Review: Leben CS-600 Integrated Amp

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by Jonny Park on May 03 '08

Leben CS600.JPG

Leben CS-600 Tube Integrated Amplifier




Every once in a blue moon, in music as in life, we are sometimes afforded a rare encounter with something which makes us wonder and re-evaluate our prior experiences and standards. I’m a born skeptic; I don’t believe in ultimatums. There is no “best-ever” in my sliding scale. Proust or Tolstoy? Beethoven or Bach? The Clipse or Mobb Deep? If there are clear answers, life wouldn’t be worth living. Yet there are those rude encounters in life and art which so shatter all our expectations, that they raise a new vanguard. In hi-fi, at least for me, Leben CS-600 ($4995 MSRP; US distributor – Tone Imports) constitutes as that rude encounter.




Being a push-pull tube integrated amplifier of limited wattage (28 wpc on EL34 driver tubes/32 wpc on 6L6GC), one might expect it to belong comfortably in the Smooth category in the Sonic Circle. Yet, its surprising dynamic power and clarity combined with the liquid fluidity of tubes place the Leben CS-600 in the Vivid family.


This is one of the instances that the Leben CS-600 subverts your preconceived notions about tube amplifiers. Just as you expect the Smooth tube sound – warm and opulent in decay (i.e. Shindo) – you instead hear tremendous slam, neutrality and transparency. Sure it has the traditional liquid fluidity to the sound, too, but pop in Valery Gergiev’s full-blooded live account of Stravinsky’s Rite of Spring, and the murder in the music – the violently ugly percussion explosions, the terrifying trombone glissandos – confronts you with force and slam that defy reason.


In “Pyramid Song” from Radiohead’s Amnesiac, one of their most poorly recorded albums, many fine integrated amplifiers failed to rein in disparate elements of the song, make the music cohere. But the Leben did so in spades. Thom Yorke’s calm but plaintive voice rose to its falsetto effortlessly, and the hiccupping, off-kilter beats keeping their ungainly 16/8 meter, as well as the ghostly wail of Jonny Greenwood’s Ondes Martenot came together like a miracle, made me lose my sense of time.


Listen to how the Leben replicates the long psychedelic guitar jam in the song “Baltimore” from Stephen Malkmus’s new Real Emotional Trash. The sly thrumming of Janet Weiss’s drums in “Hopscotch Willie” coming alive from the same album. Classical, jazz, hip-hop, electronica, rock… it didn’t matter. Any music I played through the Leben CS-600 sounded like its most transparently honest version. It made me follow every melodic line, harmonic progressions, with a kind of fanaticism that felt obsessive and pleasurable at the same time. No added sugar. No preservatives. I heard music at its most luminous capacity. 


Leben CS-600 also has a reputation for having an excellent headphone-out, so I decided to test it extensively, using AKG-701 and Sennheiser PXC-450 headphones. The Leben relays the music from the output transformers straight to the headphone-out. I am far from being a headphone aficionado, but I do a fair amount of listening through my headphones, the AKG-701s especially, as I live in a small apartment in Manhattan. Through the Leben, the AKGs’ bass response gained a sonorous depth; the pronounced treble response of the AKGs, which frequently led to listening fatigue, lost none of its clarity while gaining a warmer resonance which eliminated fatigue. As mentioned, I am not a headphone-intensive listener, but in my experience of auditioning headphone amps with my AKG-701s, no other head amp had made the AKGs sound so full and warm as the Leben did, and “full” and “warm” are not the usual adjectives associated with the AKG-701s. Sennheiser PXC-450 noise-canceling cans, which I use primarily for outdoor listening in subways, sounded remarkably close to Sennheiser HD 650 through the Leben, running passive with noise-canceling turned off: pleasantly bloomy mid-bass and crystalline but slightly rolled-off highs. With both headphones, the soundstage became deeper in dimension through the Leben. Strictly viewed as a headphone amp, Leben’s performance is off the charts. To get the most out of the Leben as a headphone amp, I strongly recommend open cans over the closed ones.

