I find it almost humorous how some audiophiles, and some audio writers, revere single-ended-triode amplifiers, as though they are rare artifacts, like thousand-year-old religious relics. SET is a mature topology -- it's swiftly approaching its 100th birthday -- but the amps produced with it are generally very low in power and therefore able to drive a small subset of available speakers. Exclusivity breeds fervor. The SET set is the most esoteric side of an esoteric hobby, populated with tube amps diminutive in stature and output power, single-driver and horn-loaded speakers, and the audiophiles who love them both.
It doesn't have to be this way! There are single-ended amps, like the Cary CAD-805 series and deHavilland GM70, that offer enough power to drive real speakers (yes, I use "real" on purpose; from my experience, most single-driver and horn speakers are grossly colored -- unreal) and therefore aren't just boutique products.
The king among real-world SET amplifiers was the Lamm Industries ML2, an amp that was widely reviewed and widely considered one of the finest amplifiers made. The ML2 was in production for over five years, a long time for an audio product, which is perhaps the reason it was replaced earlier this year by the ML2.1. New to the ML2.1 are a modified custom-designed output transformer, a higher-quality PC board stuffed with new and upgraded parts, and an upgraded power transformer that accommodates 230V operation. Ergonomic upgrades include a new easy-to-use fuse holder, a pair of handles on the amplifier's rear to protect the on/off switch and other features around back (the handles are too small for picking up the 70-pound amp), and new all-metal, gold-plated speaker binding posts.
A few things haven't changed. The ML2.1s still use a pair of 6C33C tubes, one in the output stage and one for voltage regulation, along with single 12AX7, 6N6P, 6AK5/5654 and 5651 tubes. You still have to adjust the bias and idle current with a high-quality volt-ohm meter. Finally, the price is still $29,290 per pair -- expensive, even by the standards of high-end audio.
I owned ML2 amplifiers for over four years, using them to drive a variety of speakers, often with surprising results. I still remember the day when John Giolas of Wilson Audio visited to set up the Sophias for review. The ML2s were sitting in the corner -- I didn't think they would work with the 86dB-sensitive Sophias. But John, a two-channel audiophile of refined tastes, wanted to hear the ML2s, so we connected them and let them warm up. We were astonished -- the ML2s' 18 watts not only drove the Sophias well, showing no signs of anemia, but sounded very good doing so.
Fast forward to earlier this year, after John Giolas had set up the Wilson Audio MAXX 2s for review. A month later, the new ML2.1s arrived here, and as before with the ML2s and Sophias, I thought the ML2.1s would not be up to the task of driving the big MAXX 2s. This time, I had good reason to believe that the ML2.1s would falter. I was using Lamm ML1.1 push-pull monoblocks with the MAXX 2s, and these amps, for whatever reason, didn't cut it with the MAXX 2s, sounding soft and short of power. Lamm's M1.2 Reference hybrid amps and Atma-Sphere's MA-2 Mk II.3 OTLs were both a great match with the MAXX 2s, however, which indicated to me that the MAXX 2s needed more power than the 80 watts the ML1.1s could deliver.
But what the heck -- experimentation is at the heart of being an audiophile. I uncrated the ML2.1s, installed the tubes, connected the amps to the speakers, and let them warm up, checking bias and idle current before playing any music. Again, I was astonished. The ML2.1s sounded wonderful driving the MAXX 2s -- sprightly, palpable, real. Bass was surprisingly defined and taut, so much so that I immediately pulled out Ani DiFranco's Evolve [Righteous Babe RBR030-D] and played the funky title cut at a loud listening level. The soundstage was huge and airy, the midrange almost as transparent as that of the Atma-Sphere OTLs (the reference for midrange transparency) and bass energy just seemed to flow out of the speakers. I always have paper near my listening seat for taking notes, and at this point I scribbled, "These amps never cease to amaze me." I've been listening to this combination ever since.
What makes the ML2.1 sound so good can be broken down into constituent parts -- I've mentioned a few of these in the preceding paragraph -- but what makes the amps special is much harder to define, particularly with the idiomatic language of audio reviews. When asked, I fall back on words like "natural" and "right," but what it really boils down to is that music reproduced by the ML2.1 sounds unique. Other amps may be more detailed or dynamic, sweet or sensual, but the Lamm ML2.1 has the illusive quality of making music like no other amp I've heard, including the hybrid Lamm M1.2 Reference.
I didn't have the ML2s on hand for direct comparison to the ML2.1s, but, of course, I did live with them for a long time. To my ears, the ML2.1s sound slightly more powerful (Vladimir Lamm says that both amps measure identically, however), and more transparent through the midrange than the ML2s. Bass is a bit more controlled, but just as free-flowing and natural. When the sound of all amplifiers is taken into account, both the ML2 and ML2.1 are slightly dark; I can't think of a solid-state amp, for instance, that doesn't sound bright compared to the ML2.1. To those who listen to live music closely, however, I predict that the ML2.1 monoblocks will sound just right. Their performance is not thick or flabby; music simply rolls out of them with endearing balance and purity.
Ultimate output power is still a consideration with the Lamm ML2.1 amplifiers, but the 18 watts that these amps deliver have yet to be stumped by any speaker with which I've used them, including two that I was sure would be disappointing. On the contrary, the Lamm ML2.1s clearly rival the Atma-Sphere MA-2 Mk II.3 and Lamm M1.2 Reference as the very best amps I've heard.
If you can afford to spend 30 large on amplifiers, and especially if you own Wilson Audio speakers (I would love to hear the ML2.1s with the Alexandria X-2s), you will want to audition Lamm's ML2.1 monoblocks, which are one of the very best amps on the planet. Don't miss them.
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