Performance Numbers
Power
The C9 is not short of grunt with excellent output ratings around the 16-32Ω marker which would suggest a lot of modern medium efficiency planars will have no problems being driven by the C9.
Planar headphones such as the Dan Clark Audio AEON 2 and Ether 2 at 13Ω and 16Ω respectively should pair quite well, at least in terms of voltage on its balanced output. For current performance, (which is often even more critical sub-50Ω), especially for the likes of the Abyss Headphones Diana V2 and in many ways DCA gear, you can check out our synergy testing on page 3
Another noticeable aspect of the new C9 amplification topology is a similar performance between Class A and AB in terms of grunt. Cayin’s makes no output power rating distinction between either compared to something like the E01 which also has a DOA topology.
The E01 is capable of Class A up to 105mW into 32Ω and Class AB up to 150mW into 32Ω. That is a huge difference in total output compared to the C9 but also if you wanted Class A IEMs were your only option.
Even with the excellent output power of the original tube DAP, the N8 is put in the shade by the C9 for output power with a max of 750mW (High²) so definitely, a lot of headphones will sound livelier with better dynamic range.
I would suspect at 300-600Ω you will be hitting the limits of the C9, however. The output power for 300Ω is very good for a portable solution at 320mW balanced but not desktop good so those with HD800 or beyerdynamic 600Ω desktop setups might struggle for optimal performances.
Sensitivity
It is not all about the power it seems with the C9. The SNR on the low gain is actually better on paper than the E01 which has a top-tier performance of 119dB for both balanced and unbalanced.
Now the C9 does dip below 119dB when going tube balanced but only marginally so. Considering it is a tube topology and normally these have a potentially lower rating I would say that is very impressive.
At up to 119-122dB solid-state and 117-118dB tube, that is on par with the N8 so all but the most sensitive IEM’s should yield a very quiet noise floor with the C9.
Of course, more power means a slightly inferior distortion number of 0.003% unbalanced and balanced for the C9 compared to the N8 output equivalent 0.0008% and 0.0006% THD+N rating. However, when you consider that the C9 has up to 3-4 times the power of the N8 it is perhaps unsurprising.
Line in
The C9 has two types of source analog line input. The first is what most portable amplifier users will be used to and that is a line-level input at the front of the amp for both balanced 4.4m and 3.5mm TRS inputs.
The standard line-in is a fixed voltage and we normally recommend around 2V from your source line-out unbalanced and 4V balanced to get a suitable dynamic range performance. On the line-in side, the voltage varies depending on the connection and ranges from 1.5V to 3V in high gain and up to 6V in low gain mode balanced.
PRE-Mode
PRE-mode is slightly different. This mode allows you to connect a DAC with a variable voltage pre-amp or a user-controlled volume to the Cayin C9. This allows the C9 to function as a power amplifier of sorts but that means the volume control will switch to the connected source with the variable voltage pre-amp output.
I would strongly suggest before doing that to push your source pre-amp volume and the C9 pot down to zero, (even though it is technically disabled). If you disconnect the PRE-amp source the C9 will automatically revert back to its line-in mode and the C9 volume pot will once again be active hence a volume of zero on the C9 is advised.
In PRE-amp mode, the input ratings are much higher than line-in, in some cases more than double in low-gain mode at 8.4V balanced. Pure DAC users or those that have an iDAC-6 MK2 might find the C9 as a power amp quite useful for more demanding headphones.
Furthermore, low gain and high gain can deliver the same rated power output but the low gain and high gain is 6dB different, so we need to compensate that at the input level, that’s why Cayin needs to double the input level from 4.2V to 8.4V.
Cayin C9 Sound Impressions
Summary
The C9 has not one but 4 line-in signatures, both balanced and unbalanced, as well as a PRE-amp option that is perhaps even better sounding with the right source.
Despite the myriad of potential tonal options, there is a core sound to the C9 and in a single phrase, it is best described as “natural-sounding”. That is Cayin, that is their house sound, and one which they have really gone for across all their portable gear recently.
It is a shame the N8 is not here as all I have are my aural memories and they can be quite deceptive. However, the intention seems to be quite similar to how Cayin has developed both the DOA and timbre on their previous product launches
The C9 is perhaps their more refined realization of the DOA and timbral switching system so far. It has the power and the dynamic range, but it also has the blackest background to date for sensitive gear.
And that helps, particularly on the low-end in all modes. On page 3 you will find our detailed comparison work but in summary, the C9 gives you plenty of low-end. Not a Violectric V281 wall of bass but rather excellent extension and definition that go hand in hand that marry so well with hybrid monitors and modern planars.
