Cayin C9ii - Reaching New Heights
When Cayin released the first generation, TOTL C9 portable amplifier back in 2021, it quickly gained recognition among audiophiles for its Tube/Solid-state dual timbre, direct-drive battery-powered circuit, discrete Class A/AB DAO (Dual Amp. Operation), Pre-Amp input (pure power amplifier) mode, and many other unique design and amplification techniques.
The C9 was a niche, highly specialized, and distinctive product within a very niche market, it unexpectedly brought Cayin market success and a strong reputation, showing that the market for audiophiles in pursuit of audio perfection is out there waiting for the right product
The fundamental purpose of a portable headphone amplifier lies in its core function: enhancing sound quality and broadening its ability to drive a wide range of loads. Now that many DAPs have embraced significant improvements in circuit performance, can the C9ii still achieve the same level of market recognition as the C9 did three and a half years ago? This is a question on the minds of many audiophiles. Some even ask us which offers better sound quality, the N30LE or the C9ii?
The C9 portable amplifier became a phenomenon three and a half years ago, primarily due to its innovative design and its unique and powerful features. (Insert link to a headline or the official thread in the HeadFi forum about the first generation of the C9). Today, let’s take a closer look at the new design, features, and updates of the newly announced C9ii.
Gen5 Nutube 6P1 Vacuum Tube Audio Circuit
The Nutube Timbre circuit in the C9ii utilizes a three-stage amplification design, with the core components consisting of a matched pair Nutube 6P1 dual directly-heated triode (DHT) vacuum tube and numerous Toshiba 2SK209 audio grade JFETs as buffer amplifier and buffer driver stage before/after the Nutubes.
The Timbre circuit offers three timber options:
Modern Sound: The harmonic distortion characteristics and sound signature lean more towards a modern style, with greatly reduced thermal noise and a slightly cleaner tube sound. The original C9 was designed with a similar NFB circuit.
Classic Sound: The distribution of harmonic distortion and the sound signature exhibit a classic vacuum tube amplification circuit, with relatively more thermal noise and a richer vacuum tube presentation. The N8 DAP was designed with a similar NFB circuit.
Solid State: A discrete timbre circuit with four Toshiba 2SK209 JFET transistors in a single-ended Class A source follower circuit. A clear, smooth, and fatigue-free audio output with no harshness.
Cayin introduces a new feature “Anode” to C9ii. The High/Low adjustable anode (plate) voltage further enriches and refines the range of vacuum tube timbre. The working principle is that applying different operating voltages to the vacuum tube's plate alters its operating state, ultimately affecting the sound signature of the timbre circuit.
The “Anode” plate voltage adjustment does not affect the solid-state timbre. Thus, in terms of choice of timbre, the C9ii offers four vacuum tube timbre options and one solid-state timbre, for a total of five variations. In contrast, the original C9 only offers two timbre options.
- Classic + Anode (H)
- Classic + Anode (L)
- Modern + Anode (H)
- Modern + Anode (L)
- Solid State sound
Fully Discrete, Fully Symmetric Differential Headphone Amplifier
Cayin has designed a three-stage amplification circuit to embrace the fully symmetric design into C9ii:
- Stage One: Symmetric JFET Common-source Differential input amplifier.
- Stage Two: Symmetric BJT Common-emitter Push-Pull Differential Voltage Amplifier.
- Stage Three: Symmetric BJT Common-collector Push-Pull Parallel Current
To further explore the discrete headphone amplification circuit, we have introduced the Hyper Mode on top of the regular Class A and Class AB options of the renowned DAO (Dual Amplifier Operation. The Hyper mode delivers the ultimate performance of the discrete amplification circuit in the C9ii at the expense of a shorter battery duration and and operates at a higher temperature.
A new NFB (Negative Feedback) feature is added to C9ii. This feature applies to the three-stage headphone amplification circuit mentioned above. When NFB is set to OFF, the headphone amplification circuit will be regulated by large-loop cross-stage negative feedback. When NFB is set to the ON position, the headphone amplification circuit will be regulated by local negative feedback
The effect of NFB is fairly noticeable. In our opinion, there is no right or wrong in NFB adjustment, it's a matter of personal preference, and adjustable NFB will allow the user to pick their preference on the go.
The C9 is comprehensive and innovative, these are some of the highlights:
- A fully balanced, fully discrete, feature-packed, 4-channel high-fidelity headphone amplifier delivers up to 4,100 mW per channel at 16Ω loading and 2600 mW per channel at 32Ω loading.
- Gen5 Nutube 6P1 Vacuum Tube Audio Circuit facilitated dual tube timbres (Classic Tube and Modern Tube) and Solid State timber on both balanced and single-end inputs.
- The Vacuum tube timber circuit is designed around a matched pair of KORG Nutube 6P1 miniature, low-power dual Directly Heated Triode (DHT) vacuum tubes.
- Adjust ANODE (plate) voltage (High/Low) of the Nutube to enrich and refine the range of the vacuum tube timbre in C9ii
- Three-stage fully symmetric differential headphone amplifier contributes to higher audio fidelity by reducing distortion, enhancing dynamic range, increasing channel separation, and providing a stable and consistent performance.
- Dual Amplification Operation (DAO): allows users to switch between Pure Class A and Class AB amplification modes.
- Hyper Amplification delivers the ultimate performance of the discrete amplification circuit in the C9ii
- NFB (Negative Feedback) Control to select between large-loop cross-stage NFB or local NFB applied to the three-stage headphone amplification circuit.
- Supports 3.5mm single-ended and 4.4mm balanced for both input and output, the amplifier will convert Single-ended input to Balanced audio signal before feeding through the differentiated amplification circuit.
- Dual input mode: on top of regular LINE input mode, C9ii can also operate in PRE-amp input mode (known as pure power amplifier mode) that can work with source devices with volume control.
- Employs a highly linear volume control system that is composed of a 4-channel ALPS potentiometer with a pair of MUSES72320 low noise, low distortion resistance ladder-based stereo electronic volume.
- Removable battery module that houses 4x Samsung 35E 3400mAH rechargeable lithium batteries. Users can acquire and replace the batteries conveniently to extend the battery duration when needed.
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