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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SKU: 94438313512

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Jason Dong
Lake Worth, US
★★★★★ 5
my dogs love it
Color: Orange
This interactive toy has been a lifesaver for keeping my furry friend occupied. It moves around in unpredictable ways, which really keeps him engaged and guessing. The rope attachment is a nice touch, allowing for a bit of tug-of-war when he's feeling energetic. It's durable enough to withstand his enthusiastic play, which is a huge plus. I've noticed he's less anxious and destructive when I'm not home since he has this to play with. Definitely a great purchase for any dog owner looking to provide some mental stimulation.
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Reviewed in the United States on April 25, 2026
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Verified Purchase
Douglas J
Grantham, US
★★★★★ 5
How many dog toys have you bought that just laid on the floor unused?
Color: Orange
New husky has more energy than an entire pre-school - even being walked more than three miles a day wasn’t sufficient to drain her excess energy. I threw the dice on this - and it’s AWESOME. Comes with an extra rope and an extra side piece. Rechargeable with a USB-C cable. When you turn it on, the blue LEDs flash, the entire device buzzes, bounces, and races back and forth across the floor. After a couple of days of uncertainty, my new husky LOVES this. She chases it around, grabs it by the attached rope and carries it from room to room. After a short bit of activity, the toy goes into ‘sleep’ mode, until either the dog touches it again or a timer has elapsed, and then it fires up and starts buzzing and racing around the floor again. From a full charge, the toy will keep your dog entertained all day. Bright orange color makes it much easier to find when it’s rolled behind the toilet (as it did this afternoon). Sturdy. Highly resistant to chew damage. If this one wears out or breaks, I’ll absolutely get another one.
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Reviewed in the United States on April 20, 2026
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Verified Purchase
Grant
Chelsea, US
★★★★★ 4
Puppy interactive toy
Color: Orange, Color: Orange
It’s a great toy as it keeps my 5 month old puppy very entertained! It is pretty hardy and made of good material as she tries to throw it around and chew it. She does swing it around and the hard part will hit her. She doesn’t seem bothered by it tho lol good size and minimum noise When I first introduced her to it she was a little scared but now she gets excited to play with it once it finishes charging.
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Reviewed in the United States on May 2, 2026
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Verified Purchase
LEE SANG
Draper, US
★★★★★ 5
My Dog Is Obsessed With This Toy!
Color: Orange, Color: Orange
My dog absolutely loves this toy and plays with it every day. The moving and rolling action keeps him entertained much longer than regular toys. He loves chasing it around the house and tugging on the rope. It’s also nice because it helps burn off some of his energy indoors. The material feels pretty sturdy, and charging was easy. Definitely one of the best interactive toys I’ve bought for my dog!
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Reviewed in the United States on May 19, 2026
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Verified Purchase
rebe99
Lowell, US
★★★★★ 3
Waste of Money
Color: Orange
Cool toy but my dog ate through it the second day he played with it. It is not for strong dogs. No durability. I had to throw away the orange covers and now he just throws it around.
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Reviewed in the United States on May 18, 2026

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