Leben CS300 integrated amplifier
The idea of a good-quality integrated amplifiera power amp and preamp put together in a box of reasonable sizehas never ceased to appeal to me. I owned three good integrated amps before I ever bothered to buy a stereo receiver (itself purchased before countless hearings of Linda Ronstadt's cover of "When Will I Be Loved?" and James Taylor's of "How Sweet It Is" left my enthusiasm for FM in a permanent body cast), and to this day I'm embarrassed less by the humility of an integrated amp than by the expense and expanse of some separates.
It has occurred to me: Some day, my retirement system will surely be built around a good integrated amp.
That in itself makes me wonder: If I could retire today, which integrated amplifier would I chooseassuming I still wanted tubes? And a phono section? And I had about $6000 to spend?
God is good. Over the transom came word of the interesting new Quad II Classic integrated amplifier ($5999). In the wake of that newsliterally within a day or twocame an offer to review the current edition of the Luxman SQ-38u integrated ($5990). Coincidence and momentum then conspired to spark my memory of the Leben CS300 integrated ($3395), which, while scarcely a newcomer to the market, had yet to appear in our pages (footnote 2), either single or in concert with its newer sibling, the Leben RS-30EQ phono preamplifier ($2695). (The more expensive Luxman and Quad integrateds have phono sections of their own.) Thus the idea took shape of a small survey, starting with the . . .
Leben CS300: $3395
The Leben CS300 bears an uncanny resemblance to every integrated amplifier I owned between 1970 and 1975. Seeing it todaylet alone having it in my homeis like discovering a packet of the same incense they used to burn in my favorite record store of that period (which, as God is my witness, was called Love Records). Thus the Leben may already have an unfair advantage over its competitors, at least on the playing field of my subconscious.
This line-only integrated amplifier contains a total of six tubes: one pair of 5751 dual-triodes, and two pairs of EL84 power pentodesthe latter a tube noted for its ability to work well with very low-voltage input signals. The EL84s run in class-A/B in a straightforward autobias circuit, for a total of 12Wpc. Global feedback is used, and the output transformers are designed in-house, and manufactured by what is described as a subsidiary company.
The Leben CS300 is a split-level amp, the steel floor of which is fastened inside the chassis at a point roughly four-fifths of the way down from the top; the hand-wired circuit and virtually all of the smaller component parts are mounted under that surface, with the mains transformer, output transformers, shielding "wall," and tubes mounted above. Construction quality is stunningly goodnot just for this price, but for any price. In my sample, a dozen or so old-style terminal strips supported most of the amp's capacitors, diodes, and (carbon-comp) resistors, and all of the component leads and connecting wires were neatly dressed and soldered perfectly: There wasn't a single stray strand of wire or cold-solder joint in sight.
The vintage theme carries over to the Leben's selection of front-panel controls, which include not only the usual volume and source selectors but also a balance knob and a three-position bass-boost knob, the latter allowing the user to select among flat, 3dB of boost, or 5dB of boost. Additional controls on the front panel allow the user to switch between speakers and headphoneslogically, a ¼" phone jack is located close byand to activate the tape monitor loop. Uniquely, the Leben also has a rear-panel output control: a three-position knob that allows the user to switch between transformer secondaries (or combinations thereof) that are optimized for use with speakers with impedances of 4, 6, or 8 ohms. Damn good engineering.
The CS300's line stage is said to provide approximately 20dB of gain. Because the Leben integrated amp lacks a phono stage, I used it in tandem with the Leben RS-30EQ, the company's relatively new standalone phono preamplifier.
Installation and setup
I used the Leben CS300 in place of my Shindo Masseto preamplifier and Shindo Corton-Charlemagne mono amplifiers. Because the former has a MM phono stage of its own, I supplemented the CS300 with the Leben RS-30EQ, using a 1.5m-long Audio Note AN-Vx interconnect to go from the outputs of the latter to the inputs of the former. I preceded the Leben phono preamp with either an Auditorium 23 SPU Standard or Silvercore One-to-Ten step-up transformer, for use with low- and high-output MC pickups, respectively. The Leben amp drove my Audio Note AN-E/SPe HE dynamic loudspeakers and, on occasion, my reconditioned Quad ESLs, ca 1959.
Footnote 1: In a perfect world, all storage media meant to represent analog events would themselves be analog.
Footnote 2: Leben's CS600 integrated amplifier ($5795), which uses 6L6GC or EL34 output tubes, was reviewed by John Marks in his June 2010 "Fifth Element" column (Vol.33 No.6). Ed.