SKU: 94438313512

Cayin C9II Portable Headphone Amplifier

Sale price$1079.55 Regular price$1199.50
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Description

Cayin C9II Portable Headphone AmplifierProduct Highlights 1. Gen5 Nutube 6P1 Vacuum Tube Audio Circuit Cayin has applied this vacuum tube to multiple products, including the N8, C9, N8ii, and N30LE, and now the C9ii. After years of continuous circuit experimentation and technical refinement, Cayin has equipped the C9ii with an adjustable anode (plate) voltage feature and the highly praised Classic and Modern dual tube timbre. This adjustable plate voltage feature offers two levels: high

Product Highlights

1. Gen5 Nutube 6P1 Vacuum Tube Audio Circuit 

Cayin has applied this vacuum tube to multiple products, including the N8, C9, N8ii, and N30LE, and now the C9ii. After years of continuous circuit experimentation and technical refinement, Cayin has equipped the C9ii with an adjustable anode (plate) voltage feature and the highly praised Classic and Modern dual tube timbre. This adjustable plate voltage feature offers two levels: high and low.

1.1 Dual Tube Timbre Circuit

Modern Sound: Introduces a large-loop negative feedback system, with total gain determined by the large-loop negative feedback circuit. By incorporating negative feedback over multiple amplification stages, the total harmonic distortion (THD) will be reduced significantly. The harmonic distortion characteristics and sound signature lean more toward 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: No large-loop negative feedback; each stage operates independently through local feedback, with the overall gain determined by the cumulative gain of each stage. The distortion characteristics of the tube amplification circuit dominate the sound signature, resulting in a higher THD value. The distribution of harmonic distortion and the sensor 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. 

1.2 Anode (High/Low) 

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 plate of the vacuum tube alters its operating state, ultimately affecting the sound signature of the timbre circuit. This mainly manifests in changes in audio linearity, and it will adjust the overlay, spectrum, amplitude, and ratio of second-order harmonic, resulting in perceptible audible differences.

∙ Classic + Anode (H): The richest tube sound, with intense emotional depth, suitable for vocal music with a lot of details. 

∙ Classic + Anode (L): Slightly lighter tube sound, suitable for vocals with thicker tones.

∙ Modern + Anode (H): Less tube character, with moderate smoothing in the midrange and a slight sweetness added. 

∙ Modern + Anode (L): Minimal tube coloration, without affecting resolution and definition.

∙ Solid State sound: Balanced across the entire frequency range, musical without tube coloration.

2. Fully Discrete, Fully Symmetric Differential Headphone Amplifier 

The C9ii's headphone amplification circuit is significantly different from that of the first-generation C9. While both amplifiers employ a fully discrete, fully differential four-channel headphone amplification circuit, the C9ii adopts a fully symmetrical circuit architecture. 

2.1 Fully-symmetric Headphone Amplifier

Cayin has designed a three-stage amplification circuit to embrace the fully symmetric design into C9ii: a differential input stage, a voltage amplification stage, and a power driver stage. 

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 Amplifier(emitter follower).

2.2 Negative FeedBack (NFB) 

The C9ii has an integrated precision control circuit that allows the headphone amplifier to operate in various modes such as NFB/LFB, Class A/Class AB, Hyper, single-ended, and balanced input/output modes.

On the C9ii, when NFB is on (indicator light on), the audio output presents more spatiality with stellar dynamic range, excellent transient response, and relatively fewer harmonics, delivering more neutral sound with impressive detail and speed. Audiophiles frequently associate these changes with “higher resolution.” On the other hand, when NFB is off (indicator light off), the audio output displays richer harmonics. You can hear a more cohesive and full-bodied presentation, with stronger imaging and more textured and elastic mid-bass frequencies. 

Total Sound Shaping Options:

  • Timbre: 3 options (Classic Tube, Modern Tube, Solid-state) 
  • Amplification Mode: 3 options (Class A, Class AB, Hyper) 
  • Anode: 2 options (High, Low) 
  • NFB: 2 options (On/Off) 
  • Input mode: 2 (Line, Pre)

 

Shipping Notes
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Exchange/Return Notes
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  • Final sale items are not eligible for returns or exchanges.
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SKU: 94438313512

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Im loving this mattress topper. It has added a noticeable layer of comfort to my firm mattress without making it feel too soft. The cushion is plush yet supportive and has made sleeping more comfortable overall. The bamboo feels soft and breathable. It fits on the mattress with the deep pockets and stays in place alk night. Setup was easy and it fluffed up after unpacking. If you have a firm mattress and want extra comfort without replacing it, this topper is a great option. Highly recommend
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Reviewed in the United States on December 29, 2025
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Sophia S.
Waukegan, US
★★★★★ 5
Comfortable, cooling, and OEKO-TEX certified, it’s a great way to refresh any mattress.
This 3-inch mattress topper instantly upgraded my bed with a softer, cooler, and more supportive feel. The bamboo-viscose fabric is noticeably breathable, helping regulate heat throughout the night—great for hot sleepers. The 1200GSM down-alternative fill adds plush, cloud-like cushioning while still offering balanced support for the back and shoulders. It fits securely with the deep pockets and stays in place even when turning. After allowing it to fully expand, the topper fluffs up beautifully. Comfortable, cooling, and OEKO-TEX certified, it’s a great way to refresh any mattress.
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Reviewed in the United States on December 8, 2025
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Leon
Alexandria, US
★★★★★ 5
Great upgrade for a rental apartment mattress
The mattress in my rental place is firm to the point where it almost feels unfinished. Instead of replacing it, I decided to try adding this topper. It made an immediate difference in the way the bed feels when I sit or lie down. There’s a nice cushioned layer that softens that “flat” feeling but still holds its shape. Another thing I noticed is how breathable it is. I expected thick padding to feel warm, but the airflow here feels better than the original mattress surface. Even after moving around, it never felt heavy or stuffy.
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Reviewed in the United States on November 22, 2025
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Alexa Young
Houston, US
★★★★★ 5
Soft and Comfortable Topper
I got this bamboo mattress topper for a small single bed we keep in our guest room, but I ended up testing it out myself first. The material feels soft and breathable, which is nice because that room can get a little warm in the afternoons. It adds a good amount of cushioning without making the bed too soft. After a couple of nights, my back actually felt better compared to the old mattress alone. I also appreciate that it’s machine washable, because our guest room sometimes doubles as a nap spot for my son after swim class, and spills happen. It dried pretty quickly in the dryer and kept its shape. Overall, it made the bed feel much more comfortable and fresh.
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TED
Battle Creek, US
★★★★★ 5
Added comfort for someone working night shifts
I work odd hours, so my sleep schedule is all over the place. My mattress has always felt a bit too stiff after long shifts, so I got this topper hoping it would help me relax faster. It really changed the overall feel of the bed. The padding has a cushioned lift that makes lying down feel smoother, especially around the shoulders and lower back. Instead of feeling like I’m dropping onto a firm surface, there’s a soft layer that evens out the pressure. What surprised me most is how light the surface feels. Even after staying in one position, it never gets stuffy or heavy. The airflow makes a difference when your body is trying to wind down after work. The fitted pocket also stays tight around the mattress, so nothing shifts when I move. I can stretch out without worrying about the topper sliding off.
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