Lamm Industries M1.2 Reference Mono Amplifiers
by Tim Aucremann | April 13, 2015
© www.theaudiobeat.comIn 2013 Lamm Industries celebrated its twenty-year anniversary and the company's M1.2 Reference amplifier turned ten. With many reviews already under the M1.2's belt, Im not the first to ask if it warrants yet another, especially when the amplifier has remained unchanged since its release in 2003. This review is neither a salute to an aging superstar nor a testimonial dinner for a legacy product. With numerous strong contenders in the $20,000-$30,000 range, I was skeptical about the tenability of a ten-plus-year-old product in todays market. Given the advance of technologies, the ever-shortening product cycle demanded by marketers, and the tendency of some audiophiles to get squirrelly when they don't have the latest and greatest -- and with no M1.3 on the horizon -- I wanted to know where this decade-plus-old product stood. Is this model viable going forward in stasis?
Seeing and using the M1.2 reveals its enduring character. A laconic exterior presents large functional heatsink fins on both sides of an anodized aluminum chassis, the absence of knobs, dials or curves making abundantly clear that the M1.2's heritage does not derive from a watch, a kitchen appliance or a file server. Classically attired in tuxedo black with controls and inputs arrayed business-like on its rear panel, the M1.2 exudes a hunkered-down confidence that says Power with a capital P. There is no display with a font or interface to date its age. A single LED indicates whether power is applied. One monoblock weighs in at a compact 69 pounds and features helpful handles mounted fore and aft. A pair sells for $27,190, complete with white cotton gloves.
Functionally, the Lamm M1.2 Reference is a push-pull hybrid monoblock (solid state with a single tube) capable of delivering 110 class-A watts into an impedance of 4 or 8 ohms. Signal arrives at the amplifier via RCA or XLR inputs on its rear panel then flows into two high-speed buffers (originally designed for video application,) which drive a differential cascode amplifier section consisting of matched pairs of J-FETs driving matched pairs of PNP transistors. These feed a single 6922/ECC88 dual triode vacuum tube, which in turn feeds a single-ended driver stage consisting of a pair of NPN transistors, one of which is a relatively powerful current source. A small amount (6-7dB) of negative feedback runs from the output of the driver stage to the inverting input of the differential cascode.
The driver section capacitively couples to six pairs of super-fast MOSFET transistors in the output stage. There is no negative feedback around the output stage and the amplifier uses zero global negative feedback. Within the power supply, special circuitry eliminates small DC current components arising from waveform asymmetry in the incoming AC, keeping the power transformer in the middle of its operating range and minimizing hum.
It is typical for a class-A solid-state amp to spec its rated output for an 8-ohm speaker load and if that drops to 4 ohms or the amp connects to a nominally rated 4-ohm speaker, it delivers half its output as class AB. Not so with the M1.2. If youre paying for class-A watts, by Crom, you deserve class-A watts. The amp sports a backside load selector switch that allows its user to choose a high (16-7 ohms) or low (6-1 ohms) output impedance. Analogous to the multi-ohm taps on a tube amp, the load selector switch functions internally to change the bias of the idle current and to supply the necessary voltage for delivering the amp's 110 class-A watts into either 8 or 4 ohms, as specified. Documentation notes a wide margin of safety built in and mismatching the impedance switch position versus speaker load will cause no harm, although a difference may be audible.
When the load switch is set for lower speaker impedances the amp delivers 220 watts into 2 ohms and 400 watts into 1 ohm. On the higher-impedance setting it yields 220 watts into 4 ohms, 400 watts into 2 ohms and 600 watts into 1 ohm. Thats all per the specs. Ask Vladimir Lamm on the sly and hell acknowledge that the M1.2 is capable of delivering 720 watts into a 1-ohm load. Hell then smile and say that not only can you use the amp as an arc welder (which hes done), it will drive any speaker on the market. Two sturdy pairs of binding posts can accommodate dual sets of speaker cables. The M1.2 incorporates a remote on/off system that works only when the amp is connected to a Lamm preamp or another M1.2. With the power, features and flexibility to handle a wide range of speakers, the M1.2 Reference is ready for a future its owner might not foresee -- yet.
