Cayin C9ii

Portable tube/transistor headphone amplifier with selectable voicing, 5th-gen Nutube 6P1 and a fully balanced architecture

Feedback and fine-tuning circuits — your personal sound journey

Ever wondered how different sonic characters are created? For the C9ii, Cayin’s engineers developed two dedicated tuning circuits:

Modern sound: High negative feedback significantly reduces total harmonic distortion (THD), creating a clear, clean tube presentation with minimal thermal noise.

Classic sound: Negative feedback is omitted; each stage operates independently via local feedback. The result is a sound you don’t just hear — you feel. The harmonic character of tube amplification gives music a smooth, musical “soul” and makes listening deeply engaging.

Innovative power design — efficiency on a new level

The C9-series power architecture is key to its performance. The discrete headphone power-amplifier circuits in the C9 and C9ii are fed by high-capacity 3,400 mAh batteries. This allows the design to bypass DC/DC voltage boost conversion and create an ideal power environment for analog circuits. Carefully filtered and decoupled with premium parts such as WIMA film capacitors and Panasonic POSCAP polymer tantalum capacitors, the result is both top sound quality and extended battery life — perfect for high-end listening on the go.

Premium chassis construction — style meets function

Cayin C9ii combines a robust, elegant chassis with superior heat dissipation. The transistors in the four-channel discrete high-power amplifier are the primary heat source. Graphene thermal plates and aluminum-alloy heatsinks dissipate heat efficiently and distribute temperature evenly — ensuring stable, reliable performance even under demanding use.

With the C9ii, Cayin raises the bar for sound quality, design, and functionality — modern technology and audiophile detail in a compact portable format.

Audio circuit with the groundbreaking 5th-gen Nutube 6P1

Equipped with the 5th-generation Nutube 6P1 vacuum tube, the C9ii brings the warmth and musicality of classic tube amps into a compact, energy-efficient design. Cayin has implemented this technology across multiple products — and now integrates it into the C9ii to add captivating texture and preserve the emotional depth of every recording.

Switchable anode voltage — shape your own voicing

After years of research and refinement, Cayin added a selectable anode (plate) voltage function to the C9ii, offering two settings: High and Low. Choose low for a softer, warmer presentation, or high for a more dynamic and detailed performance. This flexibility helps you drive high-end headphones optimally and tailor the sound to your preferences.

Fully balanced headphone amplifier — sound in perfect control

Cayin C9ii features a fully balanced amplifier structure that minimizes distortion, expands dynamic range, and improves channel separation. Reduced crosstalk translates into a clearer stage and more precise imaging. An integrated precision control circuit enables multiple operating modes — from NFB/LFB and Class A/Class AB to Hyper, single-ended, and balanced.

Technical Specifications