The Fifth Element #60 Page 2

So one of the first things I did after receiving both the Leben amp and ProAc loudspeakers was to play that Brian Cheney CD-R. I came to the conclusion that the CdF person had perhaps been overcautious—although at the time I felt that the intervention had probably been warranted. So, what gives?

I can think of a few possibilities. The hotel room, though small, could have been much less lively than my listening room. The CS600 used at FSI was apparently set up to use EL34 tubes, while my review sample has 6L6GC tubes—but that difference is only the 4W between 28 and 32Wpc. I also think it entirely possible that after three days of listening to all sorts of systems play all sorts of music at varying loudness levels—often more loudly than I would listen to at home—my ears might have been just plain tired, and I therefore set the playback volume higher than I would at home under normal circumstances. Because, coming to the music fresh, and relistening as recently as today, with the volume control set no higher than the 12:00 o'clock position, the Leben drove the ProAcs as loudly as I'd ever want to hear "Che gelida manina," and with no sign of strain or breakup. I just wanted to get that issue out of the way, lest my previous write-up leave the wrong impression.

The CS600 is beautiful—its look is classy retro, though not slavishly so. The gold faceplate is vertically centered in front of a taller subplate painted a restful leaf green, which leaves green margins above and below the faceplate proper, with the company name, slogan, and model number in white. Nice little touches like that abound—such as the wooden side panels' being made from solid, fine-grained Canadian white ash, which is used for baseball bats and canoe paddles.

The faceplate is dominated by the large, smoothly detented Volume Control. To the far right is the power switch, which incorporates a green LED indicating power-on. A blue LED above the volume control indicates when operating voltages have been reached. This took at least 20 seconds, but never as long as a minute. Below the volume control is a standard ¼" stereo headphone jack. At upper right, above the power switch, are two sets of small indicator lights corresponding to the proper Cathode Resistors and Plate Voltage for the 6L6GC or optional EL34 tubes. (The tube type can be selected with internal switches.) The amplifier circuit itself is of push-pull topology, not single-ended, and is wired point to point. The owner's manual includes a chart of the proper voltage and resistor settings to use with a wide variety of tubes, such as KT66, KT77, and KT88, none of which I tried. There is no remote control of any kind.

I find it touching that the CS600's owner's manual notes that the ancestor of the 6L6GC tube was used in the original McIntosh power amplifier of 1949, and that the optional EL34, or 6CA7, was used in the Marantz amplifiers of audio's Golden Age. Leben Hi-Fi Stereo obviously sees itself as carrying on an important tradition. Judging by the CS600, they have earned their place in it. The manual also mentions the 6CJ3 damper tube, which is part of a soft-start circuit designed to extend power-tube life.

The other items to the right of the volume control are knobs for Balance and Bass Boost, and a Speakers/Phones toggle. I tried the Bass Boost a few times, but didn't use it much at all. It was, I think, a not very even tradeoff, with some increment of additional bass but a more noticeable increase in tubbiness. Sorry, no free lunch.

To the left of the volume control are knobs for Mode (Stereo or Reverse, but no mono), Tape Monitor On/Off, and Input Selector (a CD input and four line inputs, but no phono stage). There are also toggle switches for Muting On/Off and Pre(amp) In/Normal, the latter so that the CS600 can be used as a power amp only.

The rear panel is just as well designed and purposeful. Inputs are RCA jacks of good quality (although pass-through and not lugged on). Speaker terminals are heavy-duty, EC-compliant, and very easy to use. There is a standard IEC inlet for the power cord, with a nearby fuse holder. Not only the top panel, but also the rear and bottom panels have ventilation slots. There is a ground lug for use with an outside phono stage.

For all my listening, I used Kimber's 8TC speaker cables ($568/8') and a 0.5m pair of Hero interconnects ($217/0.5m). These wire goods are of the strong, silent, John Wayne type—they just shut up and get the job done. I think they work particularly well with the Leben-ProAc combination.

One welcome feature of the rear panel is a rotary-knob impedance selector that ranges through 4, 6, 8, and 16 ohms. The combination of being able to select output impedance, the soft-start circuit, and the amplifier circuit's being self-biasing, means that my experience with the Leben CS600 was entirely plug, play, and enjoy, with nary a hiccup. This product is designed to take the anxiety out of owning tube amplification over the long haul.

I primarily used the CS600 with ProAc's Response D Twos, but it also saw service with ATC's SCM 40 (see "The Fifth Element" in April 2010) and Harbeth's P3ESR loudspeakers. The Leben's 32Wpc was a marginal proposition driving the large, sealed-box ATC SCM 40 on big orchestral works, such as Esa-Pekka Salonen's recording of Schoenberg's Gurrelieder (SACD/CD, Signum SIGCD173), which I recommended in my last column. The volume was in a sense adequate, but bass and dynamics were disappointing. The amp never seemed to "misbehave," but it did seem to run out of steam.

Harbeth's P3ESRs provided a happier marriage all around. Although this BBC "shoebox monitor" descendent is also a sealed-box design, it is less ambitious in the bass region, with only a 5" mid/woofer. With Luxman's DU-50 near-universal (no Blu-ray) disc player used as a source, the combination of Leben CS600 and Harbeth P3ESRs was simply glorious with Jane Monheit's Taking a Chance on Love (CD, Sony Classical SK 92495).

Once I had a fix on the P3ESR's sound, I replaced the Leben CS600 with the similarly priced ATC SIA2 solid-state integrated amplifier. As one might expect going from 32 to 150Wpc with a speaker with a claimed sensitivity of 83.5dB, the ATC showed a greater amount of better-defined bass and obviously more dynamic reserves. And Monheit's voice was just plain wonderful to listen to—the ATC is a great amplifier. However, the Leben CS600 had a certain, almost indefinable sweetness about it, and a beguiling presentation of inner detail that made me overlook its limitations in dynamics and bass.

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