Cayin C9 - Portable Amp

Thats good clarification! And tbh, actualy make sense since most usb chargers don’t have legit grounding.

EDIT: cayin, if you are reading this, a wall wart battery tray would be an awesome add on.

Edit2: and in the second version yall should realy include a battery bypass switch. Kind of surprised it doesn’t already have one tbh


Agreed, but also it would be super nice if they put the battery meter somewhere where it can be seen from the front of the unit if there are so many overcharging/undercharging issues.


The C9 gets so hot in tube/A config that I think it’s best not to charge until it cools down.

This means that if you want, you can charge the source continually and when the C9 gets low, you must disconnect, use a fan on it for a few minutes, then charge it.

If you want to listen while charging, you need to be in SS/AB mode, and I’d charge the source to full, disconnect, then charge the C9, then switch as required.

This hasn’t been a problem for me at all, with a DAP as source … If I’ve been listening for 5 hours straight (i have), probably better to take a break anyhow.

I can imagine it’s more painful with a laptop as source, but @Torq if you’re willing to just stop charging the laptop while charging the C9 a single PD charger will do for both.

@Eskamobob1 on the headfi thread the Cayin rep has said there is no planned wall wart (or linear power supply) several times. I would like that to change too, for the times I am fine plugging in, but not a high priority for me.

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All devices have to be fully charged before I leave, or they’re more trouble than they’re worth for my use case(s).

And I’m not carrying an extra/separate charger for one device that I would “like”, but certainly don’t “need”.

C9 is a hard pass for me based on its power/charging nonsense. No one needs to spend more time talking to me about it/trying to talk me into it.


Hahaha. Yup. Its the kind of thing you put up with as a desktop replacement/transportable rig, but way too much of a hassle for a sometimes use travel rig.

Out of curiosity, you used many other portable tubes? I have a phantasy ii that I quite like but am currious about other higher end options in the space to try different sounds

Hey Fellas. I gotta say this C9 looks first rate. I’m extremely interested in it and I haven’t been this excited to buy another piece of HiFi Gear in quite a while.
I think CAYIN have really set the bar high with this one. I love the option of having a lot of power to drive 300 OHM headphones with considerable ease.

I have a feeling this is a better amp than the Woo Audio WA 8, which I think is saying a lot. :wink:

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Fwiw, most daps now drive 300-600 ohm cans without much issue. Its high amperage stuff that is the issue.

Also, just so you have a heads up, the C9 and WA8 (and phantasy ii, all) have different sound signatures with different goals. I’m not entierky sure I would say one “beats” another all out as much as it simply provides a different flavor and excels in different areas (and I say this as someone who didn’t realy like the WA8 btw)


For me, and for many entrenched in this audiophile world, there is always this fascination with analog tube amplifiers. It’s old school, it’s cool and unique looking, and it has its own set of parameters to mess around with. It also provides a different listening experience for the curious ear. I’ve gone through a number of tube amps in the past: from hybrids, OTL, or SET-style tube amps for headphones and speakers, and I’ve also gone through a few portable tube amplifiers as well. While I’ve had some success with the desktop ones, the portable ones have always been mostly misses or more of “what’s the point?”

The Cayin C9 was announced a while ago and has more recently just showed up for sale. It caught my attention when it was first announced due to its looks and its specifications. It features both balanced and single-ended input and outputs, a nice sized volume knob, a switch to activate solid-state or vacuum tube circuitry, and an additional switch to active Class A or Class AB circuitry. In addition, this is a pure amplifier, and does not have a DAC, which lets users choose which pairing they want to go with it. Many portables are DAC/Amp combinations and does not give users the option to choose, which for most cases is the only way to keep them portable and have a small footprint.

The C9 comes in at a $2000 price tag, and is definitely on the upper-end of the portable amplifier market. It does, however, make up for its price tag with a very nice and high quality build, featuring an all-metal chassis that is simple yet elegant. The input/output connectors have gold rings around them, as well as the power button and volume knob to provide both style and functionality to its design.

