Cayin C9II Portable Headphone Amplifier
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.
  • Except Preorder products are shipped in 48 hours.
  • Delivery to the USA:
  1. Standard Shipping : 3-10 business days
  • If time is of the essence, please consider selecting expedited delivery for faster service.
Exchange/Return Notes
  • We offer a 30-day return/exchange service after receiving.
  • Final sale items are not eligible for returns or exchanges.
  • To process your return/exchange, please contact us at [email protected]
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SKU: 94438313512

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Darren Gray
New York, US
★★★★★ 5
Good value
Model: NewSLS50_52, Model: NewSLS50_52
Working perfectly. Install of stereo equipment and carpet left me wanting some heat and sound resistant materials.
WAS THIS REVIEW HELPFUL?YesReportShare
Reviewed in the United States on March 23, 2026
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Tharin
West Palm Beach, US
★★★★★ 5
BUY THIS ONE!
Model: NewSLS50_52
This is one of the good ones. There are other brands just as good, and manny brands are worse, but this handles well, rolls down easily, doesn't come off at all easily, and adapts to dips and curves like a champ. Appropriately heavy and dead, I'm happy with the way it smothers panel resonances and even at muffling direct sound, like a big hand over my Uncle Harry's eternally noisy mouth. You can rip the foil but you have to work hard at doing that. Remember to buy a brayer; you can roll overlaps nice and thin. Also remember to pre-wipe the sheet metal with a decent solvent like acetone or Stoddard/Varsol. It should last forever.
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Reviewed in the United States on April 26, 2025
H
Verified Purchase
Harvey
Lowell, US
★★★★★ 5
Good stuff, but watch the temp
Model: NewSLS50_52
I used this in my single cab pickup truck (89 ford.) It only took half the box (10 sheets or 25 square feet) to do the floors, but I bought the big box because I plan to do the doors, back wall, and maybe the roof as well. One thing I learned is that the temperature matters when you’re doing the installation. It was around 55F when I started in the evening, and when it dipped down into the 40s the sheets would not stick to the metal, and were hard to compress with the roller. That’s why I ended up only doing the floors and not any vertical surfaces; i will have to wait for a nice hot day. The other thing is that the foil layer on top is razor sharp at the edges, definitely wear gloves! I didn’t notice until after but I have little papercuts all over my fingers. Aside from those things, the install was easy and straightforward. The sheets cut easily with scissors, and any goo that ends up on your hands or scissors can be cleaned up with acetone (nail polish remover), or lacquer thinner. I would use this stuff again.
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Reviewed in the United States on November 16, 2023
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Lyrah
Fort Morgan, US
★★★★★ 5
Very efficient!
Model: NewSLS50_52
Amazing the difference it makes on dumping the noise. Very easy to install. Pell and stick literally! Great!
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Reviewed in the United States on November 23, 2025
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James C. Higgins
San Leandro, US
★★★★★ 5
Polyglo mit
Exact polyglo applicator mit. Works perfect!
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Reviewed in the United States on May 19, 2026

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