{"id":42744,"date":"2026-03-21T13:35:14","date_gmt":"2026-03-21T11:35:14","guid":{"rendered":"https:\/\/www.hifi-advice.com\/blog\/?p=42744"},"modified":"2026-03-29T17:34:58","modified_gmt":"2026-03-29T15:34:58","slug":"kora-csa-2120-square-tube-pure-class-a-power-amplifier","status":"publish","type":"post","link":"https:\/\/www.hifi-advice.com\/blog\/amplifier-reviews\/integrated-amplifier-reviews\/kora-csa-2120-square-tube-pure-class-a-power-amplifier\/","title":{"rendered":"Kora CSA 2120 Square Tube pure Class A Power Amplifier"},"content":{"rendered":"

Review samples supplied by Dimex<\/a>
\nBenelux retail price including VAT: \u20ac 28.199<\/h4>\n

Kora Class A<\/h3>\n

Like the entire Kora range, Kora Class A audio amplifiers are powered by SquareTube, a tube\/transistor design that provides the unique Kora sound. This is not a traditional tube gain stage combined with a transistor power section, but a fully hybrid system that simultaneously uses vacuum tubes and transistors. In essence, the tubes provide the signal voltage (the actual music signal) while the transistors provide the current (the power).<\/p>\n

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Whereas Kora’s more modest amplifiers, such as the TB 140<\/a>, are Class A\/B designs, the big Class-A amplifiers combine SquareTube with pure Class A transistor power from a highly filtered linear power supply. The output stage is designed to act as a \u201ccurrent source,\u201d like the anode of a power tube, and it operates in pure Class A. This means that the tubes and transistors always operate in their linear zone. As a result, the infamous crossover distortion is pushed back to the moment the amplifier clips. In other words, it is entirely eliminated in practice.<\/p>\n

In a Class A current source, the output-stage components operate in the middle of their specifications. In other words, the two supply voltages are fixed, and with modulation, it is the current through the transistors that varies\u00a0around the quiescent current. When the signal \u201crises\u201d, the transistors that \u2018push\u2019 will increase their current, and conversely, those that \u201cpull\u201d will reduce theirs by the same amount. It is the difference that is sent to the speakers.<\/p>\n

But on average, the amplifier always passes the quiescent current. And so, the resulting power is converted into heat. The power sent to the speaker is subtracted from the power dissipated without a signal. In addition to an unusual effect (the amplifier cools down when asked to deliver a lot of power), under normal circumstances and for low-volume listening, there is no need for a \u201chigh\u201d quiescent current.<\/p>\n

In practice, therefore, Class A Kora amplifiers operate in two modes: nominal current, which corresponds to the device’s maximum power, and a more economical mode in which the current is reduced by half. Selection between these two currents can be done manually or automatically. The \u201cauto\u201d mode allows the amplifier to operate at a reduced current, but with an automatic switch to high current mode if the signal requires it, for example, fortissimo. The transitions are inaudible.<\/p>\n

Operating in pure Class A has another advantage: because the signal comes from 60 output transistors, the power stage is insensitive to current-feedback phenomena, whether imposed by the speaker’s crossovers or by the drivers. The amplifier offers exceptional stability with complex loads, even if they are highly capacitive.<\/p>\n

To transfer the audio signal from the SquareTube (voltage) section to the power (current) section, Kora has created a pure-analog voltage-to-current converter without any semiconductors, consisting solely of precision resistors, and ensuring no phase shift.<\/p>\n

Class A Range<\/h3>\n

The Kora Class-A amplifiers are available in four models that look identical from the front panel but differ in depth, weight, and internal configurations. Essentially, you can choose between different power ratings and mono- or stereo configuration. The CSA 270 is a stereo power amp offering 2x 70 Watts; the CSA 1150 is a mono power amp offering 1x 150 Watts; the CSA 2120 (reviewed here) is a stereo power amp offering 2x 120 Watts; and the CSA 1200 is a mono power amp offering 1x 200 Watts.<\/p>\n

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CSA 2120<\/h3>\n

The CSA 2120 is a 2-channel stereo power amplifier delivering 2x 120 Watts. It is housed in a large, very sturdy wooden flight case, which just about still fits in an average European car. The case features lockable wheels, so that it can be easily moved around.<\/p>\n

