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
  • Free Standard Shipping on $100+ Orders to the USA.
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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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madeleine
Natrona Heights, US
★★★★★ 5
good quality
Size: X-Small, Color: Black (001)/White
keeps me warm during the cold months when i play golf. tight enough to move around in but not tight at all around the neck. overall a really great product. has kept up for the last 4 years very well
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Reviewed in the United States on May 19, 2026
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Ching
Los Angeles, US
★★★★★ 5
Fit and Length
Size: X-Large, Color: (401) Royal / / White
Yeah this fits perfectly. Very soft, the color pops, keeps you warm. I use these under my sweatshirts, cable sweaters, and my flannel shirts. For me it's about the arm length and how well the item contours to the body to help with warmth. Thank you for getting this right.
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Reviewed in the United States on February 23, 2026
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BB
West Palm Beach, US
★★★★★ 5
Worth it.
Size: Small, Color: Black (001)/White
Living in North Dakota, staying warm is invaluable. UnderArmour Cold Gear is the only base layer the provides warmth, KEEPS warmth, and protects from the unforgiving wind. Every winter I go on the hunt for thermals, layering options and I always find others to be saggy or incredibly tight, either way, once I begin shoveling or snowblowering, and sweating, other products become soaked, sticking to skin, unbreathable and quickly your sweat stuck to your body under layers in now creating a cold,chill, freeze to your body, and on a -10F day, it can become a dangerous situation. I honestly was hesitant to purchase UnderArmour, I felt it was too hyped up or paying for a name. BUT IT IS NOT. UnderArmour isn't a name, it is a company that has made the highest quality base layer, warmth, breathable and it really wicks sweat away; I may not know how it does it, but it works! For sizing, I ordered a small in the women's longsleeve/turtleneck black coldgear. I'm 5ft and roughly 110lbs. I like the fit, it is meant to fit your body. I probably could wear an extra small, but I like the sleeve length in the small and it fits very well. Stay warm folks!
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Reviewed in the United States on December 6, 2023
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Amanda
Waukegan, US
★★★★★ 5
Great cold gear
Size: Large, Color: White (100)/Black
Warm, very comfortable. I wear these all winter. The neck can be a little tight and the cut is definitely fitting. Its got thin like fleece on the inside that keeps you warm.
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Reviewed in the United States on November 3, 2025
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Katia
Carnegie, US
★★★★★ 4
Tight but stays in place, comfy and keeps you warm
Size: Medium, Color: Charcoal Light Heather (019)/Black
I liked this shirt because it keeps me warm when I'm outside even at negative temperatures, I can work out comfortably in it and the sweat dries out soon; also, the interior of the shirt is made of a very comfortable material. I don't like that this is very tight, cool if you want to use it under your usual sports clothes but if you want to use it as is I would suggest going up a size. I use this shirt almost every day to work out during winter time, I've washed them several times and they still feel as comfortable as the first day.
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Reviewed in the United States on January 5, 2022

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