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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4.6 ★★★★★
Based on 12 reviews
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Verified Purchase
Jeffrey Brown
Boise, US
★★★★★ 5
Durable toy for a great price! Will buy again.
Color: A Red, Size: For Larege Dogs, Color: A Red, Size: For Larege Dogs
Great toy, heavy, good size, and durable for active chewers. My two dogs like to play tug a war a lot and this toy has held up fantastically! Afterwards they tend to chew toys to pieces but this one has stood the test of time so far. Great buy!
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Reviewed in the United States on May 14, 2026
S
Verified Purchase
SHUGRLTARA
Massapequa, US
★★★★★ 4
Very tough & VERY heavy
Color: A Red, Size: For Larege Dogs
My dog is a half black lab/half pittie & a very aggressive chewer she goes through toy bones very quickly, to the point they're so slivered up within 2 days, sometimes slightly longer, I have to get rid of them, they never last long, except for whole antlers and some split antlers. Although she rarely touches the whole antlers . Anyways, this is a great tough toy for strong large breeds. It squeaks in the center if you squeeze hard enough but the toy/bone was a bit too heavy for my girl. I got her the next smaller one and she still plays with the big heavier one more than the one that fits her perfectly so go figure. It's a great product and definitely recommend for heavy chewers. I only took a star off because of the weight I was extremely surprised by how heavy it was, but that's not necessarily a bad thing depending on the dog, this size is just not for my dog. I think I've had it about a month and she does play with it, not as much as her other toys, but it's still in amazing shape even with her heavy chewing.
WAS THIS REVIEW HELPFUL?YesReportShare
Reviewed in the United States on April 21, 2024
A
Verified Purchase
Alannah Henry
Draper, US
★★★★★ 5
Squeaky Toy for Aggressive Chewers
Color: A Violet, Size: For Larege Dogs
Size is great for our big dog, he loves to chew & squeak it. engagement, our dog loves playing fetch, hours of enjoyment.
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Reviewed in the United States on May 21, 2026
E
Verified Purchase
Elizabeth
Massapequa, US
★★★★★ 3
Maybe not for super aggressive chewers
Color: A Violet, Size: For Larege Dogs, Color: A Violet, Size: For Larege Dogs
I had high hopes for this toy, I was so excited about it. I have aggressive chewers, two Malinois/Dutch Shepard mixes and a Pit. The Shepard's chewed pieces off of it in literally 5 minutes. At the ends there is a small lip and that's where they started chewing pieces off. I had ordered a second one before I gave them this one (early Christmas present) because when I received it I noticed it felt very sturdy and durable. They do like it so since they already chewed this one I'm going to see if I can shave that lip off and maybe they won't get anymore pieces off. That'll decide if I return the one that arrives tomorrow. Maybe not good for super aggressive chewers. It's very thick and seems well made. Might just be better for other dogs.
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Reviewed in the United States on December 21, 2025
B
Verified Purchase
Bethalyn
Charlottesville, US
★★★★★ 5
Fantastic for rough chewing
Color: Bule 0, Size: For Larege Dogs
Our big boy is rough with his toys and always seems to disintegrate his toys in seconds. I had seen this with hoping this will be the toy he doesn’t destroy. On day 2 now with the toy and he’s obsessed, even feel asleep with the toy in his mouth and still in one piece. Highly recommended for tough chewers.
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Reviewed in the United States on May 25, 2026

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