| PREMIERE |

⌈ CIRCLE LABS is a Krakow-based company founded in 2007. It was founded by KRZYSZTOF WILCZYŃSKI, the designer and originator. It specializes in audio amplification systems, i.e. preamplifiers, power amplifiers and integrated amplifiers. We test its flagship two-box amplification including the P300 preamplifier and the M200 power amplifier. ⌋

IGH FIDELITY” IS THE ONLY POLISH AUDIO MAGAZINE which has been reviewing so many Polish products over so many years. It is no coincidence that one month a year we devote exclusively to components, cables and accessories originating from our homeland. It comes naturally to us, because we feel obliged to promote small, often only starting domestic companies, ones we recognize something unique in, that is worth sharing with a wider audience from around the world. No wonder that we are often "midwives" of debuting manufacturers, and from time to time also witnesses of their success. This is also the case with CIRCE LABS.

There are two people behind this brand - first of all KRZYSZTOF WILCZYŃSKI, responsible for the electrical and mechanical design, and KRZYSZTOF LICHOŃ, industrial designer, responsible for their products’ unique look. The company's media debut took place on September 1st 2020, in the "Polish edition" of our magazine when we presented the A200 integrated amplifier, which also received the BEST PRODUCT 2020 award (more HERE and HERE).

The device surprised us with the top quality of its design, built and sound - the holy trinity, surprisingly rare in high-end. Let’s add to that an excellent art design and we get a complete, finished audio product. No wonder that since then the company found representatives in over a dozen countries around the world, and its devices often work in systems costing many times more than the price of Circle Labs devices would suggest.

Already back then it was clear that the A200 was just a starting point for the brand and that a separates system would be added to the lineup at some point, consisting of a line preamplifier and a power amplifier. It was a natural decision, because this is how audio companies develop. As Krzysztof Wilczyński told me, it seemed that the matter was simple - “all they had to do” (as they thought) was to add more power to the A200’s output stage, develop a preamplifier and it the new system would be ready. But things got complicated when the designer decided to reduce noise and distortion, and not just increase output. It took almost two years, but - as the manufacturer declares - they succeeded.

| A few simple words…

KRZYSZTOF WILCZYŃSKI ⸜ designer
KRZYSZTOF LICHOŃ ⸜ industrial designer

⸜ KRZYSZTOF WILCZYŃSKI, designer (on the right) and KRZYSZTOF LICHOŃ, industrial designer (on the left)

THIS YEAR WAS A BREAKTHROUGH FOR US. We have perfected our designs and opened ourselves to the world. We currently sell our products in Poland, USA, Spain, Portugal, Thailand, Russia, Lithuania and England, we are finishing negotiations with distributors in Hungary, Germany and Australia. There is more and more talk about us abroad, which we are very happy to hear. We'll see what's next ... We don't want to be a big manufacturer, that’s not our goal. We want to stay at a "boutique" manufacturer level where quality is of paramount importance.

We are perfectionists, everything we do must be of the highest possible quality, which causes many problems and creative friction, which we overcome in endless discussions, dozens of projects and prototypes, which most often end up on the shelves anyway. An example of our madness is the ribbon in the bag we pack the devices in and its color. Next we had a problem with choosing the shade of gray. Of course, it does not matter to the listener, but it creates an image suggesting what can be found inside our products. And that is purity, order, perfection, beauty - all elements that only combined translate into the desired sound.

We don't take shortcuts, all we do is based on our ideas, we don't copy or duplicate the layouts or circuits from others. We use our own solutions and "patents". It is makes our job so much harder, because we have to test and rework everything a thousand times. But it's worth it, because this way we have developed unique systems, which translates to great sound. I hope the listeners will appreciate it. After all, we put our heart into it, it’s a must if you want to create something special.

⸜ Input stage of the power amplifier

The creation of the P300 / M200 set was preceded by numerous experiments and auditions in various systems. The works lasted over a year and a half longer than originally assumed. We wanted to offer our products only after they’d been polished to perfection and hence the delays.