The C9’s tube selection is powered by Korg NuTubes. These are unique and a relatively new tube design that glow with green LEDs and are laid flat on the board. The Cayin C9 has two oval-shaped window cut-outs on the top surface of the amp that lets the Nutubes shine their alien look when activated. When off, the windows are very dark and internals are not visible.

The C9 is pretty hefty, and definitely not pocketable. It may fit into a large coat pocket, but the weight would be pretty distracting and heavy to carry. Instead, this is definitely made for bag travel, and to sit on a solid table surface when in use. Due to the amp selections and metal chassis, the C9 also gets very hot in any of the combinations, and you’ll probably want to minimize contact with it when it has been running for a short time. It will heat up the area around it.

Note: The Cayin C9 amplifier was provided on loan as part of a private review tour hosted by Cayin directly. I will be shipping the C9 amplifier to the next leg of the tour in Europe immediately after this review.

Sound Impressions

The Cayin C9 has two “timbre” modes (solid-state and vacuum tube) and two amp circuits (Class A and Class AB), giving it a total of 4 combinations of user amp configurations. There is, of course, a high and low gain setting, but I’ll just say that for headphones, I used high gain, and for IEMs, I used low gain for all my impressions.

I’ll first take a look at some of the basic power demands and general observations and then go into the different configuration impressions and finally comparisons with other portables I have on hand.

Initial Stress Test

When I first took out the C9 and got it setup, I connected my Lotoo PAW 6000 digital audio player with line-out enabled into the input of the C9. I used balanced 4.4mm interconnects, which are provided with the C9 and are quite stunning looking. The C9 also includes matching 3.5mm to 3.5mm interconnects as well.

My first stress test was to see how the notoriously hard-to-drive Hifiman Susvara planar magnetic headphone would sound with the Cayin C9, however only using the 3.5mm singled-ended output which has less power capability. I enabled Line Out on the PAW 6000 and set the switches to High Gain, Class A and Tube mode on the C9 and it was time to rock n’ roll. I put on Grace Potter & The Nocturnal’s modern classic rocker, “The Lion The Beast The Beat” and was happy audio came out, but I wasn’t thrilled that I ran to the end of the line on the volume knob.

Now mind you, it got loud enough for me to enjoy music at almost my normal listening volumes (roughly 70-75dB SPL@ 1KHz), however for some, that may not be loud enough, and this specific headphone pairing didn’t get it to even that level. Unfortunately with this, I did find the C9 to sound a tad bright, thin, and just lacking a great mid-range and smooth treble that I’d expect from the Susvara. The low-end held up fine though, surprisingly.

But, let me reiterate, this was just a stress test, and very, very few headphones require the amount of sheer power that a Susvara does and I also only tested it out of the weaker single-ended output stage. The majority of headphones and earphones I tried worked well within the bounds of the C9’s power output.

Headphones Pairing with the Sennheiser HD600

Now with that out of the way, I spent the majority of my headphone experience with the Sennheiser HD600. This is a classic reference headphone that many in this hobby have heard, and has a very well known and established tonality and timbre that appeases most people. It also pairs extremely well with most tube amplifiers, and so this was one that I had some good expectations for.

On this pairing, I kept the PAW 6000 in the chain, turned it to NOS mode, connected it as a DAC to my computer and turned on Roon and HQPlayer. I set HQPlayer to 768kHz oversampling with the Sinc-L filter and fired off some music.

First, I compared Class A and AB using the Tube mode on high gain.

In “Restless” by Alison Kraus & Union Station, I found the angelic voice of Kraus to sound really no different between either of the Class modes. In Class A mode, however, I did find the low end bass guitar to have just a slight amount of more impact, while the Class AB mode had a softer and brighter midrange.

Switching over to the live recording of Bill Laurence’s “The Good Things” from “Live at Ronnie Scott’s”, I found there were some more noticeable differences between the settings. The Class A setting had a more warm sound but with a more muted piano strike, especially around 0:54 in the track. In Class AB mode, this piano attack was slightly more strained with more resonance in comparison.

I continued to listen and moved quickly towards the mid-point of this track, where the stand-up bass solo begins around 5:38 into the track towards the end. In this case, the amp settings did not seem to make any pronounced differences.