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Freed from its flight case, this is still a seriously large amplifier. I mean, look at this beast!<\/p>\n

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The amplifier can be controlled manually or automatically for certain aspects of its operation. For instance, the amplifier can be set to automatically switch on when a signal is present at the input and switch off when the input is silent. With automatic current control (conceptually similar to Krell’s Plateau Bias), the amplifier switches to high or low current as needed, avoiding unnecessary heat and power consumption. If desired, the current mode can also be set to always low or always high. In standby, the amp consumes less than 15 Watts, and when idling, it consumes 280 Watts.<\/p>\n

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The front panel has two physical elements: a display and a button. The display features several screens that display the amplifier’s status. Standby status, heating status, a welcome message, operating status, a goodbye message, and shutdown status. If desired, the screen can also be turned off.<\/p>\n

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Around the back, there are RCA and XLR inputs, independent variable-gain potentiometers for Left and Right, and switches for Phase, Input, Auto-Power, and Current settings.<\/p>\n

Next: Review Context and Listening<\/em><\/p>\n

<\/p>\n

Review Context<\/h3>\n

The Kora CSA 2120 was listened to in the <\/span>main system<\/a>, with the <\/span>CH Precision L1<\/a> preamplifier, <\/span>CH Precision A1.5<\/a> power amp, and recently refoiled Apogee Duetta Signature speakers. <\/span>Digital sources are the Antipodes Oladra<\/a> and Grimm MU1<\/a> music servers. All interlinks are Driade Flow Link Reference 808<\/a>, and the speaker cables are Driade Flow Reference 808<\/a>. All components are powered by the PS Audio P20<\/a> PowerPlant, except for the Kora amp (due to its massive power supply) and, for a fair comparison, the CH A1.5 amp. As extra speaker candidates, I also listened to the Driade Premium Model 9<\/a> monitors and MartinLogan ElectroMotion ESLs.<\/p>\n

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The Kora CSA 2120 will be listened to on two different platforms: the Artesania Organic Line Modular Floor Platform<\/a>, and the Artesania Aire<\/a>.<\/p>\n

Listening<\/h3>\n

I will listen to the Kora CSA 2120 using three different speakers. I’ll start with the easy-to-drive Driade Premium Model 9, then move to the hybrid electrostatic Martin Logan ElectroMotion ESL, and finish with the recently refoiled Apogee Duetta Signature magnetostatic ribbon speakers.<\/p>\n

Because of its massive power supply and unusual hybrid design, I fully expected the amp to produce something like an audible click or pop from the speakers when powered on. But there was noting of the sort. This amplifier is utterly silent! After a reassuring mechanical click from the power relay, the amplifier emits absolutely nothing. Zilch. Not only is it fully silent from the speakers, but its enclosure is mechanically silent as well. Despite its massive transformers, there is not even the faintest trace of hum. This may seem trivial, but mechanical silence is by no means guaranteed with any component that has one or more large transformers, especially not with big power amplifiers.<\/p>\n

For my initial impressions, I will use the amplifier with the recommended Automatic Current control setting. In this mode, the amplifier is set to lower current use and will only switch to high when the volume level requires it. I will investigate the audibility of using High Current later, in the Apogee section.<\/p>\n

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With Driade monitors<\/h3>\n

Using an amplifier as powerful as the Kora CSA 2120 for the small\u00a0Driade Premium Model 9<\/a> monitor speakers seems like complete overkill. At 28.000 euros, the amp costs six times as much as these speakers, making it an even less obvious pairing. But, boy, does this combo sound incredible! The Kora proverbially grabs the speakers by the scruff of the neck and bends them to its will. I was astonished at the level of bass solidity and robustness coming from these small Driades, combined with utter tightness and grip,\u00a0 vivid expression, fast transient response, and off-the-scale dynamics, topped off <\/span>with superb timbral realism.<\/span><\/p>\n

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The Kora really plays to the Driades’ strengths and is especially skilled at conveying purity and quick transients, which works extremely well with rhythm-driven music. Particularly percussion, piano, and jazz, come across as very realistic. In this respect, it reminds me of the classic “fast and punchy” Naim amplifiers. Although I have heard the Driades perform better in resolution, refinement, and treble air when powered by the CH Precision A1.5, the Kora’s robustness, energy, and natural tonality draw the attention away from these areas. The overwhelming sensation is the raw energy of the performance being conveyed with captivating coherence and realism.<\/p>\n

