⌈ Leben is a small, Japanese company that is treated with great attention in its country of origin. It owes this to its founder and chief designer, Mr. TAKU HYODO. It is mentioned by Japanese magazines among the most important designers of tube amplifiers in this country. The CS600 integrated amplifier was introduced to the market in 2005. Fourteen years later, come the new version called CS600X. ⌋

1992 Triode33 | 3C33 power amplifier • KFH brand
1995 RS-35a | 6L6GC power amplifier
1998 RS-28c | E288CC preamplifier
2001 CS-200 | 6V6GT power amplifier
2002 CS-250 | 6K6GT power amplifier
2003 CS-300 | EL84 integrated amplifier
2004 CS-700 | 6CK4 x 8 power amplifier, limited edition
2005 CS-300X | Mullard EL84 power amplifier
2005 CS-600 | 6L6/EL34 integrated amplifier
2006 CS-300X | Mullard EL84 power amplifier, limited version
2006 CS-300XS | Sovtek EL84 power amplifier
2006 RS-28CX | GE 6CG7 preamplifier
2006 CS-660P | KT66/EL34 power amplifier
2007 CS-200P | 6V6GT power amplifier
2008 RS-30EQ | phonostage
2009 RS-100/RS-100U | linestage
2012 CS-1000P | stereo power amplifier
2013 CS-300F | JAN-6197 integrated amplifier
2019 CS-600X | EL34/6L6 integrated amplifier

EBEN STEREO HI-FI COMPANY has a separate room in my heart, with all the comforts. This is a brand that in twelve years, since I met it, has gained more and more respect and affection in my eyes and confirmed what I instinctively felt when, for the first time, testing their device, the Leben CS300 integrated amplifier, namely that there is magic in it.

This story begins like many other. At the beginning of 2006 I came up with the idea of honoring Japanese companies with a separate edition of "High Fidelity" magazine. I'm an admirer of audio products, CDs and accessories, and in general, the entire culture of this country, so honoring it seemed completely natural to me. Products for such an issue from such brands as: Marantz, Denon, Yamaha, Onkyo, Pioneer, Sony (back then still with the hi-fi and high-end audio department) and other devices from the wide mass market offer, were easily available.

Later, from time to time I still used this availability, but I wanted to find some special products. The first selections were quite obvious - in the no. 29 issue we reviewed, among others: the Accuphase P-3000 power amplifier, the STAX SR-007 electrostatic headphones (Omega II) + SRM-717, the C.E.C. TL51XR CD Player, Furutech E-TP80E power strip and Sumiko Celebration cartridge. Apart from Furutech, these were relatively small specialized companies, so they fit into this concept of special products perfectly.

However, I still missed something even more special, which would emphasize the uniqueness of this issue. Without much hope for a success I wrote to several companies that I knew from - I would like to say "reading", but it wouldn't be completely true - paging through subsequent editions of "Stereo Sound" magazine. In response to my emails I received just one that proved to be effective.

In a very polite manner Mr. Yoshi Hontai answered me saying that he would be happy to help in the preparation of such an issue, and although the magazine was young and completely unknown to him - HF was just over two years old at the time - he would talk to the companies he represented and see what could be done. Mr. Yoshi Hontai runs Muson company that acts as an intermediary between Japanese companies and the rest of the world.

A month later I received a large package in which I found fourproducts: RCA Oyaide PA-02 TR interconnects, Oyaide Tunami Nigo speaker cable and two integrated amplifiers - TRI TRV-300Se and Leben CS300. In the case of Leben and Tri, these were the first official tests of these brands outside Japan, and Oyaide had the first test outside of Asia.

Tests were published in September 2006, soon after all three brands found their distributors, and I asked for a special unit of the CS300 amplifier, dedicated to our magazine. Mr. Taku Hyodo, the owner of the company and its designer, responded to my request with a unique gesture and made a one-of-the-kind of the Class A, 8W power amplifier featuring unique EL84 Toshiba tubes.

