⌈ The Krakow-based CIRCLE LABS specializes in the design and production of audio amplifiers and preamplifiers. It all started with the A100 integrated, which was replaced by the A200 model sold still today. Later, the line preamplifier P300 and the power amplifier M200 joined the lineup. Interestingly, all amplifiers of this brand, both integrated and power ones, are hybrid designs, and the preamplifier is a solid state through and through. For this test we received the brand’s top set with the preamplifier and two power amplifiers to be used in monaural mode. ⌋

HE REVIEW I AM PLEASED to present to you this time is quite special and for more than one reason. First of all, some time ago I already tested the A200 integrated (and loved it!), as well as a set consisting of the P300 preamplifier and M200 stereo power amplifier. Wojtek, by the way, wrote premiere tests of these devices for you (more → HERE and → HERE. We both rated them very highly. Secondly, I, as a person who has always dreamed about having as many components Made in Poland in my reference system as possible, realizing this goal step by step, after testing the Circle Labs set ... ordered one for myself. Not because these are the best devices of their type in the world, there are some even better ones (but I can’t afford them), but because both are excellent and within my (financial) reach. And Made in Poland!

I have already received my power amplifier - I'm in the process of breaking it in - and I'm still waiting for the preamplifier. I shouldn't brag, but my unit will be a unique, or a custom one, because as a prerequisite for the reviewer's work I need a linestage with both balanced (XLR) and unbalanced (RCA) outputs. That’s what my current preamplifier offers, the AudiaFlight FLS-1 (more → HERE), and its replacement has to do the same. Why? Because sometimes I also review power amplifiers without balanced inputs, and I'd rather not use any adapters. Hence, despite the fact that the P300 is a fully symmetrical design, Messrs. Krzysztof and Krzysztof (Wilczyński and Lichoń) agreed to "spoil" their baby, they’d worked so hard to perfect, and give me what I need.

I know from various sources, mainly foreign ones, that sales of Circle Labs devices are booming. They owe the success to, what Wojtek and I have already pointed out in our reviews. Namely, on the one hand, to the (supposedly) most important thing in this industry, i.e. the sonic performance, on the other hand, to the original, elegant design, and on the third, to the well-thought-through, refined, and comprehensively tested constructions. The latter process includes not only the traditional stages of audio components development, i.e. an idea and its implementation based on measurements and listening sessions but also having the first units circulating among a variety of potential users.

They are sent to both, experienced audiophiles and laymen (no offense intended). The former offer opinions on the sound and some „audiophile” aspects of usage, and the latter ... break or damage the devices in ways that no audiophile would even think of. For the former, the most important thing is top-notch performance. Thanks to the latter, the designer has to come up with solutions to protect Circle Labs devices against potential failures resulting from the lack of experience of some users with this type of products.

Ultimately, customers buy devices that are refined down to the smallest details. Of course, this last aspect, that I mentioned in the previous paragraph, may not have a direct impact on sales. However, it has a significant one on the after-sales service, because it is not needed as frequently as with many other products. This is especially important considering that a large portion of Circle Labs amplifiers and preamplifiers are sold abroad, shipped even to other continents, and the shipping costs are quite significant today. Nevertheless, this is an aspect that is not visible at first glance but translates into the company's reputation as one of those whose devices are highly reliable.

What you can see at first glance though, is the unique design that has been in use since the very first product and continued in each subsequent one. Each Circle Labs component features a thick, glass front decorated with brass elements that visually clamp the front panel to the bottom and top panels. The latter, „clamping” front and top of the chassis, additionally features the on/off switch. All devices offered by this brand are also relatively small compared to many competitors. I mean, their width is rather typical, but they are neither very high nor deep, which will be a pro whenever the available space is limited or when a certain visual discretion is required. The metal, black cabinets are meticulously made and finished, as are the two large, equally nicely made knobs (in the preamplifier and integrated, of course).

▌ P300 ⸜ M200

TURNING THE DEVICES ON REVEALS an elegant, yet discreet backlight. In the preamplifier, in the middle of the front panel, there is a small display showing the current volume level, and the input selector is accompanied by six white LEDs indicating the number of inputs (although the selected input is indicated by a white dot on the knob itself). Both in the preamplifier and in the power amplifiers, there is a discreet, horizontal backlight above the 'bottom brass clamp'.

