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Power Amplifier
Leben CS-660P

Price: 25 900 zł

Polish distributor: Nautilus Hi-End

ul. Malborska 24, 30-646 Kraków
tel./fax: 12 425 51 20/30
tel. kom.: 507 011 858


WWW: Leben

Text: Wojciech Pacuła
Translation: Marek Dyba

Leben Hi-Fi Stereo Company, this is the full name of this manufacturer, has been quite close to my heart for several reasons. Firstly and most importantly because Leben appeared in Poland thanks to … „High Fidelity” – you might remember our review of CS-300 amplifier published in September 2006, in our first „Japanese” edition. Well, if you don't let me encourage you to read it HERE. In fact there was also another amp that had its premiere in Poland also in our Magazine - Tri TRV-300SE, but that's a different story. To get these devices for a review wasn't easy, as Japanese companies were not very „open to the world” and most of them were represented by external companies, usually so called „agents”. But fortunately Leben's Agent was a company named MuSon, and its representative for foreign operations was Mr Yoshi Hontai. His personal involvement and kindness made it possible to send an amplifier without any questions asked, any money deposit to a quite unknown, for most Japanese anyway, country in Eastern Europe. To me to be specific. That was a long shot but what a lucky one – CS-300 was namely a fantastic device working great as both amplifier in my system but also as a headphone amp. The latter feature made it were popular „star” among audiophiles who listen to music mostly via headphones. I couldn't resist and it became a part of my personal system for quite some time. To be exact until it was replaced by … CS-300 X Custom (custom made for me), based on Toshiba's EL84 tubes. I should also mention that for some time there was also another essential part of my system made by Leben – RS-28CX preamplifier. It represented really high value and got replaced only by costing 60 000 pln, custom made for me Ayon Polaris II with DC-Regenerator power supply. Of course I had tried several preamplifiers before but even though some offered a bit better sound but only when costing a lot more – small increase in performance didn't justify much higher price so Leben stayed on and on. Anyway – Leben has quite a significant place in my audiophile's history and it is also a great example of how advanced technology can be brought together with a good design and on top of that there is a Japanese care for details. Another unusual thing about Leben is it's quite low, as for high-end devices (yes, its high-end and not just hi-fi) - pricing.

That's why I couldn't understand why Polish Distributor didn't introduce to our market any other products except for already mentioned CS-300, CS-600 tested by me for „Audio” and preamplifier that was ordered specifically for me. I knew that Mr Hyodo, Leben's owner and chief designer, former Luxman's designer in its „golden age”, was mostly proud of his power amplifiers. But hey – what do I know about sales, distribution and so on (maybe I should know more about it as it could broaden my audiophile's horizons). I boldly demanded some Leben's amp for a review and I must have been annoying enough because Distributor finally delivered power amp CS-660P (also a Polish premiere). This device is based on Mr Hyodo's favorite tubes – beam tetrodes KT66 – made by Classic Components Inc., and four twin-triode 6CS7 in the first-stage amplification – made by General Electric (at least in the piece I received for a review). Power supply is based on semi-conductors but a dumper tube 6CJ3 is applied to delay a supply of high voltage (B-Voltage) to output tubes in order to protect output tubes from damage and to increase tubes life. It is quite big device covered with this wonderful gold-ish (as it is not real gold color) lacquer. Interestingly one can interchange power tubes using one of the following: EL34, 6CA7, KT77, 6L6GB, 6L6GC/5881, 350B, KT90, KT88 and 6550A. Bias and voltages can be adjusted using two switches placed on the back panel plus there are LED indicators in different colors that help you check if the setup is correct – it is described in detail in the manual. But as already mentioned the „prime” tubes that are used in this amp are Mr Hyodo's favorites - KT66. Why? Simply because his favorite amplifier (designed by somebody else) is original Quad II, of course using this type of tubes. So I didn't even try anything and just for the use of this review I listened only with KT66 tubes.