For the M200 amplifier, the Polish company POLTRAFO has designed a custom transformer whose parameters and quality certainly deserve a high-end grade and we can confidently say that in at the price level of our amplifiers no one in the world offers better transformers. Same goes for the components we use. Here, too, everything is top shelf.

An interesting fact is that the making of the chassis alone requires participation of 10 subcontractors. e.g. a front made of 15 mm glass is hand sanded, painted, fired and engraved. Each, although perfectly made, is unique. The challenge of our time is to ensure the continuity of production and supplies (while maintaining the same components) in the face of component shortages and companies disappearing as a result of the pandemic. We still manage to achieve that.

We build our products to last for years, as trouble-free as possible and as easy to repair as possible. ♦

▌ P300 & M200

DESCRIPTION OF THE TESTED COMPONENTS, THE P300 AND M200 HAS TO BEGIN with their appearance. I hope that all engineers who think that this is the least important thing in audio will forgive me, but I don't think that. Circle Labs devices are made to the best standard known in the audio world, i.e. in the same way as any luxury products intended for wealthy people are made. It all starts with a well-balanced, classy artistic design, but you can see that every mechanical and electrical detail has been thought out too. As it will turn out later, these devices use many proprietary systemic solutions.

⸜ P300 The P300 is a line preamplifier with five inputs - three unbalanced RCAs and two balanced XLRs. There are two outputs, parallel, but only on XLR sockets - the circuit is fully balanced. It is a classic preamplifier, from which all circuits that might interfere with the audio signal have been eliminated and the signal path has been shortened to a minimum. For a detailed description let me refer you to the Design section, for now let me only say that the signal flows only through a resistor attenuator and a few transistors soldered to the output board.

On the front panel there are two easy-to-use knobs, with nice brass decorative elements placed below them. Brass is also used in the top plate hosting a power switch and in the device’s feet. As I mentioned when reviewing the A200, Krzysztof Lichoń, responsible for the visual design of the devices, from the very beginning wanted to use glass, not acrylic, for the front. Each front panel is handcrafted by true craftsmen, and thus, unique and unrepeatable. He assumed that the amplifiers should look the same in a year and in ten years. The entire chassis is made of aluminum plates.

The preamplifier is controlled with a remote similar to that we know from the A200, possibly identical. It is metal, oblong and features only four buttons - two for volume control, one for "mute" function and one for changing brightness of the display. The volume can be adjusted in 1 dB steps.

⸜ M200 The M200 is a stereo dual mono power amplifier. As it turns out, the symbol of the device is not an indication of its output. The Japanese Accuphase "labels" their devices in a similar way: the preamplifiers have the prefix "P" in front of a number, and the power amplifiers feature either "A" if it is a power amplifier working in class A, or "P" if it works in AB class. The "M" used by Circle Labs is also used by the Japanese manufacturer and stands for monoblocks.

And it just so happens that the M200 can be bridged to run as a mono amplifier. Bridging is actually very easy, because one needs to plug an XLR plug into a separate input and connect a loudspeaker to the designated speaker terminals. While in stereo mode the M200 outputs 150 W at 8 Ω and 300 W at 4 Ω, which is really sufficient (my Soulution 710 amplifier offers the same power). When bridged, the output get as high as 600 W (8 Ω). As Krzysztof Lichoń told me, in fact the amplifier in mono mode offers almost 900 W at 4 Ω ...

The foundation of this device is a powerful power supply with separate toroidal transformers for both channels. They were custom made according to the company's specification of - as we read in the company’s materials - "top-class materials, by the leading company POLTRAFO". Together with the special KEMET capacitors with a total capacity of 200,000 µF, adapted to high-current operation and equipped with screw terminals, we read further, "this power supply provides a power reserve of 850 W".