The design of the M1.2 (and the M1.1 before it) derives from Vladimir Lamms research into psychoacoustics, undertaken during his work in the Soviet military-industrial complex. As a percussionist, music lover and avid listener with a university background in solid-state physics and semiconductor design, Lamm sought answers to a simple question: Why does some audio gear sound better than other audio gear? As Chief Design Engineer of Research and Development at the Lvov Radio & Electronics factory, Lamm had both the resources and large pools of test subjects for conducting hundreds of blind and double-blind listening experiments. From these he accumulated massive amounts of data about what happens when people hear certain sounds, including a complex sound like music. With data in hand he used differential equations to develop scientific models that described mathematically what he calls "the human hearing mechanism." He converted those equations into electro-mechanical models and implemented them in specific circuit topologies.
Lamm tested his circuit designs with hundreds of human listening subjects to demonstrate that, given human physiology, only a few combinations of audio circuitry will work for us as listeners. We cannot change how we perceive sound or music, even in the face of what passes for good specs. "As humans," Lamm observes, "we are created in a certain way. We perceive sound on various levels: conscious as well as subconscious or intuitive. We perceive sound not just with our ears, but with the whole body." From his research he developed a set of theoretical ideals against which he evaluates any amplifier. He called these constructs the Absolute Linearity of a System -- a sort of unified field theory of amplifier design that explains how an amplifier should measure if it is to reproduce sound congruent with the way people naturally perceive it. Without going into detail about the specific measurements Lamm uses, the basic high-level idea is this: as gain is applied the amplifier should preserve the harmonic structure and spectral balance of the musical source signal. Lamms evaluation criteria also places specific emphasis on the types and values of feedback utilized in an amplifier.
With a design based on the way we actually hear with the ears we have, the M1.2 is like a deductive conclusion that follows mathematically from Lamms codification of countless hours of real-world testing with real human listeners. If you ask Vladimir about how his ten-year-old amplifier design remains viable today, his response is emphatic: "Its foundation in how humans perceive sound remains unchanged."
Along with its aesthetics, functionality and design, the long-term viability of the M1.2 Reference comes from the quality of its parts, the quality of its construction, and Lamms focus on high reliability. Years of experience in Soviet electronics factories led him to adopt industrial-level build methodologies that incorporate component-based construction similar to those required of military-grade equipment. Lamm builds his amplifiers from discrete modules using high-quality circuit boards. He burns in each module then tests it for two hours of continuous operation before assembly, followed by another round of measurements.
Each amplifier uses a biasing circuit designed to achieve the thermal stability of its output transistors and other components. Further evidence of quality is the attention paid to boot time -- perhaps the most precarious moments for any high-powered amplifier. The M1.2 features a soft-start protection circuit where filter capacitors do not receive initial voltage for 2.5 seconds after turn on; then time relays initiate, delaying readiness for one minute to allow warm-up. If internal tests find an issue, the amp turns off and waits; if the issue resolves itself, it turns back on.
Quality and long-term viability hinge on Lamms selection of parts based on their reliability and minimal sonic signature. Vladimir has chosen Dale resistors (now owned by Vishay), Electrocube film capacitors, Roederstein film capacitors and RCD wirewound resistors. On each circuit board, transistors are matched within 1%, which means ordering three times the number of parts actually used. Lamm tests each vacuum tube prior to installation. Each completed amplifier receives burn-in for 72 hours, then yet another round of measurements. Finally, Lamm runs each amp for two hours in the companys reference system. Every M1.2 Reference comes with extensive measurements for the specific amp you purchase -- a welcome and reassuring touch.
Life in the Lamm lane
I planned to use the M1.2s with an all-tube Atma-Sphere MP-1 Mk 3.1 preamp, a unit known for delivering agile, high-resolution harmonic sophistication with low distortion and benchmark levels of transparency. Unfortunately, this combination resulted in a lower-band hum in both channels from the Wilson Audio Sasha speakers' midrange drivers. Try as we may, the hum issue was never resolved; final speculation (and I emphasize this as speculation only) had it resulting from an XLR wiring incongruity between the two units.
Potential purchasers should note the M1.2's relatively high voltage gain (39 times or 31.8dB), especially if youre thinking of pairing it with a high-output preamp. If preamp or line-stage gain is also on the high side (say, greater than 18dB,) it may help to have a volume control with shallow steps to ensure useable attenuation. Likewise a preamp incorporating a gain-reduction option (like the Lamm LL2.1 line stage) may be a consideration. Preamps featuring both balanced and single-ended outputs will find 6dB less gain on their RCA jacks. There are no hard and fast rules here, as demonstrated by the operational satisfaction I found testing with a single-ended Conrad-Johnson PV-8 preamp whose line-stage gain is a high 31dB but which featured a near step-less volume control.