This test had three phases – CS-660P is equipped with input signal choke which allows it to work with :

  • CD players (phonostages), with integrated linear preamplifier or with output voltage control – we open choke fully than,
  • CD players without output level control – we can control volume with Leben's pot,
  • linear preamp – maximum volume set in Leben.
This amp offers 2 x 40 W (at 4/6/8/16 Ω – there is a selector on the back panel), or if used as monaural 1 x 80 W. According to manufacturer this device offers a wide frequency responce from 10 Hz-100 kHz with a low distortion level (0,7 %/10 W).


Recordings used during this review:

  • Assemblage 23, Compass, Accession Records/Irond, 10-1674, CD.
  • Chet Baker, Strollin’, Enja/Warld, TKCW-32191, CD.
  • Chris Connor, I Miss You, Atlantic Records/Warner Music Japan, WPCR-25172, CD.
  • Frank Sinatra, Nice’N’Easy, Capitol Records/Mobile Fidelity, UDCD 790, gold-CD; review HERE.
  • Frank Sinatra, The Voice, Columbia/Speakers Corner, CL 743, Quiex SV-P, 180 g LP.
  • J. S. Bach, The Works of Johann Sebastian Bach. IX. Research Period, Archive Production, ARC 3162, LP.
  • Queen, A Night At The Opera, Parlophone/EMI Records, 66585, 180 g LP.
  • Queen, Innuendo, Parlophone/EMI Records, 67988, 180 g LP.
  • The Montgomery Brothers, Groove Yard, Riverside/JVC, JVCXR-0018-2, XRCD.
  • Tori Amos, Abnormally Attracted To Sin, Universal Republic Records, B0012906-01, 2 x 180 g LP; review HERE.
Japanese recordings are available from CD Japan

First try – connecting to Leben a CD player with output voltage control (output not higher than 2 V rms) wasn't a lost case as I thought it would be (basing on my experience). When using loudspeakers with moderate efficiency (86 dB and above), in middle size room (no more than 25 m2) player's output voltage of 2V worked quite fine with amps input (1,5 V) offering reasonable volume level. But all that means only that such a match works but it still doesn't guaranty satisfactory performance. But I have to tell you that I was really amazed with the performance. As all of you, who read my reviews, know I am a fan of linear preamplifiers – in my opinion it is a necessary element of a system. Apart from very rare cases where the designer created a CD player with preamplifier integrated to match specific power amplifier (like Ancient Audio did) in most cases matching of all system elements is so difficult that using high quality preamplifier is a necessity. So I was truly surprised when I heard Leben with my Lektor Air offering great performance without preamp. Sound was rich, bass well extended, dynamics high – so everything that usually is an input of high quality preamp to the system. I'm pretty sure that when I include my Ayon in the system I will have another perspective but before I do I can tell you that this is a sound I could live with.

If I was to compare Leben's sound to some other I would probably go with McIntosh Mc275 Anniversary Edition, that I once tested (HERE). It just happened that a day before I started to listen to Leben I visited my friend (also member of Cracow's Sonic Society) to listen to his new Dynaudio Sapphire loudspeakers. The main „theme” of this meeting was another ingenious power cable from Acrolink - Mexcel 7N-PC9300. My point is that this friend runs McIntosh Mc275 in his system but version IV. And his system - Dynaudio with McIntosh offered quite similar sound to this of Leben with Harpias. Similarity was mostly about the timbre – rich, bit warm, with slight accent on mid-bass that added the whole presentation some „kick” and created large phantom images. All that Leben presented in a very accurate manner without crossing the line which would imply calling its sound „non-linear”. So even though it was still a „linear” sounding amp but no doubts on a bit warmer side. I checked that using all kinds of music just to make sure I was right. Jazz sounded fabulous. Chet Baker's Strollin’, with fantastic Philippe Catherine's guitar sounded simply amazing. Lots of air, great depth and dynamics. The last feature was also confirmed while listening to some electronic music, like Compass by German dark wave group Assemblage 23. Wow! What a sound! If you listen to bands like Depeche Mode or , Jarre or any other electronic music Leben will deliver a performance you haven't heard before. Dynamics was incredible, rich, extended bass sounded so „juicy” as I heard only from mighty ASR Emitter II. Sound was not perfectly linear. There was slight boost somewhere at the edge of mid- and low-range. Apart from pros I already described there were also side-effects that might not be appreciated by everybody, because it meant deviation from neutrality and it made this amp not totally universal. Some non-musical elements sounded stronger than usually, like pedals of a piano or a „p” in Julie London's vocal on I Miss You So and so on. It sounded great but purist would have said it wasn't quite real, neutral. Treble was a bit … gentle but not because it was laid back but because its attack was a little rounded. In fact it is quite a characteristic feature of most of Japanese product – their approach is to made amps in a way that any music sounds well and not to give a listener a tool for analysis.