So, of course, I decided to mess around with the “timbre” switch. I flipped back and forth between Solid-State and Tube modes and found that the second half of the track, which is led by a bass solo, while drums and keyboard are still continuing in the background, had some more appreciable differences.

In Solid-State mode, I heard harder transients with more crisp edges, while also have more defined cuts. While in Tube mode, the transients became softer and sustain notes held longer with more decay and just an overall more euphonic sound.

At this point, I wanted to try some older music, and pulled out some classic Beatles music. On “Let it Be”, Paul McCartney’s vocals sounded much the same between any of the settings I messed with, but the most audible change between modes was how drums sounded. On Solid-State mode, drums sounded a tad thin and lean, and lacking the heft and weight I heard while on the Tube mode, which sounded more realistic and defined. I also felt the whizzing guitars and bass around the 3 minute mark sounded clearly better with the tube amp enabled.

There are many great Beatles tracks, but one of the more memorable introductions is the combination of drums, bass and buzzing guitars of George Harrison’s “While My Guitar Weeps”. In tube amp mode, this intro has a softer guitar presentation, and a smoother transition from the initial introduction to the guitar frenzy later. In Solid-State mode, the imaging is improved and things are little more separated, however, guitars are sharper but also more defined.

Some Time with In-Ear Monitors

I also spent a bit of time with various in-ear monitors on the low setting with the Cayin C9. No matter which IEM I used, I did not find any issues with hissing or noise. All of them had black backgrounds, and no trouble with any sound anomalies. For reference, I used custom Hidition Viento and Unique Melody MEST, and also some time with the universal Shuoer EJ07M, Dunu SA6, and Kiwi Ears Orchestra.

I spent most of the time here with my two customs. With the Viento, I thought the pairing was alright. The Viento is a very neutral reference monitor, with a small bass boost. The Cayin C9 tube amp had a clean signature, that had just a slight amount of warmth, but a surprising amount of air and treble quantity to it that I wasn’t expecting. It never felt harsh though with any of the IEMs, and that was good. It felt relatively sweet, especially after the initial brightness I found with the Susvara. Luckily, this isn’t the case here nor was it with the HD600.

I thought the pairing with the Unique Melody MEST was quite nice. The MEST is a quad-driver IEM with dynamic driver, balanced armatures, electrostatic-tweeters and a bone conduction driver. The MEST’s relaxed, yet exciting signature had some extra pop and reverbish sound to the low end while using the C9 in Tube, AB mode. Those Bill Laurence Trio live tracks had a nice amount of energy and an organic decay that felt very nice physically and mentally.

All in all, I think the C9 plays well with IEMs, which I will say, isn’t a typical thing with many portable tube amplifiers. Many are just too loud for most IEMs or have loud feedback from amp noise or electromagnetic interference (EMI) from phones or other wireless signals. The C9 is quiet. Very quiet.

Comparisons with…

Lotoo PAW 6000

The Lotoo PAW 6000 is my current audio player of choice when it comes to portability since it has a lightning fast UI, easy touch interface, and a really nice sound signature that is resolving yet natural without sounding too stuffy or too bright. The sweet treble is probably my favorite part of the experience.

I spent a good chunk of time using it as a DAC for the Cayin C9 and then quickly A-B switching between the player directly and the amplifier. This worked well since I was able to use balanced cables for the I/O between the two devices and 3.5mm cable for headphone listening.

The PAW 6000 surprisingly sounded a touch warmer than the C9, with just a little bit more elevation in the lower midrange and a more relaxed treble range. As mentioned previously, I don’t think the C9 is utterly bright, but I did notice it sounds like it has a little more energy up top than the other amps I have been using and own today. The C9 is also a little more precise in some ways, especially in solid-state mode. In tube mode, I do find these two line-up more comparably.

Chord Mojo + Poly

The Chord Mojo + Poly combination is new to me. I only just received it a couple days after I got this C9 and intend to use it as a portable Roon streamer while in and around my home. In my brief time with both of these amps, I have noticed the Mojo plays just a bit more warm, a little more rounded in the edges, and a little more contained. The C9 has a little more pop and dynamic energy, and again, has a more lift in the upper range.