It plows deeper than the Hugo 2 amp stage, sounds more resolving and grandiose than the simpler Oriolus BA300S, and offers a better harmonic balance than the classic ALO Audio Continental Dual Mono.
Right now, it is the most complete sounding ‘transportable’ tube amplifier for headgear and will appeal to both IEM and headphone users alike with that natural but weighty low-end, smooth and intoxicating vocal presence, and clear but liquid treble reproduction.
Class AB (Solid-State)
True to form, or for those that have heard the E01 motherboard mated to the N6ii DAP, the Class AB mode is the punchiest mode, whether using the C9 solid-state or tube timbre. It has the deepest sub-bass response and perhaps the feistiest of the 4 options for treble presence also.
If you need a sound signature with a bit of contrast to its timbre in terms of a strong bass fundamental and a little more crispness in its upper harmonic order then Class AB will be the best option, particularly when combined with the Solid-state timbre option.
Out of all the modes, AB has the coolest midrange and treble timbre but the strongest PRaT and pairs extremely well with warm but solid or weighty drivers that do not exhibit too much top-end energy.
Monitors such as qdc’s Dmagic 3D (dual flange tips) and the Empire Ears Odin sound exciting and powerful with excellent separation, deep sub-bass resolution, and clear vocal performances. Headphones such as the Empyrean have the required bass punch and gravitas as well as enough treble sparkle to prevent them from sounding boring or too ‘midsy’.
Class A (Solid-State)
The first thing you might perceive a slight drop in intensity when switching from AB to Class A but this is more to do with the tonal shift or focus Cayin’s Class A tuning brings to the table. Class A is more relaxed sounding, with a bass response slightly more neutral in terms of quantity but still with a lift in mid-bass warmth.
That also means with most monitors and headphones you get a smoother bass to mids transition and better midrange presence in comparison to Class AB’s slightly greater bass/treble bias.
The Class A solid-state treble is also a little more liquid in tone and smoother overall compared to Class AB. Combined with the mid-bass warmth you get a very smooth and sweet midrange timbre with a heightened vocal focus.
I would pick this if you are a mids man or have a monitor that excels at vocal performances or you simply do not need the more bombastic approach of the Class AB signature. Or, alternatively use Class A if you want to tone down an already high energy signature into something a little smoother such as the Empire Ears Hero‘s unabashed V-shaped performance.
Class AB (Tube)
For those of you coming from the N3Pro, the tonal shift from Solid-state to Tube is not as marked as either of those devices. There is a difference but it is more nuanced than I was expecting.
Here, the switch from Class AB solid-state to Class AB tube softens the attack a little, particularly on the upper mids and treble. Treble presence is not quite as forceful, a little bit of a fade right at the top-end to produce a more natural relaxing tone.
The low-end retains its weight and sub-bass presence so the power is still there but the decay has a bit more length to it so it sounds a little more languid and marginally warmer. Combined with that slightly more natural and relaxed top end the resulting midrange timbre is richer, denser, and slightly fuller sounding for vocals and percussion.
This is perhaps my favorite combination of DOA and timbre for monitors and headphones that perform well for bass and vocals but can at times sound feisty for treble.
Dan Clark Audio’s AEON and the Abyss Diana V2 were two excellent pairings. Particularly the Diana V2 in high gain PRE-amp mode with the iDAC-6 MK2 desktop DAC which sounded meaty and dynamic and without any treble nasties.
The DCA AEON 2 Closed treble timbre sounded a little harsh on the solid-state compared to the more even-tempered Tube sound but still requires that depth and punch Class AB can give for me.
Class A (Tube)
This is for the purists or those who want that classic tube sound. It is dreamy, euphonic through the mids and vocals, with a sweeter and lighter timbre than the richer Class AB tube option.
The shift in FR emphasis, however, is much like moving from Class AB to Class A in solid-state. You get a more neutral bass performance in terms of quantity with more emphasis on warmth and that longer decay.
The treble change up follows a similar pattern though still quite articulate, its attack has softened the decay lengthened. You could argue a slightly polite delivery but articulate nevertheless creating a roomy feel, less intimate almost ballroom type vibe.
Class A really drops the pace and pushes back on the AB aggression in a very endearing manner, allowing mids and staging width with some height to come to the fore. Crooner and jazz vocals just pair so wonderfully well with the Class A tube midrange timbre from Frank Sinatra to Julio Iglesias and onwards all have that liquid intoxicating timbre.
This is a class and timbre option tailor-made for monitors and headphones ideal for vocal enthusiasts or those who want that natural analog tone without too much contrast or low-end emphasis.
Click on page 1 below for tech inside, design, and I/O rundown
Click on page 3 below for synergy, pairings, and PRE-amp mode impressions
Click on page 4 below for select comparisons