The amplifier designer says that conceptually the M200 is closest to the SE amp topology (single-ended), while "maintaining high efficiency and output, which results in a unique sound rich with details and with beautiful timbre of SE tube amplifiers combined with the bass control of the best solid-states ". Sanken bipolar transistors work in parallel in the M200 output stages.

An interesting fact is that the tested power amplifier is a hybrid device. We have already got used to the fact that an integrated amplifier can feature a hybrid design, with a tube input stage and a transistor output stage, or a two-box system, with a tube preamplifier and a solid-state power amplifier - just like in the HIGH FIDELITY reference system. It is rare, but years ago, the Canadian company Tenor Audio proposed such a device - it was the amazing 175S power amplifier (test HERE; accessed: 15/11/2021). It is technically different from the Polish device, but the general idea is the same.

The input of the M200 features NOS double triodes by Siemens from the 1960s. The constant polarity of the circuit allows the use of only one tube, one resistor and one silver-gold signal capacitor from the reference series of the German Mundorf per channel. The manufacturer emphasizes that "such a topology made it possible to create the shortest possible signal path, ensuring extremely favorable operating parameters of the whole circuit". This section is powered by a separate copper-shielded EI transformer. The stabilized power supply uses polypropylene capacitors in the last stage of the stabilizer, and electrolytic capacitors are used in front of the stabilizer section.

▌ SOUND

⸤ HOW WE LISTENED The P300 preamplifier and the M200 power amplifier (stereo version) were auditioned in the HIGH FIDELITY system as a whole, that is, a complete separate amplifier. They were compared to a system consisting of the AYON AUDIO SPHERIS III preamplifier and the SOULUTION 710 power amplifier. The HF reference system is connected with an unbalanced cable, but Circle Labs designed its preamplifier to work in a balanced mode, so the P300 and the M200 were connected by the ACOUSTIC REVIVE XLR cable, the ABSOLUTE model.

The P300 was placed on the middle shelf of the Finite Elemente Master Reference Pagode Edition MkII rack, on the Acoustic Revive RAF-48H pneumatic platform, and the power amplifier on the top shelf of the rack, made of carbon fiber. The signal was provided by the SACD AYON AUDIO CD-35 HF EDITION player via an unbalanced (RCA) Crystal Cable Ultimate Dream cable - the player sounds better via RCA outputs. The power amplifier and the loudspeakers were connected with the SILTECH TRIPLE CROWN speaker cable.

Recordings used for the test | a selection

⸜ TOMASZ PAUSZEK, 20 Years Live, Audio Anatomy [AA-011-19-LP], 2 x Master CD-R [niewydana wersja CD] (2017).
⸜ PINK FLOYD, The Dark Side Of The Moon, Harvest SHVL 804, 1E 064 o 05249/Analogue Productions CAPP 81033 SA, SACD/CD (1973/2021).
⸜ MEGADETH, Countdown to Extinction, Capitol/Mobile Fidelity Sound Lab, UDCD 765, gold-CD (1992/2006).
⸜ LARS DANIELSSON & LESZEK MOŻDŻER, Pasodoble, ACT Music ACT 9458-2, CD (2007);
⸜ FRANK SINATRA & COUNT BASIE, It Might As Well Be Swing, Universal Music Japan UICY-94601, „Sinatra Society of Japan, No. 17”, SHM-CD (1964/2010).
⸜ FRANK SINATRA & COUNT BASIE, It Might As Well Be Swing, Reprise Records FS 1012/Stereo Sound Publishing SSVS-018, Stereo Sound Reference Record, SACD/CD (1964/2021).
⸜ FREEDOM TREE, Modern Acoustic World Jazz Rock, MMYH Records MMYHCD003, CD (2021).
⸜ DOMINIC MILLER & NEIL STACEY, New Dawn, Naim naimcd066, CD (2002).

