Lamm ML2.2 Single-Ended Triode Amplifier

Can an 18W Amplifier at 3% Distortion be World Class?

Equipment report
Tubed power amplifiers
Lamm Industries ML2.2
Lamm ML2.2 Single-Ended Triode Amplifier

The highest praise I can give the Lamm ML2.2 is that it doesn’t sound like a single-ended-triode amplifier. That may seem like an odd way to start what you’ll soon see is a rave review of an SET amp, but it reflects the fact that the ML2.2 is far more than just another low-powered SET. In fact, it is singular in its ability to deliver SET virtues while minimizing their limitations.

The ML2.2 is the latest upgraded and refined version of Lamm’s famous ML2 introduced in 1998, and the ML2.1 launched in 2004. This latest iteration benefits from having been designed after Lamm’s groundbreaking ML3 Signature, a $139k four-chassis 30W SET whose sound (when driving the right loudspeaker) can only be described as magical. The new ML2.2 features design elements Vladimir Lamm developed for that reference amplifier, including a new input stage that is similar to that of the ML3. Compared with the ML2.1, the ML2.2 also offers an entirely new power transformer, five filter chokes in the power supply (versus two chokes in the ML2.1), and a new, better-sounding circuit-board material.

The ML2.2 is solidly built but decidedly utilitarian in appearance. This is a serious piece of audio engineering, not living-room jewelry. The black chassis houses the power and output transformers at the rear, with the tube complement at the front. Those tubes include a 12AX7 in the input stage, 6N6Ps as the drivers, and a 6C33C output tube to deliver 18W of output power. A second 6C33C serves as the series-pass element in the fully regulated output-stage power supply. (A 6AK5 and 5651 are also part of the power supply.)

The power transformer has no direct mechanical contact with the chassis or covers; it is instead suspended in a vibration-absorbing encapsulating material. The output transformer (a critical component in any tubed amplifier, particularly an SET) is a custom, hand-wound design with a very low turnsratio, designed specifically for the 6C33C output tube. This transformer has three taps that correspond to the three output terminals, allowing you to select the one that best matches your loudspeaker’s impedance. The power supply includes a soft-start circuit that slowly ramps up the plate voltage to extend tube life. It takes about two minutes after turning on the amplifier for the front-panel red light to stop blinking and glow solid red, indicating the amplifier is operational. A pair of test points and trimmers on the top panel allows the user to correctly set the plate voltage and plate current. (You’ll need an accurate voltmeter along with the supplied screwdriver to perform these tasks.)

I’ve had the ML2.2s for some time but have been waiting to write about them until I mated them with a loudspeaker of appropriate sensitivity and impedance characteristics for their 18W of output power. Ideally, the ML2.2 will drive a loudspeaker with a sensitivity of at least 94dB, one that has a fairly flat impedance magnitude across the audio band and no severe swings in its phase angle (that is, a speaker whose impedance is more resistive than reactive). I found that speaker in the Magico Q7, reviewed in the previous issue. With a sensitivity of 94dB and what is apparently a benign impedance, the Q7 allowed me to hear the ML2.2 at its best. The Q7’s extreme resolution and transparency also provided a clear window on the ML2.2. Incidentally, other loudspeakers with similar sensitivities (the 93dB Venture Ultimate Reference and 94dB Lansche No.7) didn’t fare nearly as well with the ML2.2. This isn’t casting aspersions on these two loudspeakers. Rather, it just happens that they are more difficult to drive than the Q7 despite their similar sensitivities. There’s no substitute for auditioning the amplifier/loudspeaker pair before making a purchasing decision, particularly where lowpower SETs are involved.

I started this review by stating that the ML2.2 doesn’t sound like an SET. If I brought an experienced listener into my room blindfolded and played a wide range of music for a couple hours, that listener would never be able to identify the amplification as single-ended triode. For starters, the ML2.2 has an absolutely luscious rendering of tone color, yet it never crosses the line into a syrupy romanticism that would soon grow tiresome. The amplifier lacks the typical SET signature of an overly warm and ripe midband that directs the musical focus to certain instruments. And then there’s the bass, the Achilles’ Heel of SET. The ML2.2’s bottom-end extension, control, dynamics, and articulation wouldn’t be mistaken for a solid-state dreadnought design, but neither would you think that this 18W SET could deliver the kind of bass control and dynamic drive it exhibited driving the Magico Q7.

The ML2.2 is so natural, organic, and musically right—and so greatly minimizes an SET’s traditional shortcomings—that the amplifier caused me to question the modern paradigm of highpowered solid-state amplification (see my editorial “The Single-Ended Triode Paradox” in Issue 223). Have the last fifty years of amplifier design been a detour down the wrong path? Listen to, say, the new Analogue Productions 45rpm reissue of Time Out by The Dave Brubeck Quartet through the ML2.2 and you’ll be asking that question as well, no matter what your technical persuasion. Joe Morello’s ride cymbal just hangs in space with startling realism that makes it sound like it was recorded yesterday; Paul Desmond’s alto glows with a gorgeous liquidity and richness of tone color; and Brubeck’s intricate piano lines between the melody phrases on “Blue Rondo à la Turk” are conveyed with a newfound clarity that deepened my appreciation of this brilliant composition and performance. I defy even the most hardened anti-SET technocrat to listen to the ML2.2 driving the Q7 and conclude that a vacuum tube amplifier with 18W of output power at 3% THD is an anachronism and an abomination. And the argument that SETs sound good because of their high harmonic distortion rather than in spite of it simply doesn’t wash under careful listening. The ML2.2 sounds like whatever the source sounds like, with no common editorial signature from recording to recording.

What makes the ML2.2 different from other amplifiers— tubed or solid-state, single-ended or push-pull—is a sense of palpable realism and the feeling that music is being brought to life contemporaneously. The ML2.2 doesn’t sound like just a great tubed amplifier, only a little better; it provides a fundamentally different listening experience. This amplifier’s sound is qualitatively superior, not quantitatively. As I discussed in my review last issue of the Q7, realism is the ultimate goal of high-end audio, and therefore the ultimate reference standard for judging audio products. And realism is what the ML2.2 delivers, in spades. Instruments and voices sound realistic in timbre, in dynamic shading and expression, in their spatial presentations, and in the joyous feeling of people creating music before you.