The majority of review time saw the M1.2s driven by the Audio Research Reference 5 SE line stage via the preamps balanced outputs (12dB gain) with occasional appearances from the C-J PV-8. Both units worked well and the Reference 5 SE made a superb modern mate with the M1.2s. Like many C-J preamps with a phono section, the PV-8 inverted phase. The M1.2 Reference includes a second RCA input jack wired specifically for inverted input. Just install the Lamm-supplied socket cap over the unused non-inverted input and youre good to go.
Speakers were Wilson Audio Specialties Alexia and the original Sasha W/P. These moderately sensitive speakers (90dB and 92dB, respectively) represent a nominal 4-ohm load. Both can pose a challenge for any amplifier by dipping close to 2 ohms in the lower bass, so I set the Lamms bias selection switches to their low-impedance setting (1-6 ohms). When I tried the high-impedance setting, the music evinced a slightly less substantial character in the mids and highs.
Reviewer brain versus paleomammalian brain
Before looks, functionality, design and quality, the critical answer to the M1.2s' viability turns on the listening satisfaction they bring their listener. I learned that answer quickly.
From track one, I found the M1.2 Reference engaging, lifelike, and disarming. The amp caused me immediately to connect to my music, rivaling the best Ive heard in terms of overall enjoyment. I kept putting down my reviewers notepad and losing myself in the sound. Just one more tune, just one more shot of musical heroin -- Ill just hear this one and get down to business. Hours vanished. It seemed that Vladimir Lamm, with his psychoacoustic research, differential equations, and topological testing, had discovered the key to unlocking musics reproduction with a sound so appealing that it assimilated the ears immediately and without question.
If you ask him about assessing sound quality, Vladimir will tell you first that "It is important . . to know how the real orchestra sounds. We choose a reference point based on live music and compare to this point," then, once so prepared, "the problem of sound-quality assessment is almost completely solved in the first 10-15 seconds of listening at the intuitive level."
The experience we have listening to music at that "intuitive level" is rooted in primitive limbic functions of awareness -- deep in our lizard brain. McGill University scientists observed that consonance and dissonance will light up the limbic systems responsible for pleasurable and negative emotions appropriately. The non-cognitive experience of music can trigger areas in the brain sufficient to cause the release of endorphins; when they reach the limbic systems opioid receptors, feelings of satisfaction ensue. In his book What to Listen for in Music, American composer Aaron Copland talks about this in different terms, describing how a fundamental aspect of enjoying music takes place on a "sensuous plane," which is "a kind of brainless but attractive state of mind [that] is engendered by the mere sound appeal of music."
If a component or a system breaks the fundamental rules of human hearing, our music-listening brain reaches a kind of tipping point where processing of music occurs less in limbic areas and more in the cerebral cortex. If my ear/brain system detects distortion, for example an excess of third-order harmonics that cause increased loudness or forwardness from that trumpet section over there in right field, in an instant it can happen: focus is triggered, the eyes open and the non-inferential immediacy of our musical enjoyment collapses.
And so it was for me and the Lamm amps. More so than with any piece of gear in recent memory, music through the M1.2s fell immediately into place, effortlessly romancing my limbic zone. The amps were not perfect, and Ill cover some of that, but their varied, vivacious, authentically delivered reproduction brought many an evening of happy ear. You get the point. I didnt have to analyze these amps to experience their authenticity.
But enough poetic wax; you expect analysis and you shall have it. The Lamm M1.2 Reference is a well-balanced, big-picture amplifier capable of power, dynamic control, tonal veracity, refined delivery and presence. The amp is not about parsing musical minutiae or combinatorial synthesis; at its core it is about honest reproduction of the signal received. Some folks believe their stereo should sound better than the real thing. Regardless of the validity of either perspective, the M1.2's truth came closer to the realism of the concert hall than the excitement of the showroom.