Leben CS600 Front.JPG




To be safe, a certain amount of care is needed in matching Leben CS-600 with speakers. One should look for speakers that are reasonably sensitive, that perform nearly level at the stated impedance. That said, the Leben is known to handle difficult speakers with relative ease, despite specs and common knowledge. If there are speakers that you are interested in trying with the Leben but are afraid that they might be difficult loads, I suggest that you try matching them up while auditioning. You might be pleasantly surprised. (Most of the tube amplifier purchasers place undue importance on high sensitivity while shopping for speakers. For example, the Leben effortlessly commands Harbeth Super HL5s, which are rated at a mere 86 db.)


In my tests, Leben CS-600 matched best with Vivid and Smooth speakers. It is fabulous with Vivid Harbeth speakers, and in fact, with most of the BBC monitors; I know a couple of audiophiles who use Spendor SP 2/3e and Rogers LS 3/5 with their Leben CS-600. They swear by this synergy. Although I did not have an opportunity to do so, I suspect that Vivid ProAc speakers would be a great match with Leben, as well.


The Leben also plays beautifully with Smooth speakers; it played up all of Devore Super 8’s musical strengths while adding a welcome muscularity to their Smooth sound. The Smooth Zu Druid Mk IV speakers are an enticing prospect for Leben CS-600; with the Zu’s 101 db sensitivity, the Leben will likely sound like a power-beast. Whether or not you like your amps to sound like power-beasts is strictly your order of preference.


But beware of matching the Leben with Precise and Intense speakers, especially ones that are voiced too “audiophile” style. As mentioned, Leben CS-600 is not your typically warm, dark, tube-y amplifier that will temper the elements in Precise/Intense components. It will rather heighten the inherent Precise/Intense qualities, which will make the system sound too edgy or overly brightened.


I’d also recommend staying away from Emotional speakers, as one of the greatest strengths of Leben CS-600 is the transparency it brings to the music. Some of the Emotional speakers sacrifice a bit of fidelity for added warmth and liveliness. This would distort much of Leben’s ability to relay music honestly.


Likewise, in matching front-end components, I’d advise to stay with Vivid and Smooth groups and avoid Precise/Intense/Emotional. As far as cabling is concerned, I recommend cables and interconnects that are just a touch on the warm side of neutral. I’ve personally had great results with Cardas.


Holistically speaking, one should ideally build a system around the CS-600 that is slightly on the warm side of neutral, without losing precision and fidelity. This may prove trickier in practice than in theory. But it’s a tightrope-walk that will pay immense dividends when the system is completely built.

Leben CS600 Back.JPG




One of the few disappointments I’d experienced with Leben CS-600 was a certain brightness I detected in the treble, especially in the brassy passages in orchestral and jazz music. At first, I attributed that slight harshness to the amplifier itself, but it turns out that the brightness was caused by the stock Sovtek 6L6GC driver tubes. I replaced the Sovteks with Winged C 6L6GC tubes, and the brightness disappeared completely, and the sound became lush all the while maintaining its impeccable balance and punch.


The design of Leben CS-600 is ingenious. It is a push-pull design, but the designer Taku Hyodo, who is considered one of the true masters of tube amp designers in Japan, if not in the world, designed the CS-600 so that only a single pair of power tubes is used per channel: the best path to purity is the simplest path.


For the tube-rollers, there are cathode resistor and plate switches which can be toggled in various combinations to allow for a wide array of driver tubes. You can use most of the 6L6 and EL34/6CA7 families of tubes. If you are fine with keeping the top cover off, you can tube-roll with even more variety of tubes, such as KT-88s, 350Bs, etc. (should a wad of cash fall from the sky and land on my head, I would like to try Western Electric 350Bs in Leben CS-600.)


