Cayin C9: Tube sound from magic insides.

Pros: Excellent sound
Quality build
Multiple personalities (sound-wise)
Fully balanced

Cons: Large, transportable, not portable
Not mine
Cost
Size
Lack of connectivity options

Cayin C9 ($1999):Tube sound from magic insides. 4.75 stars

Cayin C9

Intro: As part of the North American C9 tour, my turn came about while I was prepping for a working vacation. No better use for the C9 than in real world situations such as this. While I did not fly, I did have to accommodate the large box for my time would be up during that working vacation. No bother, I had another in house in the same situation as well.

The C9 follows to me on the heels of the quite good Fantasy tour. Coming with mixed reviews, the Fantasy was appreciated for the long-term vision Cayin was putting out to stay competitive in this market. I do believe some of the criticism comes about due to the full-on peloton of offerings at this price right now. My review showed that as well. The C9 was just about the polar opposite. With no marketed competition save for the more “equitably-priced” iFi Black Label, the C9 goes into Chord2 levels pricewise. Another reviewer compared those so I will not. I shall focus almost exclusively on the aspects of the C9 and compare to the BL.


Specs:

Other importantant info:

• Fully balanced, fully discrete, 4-channels high-fidelity headphone amplifier delivers up to 4,100mW (at 16Ω) or 2600mW (at 32Ω) per channel.
• Select between Vacuum Tube and Solid State timber on both balanced and single-end inputs.
• The tube timber circuit is designed around a pair of KORG Nutube vacuum tubes.
• Switch between Pure Class A and Class AB amplification modes.
• Dual input mode: regular LINE input mode and PRE-amp input mode (or known as pure power amplifier mode).
• Supports 3.5mm SE and 4.4mm BAL for both input and output, the amplifier will also optimize BAL to SE or vice versa.
• 4-channels ALPS potentiometer with a pair of stereo electronic volume.
• Removable battery module with 4x user replaceable Sony18650 rechargeable lithium batteries.

In The Box:

C9 portable headphone amplifier
C9 battery module (mounted)
Rear panel glass protector
Single-ended portable interconnect (CS-35C35, 3.5se to 3.5se)
Balance portable interconnect (CS-44C44, 4.4bal to 4.4bal)
USB Type-C charging cable
Backup screws for battery module
T6 screwdriver
User manual

Gear used/compared:

LCD-3
Empire Ears Legend X (Eletech Socrates cable)

Shanling M6 Pro
Cayin N6ii (E01 motherboard)



Songs:

Alex Fox
Stevie Ray Vaughan
Elton John
Twenty one pilots
Santana
Buena Vista Social Club
Jeff Beck
Pink Floyd


Unboxing:

The Cayin unboxing of items has become an event of sorts. Coming in larger well-protected boxes, the items of choice come not only safeguarded from bumps and bruises but with room aplenty for all of the accoutrements. The same of course holds for the C9. Mimicking the unboxing of an Empire Ears item, what with the “jewelry drawers” sliding out, you get the sense of care and commitment to the process. A well protected unit usually also comes with excellent build as a result.

Sliding the sleeve off the box just like with the Fantasy, you are met with a hard-cardboard box, including clamshell-type of flaps on two sides. While the Fantasy had an overlap on the top, the C9 does not. Pulling the top up, you are met with the C9 in a hard foam insert only. It is large and pushed deeply into the insert. It takes a good bit of careful force to extract the C9 as a result. No matter, I’d rather have it over protected than under.

Pulling the side flap down, you are met with one slide drawer as opposed to the two found in the Fantasy. The sheer size of the C9 means that ½ the depth of the case is used for the unit, including protection. Sliding the drawer out using the attached ribbon, you are met with an envelope-type paperboard, which contains the user’s manual and protects the contents below. HiRes stickers and an extra back glass screen protector is included as well. Under the envelope, you will find the 3.5-3.5 and 4.4-4.4 connecting cables as well as the charging cord, the T6 screwdriver, and extra screws WHEN you lose one. I have come to appreciate the included Cayin charging cables as some of the best around for sturdiness and use. Of a good length as well, you should have no problem.