Both of these have equivalent power, though, I think the Susvara had a little more drive with the Mojo than it did with the C9. Again, this is a crazy ask for either of these amps so take that with a grain of salt. In other headphones play, I found power to not be an issue on either of these units.


Ignoring the price tag, the Cayin C9 is a very nice addition and one of the better portable tube amplifiers on the market. It has a nice high quality build, pretty Korg NuTubes, and solid feeling switches and knob. The battery life also seems pretty good in my experience especially given how much heat this thing generates and the amp circuitry.

If I had to criticize anything, it would be that its a bit large, and heavy, and not super easily transportable without a bag. It also has a hefty price tag at $2000 USD, and puts it in the upper echelon of portable amplifiers.

But that said, I do like what I heard. It does not necessarily present the stereotypical warm and liquid sound that many think of tube amplifiers, but instead softens the transients just enough while keeping the upper range active and energetic to keep dynamics alive and resolution in-tact. It definitely outperforms other portable tube amplifiers I’ve tried, albeit, those were significantly less costly. So in the end, its a big dollar amplifier for those who can afford it. Its worth a demo for sure.


Out of curiosity - now some months later- did you find a satisfactory alternative portable amp for your use case?

I travel a fair bit too. I take my Hiby R8 DAP and IFI micro iDSD Signature. The latter one can charge continuously while in use (listening to music) as the battery charging (usb-c) and music inputs (S/pidf or USB-A) are totally separate circuits. The IDSD is not a tube amp but has the extra XBass and 3D (supposedly increases staging, though most users say it doesn’t really do that) and includes Ifi iematch switch so works with sensitive iems. Anyway the iDSD is smaller/lighter, doesn’t have the charging issues C9 does and works with my other devices. I connect the R8 to the iDSD via USB or S/Pidf, works great and the SQ is great with any of my IEMS - Thieaudio Monarch, ER4-XR, UM 3DT IKKO OH10- none of which are highly sensitive IEMS.

I am thinking about picking up the C9 more for its sonic characteristics /connectivity to use at home with my full size HPs and non-sensitive IEMS. In that context, I will use a Sonore MicroRendu to connect to Roon (hard-wired to my home network) —>USB to Hiby R8 —> 4.4 balanced interconnect to C9. I could of course use a non-portable amp to do much the same thing at the last step ie IFi Zen Can, but would not have the Class A/AB OR tube/solid state options.

The charging issues are less worrisome to me in this use case. I’ve also considered the Burson Soloist 3x, but in the thread on that device in this Forum, it seems that there are frequent Qc issues leading to short-circuit /destruction of headphones - I am not reading anything like that so far about the C9…

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Not that I was really looking for one.

I liked the idea of the C9 (based on my experiences with the N8), and thought it’d be nice to have something like that for the (rare) occasions I travelled with full-sized cans than needed more juice than the SP2000 could provide/and for when I wanted some “tube flavor” from a streaming-capable source while away from home.

That was never a “need”, so I didn’t look for other solutions.

Today, the SP2000T would render it moot anyway. And I may pick one of those up at some point, but I’d rather wait to see if A&K take a similar approach with the “SP3000” (or whatever replaces the SP2000 that I have).

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I am using the C9 with SP2000 and a number of IEMs (Oriolus Traillii, EE Odin, Tia Fourte Noir, UM Indigo, IER-Z1R, …). I also have the N8.

The C9 provides such a big step up in sonic qualities (stage, layering, dynamics, details at every level) that I am reluctant to bet on future DAPs being able to close that gap without the accompanying form factor that makes the C9 a bit unwieldy. To my ears, SP2000+C9 is more than a generation ahead of N8 in both tube and SS modes (not even mentioning the class A vs AB options which provide another welcome flavor on the C9, depending on music or mood).

