Selected Comparisons
The following comparisons to the Cayin C9ii were completed using a mix of the PMG Audio Apx, Noble Audio’s Viking Ragnar, and ZMF Headphones Atrium Closed for headgear.
The primary sources included the Cayin N7 (Pre Out) and the iBasso DX320 MAX Ti balanced 4.4mm lineouts.
Cayin C9
The Cayin C9 was released in 2021, with our review published in the same year. It also won our 2021 Top Gear Award for Best Portable Amplifier.
Technical
I have covered most of the technical differences already in the review, so I will keep this part short.
The notable high-level technical changes for the C9ii over the original include the enhanced operational and timbre mode options, combined with a higher quality signal output and the quick-release battery system.
The C9 was considered a second-generation design using the spring-loaded KORG Nutube 6P1 circuit design, with the original N8 DAP being Gen1. The C9ii is being pushed as a Gen4 circuit design, and you can tell there has been some considerable progression.
That includes benchmarks such as dynamic range and SNR that are 5-9 dB higher than the older model and a battery life that has been considerably improved by around 2.5 to 3 hours on average additional runtime over the original regardless of mode.
So, whilst the PO output numbers for both old and new amplifiers are the same at 4.1W and 2.6W maximum balanced on a 16Ω and 32Ω load, the quality of that output from the C9ii is nominally better on paper and sounds subjectively superior with my tested gear.
Design
The major talking point will probably start with the size differences between these two. The C9ii is the bigger and heavier device, and with the optional semi-hardshell PU protective case, it takes on a very transportable rather than portable aesthetic.
I will say, though, that the C9ii’s new heatsink design means it runs slightly cooler than the original and even more so with the protective case on. So stacking on the top panel should not be an issue.
If you plan to use the C9ii as a transportable device, I recommend not stacking it and instead placing the source beside it. The enhanced size of the glass portals gives you a snazzier view of the tube filament green glow than the narrower versions on the C9, so it would be a shame to cover them up during use.
Despite the C9ii being the bigger of the two, its curvier side panels and softer cornering are slightly more comfortable in the hand than the edged finish of the original C9.
Transportable or portable matters less than usability for me. The quick-release battery tray, the bigger toggle switches, and the enhanced space around the C9ii’s volume dial make the newer design the more user-friendly of the two amplifiers.
That is before I show my age by praising Cayin for making the labeling on the front panel more legible to the naked eye.
Solid State Performance
This is a tricky comparison given that the C9ii has additional modes and different timbre choices. Class A, Class AB, and the Solid State performances are the safest like-for-like starting place using a balanced 4.4mm output.
Those dynamic range numbers on paper are the real deal when comparing these two subjectively in both Classes using the solid-state mode.
The C9 sounds like it is playing within itself more than the exuberant or vibrant C9ii sound. Of particular note is the Class A solid-state performance of the C9ii, which sounds slightly less relaxed than the C9 version.
I suspect this is again down to the dynamic range and amount of headroom being delivered, giving me an impression of the C9 having its ‘wings clipped’ slightly.
That translates to slightly less width, not quite as much staging depth, and a general vocal presentation that does not leap out or convey as much textural resolution.
With the C9ii, regardless of class, the solid-state performance sounds more defined, with better separation.
IEMs such as the staging king PMG Audio Apx suck that up readily with a noticeably improved channel separation and more end-to-end note play within the stereo field creating a more immersive presentation.
Tube Mode Performance
Switching to the C9ii Classic tube mode versus the singular C9 “Tube” brought a similar experience, though the dominant impression was one of improved treble extension and headroom more than anything else.
There is a nuanced tonal change in Class AB with the C9ii’s stronger treble influence sweetening the instrumental and vocal timbre and introducing additional contrast than the more rounded C9 tuning.
Combined with the improved dynamic range, the C9ii bass has slightly more snap, impact, and definition, especially using Class AB.
The Apx and the Viking Ragnar midrange performances also sounded a little richer and firmer in AB mode, though those who wish for a calmer Ragnar treble might prefer the slightly softer set of highs from the C9.
The C9ii’s Modern Tube mode is marginally more neutral tonally than the C9 singular tube mode in either Class.
It is also more immediate sounding in the mids, with a more forward vocal imaging experience and improved treble resolution, creating an airier and wider soundstage than the C9 tube mode.
Dynamics, again, are much improved right across the board in this timbre and class mode on the C9.
iBasso PB5 Osprey
The iBasso PB5 Osprey was released in late 2023/early 2024, and our review was published last year. It was also our 2024 Top Gear Best Portable Amplifier award winner.
Technical
Both use a Korg NuTube 6P1 vacuum tube voltage topology, but the PB5 is strictly tube only, whereas the C9ii DAO topology offers tube and solid-state options.