Build/Finish:

Typically, Cayin products are very well built. This would not be an exception to that rule. The C9, especially for the price comes across as well as those high dollar desktop units, which cost as much or several times more. Black is the color of choice here, and frankly it would have been all right with me had it been hot pink or chartreuse. Utilizing an all glass back for heat dissipation as well as looks, the C9 is a stunning move forward in the plain black box. Since others were to follow, I kept the already mounted screen protector on, and it shows heavy wear. Once can assume that not using the screen protector would not yield such scratches. Also, you will want to purchase protective feet, as there aren’t any, so the unit sits on that glass back whether it has the screen protector or not.

A metal shell covers the rest, complete with a cutout of sorts on the top at the front. Application-wise for the volume pot, the inset looks clean and functional with the volume dial shows only marginally above the surface. Set back on either side of that inset are oblong holes, with glass inserts showing off the Korg NUTUBES inside. Looking like cat eyes, the green of the functioning Nutube looks pretty cool. Switch to solid state and the lights go away. I will cover the Korg “tubes” under the technical section, for there is much to discuss.

The front is dominated by two things: the in and out connectivity and the volume wheel. Along the top are finely tactile “toggles” for switching from (left to right) Amp to Line Pre-Amp; High and Low Gain; Timbre-Solid State or Nutube; and Class-A or Class-AB. Dead center with two toggles each side is the volume pot. Under that “row” are from left to right: the two inputs, 3.5se and 4.4bal; the power button (too tiny for me); and the two outputs, 4.4bal and 3.5se. Labels are clear and easy to read, something some desktop gear I have reviewed of late, should take note of.

The back seems absolutely barren compared to the packed functionality of the front. To the bottom right is the battery indicator, with four reddish-orange lights indication approximately 25% each. The last one will blink when charging is needed, or “death” is impending. Centered is the USB-C charging outlet. On each side is a single T6 screw for removing the battery packet. Cayin believes a couple of things about their batteries. For one, sound may deteriorate a bit as charge disseminates. I fully believe what their engineers propose here, I have no reason not to. And second, rechargeable batteries lose their power over time (think of your Smartphone and after about 2-3 years you are lucky to have 82-87% of the intended “full” capacity at 100% charge. So this makes sense, and the batteries can be replaced with a common Li battery as a result. Marcus’s Headfonics review of the C9 goes into a bit of detail regarding this and the choice of using Sony’s Murata VTC6 as an excellent one. He also mentions the battery quality and sound characteristics as well, so check that out (page 1) for more information on battery and the choice (https://headfonics.com/cayin-c9-review/). I was able to get a bit longer than the listed 5.5hrs on the tube timbre. This could be that the unit is fully broken in as well.

I do know that Cayin makes a case for the C9 as well as Miter or Dignis I believe. The Cayin case is $99, but when you spend this much, that does not seem inordinate to me.

Technicals:

To me Cayin has had a penchant for technology for quite some time. Witness their DAP’s and how they continue to fight for a spot with the “big boys” so to speak. As such, innovation comes as a result and this in turn leads to new products. The C9 is no different, but the technology used is not new, simply the implementation. And yes, Cayin has some proprietary material within that goes a long way towards bettering this product.

Using Toshiba’s 2SK209 JFET semiconductors (quad set) discrete and buffered amplification set up, the end result to me provides a typical richness of sound of which Cayin is known. Utilizing both Class-A and Class-AB in such a device draws its own issues, but with the Cayin N6ii, specifically the development of the E01 motherboard has given those engineers the practice needed for the C9. That warmth and rich signature is what I absolutely love about the E01 and the N6ii and do not even miss the balanced connectivity. In fact, that will be my baseline for testing the 3.5se source use here.

The Korg Nutube technology is fairly new (used in the N8), and I personally read about it a couple of years ago (I think). I am a bonafide tube-sound lover and when I heard Cayin was doing this, I became just a bit more intrigued. As Wiljen stated in his excellent C9 review (https://audiofool.reviews/2021/05/21/cayin-c9/) , the Nutube 6P1 “tubes” act similar to the actual 12ax7 tubes used in many tube amplifiers. Utilizing a Direct Heated Triode (DHT) and utilizing neon fluorescence for display purposes (licensed under Noritake Itron of Japan for Korg), you get that tube glow, and sound but with a miniscule amount of power compared to “real” tubes, which aids in battery life. As Will states, consider this a modern vacuum tube with improved power handling and decreased microphonics. Heat dissipation is also better since it is an enclosed circuit. But the unit does get fairly warm, so this would be another good for the foot idea-help dissipate heat. A new take on an old technology, even if I do enjoy “pinging” a good tube amp. I am also in the boat of loving a good tube-like sound, so knowing this beforehand may help to understand how I feel about what Cayin has done here.