My plan was to move on to the next speaker pair the same day, but the unlikely setup with these small monitors produced such a captivating rendition that I kept listening to them all afternoon and postponed the speaker change to the next day.<\/p>\n

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With Martin Logan electrostats<\/h3>\n

After my positively surprising first experience, I decided to try the MartinLogan ElectroMotion ESLs with this beast of an amp as well. Like the Driade monitors, these Logans are entry-level products for their respective brands and categories, but here too, the Kora made it work fantastically! Kora describes the Class A amplifier as capable of driving virtually any speaker, even capacitive loads (such as electrostatics) or those with a difficult crossover. Well, it clearly shows! Again, the bass was articulate, upbeat, and very well-controlled compared to how I have heard these speakers perform with other amplifiers thus far. This wasn’t just my opinion; a guest who owned the same speakers also remarked on how clean and controlled the bass was, compared to what he was used to from his own EM ESLs.<\/p>\n

There is no ambivalence or reticence: the Kora simply is the boss of these speakers! The combination sounds confident and focused, and although the amplifier is always in control, it avoids sounding lean, desaturated, or analytical.<\/p>\n

By now, it has also become evident that the big Kora Class A amplifier stays true to the neutral Kora-DNA as I got to know it reviewing the Kora TB140<\/a><\/span>. Like the TB140, the CSA 2120 is not a lush or romantic amplifier, and there is no rose-tinting whatsoever. It sure can sound sweet or warm, but only if the recording is registered as such; it does not add these qualities itself. Even though it is technically a tube amplifier, it does not have the stereotypical tube sound. Not even a little bit. The amplifier simply does not exhibit the typical euphonic colorations or bass thickness associated with typical tube designs. If you want a thick, golden, euphonic sound, this is not the amplifier for you. Simultaneously, while the Kora is much closer to an excellent transistor design than to a typical tube amp, it still infuses the music with an undeniable je-ne-sais-quoi. It just does not have the juiciness or golden glow that one might expect from a Class A- or tube amp. However, this beast offers realism<\/em> like no other.<\/p>\n

For all their airy refinement, Martin Logans (and most other electrostatic speakers) have a slightly synthetic timbre, or maybe I should say they sound less organic or natural than typical dynamic speakers. This quality can be exacerbated or reduced depending on the amplifier used. In this case, while my usual CH A1.5 power amp offers greater refinement and airier treble, which I really love, it does nothing to hide the electrostatic’s flaws. The Kora, by contrast, enhances the speakers’ tonality and timbre, resulting in a more naturally fleshed-out, musically more satisfying sound than with the A1.5, all while avoiding introducing any coloration. It sounds contradictory and is hard to explain, but easy to hear.<\/p>\n

While comparing the Kora directly to the CH A1.5 with these speakers, I noticed that the Kora’s bass is not just tight and controlled, but also substantial. It’s beefier, in fact, than that of the CH. If I had been told this was a full-transistor amp rather than a hybrid tube design, I would have believed it immediately.<\/p>\n

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With Apogee Duetta magnetostats<\/h3>\n

As mentioned, the CSA 2120 is not the first Kora amplifier that I have reviewed. The first one was the surprisingly affordable TB140<\/a>, which I found impressively capable, particularly given its price. In fact, I almost bought it for my then-secondary setup. The only aspect I found not entirely ideal about this amp was that it could sound a little lean and slightly gray, and I wondered whether this sonic signature was a consequence of its price point. This planted the seeds of my curiosity about Kora’s larger models, particularly their power amplifiers. As a result, my <\/span>curiosity was already piqued even before Dennis of Dimex asked me whether I wanted to review the CSA 2120.<\/p>\n

Hearing the big Kora Class A CSA 2120 with the Duettas now, I am instantly transported back to those TB140 listening sessions. Sure, the CSA 2120\u00a0<\/span>shares the same design philosophy but improves upon it and neatly addresses my only concerns. <\/span> Just like the TB140, the big Class A model avoids the typical euphonic tube sound and instead delivers a tight, crisp, controlled, and direct sound. <\/span>However, the CSA 2120 has a much more robust,<\/span> full-blooded sound than the TB140. It’s still very, very neutral and certainly not warm or voluptuous, but it is fully matured<\/span>. Nevertheless, e<\/span><\/span>ven with such revealing speakers as the Duettas, there is no leanness or lack of body. <\/span><\/span>This amp puts meat on the bones but adds no coloration while providing an earthy, realistic rendition of whatever you play.<\/span><\/span><\/p>\n