Each chassis features four elegant, gold feet and looks great, whether in full light or during night listening sessions with the lights off. And I say this as a man who basically dislikes gold color, especially when it comes to audio components. Here it blends perfectly in with the dominant black in a way that is truly pleasing to the eye. It is a good example of discreet elegance.

Now, since both Wojtek and I have already tested sets consisting of the P300 and the M200, there is no point in writing another review of a set differing ‘only’ by the addition of the second M200, is there? Well, this power amplifier working in stereo mode is capable of delivering an output of 150 W per channel at 8 Ω and 300 W at 4 Ω. That's enough power to drive the vast majority of loudspeakers available on the market. But the output isn't everything. Even today, in the 'super-integrated' era, the majority of top systems consist of a line preamplifier and two monoblocks. The total separation of the channels allows you to further improve measurable parameters, due to the reduction of noise and distortion levels, and so on. In other words, it makes sense to offer a preamp + 2 monaural amps as the top-of-the-line set.

That’s what also Circle Labs does, although they have taken a slightly different approach than most competing brands. Instead of developing separately monaural amplifiers, exposing potential owners of stereophonic amplifiers to higher costs if they decide to replace them with monoblocks at some point, the Polish manufacturer designed the M200 from the start in such a way that it could be used also in mono mode. So if you are an owner of the M200, and use it as a stereophonic device, and one day you decide it is time to upgrade the system, all you’ll need to do is to purchase another M200 and plug in the cables connecting them to the preamplifier and speakers in a different way. Due to such a solution, you won’t lose money when selling your stereo amp. I'd say it shows a deeply thoughtful, even if an atypical approach to the customers, one the latter should truly appreciate.

For details of the design of both devices, let me refer you to Wojtek's review, as there is no point in repeating exactly the same information here. Let me only point out that since his review of the P300 and one M200 there have been minor changes applied in both of them. As Mr. Krzysztof Lichoń told me (after I offered him my first impressions from listening to the set that confirmed the goal of the change was achieved), different resistors were used in the preamplifier to achieve a fuller, more weighted sound. In my review of this set, I mentioned that the P300 is one of the most transparent preamplifiers I've ever tested, regardless of the price. For some users, it was a great advantage of this model, but in some systems, it could translate into sound that could seem too „light” or too bright. Let me emphasize - in some (!) systems.

Apparently, I wasn't the only one who felt that way, hence the change introduced by Circle Labs. And you can clearly hear it (i.e. if you listened to the earlier version), hence my first impression. In the power amplifier, on the other hand, on its back panel a small switch was added, which was not there before. It is described as "Gain".

There are three settings to choose from 0, -8, and -3 dB (in this order, for technical reasons). These values correspond to not the depth of the feedback as such, but the gain of the circuit, which decreases the more feedback we apply to it. It is worth realizing, though, that these settings influence both, gain and depth of feedback - the smallest feedback (and most gain) we get at the "0 dB" setting (and I, a fan of zero negative feedback designs, could hear that clearly too).

I’ve mentioned one has to change the way the preamplifier and speakers are connected to two M200 operating as monaural amplifiers. When you take a look at the photo of the back panel of the power amplifier, you will see traditional line inputs, XLR and RCA, and a single XLR socket below. It is the latter that is utilized when using the M200 as a monoblock and it is a symmetrical connector for a reason (more on that in a moment). Below, there are high-quality speaker terminals, separate for the right and left channels. In monophonic mode, the speaker cable from one loudspeaker has to be connected to two "minuses" in one amplifier. Under them, there are markings explaining which of them is a plus and which is a minus in this situation. Connect the second speaker in a similar way to the other amp.