Sound:

Summary: I will unabashedly state that over my two weeks, I used the C9 for all manners of testing from the economical IEM’s to a comparison with a similarly priced desktop DAC/Amp. From the first listen, I was taken. Using the Shanling M6 Pro (sacrilege!!!!) most of the time during the early moments for its 4.4bal connection, I was treated to a thoroughly envisioning time of full-bodied richness and warmth. Mind you not Legend X warmth, but that richness pervaded all comers. I would label this as a bit dark of signature, but not hindering if that makes sense. I have probably put close to 75 hours on the unit as a result. Mostly on Nutube and Class-A as my preferred signatory response.

This will be broken into four sections giving reference to all options available tuning-wise. You should find a preference as a result. I will note that mine differed from the two excellent reviews referenced above, which bodes well for those looking. While we three have similar tastes, coming to different conclusions about what the LIKED best is a good thing. Each will be treated separately.

Solid-State/Class-A:

Running pure solid state gives a detailed vibrancy to the signature even with what Cayin calls the “low efficient” mode. A bit harder to push the Legend X than the Nutube, and to me a bit thinner of sound. That vibrant signature comes across as extremely clean but with a bit less energetic sound. This is not meant for reference tuning, but a more laid-back signatory. I found this to be good with uplifting songs such as Los Lonely Boys Heaven. But if energy is needed, a switch of tone was called for. With a fairly liquid treble note, and (to me) mids-push, this choice would be excellent for vocal presentations, or possibly string music. This is of course countered by the Class-A’s warmer signature.


Solid-State/Class-B:

If you want more energy and intensity, then this probably has the most of the four. Los Lonely Boys comes across like you are dead center of two excellent concert monitors listening live. An aggressive tone is the result, with more push of the bass down low, and sparkle up top. The pairing with a warmer, richer IEM or headphone would benefit from this set up and easily adds vitality to the sound. While this has less warmth (leaning towards cold), do not think of this as analytical but rather purity. Coming out as the cleanest of signatures through the Legend X says that it can take a dark, warmer, rich IEM and tame it a bit. But not in a bad way. This is also the closest to the E01 motherboard in punchiness, which seems a bit odd to me as I love the iteration in the N6ii, but less so here. Not that this is bad mind you, just a bit different. If vibrancy and a sparkling personality is your flavor, then this would be the choice of the four, to me.


Nutube/Class-A:

It should make sense that this is my favored signature here for it provides the listener (me) with the closest iteration of a true tube sound. The laidback nature of Class-A coupled with the tubelike sound of the Nutube provides me with a sound very similar to my iFi Pro set up. A certain sweetness permeates my cranial matter as I enjoy this. You get less bass response, but that is all right, for the mids sound sumptuous in response. This is like playing with your fine tube amp through floor speakers when no one else is home. Euphoria saturates you to the cellular level. One could consider the treble response as polite, but it isn’t. I would call it as softer response around the edges. That edginess is gone and replaced by a melodic flowing of note. As another reviewer mentions, this is tailor-made for those types of voice similar to crooners, such as Harry Connick Jr or Frank. Sumptuous.


Nutube/Class-AB:

Adding vibrancy to a tube sound may seem like blasphemy or sacrilegious, but here it is not. For that added vibrancy of the AB you get more (and better) bass response, with the mids pushed more forward than even Solid-State/AB to me. The softening of the treble edge still remains, but the Class-AB tries to accommodate this by providing an excellent platform for the rest to shine upon. Another reviewer (both posted here) states that this combination provides most likely the most detail and euphony. This is an energetic tube-like sound, which could very well be the best of both solid state and tube sound. The density of tube sound comes back with the Class-AB, which was lost a bit in the Class-A. This actually presents a dichotomy to me as I prefer the lush rich, warmth of tube sound the most, except here where I favor the Nutube/Class-A combination.

