Cayin
C9ii Portable Headphone Amplifier
$2,399.00 USDPay Over Time
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Features
Three selectable timbre modes — Classic Tube, Modern Tube, and Solid-State — for tailored sonic character across any genre or headphone pairing
Three amplification modes — Class A, Class AB, and the newly introduced Hyper Mode — for versatile performance ranging from lush warmth to razor-sharp dynamics
Adjustable High/Low anode (plate) voltage switch expands tube timbre customization with perceptible differences in harmonic character and soundstage
NFB (Negative Feedback) toggle enhances resolution, dynamic range, and transient response when engaged, or delivers richer, more textured harmonics when bypassed
Fully discrete, fully symmetric differential three-stage amplification architecture for unmatched transparency and wide dynamic range
MUSES72320V ladder-based precision volume control ensures exceptional channel balance and low noise, even at low listening levels
Four replaceable high-capacity 21700 rechargeable batteries with a modular battery system for extended, uninterrupted playback
Balanced 4.4mm and single-ended 3.5mm inputs and outputs for flexible integration with portable sources and desktop systems
Pre-Amp/Line-Out mode enables use as a pure power amplifier stage in a desktop Hi-Fi chain
What's in the Box?
Warranty
When Streams Converges into One Pool
C9ii integrates Cayin's Amplification Technologies and Nutube Experience into a TOTL portable, battery-powered headphone Amplifier.
Gen5 Nutube 6P1 Vacuum Tube Circuit
After years of continuous circuit experimentation and technical refinement, Cayin has equipped the C9ii with an adjustable anode (plate)voltagee feature, in addition to the highly praised Classic and Modern dual tube timbre.
Fully Symmetric Headphone Amplifier
On top of being fully discrete and fully differentiated, the headphone amp. The circuit of the C9 ii adopts a fully symmetrical architecture. This improves transparency and supports a stronger load-driving capability.
Outstanding Sound Shaping Capability
C9II provides numerous features, amplification status, and timbre adjustments to satisfy the subjective preferences of our users, exploring their music library at different times/moods, different music genres, and different IEM/headphones.
Direct Battery Power Supply Module
The C911 uses four Samsung 35E battery cells to form a +8.44V DC power supply. Both C9 and C9ii are powered directly by 18650 batteries without any DC/DC conversion for voltage-boosting.
The modular battery tray is redesigned to fit with two quick-release latches.
KORG Nutube 6P1
Developed by KORG in collaboration with Noritake (2015). The Nutube 6P1 operates on the same principles as conventional vacuum tubes, using an anode grid filament structure to generate a warm, tube-like sound.
Compact, energy-efficient, and has a longer lifespan when compared to traditional vacuum tubes.
The Structure and Technologies in Nutube
Vacuum Fluorescent Display (VFD): similar principle to vacuum tubes, they have cathodes (filaments), grids, and anodes that allow electrons to flow and amplify audio signals.
Flat anode-grid-filament structure: allows for a smaller and thinner form factor, making the Nutube much more compact. The filament (cathode) emits electrons, which pass through the grid and are collected by the anode, just like the traditional vacuum tubes.
Applications of Nutube
While the Nutube is relatively compact, it is extremely prone to microphonics, just like any other directly-heated triode vacuum tube. KORG and VOX take advantage of the flat form factor and use the Nutube in guitar amplifiers, pedal kits, and keyboard amplifiers. The stationary desktop condition minimizes the microphonic effect.
Taking the Nutube into Portable Frontier
The "flattened" form factor and low heat, low power consumption characteristics are promising for portable audio applications. Numerous brands tried to develop products such as portable headphone amplifiers; unfortunately, the microphonic problem introduced serious issues for users, unsatisfactorily.
The Course of Vacuum Tubes in Cayin Portable Personal Audio
The dawn of the Vacuum Tube in Portable Audio (2018): Cayin surprised the personal audio community when we debuted the N8 DAP. This was our first project with KORG Nutube, possibly the first successful implementation in a portable player.
Second Generation Vacuum Tube Circuit for Portable Audio (2021): to achieve fully balanced, technically super
| Parameter | Specification |
|---|---|
| Physical Specifications | |
| Model | Cayin C9ii |
| Type | TOTL Portable Headphone Amplifier |
| Dimensions | 173.5 × 76.5 × 19 mm |
| Weight | 395 g (without leather case) |
| Housing / Construction | CNC Machined Aluminum Alloy |
| Color | Silver Gray |
| Technical Specifications | |
| Amplifier Architecture | Fully Discrete Solid-State with Selectable Vacuum Tube Timbre Circuit |
| Vacuum Tubes | KORG Nutube 6P1 × 2 (Dual Triode) |
| Timbre Mode | Solid State (SS) / Vacuum Tube (Tube) |
| Amplifier Operation Mode | Class A / Class AB (User Selectable) |
| Gain | High / Low (User Selectable) |
| Volume Control | JRC MUSES72320V 4-Channel Electronic Ladder Attenuator PVD Gold-Plated Brass Volume Knob |
| Audio Specifications | |
| Output Power — 4.4mm Balanced (Class A, High Gain) | 1600 mW @ 32Ω |
| Output Power — 4.4mm Balanced (Class AB, High Gain) | 3800 mW @ 32Ω |
| Output Power — 3.5mm Single-Ended (Class A, High Gain) | 400 mW @ 32Ω |
| Output Power — 3.5mm Single-Ended (Class AB, High Gain) | 950 mW @ 32Ω |
| THD+N | < 0.001% @ 1 kHz (1 Vrms output) |
| SNR | > 120 dB |
| Frequency Response | 20 Hz – 60 kHz (−3 dB) |
| Output Impedance | < 1Ω |
| Crosstalk | > 90 dB @ 1 kHz |
| Connectivity Specifications | |
| Input Ports | 4.4mm TRRRS Balanced Input 3.5mm TRS Single-Ended Input |
| Output Ports | 4.4mm TRRRS Balanced Headphone Output 3.5mm TRS Single-Ended Headphone Output |
| Charging Port | USB Type-C |
| Power Specifications | |
| Battery Capacity | 10,000 mAh (2 × 5,000 mAh Lithium-ion) |
| Playback Time (Class AB, SS, SE) | Up to ~12 hours |
| Playback Time (Class A, Tube, BAL) | Up to ~8 hours |
| Charging | USB-C; supports Quick Charge |
| Charging Time | Approx. 4 hours |
| Additional Information | |
| In the Box | C9ii Portable Amplifier USB-C Charging Cable 4.4mm to 4.4mm Interconnect Cable 3.5mm to 3.5mm Interconnect Cable User Manual |
| Compatible Sources | Any DAP, DAC, or source device with 3.5mm or 4.4mm analog line output |