention to component layout to improve the air flow, even attaching PBS (pyrolytic graphic sheets) to those parts generating more heat.  But overall, my typical C9 use was Balanced, Tubes, and Class AB where I was getting a little over 9hrs of playback time.


I have talked about Korg NuTube 6P1 (a dual channel triode vacuum tube) back in my N8 review.  Just as a recap, while NuTube operates exactly like a triode vacuum tube, the tech behind it is based on a vacuum fluorescent display technology, like LED.  These NuTube modules require less power than a traditional vacuum tube, smaller in size, have a much higher reliability with 30,000 hours of continuous life expectancy, all that while still providing a sound characteristics of vacuum tube sound.  And just like with a vacuum tube, there is a warm up period, thus when you switch to tubes there is a short “warm up” delay.  And similar to N8, to eliminated microphonics associated with these tube modules, Cayin designed a custom-built shock-absorption silicone housing and a spring-loaded suspension system.


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

19 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.


  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.


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