And now, another important thing to remember. In order to use the full potential of each of the bridged amplifiers (that is, for the entire circuit to work, and not just half of each in each device - these are dual mono designs) they have to be fed with a balanced signal. The P300 preamplifier, although a balanced design, does not perform a symmetrization of the signal, so if you run an unbalanced signal to P300’s input, it will convey it to its outputs in the same form, even via XLR output. If that’s the case, the amplifiers operate at the half output (as only half of the circuit is engaged), despite being bridged. In other words, without a balanced source, don’t bother to use two M200s.

▌ SOUND

⸜ HOW WE LISTENED The tested set was delivered to me straight from the Warsaw Audio Video Show 2022, where it was presented with the Dynaudio loudspeakers, my favorite Transrotor turntable, the LaRoccia Reference TMD, and the Accuphase CD Player. Talking to Grzegorz Wyka from Nautilus, the distributor of all these brands, who presented the system at the Show, I reminded him that I didn't really have any balanced source. I did not know at the time that I would return home from AVS with the Lumin T3 (more → HERE), which is a balanced audio files player.

So, instead of just Circle Labs components, Nautilus delivered also OCTAVE PHONO MODULE, featuring the XLR Direct Drive output module. Its advantage is not only the XLR outputs themselves, but also the symmetrization of the output signal. Thanks to this feature, it worked perfectly during the show and then in my system with the Circle Labs set. It was fed with the signal from my J. Sikora Standard Max turntable with the KV12 tonearm and the Air Tight PC-3 cartridge. And so, I had the right, balanced sources at my disposal, both analog and digital, and hence was able to use the full potential of Circle Labs amplifiers.

The set consisting of the Circle Labs P300 line preamplifier and two M200 power amplifiers was tested in an unusual way, because, as I mentioned earlier, I had to use borrowed devices - Lumin T3 for the digital front and Octave Phono Module for the analog one. In both cases, however, they were fed signals from my standard/reference devices, namely:

• DIGITAL FRONT END: NAS with linear power supply, via optical LAN separator to Silent Angel Bonn N8 switch with Forester linear power supply, and David Laboga Digital Sound Wave Sapphire LAN cables,
• ANALOG FRONT END: J. Sikora Standard Max turntable with their KV12 tonearm with Soyaton cabling and Air Tight PC-3 cartridge. The Octave phonostage was additionally supported with Black Box Preamp.

The tested amplification replaced the excellent class A amplifier from Max Magri, i.e. the GrandiNote Shinai in driving GrandiNote MACH4 and Ubiq Audio Model One Duelund Edition loudspeakers (interchangeably). I was also interested in the difference between the sonic performance of one M200 in stereo mode and two of them in mono mode.

WHEN I STARTED LISTENING TO THE CIRCLE LABS SYSTEM I didn't know about the changes introduced in the preamplifier, nor about the additional importance of the gain switch (the one in both amps pointed to 0 dB). Remembering well the earlier listening sessions with the P300 with one M200, the first thing I noticed almost immediately was: clearly more weighted, fuller sound. And then: the bass seemed to extend lower, although this impression was more due to the better weighting of its lower range than the actual, "magical" expansion of the MACH4 speakers’ range. And all this was clear to me already after the first track from Victor Wooten's A Show of Hands 15”, the debut album of the master of the bass guitar, re-released on the 15th anniversary of the original release date. With all this "deepening" of the bass, it did not lose anything from its quickness and tightness, and even gained in terms of differentiation.

Although this is a solo album, just two hands, and four strings, as one of the reviewers called it, the Circle Labs set was able to fill the whole room with the real richness of the sounds of a single bass guitar, creating a convincing, attention-grabbing, or highly interesting musical spectacle. Wooten's performance had a great drive, power, and energy, and then in the next track it sounded delicate, yet still extremely colorful and dynamic, although this time the equally good micro-dynamics played a greater role.

Anticipating events a bit, because this way of covering the listening sessions will probably be clearer for you, let me already tell you, that even with loudspeakers as easy to drive as my GrandiNote, with such a "simple", played on one instrument, music, two bridged M200 offered < b>fuller, more powerful, even more convincing, having an even better drive, sound. And it wasn't bearly noticeable but obvious and clear. And yet earlier (and again later, when I wanted to confirm the observation) when listening to one unit working in stereo mode, nothing was lacking, it was also an excellent presentation.