This was the first "dedicated" issue in the history of the "High Fidelity" magazine; since 2008, every year we have celebrated Japanese products in May, celebrating at the same time our magazine's anniversaries. Since then I have tested all Leben products, almost all Oyaide and Acrolink ones, I hosted Mr. Ken Ishiguro, owner of Acoustic Revive in Krakow (that's yet another brand from the Muson "stables") and made friends with Yoshi-san first and then with his son Elia-san.

| CS-600

The CS300 was a small, wonderful amplifier that became a benchmark device for other manufacturers. Since its premiere in 2003, it has undergone several changes. First, a special version called CS300X was developed, with a choke in the power section, better tubes, etc., followed by its version with Sovtek output tubes - the CS300X (S); in this version it was known for the next few years.

In 2013, the company presented a new model, which from the outside did not differ from the previous ones, and in the name only one letter was changed - the CS300F. However, the device was modified in a rather serious way inside. Instead of the EL84 power tubes, General Electric JAN-6197 (6CL6) originally designed for use in computers were used.

The "300" family is not, however, the only series of integrated amplifiers from this manufacturer, because since 2005 the CS600 model was also present in company's lineup. In short, one could say that it is a bigger, more power and slightly more functional version of the CS300. The devices looked almost identical and if it were not for differences in dimensions and additional knobs, it would be difficult to distinguish them.

The real difference was hidden inside. The CS600 is an amplifier that allows different types of output tubes to be used. (For some time, while the stock of tubes lasts, the CS600 and CS600X will be offered.) As standard tubes the 6L6GC (5881) beam tetrodes are used, but you can also use popular EL34 pentodes (their American version bears the symbol 6CA7 and it is slightly different). This required a change in the anode voltage and the cathode resistor value - these are changed by switches placed inside the amplifier, and the selection is indicated by LEDs on the front panel.

| CS-600X

Changes in Leben's lineup happen extremely rarely. - the case of the CS-300 is special, due to its extraordinary popularity. All other devices are manufactured for many years, without any upgrades/changes. Information released about the new CS600X was a big surprise. Yoshi-san, who is mainly responsible for them, will tell us about the implemented changes and reasoning behind them.

YOSHI HONTAI
MusonPro | CEO

YOSHI HONTAI during Munich High End Show 2018

The mains reasons to replace CS600 with CS600X, were:

1| It's difficult today to purchase a larger quantity of the 6CS7 tubes, and our stock is limited (we have only 400 pieces for 100 amplifiers).
2| A compatibility of the 6CS7 is not too good.
That is why Leben decided to modify the circuits of the amplifier, based on Mr. Hyodo's suggestions, in such a way that instead of a single 6CS7 we could use two tubes: 12AU7A and 12BH7A. It means that two tubes share a task of a single 6CS7.

The advantages of the CS-600X are as follows:

a) the 12AU7A and 12BH7A tubes are currently manufactured, so there is no problem with availability,
b) since there are also many NOS 12AU7A and 12BH7A tubes on the market, it should be easy to use some of them and to enjoy the sound known from older units (I don't have to add, that the CS-600X accepts a few different output tubes, as specified on attached list),
c) Leben features high quality anti-vibration aluminum feet (same ones as in the CS-1000P).

Archival photo of Leben's transformer, it's a version for external customers.

Let me add, that all transformers and chokes used by Leben are made in-house - this is one of the most important skills of its employees. There was even a plan at the time to sell these transformers to external companies, but we decided that they should stay in the "family."

Functionality | Leben CS600X is a typical Japanese product - it is very traditional in appearance and in design, and has many features that over time other manufacturers got rid of. It's an integrated, unbalanced tube amplifier - and it's a fully tubed one, as the power supply is also based on a tube. There are a lot of knobs on the face-plate, with the largest one being volume control. Next to it there is an input selector, another know that operates the loop for recording and one more to switch channels. On the other side there are two more – one for balance between channels and another for the "Bass Boost" system, which boosts low tones by 3 or 5 dB.

