Sound Impressions
The following sound impressions of the Cayin C9 were completed using a mix of the PMG Audio Apx, FIR Audio’s Radon 6, Noble Audio’s Viking Ragnar, and Dan Clark Audio E3. Throughout the main source was Cayin’s N7 in lineout or PRE mode.
Summary
The C9ii is an absolute tour de force of a portable tube amplifier with far superior dynamic range and a blacker background than the original C9. It sounds bigger and bolder, with a plethora of sound-tweaking options ranging from warm and chilled to upfront and bombastic.
The combinations of amplification modes, timbre choices, and technical adjustments possible with the C9ii ensure that sensitive IEMs up to demanding headphones such as the E3 are not short of power or tonal synergy.
Only those who crave a dead neutral amplification with lightning-short decay traits and exuberant treble would be disappointed with the C9ii’s output.
The C9ii’s core tuning can best be described as sounding natural, with impressive depth, a smooth vocal delivery, and excellent dynamics. Unless driving a sensitive IEM via its PRE input (which I would not advise doing), tube ping and background hiss during playback are nonexistent.
It can push back staging to a very relaxed yet deep and tall imaging experience, it can flatten it out a touch, or it can completely immerse you from all corners or suck you right into the recording performance.
However, there are enough differences in each of the C9ii’s modes to warrant some individual commentary. It’s a tricky sound signature to pinpoint precisely in just a few sound bites or sentences, but that should be considered a strength of this amplifier rather than a weakness.
Operational Modes
The C9ii sound is at its most neutral when using Class AB combined with solid-state mode. This is a clean tone, punchy when it needs to be, and with decent depth, though with more discernable treble overtones than Class A.
It’s the type of amplification presentation that suits IEMs or headphones with an already warm sound signature, and you want to introduce a bit more contrast in the timbre or keep the lows from excessive bloom.
I found Class AB/solid state to excel with monitors such as the VE10, whereas Class A or hyper tended to exaggerate the dynamic driver’s lows, leading to excessive bloom and a lack of midrange clarity. Class AB/SS kept this solidly in check without any loss in impact or depth.
Class A/solid state is a smoother, more relaxed mode. Its tonal coloration biases more to the warmer and sweeter side, with a longer note decay.
It is not as mid-bass punchy or as tight sounding in its delivery as AB, but it can extend deeper, providing a denser, more prominent sub-bass response from my paired gear.
Hyper Mode is the most vibrant and gut-wrenching of the 3 modes, especially with hybrid IEMs with a decent dynamic driver for the lows.
Similar to my thoughts from the N6iii review, this is a hybrid of Class A and Class AB magnified in terms of dynamics, producing a more aggressive ‘bigger sound’.
At times, I found this overwhelming for monitors such as the VE10. However, if you have an IEM or headphones that can project a huge soundstage, such as the Ragnar or the Apx, its enveloping bass-heavy sound and enhanced vocal immediacy are welcome traits.
Timbre Circuits
The C9ii’s Classic tube mode is more relaxed and creamier sounding than the Modern mode. It is not as airy on the highs, and to some degree, the staging width shrinks a little for backing instruments, putting more of a spotlight on vocal imaging.
What it does have is a bit more fullness to its note delivery compared to the Modern tube mode, backed by a denser sub-bass performance, especially in Hyper Mode and Class A mode.
Class AB is a little more contrasty, with airier highs and improved staging width over Class A in Classic mode. However, both amplification stage options do not stray that far away from a chilled and forgiving tonal quality.
Hyper Mode amplifies all of the above into a more dynamic hybrid of A/AB. This was my preferred setting with the Dan Clark Audio E3.
I found the solid-state version was maybe a little too edgy with the E3, and Modern was too focused on the highs despite sounding smoother than the SS mode.
Classic with Hyper Mode did a wonderful job of softening treble overtones, injecting some welcome natural warmth into the mids, and creating an enjoyable, denser set of lows.
The C9ii’s Modern Tube timbre setting has a sweeter sound, with more headroom and staging width. It’s not as dense-sounding, providing more space for backing instruments to be heard.
I found Modern Tube with Class AB a better match for closed-backs such as the ZMF Headphones Atrium Closed, where you want firmer control on the lows, maximizing headroom to keep it as open-sounding as possible.
If you find Modern Tube slightly bass-light and want more depth to your gear’s performance without losing headroom, then Hyper Mode will do that with monitors such as the spacious-sounding PMG Audio Apx.
Anode Modes
I tend to refer to the two Anode Modes as “tube” and “even more tube’ and yes, they only work when the C9ii is in tube mode.
The basic difference is how rich and dense you want that tube sound to become and how well separated you want your mids, and that might depend on your paired gear’s stock sound signature.
Generally speaking, I found the low Anode setting a bit more balanced sounding for the likes of the E3 and the Composer from Austrian Audio, two headphones that have a clean set of highs and a decent bass response.