Interestingly, a set of three Circle Labs devices compared to two presented this "simple" recording also in a more open way, I would even say more spacious, even though, due to the nature of this specific album, there isn’t much space on it. I liked the presentation so much that I followed suit, but this time I used my turntable and Octave Phono Module. I played another solo performances, this time by our Polish masters of their instruments - Marcin (double bass) and Bartłomiej (drums) Oleś from the Alone Together album. Maybe this time I already had some expectations, but I don't think they significantly affected the perception of the presentation. And it was similar - the P300 + 2 x M200 set again offered a fuller, denser, more saturated and weighted, bursting with more energy, and at the same time more open, and airy performance than one M200 amplifier in stereo mode.

Thanks to the drums (cymbals, to be exact) I now had a good insight into the upper part of the band too, and with the tested system it seemed not much, but still, more effortless, and at the same time more resonant and vivid. It seemed to me that the decay and reverb were a bit longer, and thus the whole presentation sounded even more real, and more natural. Certainly, the energy level of the treble was higher, as if each stroke of the drumstick was a little more powerful.

Although this element was not an advantage of the system featuring two M200s, I still have to mention how well the Polish devices rendered the atmosphere of each recording. On this specific Oleś brothers album, as well as on the Spirit of Nadir that I listened to later, it is the very special atmosphere that invites or convinces listeners to get completely immersed in music. The single M200 does it just as convincingly, and let me credit the tube input stage of this hybrid design for that. This is the purpose (in my opinion, obviously, and only one of them) for using tubes in Circle Labs amplifiers (even power ones, which is quite unusual).

I have already mentioned the great low end, and the treble matching it, so far omitting the key part of the range. In this way I did not mean to create the impression that the extremes are the central elements of the performance of the tested set, that they relegate the midrange to a subordinate role. I just meant that it is within their range that one can hear the difference between using one and two power the easiest.

The midrange, just like with the A200 integrated, is always excellent, I mean as long as the recording allows it. I can't help it, but I have to keep pointing out the same features - density, saturation, smoothness, and fluidity of the sound, combined with clarity, openness, and a very good resolution providing a huge amount of information, details, and subtleties, as well as very a good differentiation (within the whole range). And it is probably so due to the fact that two M200s deliver even more information at the micro level in the midrange than one, which gives the pair an advantage (in this part of the band). I’ll risk another assessment - I believe that the tested set is the most neutral sounding among Circle Lab’s lineup, and yet it definitely shares the DNA with it. It is still, first of all, a natural-sounding setup, but just a touch more neutral at the same time.

The advantage of two M200s over one in terms of the micro-dynamics is probably a result of the improvement of at least some parameters, or, as indicated before, reduced level of noise and distortion, which translates into a cleaner sound, and easier, better access to the wealth of the "plankton”, or tiniest pieces of information, that only in their total mass actually make a huge difference. It’s what makes music sound more natural and even more convincing and engaging. I think that these are the features that in the case of this set are superior to the purely audiophile ones, which confirms again the shared DNA with the A200 integrated. The tested components are, in my opinion, unique tools for creating something more than just listening sessions - real musical, immersive, touching experiences. Even two M200s do not make the sound as tangible, and present as top SET amps, but against most of the solid-state competitors, at least those that I know, Circle Labs set wins easily when it comes to three-dimensional aspects of the presentation, and imaging.

With them in the signal’s path (assuming the appropriate character and class of the source one uses) from the loudspeakers, although this is by no means a precise definition, as the sound appears not to come directly from speakers and we rather get a „wall of sound” in front of us, flows the Music (yes, with the capital 'M'), and lively emotions. They flow in a way that makes one forget about the recording/carrier/replay system that actually are there between the music and the listener. All those obstacles that stand between the fan of live music and the performers captured in the recordings almost disappear. Almost, because there will always be a difference between live music and its recording, regardless of how good the recording, and release are or how high quality the playback system is. For me, the whole purpose of being an audiophile and having a top-quality system is to try and minimize this particular difference. The tested system does it really, really well!