THERE ARE TECHNICAL REASONS FOR DEVELOPING SEPARATES SYSTEMS INSTEAD OF INTEGRATED AMPLIFIERS. The idea is to minimize noise and distortion, reduce crosstalk, and increase output. Of course, it's not that every two-box amplifier is automatically better than the integrated at the same price level, it's not like that. After all, having to develop a preamplifier and a power amplifier, the designer has to think about them differently than about an integrated device in one chassis, which requires experience. In turn, the user has to think about an additional power cable and interconnect, i.e. elements that significantly modify the sound and make the investment more expensive.

On the other hand, it is no coincidence that at the top high end level you will find almost exclusively two-box amplifiers with a separate preamplifier and power amplifier. Even fantastic integrated amps, such as KONDO ONGAKU, ACCUPHASE E-800 |PL|, SOULUTION 511, or Circle Labs A200, can’t change that. You have to accept the fact that the most expensive systems consist of two, three (with monoblocks), and even four or more elements (with additional, external power supplies).

A result is not always the same, i.e. the sound changes differently when we switch from the integrated model to the separates. In the case of the tested brand, the separates system does not sound so impressive at first as the A200. The Circle Labs integrated attracts attention from the very beginning, although in an unobtrusive, non-fatiguing way. The combination of what we see, and we see a relatively small product with large and refined sound, also matters.

The P300 and M200 are already automatically positioned higher, because it is a separates system - more expensive, larger, more mechanically complex than the A200. So there is no "visual" bonus. But also the sound is so different that when listening to the P300 and M200 you do not have the impression of "incompatibility" of what you see and what you hear. The system in question offers a much more sophisticated, more nuanced, and thus less “tangible” sound than the Circle Labs’ integrated.

The thing that both amplifiers of this company share, and which is really not much worse than in the reference system, is the speed of the sound. The dynamics of the tested amplifier is simply excellent, both when it comes to micro-events and larger scale ones. Which I appreciated while listening to the FRANK SINATRA and COUNT BASIE’s It Might As Well Be Swing from 1964, recently released on SACD by the Japanese magazine "Stereo Sound".

| Our albums

⸜ FRANK SINATRA & COUNT BASIE
It Might As Well Be Swing

Reprise Records FS 1012/Stereo Sound Publishing SSVS-018
Stereo Sound Reference Record, SACD/CD (1964/2021)

ON FRANK SINATRA's forty-second album It Might as Well Be Swing, released in 1964, three giants of popular and jazz music of those years met: Sinatra, BILL 'COUNT' BASIE with his band and responsible for the arrangement, QUINCY JONES; for the latter it was the first studio session with Sinatra, while the singer previously worked with Count Basie on the Sinatra-Basie (1962). It Might as Well Be Swing brought one of the singer's greatest hits with the opening song Fly Me to the Moon.

The album was produced by SONNY BURKE (Joseph Francis "Sonny" Burke, 1914–1980). He was one of the best and most sought-after arrangers and producers, who as musician in the 1940s and 1950s collaborated with such celebrities as Tommy Dorsey, Peggy Lee, Bing Crosby, The Andrews Sisters, The Mills Brothers, Ella Fitzgerald, Mel Tormé. As the artistic director of Reprise Records, belonging Warner Bros. Records, he produced several Sinatra's albums.

LOWELL FRANK was responsible for the recording process, and the recording sessions took place in United Recording Studios in Hollywood in early June 1964. The original release included 12" stereo and mono records, as well as a set of five 7" singles. The first digital version on CD, was released in 1986 in the USA. We had to wait for the next one until 2009, when LEE HERSCHBERG remastered the album in the 20-bit technique.

On its basis, two years later in Japan, the Sinatra Society of Japan released this material on the SHM-CD. The SACD version we write about was released in 2021 thanks to the "Stereo Sound" magazine. The remaster was prepared by KOJI 'C-CHAN' SUZUKI, working at Sony Studios in Tokyo (more HERE).