However, dont mistake honest realism for boring sameness -- quite the contrary, in fact. What made the M1.2s so compelling from note one was their presentation of naturalistic timbre from instruments and voices. Somewhat short-changed by the optical analog "tone color," timbre is the key psychoacoustic correlate of the engineers sound quality. At the level of a simple note, timbre sums up how we perceive that combination of fundamentals, harmonics and overtones within the context of the notes' dynamic intensity. Within the framework of music, you only need a few notes to recognize what you hear and assess if it is live or reproduced. What I heard from the M1.2s depended on the recordings I played and the character of the upstream system. Im well familiar with the qualities of live music, and the Lamms presented them without added sweetness or coloration. They gave no sense of Photoshop sharpening or Technicolor hype. Music lacked that dry flatness Ive sometimes heard from all-solid-state designs; neither was there any euphonic luxuriance as Ive heard from some all-tube amps. If the Lamms brought anything to the music, it was a kind of plain-faced authority and confidence. With the M1.2s, the music was immediately compelling and naturally honest.
Some find the overall sound of the M1.2 as slightly dark; and by contrast with certain amps there is that relative difference. I found the M1.2s sounding whole within themselves, and from the perspective of their overall presentation, music teemed with harmonic information, with the antonym of their tonality being not light but lean. Overall frequency balance lacked discontinuity; there was no coming forward or peakiness from the likes of sopranos or trumpets, and no midbass enhancement.
Picking nits, in the very lowest bass -- roughly that area where the Sasha drops to a gnarly sub-2-ohm impedance -- the M1.2s sometimes evinced a wee bit of less-than-defined warmth around the edges that I heard as bloom, with a very slight reduction in tonal articulation. I had to focus to hear this, however, and it did little to alter my sense of the amps overall honesty. It was part of the character, not a character flaw. I dont hear razor-honed transients from bottom-octave double basses or pianos in the concert hall. Soundstage depth and width were excellent, sometimes expanding room boundaries based on the recording at hand. I believe the preamp and the Lamms tube also played a role in the amp's depiction of space and acoustics. Performers were properly in place and palpable, although they evinced less-than-laser-sharp image outlines.
Double bassist Ferrucio Spinetti and soprano Petra Magoni team up on their CD Musica Nuda [BHM 1026-2] to offer jazzy covers of popular songs sung in English and Italian. Given the instrumentation, the music is very sparse and the combination of different tonalities is, well, different -- fun to my ear in limited quantities. This disc had its moments, though ultimately it was more entertaining for its sound than its edgy music. (Proving once again, you cant punch your ticket to limbic land with hardware alone.) The recording thrusts at you, and the Lamms conveyed its raw immediacy and naturalness with open-eared clarity. Magonis voice is raucous and rangy and Spinettis classical training belies an inventive spontaneity that runs all over the octaves. Several tunes, such as the groups covers of "Roxanne" and "Eleanor Rigby," featured Spinettis martelé technique of punching or hammering a string with his bow. The M1.2s showed both power and nuance as they delivered the unique tonal complexity of Spinettis bow strikes with fine-grained dynamic contrast. His double bass was closely micd, and the impact of each string under attack was felt as much as heard, followed by the resonance of its decay bouncing around in the basss sounding chamber.
On "Guarda che Luna," Ms. Magoni demonstrated incredible breath control as her voice jumped octaves instantly, pulling notes into the ether for what seemed like eternity. The Lamms caught the taut, restless emotion she brought to each tune. Both musicians carved a presence in the space between the speakers. A welcome absence of post-production reverb meant each performance arrived with a vivacious and concentrated realism. Differences were obvious between the Sashas slightly cooler inverted metal tweeter and the Alexias mellifluous silk dome. With the Alexias in play, the performers presented with lifelike proportion, as I experienced an improved sense of height information versus the Sasha.
Listening to Esoterics remaster of Loren Maazel conducting the Vienna Philharmonic in Sibeliuss First Symphony [Decca SXL 6084/Esoteric ESSD-90020], I knew it was the finest recording Ive heard of this work, and probably the finest SACD recording of any symphony Ive played in my system to date. Here is the Decca sound at its best: a full orchestra well recorded in 1963 by legendary producer John Culshaw and engineer Gordon Parry in Viennas Sofiensaal recording hall, Deccas primary venue in Europe for many years. A precocious and daring Maazel drove the Wieners in a compelling performance that laid bare the inventive genius of Sibeliuss first symphonic offering.