With three switches below, you can activate the input from an external preamplifier (or from a source with its own volume control), mute the signal ("Mute") and change the output from speaker ones to the headphone. This is an important switch, because one of the most important advantages of Leben amplifiers is their excellent headphone output, which is placed here unambiguously, because under the volume control knob. And there is also a power switch with its own orange diode and two pairs of LEDs, in red and green, indicating positions of the switches, that allow user to set the anode voltage and the cathode resistor for the output tubes.

The input sockets - gold-plated RCA - are placed in two rows on the back panel. Next to them, there are two more pairs - an input to the power amplifier stage and a recording output with a fixed level. There are only two pairs of loudspeaker outputs, which is not common for tube amplifiers. With such an arrangement, we have to carefully choose loudspeakers and their impedance determined by the amplifier's manufacturer. Some solution is the possibility of re-soldering the output transformer taps, or simply using two outputs - usually for 4 and 8 Ω impedance.

The Leben CS600X is much more convenient for use and more versatile. Although it has a single pair of loudspeaker outputs per channel, a switch is located between them to select the transformer taps - we can choose up to four different loads: 4, 6, 8 and 16 ohms! This last value will be useful, for example, with fantastic, 16 Ω Falcon LS3/5a.

Tubes | As already mentioned, one of the hallmarks of this amplifier is that we can use various output tubes in it. The default version comes with low power tubes, dual triodes in the preamplifier - 12AU7A and 12BH7A - and EL34 output pentodes. The tested unit featured the ECC802S and 12BH7-A made by the Slovakian JJ Electronics in the preamplifier section. These are ultra-low noise versions - they operate here in the SRPP (Serial Regulated Pull-Push) system.

The output stage featured the EL34EH model from the Russian company Electro-Harmonix. 6CA7 / EL34 tubes are one of the best-known audio pentodes, invented by Philips, characterized by high input sensitivity and high output power; historically, they were used in most Marantz tube amplifiers. In this configuration, the amplifier's delivers 2 x 28 W (at 1 kHz), which achieves an anode voltage of 410 V with a 460 Ω cathode resistor.

However, one can order the CS600X with 6L6WGC / 5881 tubes. The 6L6 is a 30 Watt beam tetrode, originally designed in a metal housing, not a glass one. Over time, it was upgraded to 6L6GA, 6L6GB and 6L6GC models. This tube was designed for use in professional devices, for example guitar amplifiers and power amplifiers.

For the first time in home audio there were used in the first Marantz amplifier, the 50W-1 model from 1949. Another known device from this manufacturer using 6L6 was the MC-240 amplifier from 1955. With these tubes, the CS600X achieves a power output of 2 x 32 W, at 450 V anode voltage and with 680 Ω cathode resistor. But there are even more options – using appropriate combinations of anode voltage and cathode resistor values the tested amplifier allows us also to use the following types of tubes: KT66, KT77, KT88, 6550A, 6L6GA / GB / WGB, and even 350B.

And there is one more tube - the 6CM3 / 6DN3. It operates in a power supply section with a choke. This is not a typical rectifier, although it consists of two diodes. Originally it was developed for horizontal deflection circuits in TV sets. In the technical descriptions from these times, we find the remark that it should not be used as a rectifier, but with time audio engineers have learned how to use it. The CS600X features a NOS 6DN3 tube made by the American company Sylvania.

Appearance and design | Leben amplifiers can not be mistaken for any other brand's. They feature gold fronts with dark green elements. Also knobs are gold. The appearance resembles devices from the 1970s, for example by Luxman. And not without a reason - Mr. Taku Hyodo, its founder and designer, was responsible for the designs and production of the most famous tube amplifiers at Luxman.