Same as in terms of music, arrangement, etc., also in terms of sound quality, it is a very good album. It is not the best recording of Sinatra's voice, but when it comes to wind instruments, it is a gem. The sound of the is not the same in all tracks and it changes between recordings. For example, the More… song has a higher center of gravity and Sinatra's vocal is "thinner" than in the Fly Me to te Moon. But the whole has a remarkable momentum and dynamics, because the whole band was recorded together, with the channels open. Therefore, while the instruments are assigned to the left or right channel, you can still hear their reflections in the other channel.

The 2009 remaster, released in Japan in 2010 on the SHM-CD, to which I compared the "Stereo Sound" release, is very good. And yet, compared to the SACD version, it doesn't stand a chance. The latter has better saturated colors, there is more information about space, dynamics, room acoustics. Interestingly, the previous remaster, made in the 20-bit technique, has the bass extended more strongly. But it is also a bit too blooming. The SACD version sounds faster and cleaner. On the other hand, Sinatra's vocal is fuller on the new version and you can hear that the bass was slightly cut so that you would not hear any "pops", or stronger "Ps" in the vocal. And these are a part of the recording and this is how they were shown in the latest remaster.

The new version of the It Might as Well Be Swing on the SACD is simply much nicer and musically fuller. There is dynamics and speed, but most of all there is Sinatra's strong and full voice. All of this is well-balanced and internally "lively", while earlier releases seem more sterile. ♦br />
⸜ online.STEREOSOUND.co.jp

THE POLISH AMPLIFIER PLAYED the SINATRA’s album quickly, with a swing - it's Count Basie with his orchestra after all! - but also in a balanced way. The tonal spectrum was wide, I didn't notice any emphasis on any sub-range, except maybe the mid-bass, which is slightly emphasized with Circle Labs, and the lower one, which is not as low as with the reference system. "It is not that low" does not mean, however, that "it is not low" - the M200 will surprise many owners of powerful amps of some reputable brands with the ease with which it will show drums on the Sinatra and Basie album, or a powerful, low electric bass from the new FREEDOM TREE’s Modern Acoustic World Jazz Rock, which is a "live in studio" recording.

The Polish amplifier does not present sound as close as the reference system does. It shows the events a little beyond the line connecting the speakers, in which it differs from the A200. So it will be a system for those who appreciate „breath”, or broader perspective, that is, viewing the whole performance not in the near field, but with a kind of "frames" from the air, surrounding the events on the sides. When we bring the sound closer, these "frames" disappear and the sound fills the entire "picture".

And this is why the Circle Labs separate system sounds in a short listening session in a less impressive, or showy way than the A200, but also why it is more sophisticated. Because it is a system that will perfectly show the internal tension between LARS DANIELSSON and LESZEK MOŻDŻER on the Pasodoble, or the mastery of the DOMINIC MILLER & NEIL STACEY duo on the New Dawn. Both duets were shown in a beautiful way, in a large panorama, but also with the awareness that with only two performers we have to "sit" closer than at a concert of a large ensemble, so they are shown closer to us.

The amplifier coped very well with showing not only the powerful dynamics, as I have already mentioned, but also micro-details, such as fingers travelling the strings on the Rush Hour, or the sudden, dynamic hits of a single key in the Pasodoble. It seems that it will be difficult to find any loudspeakers on the market that would embarrass this amplifier with their low efficiency, or even lower impedance or the associated phase shifts. The M200 will drive them all without a problem.

It is a highly resolving system and there is no doubt about it. It is also a tonally well-balanced system, which is also clear from the very beginning. But it is also a system that shapes the sound in its own way. It shows the events further away from a listener, behind the line connecting the speakers and accentuates the 400 Hz range - as I have already mentioned. At the same time, it is not an amplifier that sounded "tube-like" in the sense that it does not saturate the bodies, but rather shows them from a perspective, for is one of the highly acclaimed qualities of the A200. And the perspective requires showing the whole picture first of all, not its individual components. Despite that, despite the fact that there is no „warming up” or „boosting” of the sound, it is a smooth and fluid presentation.