After being spoiled by the C9 sound, my hope for a more transportable alternative is primarily with the upcoming L&P 2022 TOTL model - supposedly they are going to fix the major usability constraints with their current lineup; they would also have to step beyond the LP6Ti sound, this could result in a possible tradeoff where the C9 would still be a bigger amp (in all ways) but L&P closing that gap, and leapfrogging on the DAC side of things.

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I don’t doubt the SP2000 + C9 combo is fantastic.

It’s just not relevant to me anymore.

I’ve no plans to travel with full-sized cans in future, and there’s no way I’d carry an external amplifier to listen with IEMs.

The SP2000T (or an SP3000T) would be interesting to add tube flavor to a natively streaming capable DAC. Not because I think it’s equivalent to or better than another DAP paired with the C9. Even then, it’d be mostly a novelty.

Anymore, I can barely be bothered to carry more than my iPhone and AirPods Pro (which between them, constitute at least 90% of my travel/mobile listening now).


Been there … I have taken a step back from that extreme to where my maximum mobility scenario still has me carrying LP W2 dongle with a wired IEM. AirPods Pro for communication and audiobooks only …


Honestly, if you want to use IEMs with the amp and have something mostly for desktop use that happens to be portable I would go WA8 over C9. Its much cheaper used and technically much higher performing IMO. I know there is the appeal of the multiple modes on the C9 but tbh I find the class A tube to be the only one that really makes sense in terms of SQ and even then, better SQ can be had much cheaper. Obviously this does depend on what headphones you will be running but I honestly cant think of a single case I would take a C9 over one of my other portables regardless of what I was using. Even further, I think you can get better SQ for the same (or maybe less) money portable by splitting into two devices to be used by use case (something like a WA8 for tubes and BX2 Plus for high powered stuff would be a very good shout for more normal/inoffensive soundings that play better with more options, and there are tons of even better options if you want to get more obscure).

You hit an important point “depends on which headphone” - e.g. with UM MEST Indigo I prefer SS AB; depending on genre Tubes A or AB both come in handy. Nice to have these options available oob.

Esp. AK SP2000 benefits a ton from use with C9 (interestingly finding N8 to be a less ideal pairing). SP2k + C9 compared to WA8 are 2 categories higher in DAC as well as amp performance, I using the iFi Traveller case (link) that fits this combo (and cables) like a glove.

Only potential change next year that I expect for me to improve on this ensemble could be the (not yet officially announced) Luxury and Precision LP7 Ti. I don’t see N8 mk ii or SP3000 (if they are even in the cards for 2022) as making enough of a difference for my use cases, as likely those would be incremental improvements - not enough to dethrone my new favorite combo?


To each their own i guess. While I do think the dac in tge wa8 is pretty lacking even just use sp2k LO into either c9 or wa8 I do feel the wa8 is more technicaly capable with better seperation, texture, and timbre than the c9 (woukd say they are about on par in terms of micro detail). The c9 does kick harder but for iems i don’t find that matters much to me. Uktimately it’s about being happy with what you have. I find myself better suited by other gear but if you like something no need to change it up

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I used to carry a camera bag full of mobile equipment, backup batteries, cables and adaptors, but no more.

Your statement brought a smile to my face, as I too have pared down my mobile rig to the minimum:

iPhone → LooToo Paw S2 Pentacon → U12t

My mobile rig requirements now are:

  • sound quality
  • simplicity
  • light weight
  • minimal batteries


I get the portability thing but I’m not parting with my C9. Why? I can listen to needy cans and still be “present” with my wife. I’ve been getting s**t about being in my office (read: man cave) too much.

It took me a long time to get off the idea of needing a DAP etc.

For me, the big shift happened when I came to terms with the reality that I cannot properly exploit the clear quality advantages of a TOTL DAP or dongle, driving high-end IEMs from lossless source material in an airport, on a plane, or around other people.

They were not proving to be any more enjoyable (even though I could tell the difference), than just using the iPhone into the AirPods Pro.

In fact, if anything, being aware that the better gear’s performance (or the enjoyment potential from it) was being so heavily compromised by outside noise and distractions, made them more frustrating for me.

It’s all about personal priorities and situations of course, and mine have shifted a lot!


Nice write-up! Thanks for sharing it here.

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