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FI magazine, Vol. 2, issue 1'1997
Dick Olsher

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THE WORLD'S BEST AMPLIFIER? THE LAMM ML1.

From Brooklyn (via Russia) with love. Hand-crafted in Brooklyn, much like vintage Marantz gear, the ML1 blends old and new technology, East and West, to forge a sublime statement in power amplification. It is in a real sense a child of the times, as it owes its very existence to the political cataclysm that has reshaped the former Soviet Union.

Democracy in Russia has definitely impacted the U.S. audio scene. First, Russian tube production has been flowing steadily westward. Brands such as Sovtek and Svetlana have become as familiar to tube-o-philes as GE and RCA, and have re-populated the ranks of quality power tubes. Tube types unknown in the West because they were developed for military applications (e.g., the 6C33C) are now generally available. And second, the recent influx of Russian designers has greatly enriched high-end praxis. Meet Vladimir Shushurin -- Mr. LAMM INDUSTRIES. Here's a man with twenty years of electronics design experience and an intimate knowledge of Russian tube technology. Who better than Vladimir to extract the full sonic potential of the 6C33C--a brutish looking power triode? From MIG jets and Russian tanks, this tube has recently found its way into audio amplifiers.

The 6C33C tube is awesome, almost frightening in stature-- not the kind of tube you'd want to meet in a dark alley. It's not pretty-the glass envelope is as appealing as a cow's behind--but it's rugged, can dissipate considerable heat, and is noteworthy for an exceptionally low output impedance. The latter is an important parameter for output transformer-less (OTL) designs, and helps explain the recent emergence of the 6C33C as the king of OTL tubes.

But Vladimir actually believes that the 6C33C is even better for transformer-coupled push-pull applications--the major benefit being a significant reduction of the output transformer's turns-ratio. As less turns translates into a much more extended bandwidth, an output transformer's eternal struggle for extension at the frequency extremes can be easily fulfilled with the 6C33C in the circuit. The ML1 uses two transformers: an E-I core output transformer and the toroidal power transformer that is suspended in a special encapsulant which almost completely absorbs even the residual mechanical vibrations and resonances. The amp's power supplies also incorporate three chokes manufactured by Hammond.

The ML1 chassis is generously proportioned, oversized by design--the idea being to provide an adequate heat sink for the output tubes which generate considerable heat. No sea of output tubes here. (Simper is usually better, anyway.) Just a single pair of 6C33Cs is deployed to generate a clean 80 watts of power in to 2, 4, and 8 ohm loads. However, there's plenty of headroom--up to 180 watts on music signal. The output stage is biased for rich-A class-AB operation. Very little overall negative feedback is used.

Judging strictly from its external appearance, it would be natural to mistake the ML1 for an all-tube unit. It is in fact a sophisticated hybrid design. Vladimir describes himself as basically a tube man who knows transistors. Anybody who doubts that should check out his model M1.1 monaural power amp (see Ken Kessler's review in Issue 6). Innovation begins right at the input stage where a 12AX7 dual-triode is joined by a Wilson current mirror consisting of all Motorola transistors. The driver/buffer stage following the second voltage gain stage (12BH7 twin triode) uses a quartet of Hitachi high-frequency MOS-FETs. These devices are factory-matched and operated at only a fraction of their rated dissipation. Instead of recycling old circuits from the '50s or '60s, the ML1 marries solid-state and tube technology in order to coax the best sound possible from the 6C33C.

Meters and pots are conveniently provided on top of the chassis to allow monitoring and adjustment of the mains voltage, idle current, bias voltage, and balance. At the flick of a switch you can monitor the operating point and status of the amp. A long-blade screwdriver is thoughtfully included as an accessory to facilitate pot adjustments. Expect to have to tweak the bias and balance over the first fifty hours or so of use; it takes about that long to break in the 6C33Cs. After that, the operating parameters will stabilize, and you'll have little to do for the next 10,000 hours or so of use--except enjoy the music. However, operating the tubes beyond the recommended idle current of 0.3 amps or at elevated AC line voltage will shorten tube life.

An extensive array of protective features merits attention. First, a "soft-start" circuit protects the power supply by limiting large in-rush currents when the amp is turned on. Second, according to Vladimir, the design notes for the 6C33C recommend a two-minute delay in applying plate voltage after the filaments are energized to prevent thermal shock and extend tube life. The ML1 incorporates such a circuit. I know of no other designer that adheres to recommended practice. Finally, there are several fuses provided. In addition to an AC line fuse, there's a 1.25 amp fast-blow type (internally mounted) in the plate circuit of the output tubes, and a thermal resetting fuse controls the internal temperature of the power transformer. I did pop the 1.25 amp fuse on one channel while driving the amp hard. The maximum plate current is 0.75 amps, so that the 1.25 amp fuse should in theory be adequate. However, when the aC line voltage drifts above 120 volts, it's possible to pop the fuse. To eliminate the inconvenience of having to remove gads of screws to change this fuse, a 1.5 amp rated fuse will be used in all future product. (LAMM note: this modification has already taken place).