However, I could well understand if someone wanted to switch to the High Anode mode for both, given its warmer, denser sound and more prominent vocal imaging. High Anode’s generally fuller mids and vocal performances add some nice weight and richness to either headphone’s presentation.
Negative Feedback (NFB)
This was the only C9ii coloration option I was not too fussed about. It works in all modes, but the immediate effect is a perceived lowering of the volume and a slightly softer, gentler delivery rather than the firmer, more dynamic sound signature when turned off.
I suspect that if you feel your preferred mode is a little too in your face, then turning on NFB can introduce some calm to the presentation, lowering the potential for listening fatigue in the process.
Synergy
Noise
Since the C9ii’s pitch is its tube amplification and refined amplification, the potential for noise is a topical concern, specifically hiss, microphonics, or tube ping.
The short answer is that it is excellent and perhaps the best I have heard of a portable tube amplifier. Even its nearest competitor, the iBasso PB5 Osprey, has a small element of microphonic ping on initial jack insertion, which the C9ii does not suffer from
However, the long answer is that it depends on how sensitive your gear is and what specific power level you are providing from the C9ii since the wrong setting can invite noise.
For example, the Vision Ears VE10 is a fairly sensitive IEM, but there was zero microphonics or hiss in low or high gain settings using solid state or tube timbre options with the standard balanced line input. The channel balance was also surprisingly accurate on low volume.
However, switching to a PRE with volume control from a Cayin N7 exposed a lot of hiss and microphonic ping. That is too much power for such a sensitive monitor, so it’s no surprise that the noise floor was too high for the VE10.
For demanding headphones such as the Dan Clark Audio E3, all gain, DAO, and timbre modes in a standard lineout or PRE presented no noise or ping issues in the C9ii tube timbre modes with good channel balancing.
The lesson here is to pick the right line input setting for the gear you are using, and you should have zero noise concerns with the C9ii.
IEM Pairings
I tested 4 monitors, including the FiR Audio Rn6, PMG Audio’s Apx, Vision Ears VE10, and the Noble Audio Viking Ragnar. What I found was some incredible flexibility in finding the right setting to suit the tuning of each.
So, rather than tell you how each sounds with each setting, I felt it more appropriate to tell you what my preferred setting was.
For example, the VE10 sounded alive and agile with the C9ii’s solid-state mode in either Class A or AB. The tube timbre introduced too much bass bloom, slowing down the perceived speed and dulling the definition of the VE10.
I much preferred the pacier, tighter sound of the solid-state setting, with Class AB getting a slight nod over A to ensure the vocal presence was not too relaxed sounding.
The C9ii Hyper Mode brings a very heavy bass response, but the VE10 vocal imaging can sound too aggressive. This combination only really worked for sparse RnB and Rap genres where bass and vocal mixes are dominant.
It was the opposite for the Apx and the Viking Ragnar where the Hyper Mode excelled. Both have slightly relaxed vocal imaging with cavernous staging dimensions. The more dynamic and fuller-sounding Hyper Mode filled both soundstages beautifully.
I would keep the Ragnar in a tube mode, preferably AB with a high Anode setting to smooth out its feisty highs. The Apx was more flexible in terms of preferred timbre modes.
The Radeon 6 was the most flexible pairing. I could listen to it in either solid state of tube mode, Class A or AB. Hyper Mode will depend on your sensitivity to enhanced mids, but in some instances, its neutral tuning kept that region in check, making it a very nice choice for pop and rock.
Headphone Pairings
I tested the 300Ω ZMF Headphones Atrium Closed, the efficient Austrian Audio Composer, and the closed-back Dan Clark Audio E3.
I preferred the Composer in a Classic tube Hyper Mode with a low Anode setting. This provided the most ‘filled-in’ soundstages with the juiciest bass response and smoothest vocal and treble delivery.
Both Class A and AB sounded a bit flat for my tastes, with the solid-state mode creating an edgier set of highs, making it a little too neutral for relaxed listening. The High Anode mode sounded too rounded in note timbre through the upper-mids, with the low anode mode creating more headroom and air.
The E3 and the Atrium will respond very nicely to the PRE setting. I found that the E3 in PRE had a more granular level of control on the volume with the additional Vrms better suited to the higher impedance Atrium Closed dynamic range performance.
Both sounded excellent in Hyper mode, with improved dynamics, better soundstage fill, and a firmer, more immediate vocal delivery. However, I would pick the Classic tube mode with a low anode setting for the clean-sounding E3 and the solid-state low-anode mode for the smoother Atrium Closed.
That is my personal preference, as I am sure a lot of hardcore Atrium fans will enjoy the smoother, creamier delivery of the Class A, high anode tube setting. However, the boomier closed-back version sounds more controlled on the lows with the solid-state setting.
The E3 is all about making it as smooth, tall, and deep as possible, which is why I switched between Class A and Hyper mode, depending on my mood.
Class A is more languid-sounding, with less upper midrange edge, but I kept Anode on low to retain air and sparkle, with the high Anode mode sounding duller.