The amplifier is also absolutely agnostic when it comes to the music played, each of its genres is unique and special to it. It will play with equal commitment swinging Sinatra, jazz rock Freedom Tree Trio, jazz, as well as powerful, hard music, such as the released in 1992, and remastered in 2006 by Mobile Fidelity, MEGADETH’s Countdown to Extinction. It is, incidentally, one of the extremely rare cases of hard rock releases prepared by an audiophile label. I can only think of albums by Faith No More and Nirvana, also released by MoFi, and the debut of Rage Against The Machine from 1999, released by Audio Fidelity, on SACD.

But what I wanted to say is that the amplifier played the Megadeth album in an open way, did not close it in with warmth - this is not a "warm" amplifier. It showed an open midrange, but it did not brighten the cymbals, which were slightly rounded during the mastering prepared by Shawn R. Britton. The Mobile Fidelity Labs mastering system consists mainly of tube devices, prepared, among others, by Tim de Paravicini, who passed away some time ago, which can be heard in sweetening the treble and emphasizing the bass. The Polish amplifier showed it nicely, adding nothing by itself.

Perhaps those who like fleshy and very low bass will have to carefully select proper cables and loudspeakers, or just look for other amp. However, they will probably get it along with some coloration, because the Circle Labs amplifier is absolutely clean and transparent for any recording, which we will not get elsewhere for the money. But, as always, you get something for something else.

▌ SUMMARY

THE TWO-BOX AMPLIFIER, consisting of the P300 linear preamp and the M200 power amplifier, will appeal to you. I say this with full conviction and I mean both its artistic and sonic design. The sound of this amp is clean, it is fast and open. But it is also resolving and this system does not brighten details, does not look for "dust spots" where the sounds of the instruments are important.

It shows events in perspective, without bringing them closer to us. The A200 also did something similar, but the momentum was smaller, and thus the perspective seemed closer. We do not get the saturation and fleshiness known from tube devices, this is not the point here. But we also get everything we need, because the amplifier doesn’t take anything away either - it is just balanced and incredibly reliable in what it does.

The P300 and M200 are beautiful - literally and figuratively - examples of musical sensitivity combined with an engineering ethos, all in a great looking package. This is a real high-end system realizing the trinity of design, workmanship and sound at a very high level.

▌ DESIGN

The CIRCLE AUDIO TWO-BOX AMPLIFIER consists of the P300 line preamplifier and the M200 power amplifier. The preamplifier is a solid-state device, and the power amplifier is a hybrid device, with a tube input and a transistor current section.

The appearance of the devices is brilliant and is defined by glass 15 mm thick fronts with ground edges. In the center you can see a stylized sound wave, and at the top there is a brass decorative element with a standby button. The chassis are made of thick aluminum plates. Their tops have been cut in a pattern reminiscent of the retro style of MANLEY LABORATORIES, and front panels of expensive radios from the 1930s.

Both the preamplifier and the power amplifier stand on three aluminum, brass-colored anodized feet with a rubber inserts - two at the front and one at the back.

▌ P300

⸤ FRONT AND REAR Although the P300 has an outline that is exactly the same as the M200, it is lower than the latter. On its front panel there is a two-element white LED display - its brightness can be adjusted using the remote control in a few convenient steps. On the sides there is an input selector knob and volume control know; white LEDs are placed around the former. The main power switch is placed on the rear panel, but - as I said - on the brass element at the top, there is a "standby" switch.

The back also looks very good. There are three pairs of high quality RCA sockets from the American company CMC from the Super Cu series, two pairs of gold-plated XLR inputs and two pairs of the same outputs; these come from Neutrik. There are no RCA outputs, it is worth remembering.

⸤ INSIDE Similar to the A200 I tested, the P300 looks very simple, but - as I said back then - the best devices hide a complex idea and hundreds of hours of "subtraction". As Mr. Krzysztof said then, initially he multiplied the circuits, correcting everything he could, until he reached 100 (!) transistors. Then he began to simplify everything. Ultimately, outputs and inputs received separate PCBs with relays, in which the input signal is selected.