After its acquisition by the Alpine concern and the transfer of production to the northern part of Japan, in 1979 (he was then 30 years old) he founded his own company Kouri Denki Co. (KDC), producing PCBs and electronic components. Since he was also a collector and tubes enthusiast, he started to build amplifiers for cafes, clubs, etc., under the KHF brand. In 1992, with the Triode 33 amplifier featuring 3C33 tubes, he returned to the audio industry for good. The Leben company was established a year later.

Anyway, the CS600X looks great, combining a golden front and back with a massive dark gold top plate and wooden side walls made of Canadian ash wood. It also weights a lot - 23 kg. There is no remote control, digital-to-analog converter, Bluetooth receiver, WiFi connection, or streamer, this is a "clean" amplifier. It features only linear inputs. The circuit was assembled using the point-to-point method, without printed circuit boards, using high quality, selected components.

CS600X is a beautiful example of Japanese engineering.

| HOW WE LISTENED TO IT

The Leben CS600X amplifier was tested in the "High Fidelity's" reference system, placed on the shelf of the Finite Elemente Pagode Edition rack. The source was Ayon Audio CD-35 HE Edition SACD player, and the speakers were Harbeth M40.1. The signal from the player to the amplifier was sent via Crystal Cable Absolute Dream interconnects (silver with an addition of gold) and Acoustic Revive RCA-1.0 Absolute (silver-plated copper). The signal to the speakers was sent using the Western Electric WE310A NOS cable. The Oyaide Tunami GPX V2 The Ultimate chord was used to power the amplifier.

The amplifier was compared to a system, consisting of the Ayon Audio Spheris III preamplifier and the Soulution 710 power amplifier, as well as the modified version of the Leben CS300X (S) amplifier. The sound of headphone output was checked using HiFiMAN HE-1000 V2 (magnetostatic) and Sennheiser HD800 and AKG K701 (dynamic) headphones. The reference was the Ayon Audio HE-3 headphone amplifier.

Without knowing the technical details of the new Leben amplifier, and only listening to it, one could easily confuse its performance with a large, solid-state power amplifier, at least in terms of power and sound volume, as well as bass extension. This is a large device, heavy, so it should deliver this type of performance, but it is also a tube-based one. And the tubes in terms of output can't really win against transistors.

Leben, however, seems not to recognize such technological limitations. It presented, for example, the Fusion. Best Sound Selection - a new release of the "Stereo Sound" magazine, a selection made by its editor, Mr. Yoshiro Obara - in an incredibly powerful way. There was pretended extension or volume of the sound. There WAS a powerful bass and THERE WAS a real volume.

Fusion is a quite specific musical form, also in terms of the strategies used during recordings. In short - it's a soft, quite compressed sound, but using an analog compression, it is mainly obtained by a strong saturation of the tape, up to +6 and even +9 dB. There is no particular resolution and selectivity, but there is a pulse, rock, softness and harmonies. Leben beautifully presented all these elements, highlighted them. Because it offers a similar performance, which made it "sympathize" with the recordings in question.

It's an amplifier with a big, soft, thick sound. So you can say that it sounds "warm". However, you should listen to some recording with lots of information in the upper part of the band - it's about information, not about brightening - let it be Go Right, one of the best-sounding albums from the "Polish Jazz" series (although it was only included in it in 2016, hence it became the track number '0'), and you will hear something that will force you to shrug the suggested "warmth" off. The cymbals from this album sounded beautifully, because they had proper weight, power, but they also with a natural, long decay. Leben;s treble delivers a lot of information in a powerful and unambiguous way.

So we can say that it is an amplifier sounds in an open way. And it does. The device does not mask anything, does not push it deeper into the stage, tries to be faithful. It is the type of openness that seems to say: "I know will tell you, but I will do it in my own way". After all it is a tube amplifier and one with an excellent EL34 tubes application. What I am talking about, i.e. an open but also warm and resolving and vibrant and rounded sound, is a set of feature that I've heard on this level with these tubes only once before, with the Kondo Overture II. It's a about utilizing all EL34's advantages while overcoming its limitations.