As with any other power amp, the ML1 needs proper care and feeding to reach its full sonic potential. It should ideally be used on a dedicated AC circuit with a high-quality power cord but without the intervention of isolation transformers or any other line conditioners. Plan on about fifty minutes of play before the amp will sound its best. It takes that long for the chassis temperature to stabilize.

Furthermore, its diet should consist primarily of moderate impedance loudspeakers. With a source impedance of just over 1 Ohm, its damping factor into an 9-Ohm load is a respectable 7. And, more importantly, the damping factor remains constant with frequency over the entire audio bandwidth. With lower impedance loads, however, the potential for more substantial load interactions exist, and current delivery also becomes an issue. Peak current output is about 9.5 amps into 2 ohms, corresponding to 180 watts. That ought to be adequate for all but the most demanding of dynamic loads. A case in point is the PBN Audio, which wasn't entirely enamored with the ML1. PBN's Montana is a prime example of a loudspeaker that thrives on high-current solid-state juggernauts.

In the reference room, and partnered by LAMM's exceptional L1 line-stage for reasons of synergy, the story was considerably different. The Sound Lab A-1 ESL, a notoriously difficult load, went into a protracted orgasm.

Buckle up, folks, and hold on to your listening seat: the ML1 is lightning quick. Transients were unleashed without any discernible hesitation. With all that speed came incredibly control and clarity of expression--free from that unholy trinity of transistory treble gremlins: brightness, hardness, and textural grain. Elucidation of sibilants was exemplary. Early digital recordings, while still unpleasant to the ear, were nevertheless accommodated without any further insult. Rachmaninoff's Symphony No. 1 [Decca 411657-2] came off better than ever before. The tempestuous character of the music was readily conveyed while the various orchestral threads were there for the picking.

Bass definition and impact scaled new heights with the ML1. I couldn't believe my ears. The A-1s really kicked. Tight, real tight, bass lines with an amazing boogie factor, and enough crunch--I'd say about an 8 on the Richter scale--to almost make me swear off dynamic speakers. No tube amp in my experience is capable of this level of conviction through the lower octaves.

With such a sure hand at the frequency extremes, it was all the more surprising to realize that the ML1 gift-wraps the midrange and hands it to you on a silver platter. The critical midband was always suave sounding with an innate feel for harmonic colors. Female voice as in Her Highness Kathleen Battle's Baroque Duet with Wynton Marsalis [Sony SK46672] was divinely velvety, sweet, and compelling--a veritable gestalt of a singer in my room. Reproduction of the music's hidden nuances--micro-modulation in volume and frequency--was so good that Ms. Battle's full palette of expression was discernible.

Listening to Eric Clapton's Unplugged album [Reprise, 9-45024-2], it occurred to me that Vladimir and Tube God must have conspired on this one, for suspended before me was an almost perfect fusion of solid-state and vacuum tube virtues: quick attack, clarity, and visceral bass combined with textural liquidity, Cezanne-like solidity in portraying image outlines, micro-dynamic conviction, and a remarkable feel for ambient clues. ...let me state that such tonal balance neutrality is an admirable trait.

...So let me get back to the rhetorical question raised in the title regarding "world's best" stature. The point I'm trying to underscore is that there's no such thing as a universal power amp. Any great amplifier, as is the case with the ML1, can only sound great when mated with an appropriate load. The underlying fallacy of any Recommended Components list you care to name is the notion that Class A speaker and amplifiers will perforce yield Class A sound. Audio is about system-building, and that's where Fi comes in with specific recommendations that leave nothing to chance.

...Despite its 80-watt rating, the ML1's considerable headroom can deliver the goodies into most real-world loads, including reactive loads such as the Sound Lab A-1. Its iron-fisted bass control, textural suaveness, excellent detailing, and transient finesse should earn the ML1 a buss load of converts. It stacks up well against all contenders. Do try to audition it with the LAMM L1 line stage, as this combination really cooks. Looking at the price tag, it should be clear that this is an amp for the working rich. Even though it's offered at a premium relative to the likes of the Air Tight ATM-3, the ARC VT-150, and the Conrad-Johnson Premier 8, the ML1 deserves your full and undivided attention.

 

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