From the start of the music, my ears felt immediately at home with a Lamm sound that was both highly resolving and easefully natural. The symphony began with a plaintive solo clarinet faintly rising as if from fog, its beautiful tone shaped by the musicians artistry. Tiny variations in control technique such as embouchure strength yielded even tinier vibrational changes in air pressure and timing that happen within microseconds. Thanks to the Lamm amps reproduction of fine detail, I sensed the clarinetists breath against his reed, how his first notes leading edge initiated as nearly formless yet with its tonality fully developed. The technique is difficult, and the M1.2 caught the subtle artistry of its brief life. The rumbling of a solo kettle drum, struck faintly with soft mallets, played in the background. Despite the low volume, each strike was articulate and clear with a tone I only could describe as copper colored. The timpani offered the first hint of acoustic space as its sound rose upward and off the halls back wall. The M1.2s facility for reproducing microdynamics and micro-intonation revealed the quality of Esoterics SACD remaster.
From this simple opening, tremolo violins entered and the Lamms made obvious the voluptuous tone of the full Vienna Philharmonic string section, proving they could do beauty as well as truth. Instruments glided in and out as shifting patterns of light and darkness, like clouds moving across the sun in a time-elapsed movie. With the full orchestra laid out before me, my ears could roam easily across contributions from sections and soloists, and then pull back to the whole -- just as I find myself doing in the concert hall. The music engaged the orchestra in a series of calls and responses from different instruments that enfolded and overlaid each other to create a rippling textural effect across the soundstage. Solo woodwinds appeared as tonal points of interior light. It was easy to follow the inflections and emphases of instrumental lines within the overall dynamic gradient and rhythmic context of the work as a whole. Bells struck with rawhide hammers brought discrete flecks of ornamentation from the orchestras rear, their metallic tones rich but absent the triangles pointed edge, their sound rising not piercing. Sections of double basses and cellos entered bowed and plucked with definition, the tones of each gaining depth with resonance off their wooden bodies. With uncanny realism, trombones and tuba sounded in lower registers and trumpets in higher, the brass vibrant with proper golden brassy tone from each according to its octave.
While the Lamm amps did not strike me as unusually fast, they demonstrated a nimble proficiency with signal timing. This was evident from their coherent control of the Alexias drivers in a way that led the speakers simply to disappear. Likewise the amps' preservation of decay and reflection yielded to my minds ear a coherent picture of the physical and acoustic performance environment. The Sibelius piece offered as natural a depiction of a large orchestra in a hall as I have heard reproduced. It was easy to hear how back- and side-wall reflections from each instrumental section defined their specific locations as portions of walls came alight with reflected sound when instruments near them played. The Lamms made obvious how different instruments projected their sounds differently into space. The psychoacoustic sense of presence coupled with musical vibrancy and performance virtuosity delivered the kind of concert-hall experience that makes all the equipment fuss and bother worthwhile.
Here was what it's all about -- the music made the stereo go away. In as fine an example of musical texture as Ive heard, the symphony rippled and flowed clearly across sections and soloists with different dynamics and attack. I sensed the orchestra as a singular entity, a moving, four-dimensional sonic carpet laid out within the acoustic space of the Sofiensaal.
The Lamms had plenty of power for my modest 17 x 22 x 9 listening room. Considerthose portions of "Siegfrieds Funeral March" from Wagners Götterdämmerung [Deutsche Grammophon 289459141-2], where the brass orchestration includes: three tenor trombones, one bass trombone, four Wagner tubas, one contrabass tuba, three trumpets, one bass trumpet, and four horns. Götterdämmerung is a depiction of the burning, flooding, and renewal of the world. It's gravitas music meant for volume, and I use it to assess my rooms acoustic integrity while listening for congestion or distortion. With the full orchestral host engaged, conductor von Karajan asked for all the weight, heft and crunch the Berlin Philharmonic could muster in attacking big crescendos. Despite double- and triple-forte demands, the M1.2s held it all together, summoning their reserves and controlling the Alexias woofers. With lower brass falling then rising against a background of massive timpani whacks, not only were lower registers forthright with intonation and definition, the bowing articulation and harmonics from upper-octave violins, violas and cellos resolved with clarity. While I heard a wee bit of low-octave bloom, the Lamms carried the day, as musical lines failed to compress or unravel; nothing caused me to wince, distracted from the musics majestic ferocity.
