Hi guys, recently acquired my own C9II and just wanted to leave some brief impressions of it, since I do believe it is currently the best sounding (with some nuances) "portable" amp on the market.
First of all, there are a ton of options for sound shaping available on the c9ii, so I'll cover my impressions of each individually and how it impacts the sound, then my personal preference. Won't be speaking of High Gain though, as I never had a reason, or an IEM to warrant that kind of output on.
I've been feeding the C9ii with an AK Sp3000 Copper with a custom EA 12 wire Chiron/Caliburn Interconnect with my IEM of choice for it being my CIEM Indigo connected with an EA Hades II cable.
Amp Modes:
Type A: I find type A to be very smooth and warm, the overall tonality isn't a preference of mine but it does offer a pleasant listen experience if you're a fan of the Cayin sound and type A amps in general. There is a bit less dynamics to this amp mode than the others with vocals that sit front and center, bass that extends well with lengthy decay and light amounts of bloom into the lower mid range but not intrusive at all. The highs are very smooth and lack any bite, which for me isn't preferable. I do find the stage feels to be a bit smaller with this setting than the others, but it's likely due to how the vocals are placed relative to the rest of the mix.
Type AB: My personal preference, highly dynamic, tight and fast bass with mids that are neutrally placed and treble with a defined edge. The decay is faster here than type A with no bloom and a bit colder tonality than type A.
Type - Hyper: Probably my least favorite of the three, it retains a lot of smoothness from the type A described above but gains a large quantity of bass, which for me felt boomy and kind of dramatically "overdone" sounding, other than that difference in the bass, i found this to be largely the same as type A with maybe a slight increase in staging size.
Timbre Modes:
Modern Tubes: My favorite, this offers a massive stage, incredible imaging that is pin point and holographic with amazing layering and technical strength. There is a light amount of warmth typical of nutubes but not overly warm and retains a very good treble sparkle and edge when combined with type AB amp. The mids are pushed slightly forward but never "in your face". The bass region remains well controlled and has good punch and rumble with good dynamics, only really falling short of the Solid State mode by a small margin but the staging/layering and imaging gains are well worth it. The modern tube mode also retains great air up top which a lot of nutube implementations (other than the iBasso PB5) typically fall short on.
Classic Tubes: Much like type A, this mode is very smooth and "relaxing" with notes gaining weight and size, blending seamlessly for a very cohesive sound. The overall staging/holography here I feel is quite a bit less than the Modern tubes, due to the gain in weight and note size, there is some obscuring of minor details (FWIW, I listen to a lot of metal/rock so this may be less of an issue with other genres). Similarly, Classic tubes are also less airy than the Modern implementation while also being warmer across the bass and mids and darker up top with much less treble sparkle.
Solid State: If you're familiar with the original C9, not much has changed here relative to the sound profile it is aiming for. That is, a more dynamic, bassy presentation with lightly recessed mid range and a treble with a fair bit of smoothness without losing much sparkle (personally, the best treble presentation for me is still the Modern tubes, but other owners I know with the C9ii prefer solid state). Staging and Imaging are great here as well, but not as holographic and grand as the tube modes, but that is to be expected of any tube vs SS implementation as long as it isn't botched.
Anode Modes:
Low: The biggest difference in the Anode modes comes in the mid range with only small effects to the surrounding FR. In Low anode, the mids are a little colder and thinner with slightly less forward nature, depending on your above combination, you'll either have neutrally (low anode, modern tube, type AB) or forward mid range (low anode, classic, hyper or type A). There is more space surrounding vocals with low anode mode but there is slightly worse layering when compared to High anode. As a result of the mids changing, lower treble does feel slightly more prominent and mid bass has more room to play into the lower mids but, in my testing, never muddied or obscured any vocals.
High: I keep High anode on between these two, as the increased layering and slightly thicker mid range works well with type AB amp to balance out the neutrality of it's mid range placement pushing mids slightly forward without losing detail/staging. A combination of high anode, classic tube mode and type A or hyper amp results in a VERY "real tube" sound which is smooth, warm and holographic, so those who have dismissed nutubes in the past as "not tubey enough" can look to the C9ii to fulfill your love of tubes.
Finally we have the last option available, which is negative feedback (NFB) on or off. I didn't play TOO much with this option, but the general difference here is, with NFB on, you'll have a pulled back, you're in the 5th row seating kind of sound, with a more ethereal sound but doesn't feel as "clean" (hard to describe this, it's something you have to hear to really get) vs with NFB off you have a cleaner, 1st or 2nd row presentation with a more cohesive sound and what I felt to be better imaging and layering in all of my A/B testing of the two.
My go to settings are Amp type AB, Modern tubes, High Anode and NFB off, low gain. This gives the C9ii the best technical strength with untouchable imaging accuracy, staging width, depth and height with amazing layering capabilities while being highly dynamic and detailed. The great thing about the C9ii, much like the C9 and later the n30le, is that you can mix/match and experiment to find a sound that works for you or fits the music you want at that moment, all on the fly.
, but it takes the C9ii to the next level for sure.