The attenuator section is similar to the one I saw in the A200 and it is based on a relay-switched SHUNT resistor attenuator. The designer of Circle Labs, instead of reinventing the wheel from scratch, opted for a ready-made Khozmo circuit with relay-switched SMD resistors. The layout is however modified by Circle Labs.

After attenuation, the signal goes to the preamplifier PCB - in the A200 it was the input section of the output stage, here it is a transistor circuit with eight transistors per channel - it is a fully balanced circuit. These are the latest JFET and BTJ transistors in the proprietary Circle Amp topology. As Krzysztof Lichoń told me, "the idea was to build a preamplifier with the shortest possible signal path, so the whole path is "glued" to the rear panel, with the least possible number of gain stages and the wiring kept to a minimum”. The output sockets are soldered in. The signal from the input runs to the attenuator, and then straight to the output.

It is worth paying attention to good passive components, including Elna Silmic electrolytic capacitors, as well as an excellent volume control encoder. It is almost always a small, inexpensive element, so the user turns the knob without feeling that he is interacting with a sophisticated product. Here it is different - the encoder in the P300 has a solid, aluminum housing and an element that makes user feel its inertia.

The power supply is built around two medium-sized Hahn LL type transformers, one per channel. The voltage stabilization circuit is very interesting. It is a cascade, discrete circuit (without integrated circuits) with input and output transistors, using LED arrays. I asked the designers about it and they told me that they were looking for components with a noise lower even than the Zener diode and it turned out that the best is a circuit with many classic LEDs. In order not to expand the PCBs excessively, matrices were used for this, usually working as "dot matrix" displays.

▌ M200

⸜⸤ FRONT AND REAR The front of the amplifier is large, but not boring at all. This is due to the sound wave already mentioned when describing the preamplifier, but also a white bar indicating that the power is on. On the back there are two pairs of WBT loudspeaker sockets from the nextGen series, RCA line inputs from CNC and XLR from Neutrik, as well as one input for connecting the amplifier in a "bridge" mode - the M200 can then work as a monophonic power amplifier offering a much higher output.

⸤ INSIDE Writing about the A200, I suggested that the tubes used there work in a preamplifier circuit. This turns out to be not entirely true, because the tube board - not the same, but similar - that we saw there, was placed at the input of the M200 power amplifier. The tube circuit used in both, the A200 and M200 is fully autonomous from the power stage. It is necessary because the Circle Power output circuit has a low voltage gain (approx. x3 which would give a sensitivity of approx. 20 Vp-p).

The designer says, that in this case it falls somewhat outside the traditional definition of a preamplifier and proposes that this stage be called a "preamplifier" when referring to the A200 or "voltage stage" - in the case of the M200. It includes very interesting, rarely seen tubes - a special version of the ECC88 by EGB (Siemens), the ECC8100, designed to work in cascade circuits, with a neutralizing grid, etc. These are constant bias tubes, with the bias provided by the batteries placed nearby. The coupling with the rest of the system is handled by polypropylene, silver-gold oil capacitors from the Mundorf, from the Supreme series. Output stages are bolted to aluminum plates, to which also the heat sinks are bolted. They use four JFET transistors in the control section and two pairs of bipolar transistors working in a parallel push-pull circuit, namely the Sanken (2SA1294 + 2SC3263). As you can see, both the number and type of transistors are different from those used in the A200.

However, it is the power supply that occupies the most space inside the chassis. It turns out that the amplifier is a fully dual mono design, with separate power transformers for each of the channels. These are huge, toroidal transformers of the Polish company Poltrafo, 400 W each. They are supported by eight, very large filtering capacitors from Kemet, with a total capacity of 200,000 μF.

The preamplifier and amplifier circuits look extremely solid, nice, clean and simply very professional. ■

Dane techniczne (wg producenta)

⸤ 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 (-3dB)

⸤ 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 | 900 W / 4 Ω