A brief contrast
With the original Wilson Sashas in-house, I had the opportunity to listen to them through the 250-watt all-tube Audio Research Reference 250 monoblocks ($26,000/pair when still available). The Reference Phono 2 SE phono stage and the Reference 5 SE line stage formed an all-Audio Research amplification system. The Reference 250s carried further Audio Researchs best-in-class sense of air, space, and soundstage dimensionality. Listening to an LP of Okko Kamu directing the Berlin Philharmonic in Sibeliuss Second Symphony [Deutsche Grammophon 2530 021], I could count the cellists, perceive where each member of the woodwinds sat relative to one another and easily follow how musical lines were handed off between sections. While image outlines from the M1.2s were not as defined, the Lamm amps offered very slightly better soundstage layering and depth. I had only high praise for the Reference 250s. With their tops off they were slightly quieter, very quick and articulate on the front end, with a fine sense of decay on the back. The latest Audio Research Reference gear approaches OTL-like clarity; the Reference 250s were slightly more pellucid, though the Lamms transparency improved significantly with attention to isolation (see sidebar). By way of contrast, tonality from the Reference 250s was slightly closer to silver in the upper mids and highs, but never forward. Only by close focus to lower bass did I hear slightly less weight than that offered by the M1.2s, although the Reference 250s' low-end resolution was a touch clearer.
In the end, non-musical attributes may tip ones considerations. The M1.2 is a solid-state unit with a single tube, while the Reference 250 uses eleven valves per monoblock. The Lamm amp is single-ended with balanced inputs; the Reference 250 is fully balanced. In summary, each of these amplifiers has its own strong sonic appeal, and Id love to own them both.
Put the viability question to bed. Even a dozen years after their introduction, the Lamm M1.2 Reference amps are thoroughly modern. In my system they made a superb match with both the Wilson Sasha and Alexia speakers on one end and the Audio Research Reference 5 SE and Conrad-Johnson PV-8 preamps on the other. They delivered sound with concert-hall authority, realistic tonality and unflinching honesty that caused me to immediately engage with the music. The emotional pleasure we get when we lose ourselves in music and arrive at that locus of disbelief, slipping out of our audio systems and into the reality of the performance, is the apex of enjoyment for many an audiophile. Its what I call the audiophile miracle, a kind of sonic transubstantiation whereby metal, glass and wire turn into joy.
The Lamm amps are limbic-driving joy machines -- miracle makers that kept me up all night begging for just one more record. These are amps for musicians, not analyticians. The M1.2 Reference is a viable contender for todays amplification needs and joins a small group of other amps Ive heard that I can only describe as thoroughly, ultimately satisfying.
Price: $27,190 per pair.
Warranty: Five years parts and labor.
2513 East 21st Street
Brooklyn, NY 11235
Power, isolation and tube rolling
Every amplifier operates within a context that impacts its performance. Im a strong proponent for attention to audio-room infrastructure: proper acoustics, clean signal and power, and vibration control or isolation. The Lamm M1.2 Reference amps responded positively to specific infrastructure improvements, convincing me I had not yet found limits on the quality of their musical reproduction.
Assuming his amps and preamps receive power through dedicated circuits, Vladimir Lamm recommends against using them with power conditioners. I can attest to the M1.2s sounding clearer and more resolved across all frequencies when I switched the monoblocks from the house circuit to each having its own 20-amp dedicated line. Adding a dedicated Shunyata Typhon conditioner in parallel (i.e., to the other socket on each amps duplex) further improved overall clarity, image definition and leading-edge transients, while reducing vestiges of high-frequency grain.
Hearing the Lamm amps after break-in, I found image outlines were less than sharply drawn. I heard similar when reviewing the Lamm LL2.1D line stage several years ago and thought this was a character of the Lamm sound. I was wrong. Upon mounting each amp on four Stillpoints Ultra SS isolation devices, not only was there an increase in overall clarity, previously soft or amorphous images were more distinctly drawn and dimensionality improved. On studio recordings I heard resolved differences between actual performance acoustics vs. post-production add-ons. There are other options here, such as the Silent Running Audio amp stands that Marc Mickelson uses with these amps. I am convinced you will not hear them with their designers best intent without some form of effective vibration isolation beneath them.
Much of the M1.2s sonic character comes from its voltage gain stage, where a single dual triode drives six pairs of MOSFET power transistors in the output stage. Vladimir Lamm acknowledges that tube rolling happens and tacitly approves by including documentation permitting use of any member of the 6DJ8 family (6DJ8, 6922, 7308 and their Euro-designation equivalents), along with varieties of the spec-alike Russian 6N23P. While the various options all meet certain electrical specifications, valve manufacturers inevitably bring their own sonic signature, while the tubes place of prominence in the amps design assures that signature will influence the sound it reproduces.
