SKU: 94438313512

Cayin C9II Portable Headphone Amplifier

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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)

 

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SKU: 94438313512

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Dee
Lexington, US
★★★★★ 5
Intriguing
Format: Kindle
An intriguing story that played out slowly while introducing some unique characters. The story became quite fascinating to read as these same characters provided startling revelations to their lives. As their relationships evolve, more drama and mystery is revealed adding to my fascination. I can’t wait to read more.
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Reviewed in the United States on May 27, 2026
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Darcy Smith
Waukegan, US
★★★★★ 5
Outstanding Story!!!!!!!
Format: Kindle
Oh I loved this story. Sera is such an amazing, fun character. She has so much fire inside of herself. She has humor that makes you laugh with her sassy comments. The guys are fantastic. I don’t feel as if we really have gotten to know who and what they are but they are such a mix of fae. The story is extremely well written and developed. It had me pulled in and didn’t let go. There was so much action, drama, and suspense. Then we get to the ending and goodness there is so much going on. This ending was a major cliffhanger and I absolutely can’t wait to see what happens next.
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Reviewed in the United States on March 12, 2024
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Kathleen G. Bohle
Dallas, US
★★★★★ 5
Exceptional
Format: Kindle
I think this an exciting entertaining story different from other fantasy reverse harmen story. I love the 1st book in this series and hope it continues to weave a story of friendship, love and disappointment as well as sadness. The cliffhanger was gripping and held you in suspense that waiting until the next book was released was almost too much. I’m so glad I waited to read this series until the majority of the books were released. Katie May and Quinn Arthur’s are wonderful writers and I’m looking forward to reading more from both of them.
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Reviewed in the United States on April 23, 2025
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Johanna J
San Leandro, US
★★★★★ 3
I don’t mind a cliffhanger,
Format: Kindle
but I dropped at least one star because of the obnoxious gloating of the author after the cliffhanger. Seriously - I don’t understand making your readers angry because you’re smug and expecting them to keep reading your books. I was very definitely enjoying the series. Now I have a bad taste in my mouth and mixed feelings about continuing the series.
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Reviewed in the United States on April 9, 2025
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Stephen Wiggs
Belleville, US
★★★★★ 4
The series as a whole so far 5/25
Format: Kindle
I read reviews before going into this book and I don't agree with one of the more harsh ones on the main trigger she had. It is stated clearly in the forward and it wasn't as blase as it was made out to be. It definitely is touched on more and hasn't just been brushed off as the series goes I definitely would recommend reading it. It's a good series just be for-warned I like the series as a whole. The characters are awesome I adore the fmc shes cute and adorable but also a badass. Though there are a bunch of holes for her that I feel like just got left out. The guys are interesting and shout out to yall for not making Gage a dragon. I'm tired of the broody ones who don't wanna talk aboit what they are being Dragons. Ki is my favorite You can definitely tell if is written by 2 different people though because the phrasing just doesn't match up and wouldn't be something people that age says. And it flip flops between them. I feel like there's substance without substance. We are 4 books in and we don't really know much back story on literally anyone more than right under surface deep. There are definitely favorite MMCs which is kind of disappointing since some get shoved to the wayside. Specifically both of the best friends. They're basically useless and it's made obvious as the books go on. As well as all the men are ungodly self deprecating. I enjoy the plot line for the most part like I said I enjoy the series its different and refreshing. I do feel like the series is being dragged out though unfortunately. And the latest cliff hanger was just meh. So hopefully the next book is the last one.
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Reviewed in the United States on May 8, 2025

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