Source:

Using the Shanling M6 Pro (Turbo DAC, which is both Class A and AB; it’s a Shanling thing) for its 4.4bal connectivity, I could happily sell all other wares, except for my workout set up and be very, very happy. Tidal through the duo sounds sublime and full. Yes, I know Tidal “Master” has replaced MQA, but I like the bit of added richness Tidal provides to the signature. Both the Legend X and LCD3 shine on this set up and this makes me happy.

Using the Cayin N6ii with the E01 motherboard may seem a bit redundant, but for the four options on the C9. Utilizing the 3.5se connectivity (but both balanced and unbalanced headphone/IEM’s) I found the pairing to be quite complementary. The excellent rich tonality of the N6ii worked effortlessly with the vibrancy to richness of tone emanating from the C9. This allowed me to tailor each song as needed or each artist.

The C9 showed its mettle across some pretty fine DAP’s and could easily hook into a desktop set up as well.


Comparison:

Cayin C9 ($2000) v iFi Black Label ($599):

One would think this is a completely unfair comparison due to the price. Those people would be only partially correct. The BL provides massive amounts of power (but uncontrolled sometimes) for the price and includes iFi signatories such as Bass Boost and 3D+. this was the first quality headphone amp I purchased and for a reason. I could tailor to specific signatures using the settings listed above and the IEM-match switch, which accommodated various impedance IEM’s. A transportable amp, which came ahead of many others, the BL is a marvel of technology and can back it up beyond the gobs of abundant power. Good sound can be tailored using the Bass Boost and 3D+ yes, but the overall signature to me belies that richness, which pervades most iFi products. I fell for it upon review, and shortly purchased one after.

But as good as the BL is, you are limited by IEM connectivity, with no balanced option. That said, you have more connectivity options source-wise than the C9, moving it nicely into the desktop realm. There are more than enough positives to make the case for the BL, even sound-wise, but the C9 is simply superb, with on the fly (easier to use) options to tailor that sound quality, on a frame, which is more accommodating to usage. You decide, both are fabulous.

Finale:

At some point you must decide a level at which you should stop. What that level is, will be completely up to you. But I challenge you to add up all you have spent on audio goods in the portable demesne (those who are new are excused, and immune so far…). Tally every DAP, every DAC, every amp you have purchased over the years. My guess is that you have spent significantly more than the price of the C9 (I know I am guilty as all get out) or you are fast approaching that level. Now, I do not fault, in fact I applaud those who are satisfied with a more economical outlook in our hobby and are completely happy. In fact, I would be a bit (quite a bit) jealous of your self-control and appreciate that satisfying outlook. You will go far in life and much left over for you to thrive upon in your older years.

But for those who have spent more, much, much more; you may just be a target for the C9 (and others, please do not take this as a slight to anyone; it isn’t). For you see sometimes a device comes along that allows you to reach that level of satiation and you are content; much the way those who value economy over price (again applauded). I reached that level in IEM and DAP with significantly different purchases. I have heard “better” of each, but those better ones do not fit my tastes preferences of said purchases. The C9 is one of those devices that comes along and knocks you silly with a reorientation of what you feel is the appropriate level. A reorganizing of your cranial matter into semi-competent thought processes of needs tied to satisfaction. You hear it. You cannot believe something such as this can sound so delicious. You cannot understand why at this price you are re-evaluating what you have in order to quantify the C9.

It is indeed expensive. More than most would ever spend, and for good reason. This is a larger purchase. But if you tally all of your purchases in this segment and realize you have spent more, this may just be the device, which realigns those purchases into sales. Sales, which can fund the one device, which will satisfy the needs across those previous purchases. Even if you squirrel away a purchase of lower price for your everyday needs, the C9 could still very well replace and replace with exemplary sound qualities the other equipment sold and you will be satisfied. You will be thoroughly satisfied I say, and it will be all right. It will be all right for your journey has taken to this point where you can sell, without regret, those lower priced items (which may be quite fine and good) with the C9, and call it a net gain, or net even in the end.

Do I wax poetically too much about the C9? Maybe, but it is of such versatility that this can be justified. With the ability to run four sound options and two types of hook ups, you have pretty much all the versatility you need. It does lack those added connectivity options, but that will be all right for the sound signature is so good you will be fine. Just fine.

I again thank Cayin and Andy Kong for the inclusion in the C9 tour. It is a fabulous unit, which while expensive can function across many levels. On to the next lucky person it goes.