Merely switching out the stock Sovteks with Winged C 6L6GCs or EL34s will make the Leben sound $1K above its price, in my opinion. Then just imagine how the CS-600 responds to the various NOS tubes! With its incredible versatility, you can fine-tune Leben CS-600 to virtually your exact preference. As for me, I prefer using 6L6GC tubes over EL34s. With EL34, the sound is more typically tube-y: very lush in the midrange, bloomy bass, and the treble and the mids presented forward. The music becomes very extroverted with an intoxicating midrange. But it comes at the cost of losing some of the detail and balance of the music (this may not be the case with NOS EL34s like the Mullards). With the kinds of music I listen to, I found 6L6GC tubes more to my liking.




For an integrated amplifier, Leben CS-600 is relatively pricy at $4995, especially because of the weak dollar. It’s obviously impossible to recommend the Leben to a novice audiophile strapped for cash, but for those discriminating listeners who are willing to pursue the best from their music, I can make this recommendation without the slightest hesitation. Those days are long gone when integrated amplifiers were looked upon as a poor-man’s solution to getting into mid-fi, forgoing the route of separates. The market is now rife with no-compromises $10K+ integrated amplifiers which purportedly offer performance commensurate with the separates. In comparison with such models, then, Leben CS-600 is a clear and relative bargain. The music from a system centered by Leben CS-600 will sound truthful, honestly powerful, and beguiling in beauty of tone. It will best and out-perform systems consisting of separates costing many times more.


On a personal note, I remember shopping for audio gear with my father when I was a kid. He would lift each equipment to gauge its heaviness. He told me that generally, heaviness equaled quality. Of course that’s superstitious rubbish, but somehow, his remark had stayed with me all through these years. Lifting up the Leben CS-600, I almost strained my back. I couldn’t believe how heavy it was, and I immediately thought of my father’s pseudo-scientific comments.


Perhaps other users will have a similar experience with the Leben, will be transported to the past. Even before turning on the amp for music, most people will be smitten with its looks: its faceplate in a luxuriously golden matte, highlighted by the gleaming golden knobs, the two thin strips of aqua-blue serving as upper and lower borders of the faceplate. The rosy wood side panels made of real Canadian white ash. The fit and finish of this amplifier is simply not of this era, and hearkens back to the times when style meant something more substantive than “skimpy minimalism.” To the lost times when things were meant and built to last.


Leben CS-600 achieves a flawless harmony of form and function, in which the visual aesthetics perfectly reflects the musical performance. The CS-600 is an integrated amplifier which will not prove easy to replace for an upgrade, and qualifies without reservation as an exit-level component. At least in my system, as I suspect in many others, it will stay put for many years: Leben CS-600 is a classic, today.


Nice review imho - thank you!
Thanks for the kind words, Donald! Glad you enjoyed it.
This dude can write! Nice job mapping your musical tastes in your intro piece, though the phrase "I'm an omnivorous, promiscuous slut..." caused a bit of a shock when juxtaposed so closely to the photo of you with your beautiful young family. Enjoyed the review. Looking forward to future contributions.
Hey, thanks, Russ. Appreciate the good word. I should have a series of reviews on analog gear coming up... And yes, I guess the juxtaposition of the words 'omnivorous slut'& family pic is a bit unfortunate, but hey. Just trying to keep y'all on your toes! =) See you around.
I use the smaller leben CS-300 with Harbeth Compact 7-es2s. It's a phenomenal combination. I wouldn't mind the CS-600, but as the reviewer says about his CS-600, mine will stay put too. I changed the Sovtek tubes for Russian Mullard copies, and though many will frown at Mullard copies, they would be mistaken to do so. The Leben goes much deeper and much more detailed with them and the overall results are superb.
Good to know about the Russian Mullards, Ron. I've been told the same, too, to stay away from the replicas of the Mullards, but you never know until you hear them: one of the only truisms in audio. I have Winged C EL-34s in there now. They're okay. Great midrange & bass performance, but I hear the tube glare. I'd like to try the Siemens or the Mullards, but I think I'm going to try some KT-77s. From all reports, JJ KT-77s sound great, but some earlier incarnations had reliability issues. Those issues are purportedly dealt with, but I think I'm going to wait for the Genalex reissues of KT-77s. Thanks for reading, Ron.