The PB5 does not have timbre modes, a PRE mode, or an option similar to NFB. Save for a high/low gain switch at the back, it’s a fixed tuning output.
Combined with VCEsat dual transistor-based current amplification and an internal 6 x 900mAh (3 x 8.4V) battery supply, the PB5 Osprey has a rated maximum output voltage of 9Vrms (4.4mm), capable of 1700 mW output power under a 32Ω load.
That is lower than the C9ii at 2.6W into the same load in any of its operational modes. iBasso has refrained from publishing any comparable dynamic range or SNR numbers to make a judgment call on distortion, but I can say microphonics is more present in the PB5 2-step suspension design compared to the C9ii on the initial operation.
The 24-step potentiometer on the PB5 delivers excellent channel balancing at low volume levels and combined with its sibling, the D16 DAC, you can get a very high granular level of control on volume.
Battery life benchmarking between the two is variable. Since the PB5 is a single-mode amplifier, it has one weighted value at 10.5 hours average playback time.
The C9ii battery life can be shorter at 8.5 hours minimum on a balanced Hyper Mode tube setting but also much longer at 13.5 hours going balanced in Class AB mode.
Why am I not quoting single-ended numbers? The PB5 is balanced designed only, meaning there is no 3.5mm output. If that is a deal breaker for you, then the C9ii is the correct choice.
Design
The stripped-down approach from iBasso means the PB5 is far smaller and lighter than the C9ii. Of the two amplifiers, the PB5 is far more portable and perhaps simpler to use.
However, aesthetically, it’s very old-school, with an edged boxy design, though the top glass panel does a decent job of showing off the similar green filament glow from its NuTubes. Both devices do have a satisfactory heatsink application on the side panel, but you can tell the C9ii machining is on another level in terms of finishing.
My major gripe with the PB5 is the labeling. It’s etched so it will stand the test of time, but it is so tiny that I need glasses and a phone torch to read the letters. There is enough space on the chassis to make the font size a little bit bigger and more legible, something which the C9ii excels in.
The PB5 also uses Rocker-type miniature switches flush to the chassis, similar to the original C9, and has slightly recessed ports on the front panel. That means the PB5 does not need the guard rails of the C9ii to protect the controls on the rear panel, saving on length and weight.
There is no 3.5mm PO, just a 3.5mm/4.4mm LO and a 4.4mm PO on the PB5. It is a strange decision from iBasso. I would have dropped the 3.5mm LO in favor of a 3.5mm PO if it was up to me, but I guess if you are pairing it with SE sources only, it has value.
Both volume dials work exceedingly well, with plenty of space to access them and a nice grippy finish that prevents slipping when turned. Arguably, the C9ii ALPS pot feels and looks more premium, though.
Performance
Since the PB5 has no switchable modes, this comparison will focus on how it compares to the various tube timbre and Class modes of the C9ii NuTube output.
The PB5 kind of follows iBasso’s generally favored neutral bass imaging, meaning it’s a bit punchier than the C9ii (in any class or timbre more), but it projects more staging width with my paired IEMs and is more upfront in the mids and lower treble.
The C9ii, in all classes and timbre modes, has a weightier, denser sub-bass presence with more warmth and smoothness through the rest of the range. The staging is a bit deeper sounding with the IEM combos I tried, including the Apx and the Ragnar.
The closest you can get to a similar presentation between these two amps is probably Modern mode combined with Class AB on the C9ii. It’s the airiest of the mode combinations and the most neutral of the timbre modes.
Once you drift away from that combo, the C9ii starts to take on ever-increasing degrees of warmth and sweetness until you get to the opposite side of the spectrum with Class A and Classic Tube mode, which sounds far richer in its coloration with a much denser albeit comparatively languid bass response.
Of course, you can up the stakes with Hyper mode and a High Anode setting, which makes the PB5 sound like it has a comparatively lean bass response. However, that can come at the expense of a little staging space and clarity when any recording’s bass energy gets a significant uplift.
Both have solid noise floors once they settle down, but on the initial start, the PB5 does have a more noticeable tube ping for the first few seconds when paired with sensitive gear.
Phatlab Chimera
The Phatlab Chimera was launched in 2020, with our review published in mid-2021. It is priced a bit cheaper than the Cayin C9ii but has a similar target audience.
Technical
The Chimera represents the other side of the portable tube amplifier market dominated by the likes of Woo Audio and Phatlab, to name but a few.
This amplifier uses a more traditional subminiature tube design rather than NuTubes with dual Jan 6418 filament-type low-power consumption pentodes used as triodes in the circuit.
That means it is more susceptible to tube microphonics or ‘ping’ when bumped or upon initial startup, though it goes away a short while after. This is an issue I have yet to experience in my testing of the C9ii.
There is some commonality, though, with both amps providing a switchable tube and solid-state amplification topology with 2 gain stages, high and low. More than that, the solid-state design inside the Chimera is also a JFET transistor design.