Because although the bass is soft, it is also surprisingly well controlled and extended. I have already mentioned the Fusion. Best Sound Selection album and that's were the bass pulse was heard the best, ultimately it is a music genre that is based on it. But two other albums impressed me even more: Aquavoice's Silence and Also Sprach Zarathustra by Richard Strauss conducted by Herbert von Karajan. Both of them showed a very characteristic feature of this Leben: it builds a large volume of sound, he does not shy away from mass, from slam. This is not a muddy sound that some associate with EL34 tubes, but an agile, energetic, powerful one.

So how is it different from the reference system, that is from the monster, which is the Soulution 710 power amplifier? Generally speaking - not how one would expect it to. There is both, momentum and power, and dynamics, and richness. But we also known that Leben's output is many times lower, it is also much cheaper. This can be heard in the way of sound formation, including bass. It has the form of a drop, with a mass in attack, which smoothly, but irrevocably, flattens in the direction of sustain and decay.

The point is that more expensive and more powerful amplifiers, whether my reference system, or Kondo OnGaku, or other, high-end devices, offer a better balance, i.e. they more accurately present the body of sound, they are more resolving. Leben greatly differentiates recordings, because I had no problem to point out the differences between the various releases of Wes Montgomery and Wynton Kelly Trio's Smokin 'At The Half Note, (the first US edition, "Verve Master Edition" and SACD by Analogue Production).

But there is something else – best integrated amplifiers integrated in this price range, but solid-state ones, say Accuphase and Luxman, have a slightly better shaped sound structure. They better select events and organize them, even though their sound is not as refined and smooth as with Leben. But when it comes to bass, besides a slightly, but only slightly, better control in the lowest range, these solid-state devices are not able to outperform Leben. Wow!

| Headphones

One of the basic advantages of the CS300 amplifier, apart from its performance, design, make and finish, was the excellent sound quality of the headphone output. The CS600X outperformed any version of the CS300, even the one I had, and by a large margin. The high output translates into an excellent control of headphones. The HE-1000 v2 from HiFiMAN, or magnetostatic headphones, are not particularly demanding on paper. Experience, however, tells me something else, that the more power, the higher quality power (that is, related to current efficiency), the better they sound.

And so is the case with the tested Leben. It drove the HiFiMANs just perfectly. The slightly soft, forgiving character of the device, combined with the open, clean top end and high dynamics allowed the headphones to sound in a way they never had before, and allowed to me to lay down enjoying the sound without questioning if the performance could be further improved.

The amplifier offers a wide soundstage and large volume of sound. A bit sweet, but also resolving. And the bass ... You see, all tone corrections are banned in audio. Eliminating them from the signal's path was a good idea, because most of such circuits were really bad. Simplifying the signal's path translated into a clearer sound, and after some time also into a better resolution.

Those who designed such circuits correctly, however, were quite right to keep using them. I mean such brands as Accuphase, Luxman, Leben - although the latter uses only bass correction, and only in two steps. Listening to the latest Accuphase devices with headphones I used tonal corrections on regular bases, because it simply improved sound quality. It is the same with Leben – almost all the time I used the +3 dB setting of the "Bass Boost". I don't mean that without Bass boost the sound was bad, not at all! It wasn't also too light or dry. It's just that once used it seemed like a natural choice.

Using this setting I got a low, dense sound – similar to the one delivered by my Harbeth M40.1 speakers. I could additionally change the color and emotional temperature by adjusting impedance of the load. The principle was that the lower the impedance, the lower and warmer the sound.

Such a sound character encourages us to keep listening to the music for a long, long time without any fatigue, without irritation. It allowed me to listened to all six albums from the "Polish Jazz" series prepared for a review to be published in the same issue of the "High Fidelity" as the Leben. I did it with pleasure. I was particularly impressed by two albums: Janusz Zabiegliński and His Swingtet's under the same title (vol. 9 1967) and Laboratory's Quasimodo (vol. 58, 1979), each of them for a different reason.