Same as my favorite SETs, the P300 + 2 x M200 system perfectly recreated the mood of any given recording. Thanks to this feature, with the right music, the presentation was beautiful and relaxing, but when needed, it burst with energy, it was amazingly lively and dynamic. That's why this system is so versatile and should appeal to lovers of almost any musical genre. I enjoyed equally listening to the vocal performances of Luciano Pavarotti, Janis Joplin, Louis Armstrong, and Eva Cassidy. The Polish set beautifully rendered both the timbre and texture of each voice, but also the characteristic features of both the voice itself and its owner. The momentum, power, and huge scale of Luciano's divine voice, the amazing energy of Janis’, the calmness, strength and hoarseness of Louis’, or the delicacy and melancholy of Eva’s - each one was different, but each sounded great and real. And all this was really not much inferior to the sophistication and this unique, organic feel that sets the best SET amplifiers I know apart from any other designs.

However, when it came to a large orchestra, or rock bands such as Aerosmith or AC/DC, the increased output and excellent speaker control offered by this Circle Labs set, also compared to the single M200, made a difference. The reviewed set was able to create a spectacle whose energy, dynamics, and just the pure fun of listening to it, achieved a very, very high level. Actually, higher than any SET amplifier is able to deliver even with speakers that are so easy to drive.

Apart from my „audiophile patriotism”, I believe that regardless of where and by whom these devices were designed and made, they do offer a truly high-end sound and can easily compete with many, even more expensive products of well-known brands. This does not mean, of course, that the P300 and M200 are the best preamplifier and power amplifiers in the world, but only that they are excellent in every respect, and due to the price, they are highly competitive offering an amazing value.

▌ Summary

I CAN EASILY IMAGINE myself owning and using a high-quality SET amplifier and the tested Circle Labs set in my (private) system. I can also imagine that I listen to the music using either one or the other benefiting from their inherent qualities depending on the albums being played. Such an assumption is easy for me because, I already own M200 and am waiting for my P300. Who knows, maybe in the future, I will order another M200, although for that to happen I would first need to replace my current sources with balanced ones.

Nevertheless, hereby I strongly recommend listening to Circle Labs' top setup to all of you on the market for a new amplification if you expect a high-quality sound and versatility allowing you to play almost any music in a uniquely natural, engaging, smooth and coherent, and at the same time dynamic, energy-saturated way, with great bass and excellent PRAT. The reviewed set will offer you a unique emotional experience, making you feel (almost) like a participant in a live event. To complete this setup, you will also need balanced sources and high-class, but almost any (in terms of design or efficiency) loudspeakers (plus cables, power supply, etc.). I can guarantee you a unique visual (due to the classy, elegant design), sonic and emotional experience.

Will the sound of the P300 + 2 x M200 suit your taste and expectations as great as mine? I don't know, but for sure it will be one of those unique experiences, that is not so easy to come by in audio, especially at this price level, which is quite high on the one hand, but on the other, it is still very far from the top products proposed by many competitors. For me, next to J.Sikora turntables, LampizatOr DACs, GigaWatt power supplies, and products from several other brands, this is another proof of the famous catchphrase: "It is good because it’s Made in Poland!". Congratulations to the Circle Labs team! Great job! ■

▌ Technical specifications (according to the manufacturer)

⸤ P300
Gain: 8 dB
Line inputs: 2 x XLR, 3 x RCA
Line outputs: 2 x XLR
Input impedance: 33 kΩ / RCA, 66 kΩ / XLR
Output impedance: 15 Ω
Frequency range: 2 Hz - 500 kHz (-3 dB)
Dimensions (W x D x H): 430 x 342 x 127 mm
Weight: 10,60 kg

⸤ M200
Frequency range: 2 Hz -1 MHz (-3 dB)
Nominal output:
⸜ stereo 150 W / 8 Ω | 300 W / 4 Ω
⸜ mono 600 W / 8 Ω | 930 W / 4 Ω
Sensitivity: 0.85 V (@ full output)
Gain: 35 dB
Input impedance: 100 kΩ
Dimensions (W x D x H): 430 x 355 x 178 mm
Weight: 20 kg