As with the other two speakers, <\/span>there is a commanding level of control with magnificent bass tightness and articulation, but with the very open and direct Apogee Duettas, this can become a little too much. <\/span>This is where the switchable Current Level comes in!<\/p>\n

Next: Automatic Current versus High Current and Conclusion<\/em><\/p>\n

<\/p>\n

Automatic Current versus High Current<\/h3>\n

So far, I have been listening to the Kora using the recommended Automatic Current control setting. Now was the time to investigate the audibility manual Current setting.<\/p>\n

While using the Kora in Automatic Current mode with the Apogees, not a complex load but relatively low-sensitivity, I noticed that the Current Indicator flashed from Low to High on high peaks in the music when playing a little louder. This was a tell-tale sign that the speakers required a little more than the amp would deliver in its Low Current mode. But that’s what the Auto mode is for, right? Kora also writes in the manual that the transitions are inaudible, and I can confirm this is the case. However, they do not claim that Low, Auto, and High modes all sound the same. And indeed, they do not!<\/p>\n

When switching from Automatic to High Current, the Kora responds as it always does: in utter silence! There is no click, hum, or pop, just the apparent change of mode. In the sonic presentation, however, the change is far from subtle. In this mode, the sound becomes noticeably more organic, fluid, and free-flowing, while retaining all of its virtues in High Current mode.<\/p>\n

The claim “elevating the entire performance” is so often made in the industry that we’ve all grown weary of it, but the big Kora truly delivers. The High Current Mode is not a case of trading one set of virtues for another. Rather, it’s keeping what’s there and making it better. In a way, the Kora now sounds more like what you expect from a big Class-A amplifier, but the sound remains crisp and tight, with a more natural flow, and increased charm. To be very clear: the uplift in naturalness is achieved without adding coloration or thickness, without reducing dynamic behavior, and without slowing the pacing. If anything, I felt that the amplifier was now more dynamically differentiated!<\/p>\n

High Current for efficient speakers?<\/h3>\n

It seems logical to expect that High Current mode is only required for low-sensitivity speakers. But of course, I had to prove or disprove this suspicion. So, to be certain, I briefly repositioned the easy-to-drive Driades and repeated the test. To my surprise, the increase in fluidity and flow I noted with the Apogees was also evident with these small monitors. Sure, it was less required, but very welcome nevertheless.<\/p>\n

The only downside of using this mode is, of course, the increased power consumption. Pretty soon, the amplifier becomes quite warm, to the point that it can raise the temperature of a small room. Conversely, the Kora becomes only “normally” warm when using Auto Current mode. Sonically, however, it is clear that the Current Modes serve a valid function, and I highly recommend experimenting with this.<\/p>\n

After this little detour, let’s get back to the Apogee Duettas.<\/p>\n

At 28.000 euros, the CSA 2120 is priced firmly in the high-end. When considering that their entry-level amp is “only” 5.700 euros, 28k is a very substantial jump. But as soon as you see this beast in real life, you realize that it buys a huge amount of real estate! Naturally, a bigger amplifier is not necessarily always better than a smaller amplifier; rather, the inverse is usually true. However, this is another area where the CSA 2120 shines, and with any speaker: coherence! Unlike many big power amplifiers with many output transistors, the Kora Class A does not sacrifice coherence for power. When it comes to Kora amplifiers, bigger is definitely better.<\/p>\n

It’s interesting how expectations are sometimes proven entirely wrong. For instance, the Kora hybrid tube amplifier sounds less like a stereotypical tube product than the Halcro Eclipse<\/a>, which is a pure transistor design. Sure, the Halcro is twice as costly as the Kora, but it’s still a good reminder to always keep an open ear! When I purchased the CH A1.5, it was 31.000 euros, close to what the Kora currently costs. But time flies, and I just realized that I wrote that review already back in 2019. Right now, the A1.5 costs 42.000 euros. Nevertheless, given that the CH is my resident reference amplifier, it still makes sense to compare the two.<\/p>\n