The Zabiegliński's album is available for the first time in the stereo version and it offers an outstanding stereo. This is now my second, after Go Right, favorite album of this series. Leben presented its lightness and gravity, pulse and sound chiseling at the same time. On the other hand, with Quasimodo it fantastically conveyed what Jacek Gawłowski managed to do with this record, while mastering it. The annoying compression disappeared and the leader's bass was low, rich and deep.

It was the type of sound I like and value and which is - in my opinion, but I will not pretend otherwise - the only right one. Saturation, emotions, beautiful imaging, all this meant that I wanted "more". And even my Ayon HA-3 was not able to captivate me so much. The Austrian headphone amplifier offered a cleaner, more direct, but also lighter sound and it required a more careful headphones selection.

Leben is also completely different in that that it plays at its maximum with any headphones. Or in other words: it allows any headphones to be at their best. Each and every headphones model that I have sounded well, addictive with it. I could easily hear their "own" sound, but it was complemented by Leben's charm.

And so – the AKG K701 presented their excellent midrange, closed top and quite shallow bass. After using 3 or even 5 dB of “Bass boost”, their sound filled in and perfectly balanced with the high tones; I have never heard such a good treble from these headphones before! Sennheiser's HD800 also played mainly in the midrange region, but they showed a much wider range of sound and at the same time a perfect stereo presentation (I mean as for headphones, of course). They did not need bass boost to do that. The HiFiMAN HE-6, probably the most difficult ones to drive, found a lifelong partner in the CS600X. Bass, perfect treble, much cleaner than Sennheiser's, deep, massive bass, beautiful midrange – they never sounded so good before.

| Preamp In

The CS600X features an input described as "Preamp In", which the manual describes as intended for an external preamplifier. These type of input allows usage of a higher class external preamplifier or use the volume control applied in the signal source - a digital player or a phono preamplifier. Since the Ayon Audio CD-35 HF Edition SACD player features a volume control, I did try out this option as well.

The first surprise: the Leben potentiometer also works when Preamp in is used. Almost always, such inputs bypass the entire preamp section, along with the attenuator, but not in this case. But it is also typical solution for Leben, because they equip even power amplifiers with attenuator in their inputs. One uses it to adjust output voltage of the preamplifier to the sensitivity of the output stage. That is still a unique solution for an integrated amplifier.

The second surprise: the device without the preamplifier loses its charm, as if its preamplifier was the heart of the whole device. The sound flattens and looses some richness. The bass is slightly better articulated, has slightly better selectivity, but its mass and density disappear. To be honest, I did not like what I heard, so I quickly returned to the classic layout, with the CS600X operating as an integrated amplifier.

| SUMMARY

It just so happened that within a short time I listened to two great reasonably priced devices - last month it was the Mytek Brooklyn Bridge streamer, and now it's the Leben CS600X. I have not heard such good audio products in a long time. Leben charms with beautiful timbre - this is just a given with Japanese amplifiers - but Leben also offers great dynamics, great bass and spacing, that is elements that are not commonly associated with the EL34 tubes.

This is an extremely functional device, because it is also a high-end headphone amplifier and one can used various output tubes in it. The only thing missing is a remote control. Everything else is great! That is why I have to award it with the RED Fingerprint and give it my fullhearted recommendation. ■

Technical specifications (according to manufacturer)

Tubes:
EL34EH Electro-Harmonix
ECC802S, 12BH7-A JJ Electronics
6DN3 Sylvania (NOS)

Output (@ 1 kHz):
tubes EL34 – 2 x 28 W
tubes 6L6 – 2 x 32W

Frequency range: 10 Hz – 100 kHz (-0.1 dB)
Input sensitivity: 900 mV (20 W)
Impedance loading – loudspeakers: 4/6/8/16 Ω (selectable)
Loading impedance – headphones: 300 Ω
Power consumption: 195 W
Dimensions: 450 x 360 x 142 mm
Weight: 23 kg