Here are abbreviated notes from tube evaluations I did using solo violin music of Arthur Grumiaux playing Bachs Sonatas and Partitas (CD [Philips Classics 438 736-2]) and Sibeliuss Second Symphony with John Barbirolli conducting the Royal Philharmonic Orchestra (LP [Chesky CR-3]).
JJ 6922: The stock tube is quite serviceable. Here the M1.2 sounded open and clear with decent high-frequency extension but somewhat limited bloom, occasionally bordering on (but never quite reaching) stark, with an occasionally whitish touch. Its probably the most consistent, best-sounding, lowest-noise, and reasonably priced off-the-rack 6DJ8 family member available today.
Siemens 7308, NOS mid-1970s: In contrast to the JJ 6922, the Siemens 7308 it is a touch more easeful and sweeter, slightly warmer and darker with richer mid-to-low-bass harmonics and improved bass articulation on the Sibelian cellos and basses.
Amperex 6DJ8, NOS Holland, 1975: Warmer than the JJ or Siemens with nice air and bloom -- more humid than dry -- but not quite as harmonically complex. I heard less of the body of Grumiauxs violin. Orchestral bass had weight but occasionally lacked firm articulation; nonetheless a nice choice over stock.
Telefunken 6DJ8, NOS late 1960s: Open, clear and revealing, neither warm, dry nor sweet. Very nice bass articulation, here the M1.2 sounded refined with improved soundstage dimensionality and harmonic complexity; a rare teeny bit of hardness on upper-treble trumpets.
Amperex 7308, NOS 1967 JAN Orange Globe logo, USA: A slightly bolder, more upfront presentation that is not quite as warm as the other Amperexes, but with no sense of hardness. The M1.2 showed off its excellent frequency balance, articulate bass and ability to deliver atmospheric bloom and hall definition. A solid choice.
Amperex 7308, NOS 1965 USN-CEP/JAN, USA: My notes say a very very nice tube. It is a combination of the Telefunken above and the Holland 63 Amperex below. A favorite. Here, the M1.2 revealed the complexity of Grumiauxs string tone and the rich resonance -- the dark and shady corners -- of his violins body. Excellent attack, decay and sense of recording hall acoustics.
Amperex 7308, NOS 1963 Holland PQ shield with two stars: A bit warmer than the Telefunkens but not warm-warm; rich but not cloying, harmonically dense string tone. The M1.2 was at its best here, with high resolution, no suggestions of hardness, an expansive open character, and excellent bass without exaggerated transients. A balance of strengths yield a soundstage perspective a few rows further back in the hall. My favorite tube with the amp.
Analog: Teres 320 turntable with Verus rim drive, Tri-Planar Mk VII U2-SE and SME Vd tonearms, Transfiguration Orpheus phono cartridge, Silver Audio Silver Breeze phono cable (SME), Stillpoints Ultra LPI record weight, Audio Research Reference Phono 2 SE phono stage.
Digital: Ayre C5xeMP universal player.
Preamplifiers: Atma-Sphere MP-1 Mk 3.1 with phono stage, Audio Research Reference 5 SE and Reference 10, Conrad Johnson PV-8.
Power amplifiers: Atma-Sphere MA-1 Mk 3.1 and Audio Research Reference 250 monoblocks.
Loudspeakers: Wilson Audio Specialties Sasha W/P and Alexia.
Interconnects and speaker cables: Shunyata Research Zi-Tron Anaconda (full loom), FMS Zero.
Power distribution and conditioners: Shunyata Research Hydra Triton and Typhon.
Power cords: Shunyata Research Zi-Tron Anaconda.
Equipment support and isolation: Silent Running Audio Scuttle equipment rack; Mondo Designs amp stands; Stillpoints Ultra 5, Ultra SS and Ultra Mini footers.
Acoustic treatments: Stillpoints Aperture panels, Michael Green CornerTunes.
Accessories: Acoustical Systems UNI-Protractor, Wally Malewicz Analog Shop, Feickert protractor, USB microscope, Fosgate Fozgometer, Loricraft PRC-3 and Audio Desk Systeme record cleaners, Shunyata Research Dark Field cable elevators.