The CH A1.5 is a very heavy amplifier, and large by normal standards, but the Kora CSA 2120 makes it look rather small! The CH A1.5 is a full-transistor design, and although it does not sound quite as liquid and free-flowing as the Halcro, it is lusher and more fluid than the Kora. The CH is also more highly resolving, airier, and more refined. On the other hand, to my utter astonishment, the Kora has an even tighter grip on the Apogees, making them sound crisper, more direct, and more robust. It’s crazy, but when it comes to the bass, the Kora has basically Class-D-like control. The Kora’s user guide describes the power stage as insensitive to current feedback phenomena and the amplifier as offering exceptional stability with complex loads, even when highly capacitive, and my tests have triple-confirmed this!<\/p>\n

Although the Kora performs well with the Dueattas, especially in its natural timbre, immediacy, and impressive control of the speaker, I ultimately found this pairing less appealing than the CH A1.5 pairing. This isn’t just a matter of inherent quality or personal taste; it mainly comes down to the voicing of these products. The Kora sounds earthier, fuller, and darker than the CH, which is comparatively airier and more light-footed, while the Duettas themselves are quite voluminous and full-bodied. As always, choosing the right match is just as important as the overall quality of any component.<\/p>\n

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Platforms<\/h3>\n

Of course, it is neither fair nor wise to compare two amplifiers on different platforms. However, whether on the very solid and relatively straightforward Krion-Panzerholz Modular Floor Platform or on the complex steel\/Carbon Fiber rack-in-a-rack Aire Platform (basically a low Exoteryc Rack), the Kora amp sounds solid, robust, and always in control. Nevertheless, the two racks still have a marked influence on the sound.<\/p>\n

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In a nutshell, the Modular Floor Platform further enhances the amplifier’s inherently robust bass and natural, acoustically convincing midrange. The Exoteryc platform, on the other hand, strikes a more light-footed balance, adding fluidity, flow, and treble air. In this case, for my ears and with the Duettas, the Aire platform was definitely a better match.<\/p>\n

Diptyque<\/h3>\n

When the Kora was delivered, \u00a0Distributor Dennis\u00a0<\/span>f<\/span>rom<\/span> Dimex<\/span> told me how amazingly well this amplifier performed with the Diptyque magnetostatic speakers. Of course, a distributor of both brands would say that, wouldn’t they? However, after hearing the DP 140 MkII<\/a> extensively in my system on two separate occasions, I think I am in a good position to predict how they would perform in unison.<\/p>\n

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The Kora CS2120, with its robust and voluminous bass, and its full, natural, and slightly dark tonality, should indeed work highly synergistically with the lean, open, bright, and superbly airy Diptyques. It’s too bad I don’t have these speakers here now to put this to the test, but I’m confident they would pair superbly with the CSA 2120.<\/p>\n

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Conclusion<\/h2>\n

The Kora CSA 2120 SquareTube pure Class A power amplifier has a remarkably unique set of abilities. It maintains a vice-like grip on any speaker I tested, delivering tighter, more robust, and more solid bass than any other amplifier I know, whether tube or transistor.<\/p>\n

Uniquely, this amplifier’s immense control does not come at the expense of a lean, harmonically deprived sound. On the contrary, while the CSA 2120 is certainly not warm or lush, it possesses a full-bodied tonality, with a highly realistic rendering of timbres and textures.<\/p>\n

Although this is a special hybrid of tube and transistor, it remains very neutral and uncolored, and it simply does not exhibit the typical euphonic colorations or bass thickness associated with typical tube designs. Not even a little bit. Instead, this amplifier relays what’s in the recordings without any sugarcoating. If you are looking for a lush, golden, euphonic sound, this is not the amplifier for you.<\/p>\n

However, if you are looking for a muscular yet natural and realistic-sounding amplifier that will drive anything with gusto, whether small monitors, electrostatics, or magnetostatics, the Kora excels with authoritative control, solidity, and impact.<\/p>\n

Associated Equipment<\/a><\/p>\n

External Links<\/h3>\n

Manufacturer: Kora.fr<\/a>
\nDistributor for the Benelux: Dimex.nl<\/a><\/p>\n

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