Oh my! What a sound! After couple of days of listening to some other system I came back to Leben – it is incredibly involving sound offering full musical satisfaction. It is not a perfect sound but it offers huge amount of emotions and allows you to enjoy the music as only very few other audio devices can. No wonder that Jeff Day, „” editor chose this amp for his system (test HERE), and Sixmoons awarded Leben with their 2008 Annual Award. But I was supposed to write about the sound of Leben + preamp. It was one of the very rare occasions when I had doubts which option would be better – CD with integrated preamp with CS-660P or the „full” system, meaning external preamp included. I am missing an option of system with CD with output voltage control or without it and using a pot in Leben, on purpose.

Not that it doesn't offer a good sound – it does but I think it makes much more sense to drive this power amp with higher sensitivity offered by preamp. It would be even more important if your listening room is bigger than 25 m2. Otherwise bass range could be bit too big and without proper control. But lets go back to the merits – Leben driven directly by Lektor Air, without any external preamplifier delivered more resolution in the sound – more than with Ayon Polaris II and surely more than with Leben CS-28RX. Not that the differences were huge but if one was a fan of great resolution, openness of the sound than I would recommend this setup – Leben + a CD player with output voltage control.

Including a preamp to the setup adds some elements that are hard to resist. First element is a better bass-range control. I think it is a key feature you should focus on when searching for a preamp. Leben's bass is quite punchy, rich and colorful. One of my friends who visited me to listen to Black Stork – a turntable from Lithuania ( combined with CS-660P noticed that although bass-range was very energetic but his impression was that it was bit pumped up, stronger than it should have been. And yeah – he was right – Leben sounds bit „low” because regardless if we listen to not so powerful acoustic bass or very powerful, very extended electronic bass we always get a very strong, deep sound. I'm very sure of that. In my opinion that effects in not so great bass-range differentiation as some other amplifiers offer. There will be plenty of bass in each recording. One necessary comment – in this case lots of bass does not mean boomy or tubby one, also it does not interfere with listening process. When listening we know that there is a little bit more in the low range than in live music and we know that it was designers idea. On the other hand all other amplifiers sound seem to be washed out of emotions and having dry sound when compared to Leben – even my own Luxman M-800A. It seems that a „happy medium” is yet to be found. But for now until somebody finds it, I have to admit that if you look for emotional musical experience – surprisingly Leben is your answer. I guess same choice was made by most of McIntosh Mc275 owners as this device offers sound of similar characteristic. Leben has more resolution and more colorful sound than American competitor, but general sound signature is quite similar. But there are reasons to design this amp to play like that. One of them is that this amp would likely work together with Leben's CS-28RX preamp. This device was a part of my system for a long time and I still appreciate it a lot today. I would describe its sound more as „analytical” than „tube sound”. Now I realize that it was created to work with Leben's amp (McIntosh MC275, Pass amps and so on). Other reason might be loudspeakers it is supposed to work with. It is not a coincident that above mentioned Jeff works in one system with Harbeths (M40.1 to be specific). These are shelf speakers, although quite big ones and such a boost in bass-range is a blessing for them. Same goes for systems with fullrange speakers. I bet that if you use Leben for such loudspeakers you will find the missing element of the puzzle.