Though not as powerful as the C9ii’s maximum 2.6W at 32Ω balanced, the Chimera can still deliver a fairly healthy 1W on a similar load for its 4.4mm output.
Its SNR numbers are 1-2 dB lower at a maximum of 110 dB listed, though it does not distinguish which mode this weighted measurement is and on what load. If it is in optimal conditions, then it is a good 10 dB lower than the peak SNR performance from the C9ii.
It is a similar comparison for battery life with around 10 hours peak and using an older micro-USB charging system. The C9ii can drop to lower at 8.5 hours on a balanced hyper mode setting but up to 17.5 hours on Class AB single-ended. The Chimera battery is not user-replaceable either.
Design
The Chimera is a shorter, lower-profile amplifier and about half the weight of the C9ii. However, it’s just as wide as the Cayin with a similar curved heatsink-infused side panel finish.
I rate the Chimera physical engineering quite highly. It has a robust design with similar toggle switch systems and is also well-protected with a solid guard rail system at the front panel and a recessed bay at the rear.
The only quibble I have is the volume dial positioning, which is right up beside the right guard rail, meaning only one side is available for your fingers to touch a rather smooth surface.
There is far more space with the central positioning of the C9ii ALPS potentiometer, meaning it’s easier to access and get a hold of its gripper finish for granular volume adjustments.
Both have good control labeling, perhaps more so on the Chimera, whose bold lettering makes it very easy to read, even from a distance.
The toggle switches on the C9ii feel like they have better damping. They are smoother in operation with a quieter action compared to the clunkier, more resistive, and noisier Chimera switches.
The operational mode switch is at the rear of the Chimera rather than on the front, and you will find no further timbre or tone controls similar to the C9ii. It also only accepts a single-ended 3.5mm line input and has no PRE or balanced line input options.
Performance
In every mode and at every level or aspect of their performance, the C9ii is a big upgrade on the Chimera’s performance. The C9ii costs a lot more than the Chimera, but when A/B testing, I think it easily justifies the additional expense.
Before we even talk about tonal and technical differences, there is the noise floor performance gap. The Chimera is far noisier with IEMs, with background hiss in JFET mode and plenty of echoey microphonic pinging in tube mode.
It is also the kind of ping that lingers when tapping the housing, so the suspension is nowhere near as good as the C9ii NuTube’s quieter setup.
All this affects their respective backgrounds and dynamic range with sensitive gear. The C9ii has a darker, blacker background and a vastly superior level of dynamic range throughout as a result.
The Chimera’s tube mode is airy, with more midrange bloom than its JFET mode, giving it a more stretched, taller sound. However, both modes sound relatively flat and unremarkable compared to the more elaborate layering and staging depth of the C9ii.
I find the Chimera bass fairly punchy, with a bit more dryness and a shorter decay in JFET mode. The C9ii’s equivalent solid-state mode is smoother yet more natural sounding to my ear and with a better harmonic balance.
Despite the Chimera’s tube mode sounding smoother and more inviting than its JEFT mode, it’s still relatively lean and raw sounding compared to the more immersive C9ii performance.
My Verdict
The Cayin C9ii is the most complete portable tube amplifier on the market today. It’s a big fella, but it delivers big power with a broad range of tuning options to satisfy IEM and headphone users alike.
The underlying strength across all the modes and timbres is the amplifier’s dynamic range performance, which is a clear step up from the original model. If you need a reason to upgrade, then this is probably the first point to consider.
Beyond that, everything is about choice, from matching the right gear to the right tonal coloration or the best output power setting to drive the correct headphones. The C9ii has a ton of flexibility, much more so than its nearest portable tube amplifier competitors.
It is one of the most expensive portable tube amplifiers out there right now, but given the diversity of features and its stellar performance, this might well be justified for many potential owners.
Cayin C9ii Technical Specifications
- Gen5 Dual NuTube Circuit
- Hi-End Audio PCB with TOTL Components
- Fully Symmetric Discrete & Balanced 3-Stage Amplifier
- Dual Amp Operation Class A & Class AB + Hyper Mode
- SS | Modern | Classic Timbre Toggle
- Adjustable Anode (Plate) Voltage
- Local or Large-Loop NFB Toggle
- Dual Input Mode: Line | Preamp
- USB-C: QC3.0 & PD2.0 Fast Charging Support
- Direct Battery PSU Module (Batteries forming an 8.4V PSU)
- Quick Release Battery Tray with x4 18650 Samsung 35E Batteries
- Power: SE: 1.2W into 16Ω | 700mW into 32Ω | 80mW into 300Ω
- Power: BAL: 4.1W into 16Ω | 2.6W into 32Ω | 320mW into 300Ω
- Dimensions: 165x88x30mm | Weight 650g
