Leben CS-600 power amp

After giving me for a test period the Air Tight ATM-1 power amplifier, Canyon Audio gave me the Leben CS-600 integrated amplifier for a comparison. I was mainly interested in the power stage, therefore I was more tempted by the Leben CS-630 power amplifier, but Canyon can't borrow me his “still in box” CS-630 unit, while the integrated version had already done its break-in period and had also the “pre in” switch to use it as a power stage.

The Leben CS-600 is a Japanese fine art-work, probably made by one of the Luxman designers. Its 22.5 kg express the weight of all the good stuff which are inside and in particular of the transformers and choke parts (all labelled by “Leben”). The main voltage if filtered by a huge choke, placed between the main transformer (on the right) and the output transformers (on the left). Differently from the Air Tight the rectification is not done with tubes, but diodes. The 6CJ3 tube on the left is used only as “main voltage damper”, to preserve the life of the precious tubes.

The basic scheme is a Williamson push-pull. The preamplifier stage and phase splitters are based on four NOS Sylvania 6CS7, while the output stage is based on the 6L6 (or KT88, KT66) tube for an output of 32 W, but can be easily configured to use the EL34 (or KT77) for about 28 W, using two internal switches. The switches change the cathode resistors and the plate voltage. This unit came with four Sovtek 5881/6L6, made in Russia, and Canyon told me not to “play” with other tubes, sigh!

The CS-600 has a lot of “controls”, including the output transformers taps optimized for loudspeakers with 4, 6, 8 and 16 Ohm. For my AZ Adagio I have used the 6 Ohm tap. It also has a “bass boost” control, for linear response or +3 or +6dB of increase on the lowest 100 Hz. Since this control is implemented in the feedback loop, also the total gain slightly increases. To conclude this short description, the Leben CS-600 is larger than my CJ MV55, even if the main output transformers are quite similar, but the output transformers of my MV55 are smaller (not so on the CJ MV60, which uses the “Premier line” transformers) and my CJ does not have such a big choke on the main voltage filter. This Leben integrated amp offers also a headphone output, which experts claim that is very well sounding, but I have not tested it.

Since I was interested in comparing different power stages, I have used it connecting the pre-input RCA plugs with the output of my CJ Premier preamp and have set the black knob on the left to “pre in”. Since the first impression, this Leben appears to be a “modern” amp, meaning that it has a very high resolution and extension in the high frequencies. Differently from the Air Tight, this time the bass response was much “tighter” and so the tonal equilibrium was more balanced than with the ATM-1. But, sincerely speaking, I was missing the Air Tight midrange, a little forward but really “magic”. The following days, I could listen as the performances of this amp were all good, but... they were not so exciting as its fame was pretending and also as its level of construction seems to confirm (see pictures below).

Based only on the experience made with my CJ preamp (maybe there was an impedance mismatch?), this amp is a good amp, but nothing more. I think that for about 5000 E you can buy a better power amp stage. Period.

Then it come the visit of my friend Znort. I know that he was expecting something very good, because a friend of him (let call him “Nick”) told him that it was one of the best amp he have tried. On the other end, Znort confirmed my “not too much exciting” judgement. Then I decided to give to this amp his last chance: I turned off my CJ pre and connected my phono and CD player outputs to the CS-600, using it as an integrated amp. Immediately the CS-600 became “alive”. It was much better!

The resolution of the finest details was even higher, the bass was even more defined, the soundstage become deeper (but not larger) and, what impressed me more, the dynamic was much more involving, giving that feeling of “life music”, which before was missing. I then auditioned the CS-600 as integrated amp for another week and the sound seems to improve day after day. It has no problem with big orchestra like the Muti Rite of Spring, MFSL-1-519, where it does not loose its control or balance (I think that this very good dynamic has something to do with the big filter choke...) It has no problem with camera or solo music (in particular for the string instruments like lute, harp, guitar...), where its high resolution let you “see” the instrument.

The only “against” which I can do to it is a sort of small veil in the midrange, which I was able to feel in particular with the human voices and which negates to a very well sounding performance the status of really true and exciting music. Let say it in this way: the problem that I'm trying to describe is similar to that noted when I was listening it as power stage, but now you can feel it at a much lower level than before. Nick told to my friend Znort that this problem, but also a bass response a little too “fat”, is completely due to the Sovtek 6L6 tubes. He have tried many different output tubes and have found his Nirvana with four very expencive NOS KT66 (GEC/Marconi).

In conclusion, I was really surprised to listen an integrated amp which sounded worse with my CJ Premier preamp than when used with its own preamp stage: or these Sylvania 6CS7 are much better than the CJ GE 6GK5 or there is some mismatch with the Leben pre input. In any case, if you consider to buy it as a good integrated system (preamp, power stage and headphone amp) you will understand that 5000 E is a good price for the performances that this system can offer you. Moreover, if you know that Canyon Audio is selling this demo unit for just 3500 E. The only problem that I have found on this unit is the little of noise coming from the main transformer and choke. Ah yes, I forgot to mention that there is no remote control, so you have to sit up every time that you would change the volume. Since I'm not doing any type of business with Canyon, if you are interested, please contact directly him at canyon.audio@siol.net.

A part from the price, that is the best integrated amplifier that I have auditioned in my home. Period.