I somehow focused on a bass-range but if you listen to Leben yourself you should understand why. Don't get me wrong – bass-range is not separated from the rest of frequency range – Leben's sound is very coherent throughout whole range. And you never get to think that this is a slow sound! There was only one similar case in my experience – my test of Hansen Audio Prince v2 loudspeakers. First impression might suggest bit dark, warm sound at least if you compare it with other amplifiers. But the more you listen to it more you understand it the more you realize that it sounds more like live event. When on Groove Yard by The Montgomery Brothers solo starts it starts seriously, strongly with power and dynamics. Even my Luxman couldn't show it in such an exciting way. And the treble. It is perfectly matched with mid-range – in fact so well that I shouldn't even talk about two separate frequency ranges. When I tried to analyze it anyway I could tell that treble was a little bit warmed up and rounded. The top end is not the best in terms of resolution I've ever heard. Cymbals are vibrant, natural sounding but their highest sounds are slightly laid back but it is obvious that it is done for a reason – that was designer's intention so that this small part of the range didn't „compete” with the rest. It didn't matter if it was Nice’N’Easy by Frank Sinatra from Columbia's vinyl edition of The Voice or the new re-edition of Queen's A Night At The Opera - there always was this element of sound that made it more „civilized”. It is of course a slight deviation from neutrality but in my opinion very thoroughly considered by Leben's designer. No matter which recordings I listen to, they all sounded great with Leben. Top high-end devices like 300B amps - Reimyo PAT-777 and Ancient Audio Silver Grand Mono) present it at the same level of performance but they achieve it not by playing with timbre and attack but thanks to almost perfect resolution and linearity. But they are on quite some different price level. To offer similar performance but with much lower price you need to use some tricks – like Leben did.

This Magazine is called „High fidelity” so I should recommend devices with most neutral performance. But for me this „high fidelity” means not only the sound itself but also some intellectual and emotional content included in music. And Leben fulfills my definition perfectly. Even better than perfectly as it add something that was not really included in the recording and what effects in the fabulous final effect. It might not be the most „linear” power amplifier, with best resolution that I know but like other hi-end and top hi-end devices it fulfills basic assumption of audio equipment: without losing from the sight something we might call an „absolute sound”, they try to fulfill also all other requirements placed for „Hi-Fi” devices, and it goes one step further towards emotional charge that is brought to the music by real instruments. Leben's imaging is excellent but mostly when we listen to what is going on in the front, closely to us. Here the ability of differentiating, precise defining of all elements on the stage is outstanding. But the Japanese power amp can't match best 300B amp when it comes to showing details of „back corners” of the soundstage. This kind of sound suggests that sound is „moved” to our room to be presented here rather than to show acoustics of the room where music was recorded. But … nothing is perfect…


CS-660P is a power amplifier made by Japanese company Leben (full company's name is Leben Hi-Fi Stereo Company). It's a stereo amp offering output of 2 x 40 W, but can be also used as monaural amp offering 80 W. First stage amplification is based on four (two per channel) double triodes 6CS7 by General Electric (NOS). Output in classic ultra-linear setup is modified similarly to QUAD's II, and based on beam tetrodes KT66, working in push-pull configuration in AB class. As already mentioned there is one more tube in the top panel – so called „dumper”, that is applied to delay a supply of high voltage (B-Voltage) to output tubes in order to protect output tubes from damage and to increase tube life. In fact this is not its only „job”, because that could be done by semi-conductor elements, but it also influences the sound – its another vacuum tube in signal's path after all. It looks like the idea behind it was to combine strengths of semi-conductor's rectifier (speed, linearity and so on) with these of rectifiers tube – elimination of lots of noise, and „soft” reaction to sudden voltage spikes. I can't tell exactly how the tube influences the sound but I'm sure it does. Every output tube is accompanied with green LED that indicates proper functioning of a tube. That means also automatic bias adjustment. Behind the tubes there are output transformers – made in house, and behind dumping tube there is power transformer. The latter is a bit noisy but it might depend on your power grid as in my room noise changed depending on time of the day. On the front panel there is a mechanical on/off switch with green LED and a knob of a choke that is connected to device's input. At the back panel you will find a pair of high quality RCA posts made by Canare, that interestingly are mounted in XLR fashion (Leben is using such posts in high priced models), and two pairs of gold-plated speaker posts. There is a switch between posts that allows us to change input impedance depending on which loudspeakers we have (4/6/8/16 Ω). Another switch lets us chose if the amplifier works in stereo mode or in monaural. Another two toggle switches allow us to chose proper setting depending on which tubes we shall use. And last but not least there is also IEC socket.

The inside looks quite simply but that is quite characteristic feature for most hi-end tube amps. Signal goes from remarkable Canare RCAs with shielded wires to the front of the device, to big Alps „Blue Velvet” pot, and then to input triodes. All low signal wires come from Hitachi. There is mostly point-to-point assembly except for few tiny PCBs, but these are used strictly to make soldering easier. Japanese polypropylene capacitors take care about coupling between input and output tubes. Most resistors are also of Japanese made. There are excellent capacitors Nichicon Fine Gold serving cathode current for output tubes. By the way for triodes they use also very nice Elnas. Power supply is based on huge power transformer with several secondary winding. Anode voltage for all tube is rectified in a full-wave bridge, composed of two semiconductor diodes (it is a setup with central transformer's tap), and the voltage goes from it to dumper tube. There are six large capacitors for output tubes and two more for input triodes that help to dump current pulsation. Triodes are served by great Elna's caps including Red Cerafine. It looks like filament current is not rectified. The whole design is ordered, neat – as I said earlier - simple.

Technical data (according to manufacturer):
Tubes: 4 x KT-66, (EL34/6CA7 - option); 4 x 6CS7; 1 x 6CJ3
Output power: (stereo) 40 W x 2 (KT-66) at 1 kHz; (monaural) 80 W x 1 (KT-66) at 1 kHz
Frequency response: 10 Hz – 180 kHz (-3dB)
THD: 0,7% (10 W)
Input sensitivity: 1,5 V at 40 W
Input impedance: 100 kΩ
Output impedance: 4/6/8/16 Ω (selectable)
Power consumption: 230 W
Dimensions: 415 (W) X 480 (H) X 320 (D) mm
Weight: 17 kg

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  • CD player: Ancient Audio Lektor Prime (tested HERE)
  • Phono preamp: RCM Audio Sensor Prelude IC (tested HERE)
  • Preamp: Leben RS-28CX (tested HERE; soon to be changed to Polaris II, tested HERE)
  • Power amp: Luxman M-800A (tested HERE)
  • Integrated amp: Leben CS300 (reviewed HERE)
  • Loudspeakers: Harpia Acoustics Dobermann (tested HERE)
  • headphones: AKG K701, Ultrasone PROLine 2500, Beyerdynamic DT-990 Pro, 600 Ω version (reviewed HERE, HERE, and HERE)
  • interconnects: CD-preamp: Wireworld Gold Eclipse 52 (tested HERE; soon to be changed to Acrolink Mexcel 7N-DA6300, article HERE), preamp-power amp: Velum NF-G SE (tested HERE)
  • speaker cable: Velum LS-G (tested HERE)
  • power cables: Acrolink Mexcel 7N-PC9100 (CD; reviewed HERE) and 2 x Acrolink Mexcel 7N-PC7100 (preamp, power amp (reviewed HERE)
  • power conditioning: Gigawatt PF-2 Filtering Power Strip (reviewed HERE)
  • audio stand Base
  • resonance control: Finite Elemente Ceraball under the CD (article HERE ) Turntables change continuously, as do cartridges. My dream setup: SME 30 with Series V tone-arm and Air Tight PC-1 cartridge (also in the PC-1 Mono version).