Line Magnetic LM-211IA Integrated Tube Amplifier

I postponed writing this review for quite some time, being aware that reviewing a component I own and use as a reference might not be very useful to the reader. I mean, the LM-211IA is the best amplifier I have ever had in my system, and since I have never heard anything better, there is nothing else I can say other than to praise its virtues and express my positive feelings toward its performance. This, I guess, might be rather boring to read, and that is why I was thinking of writing this review only after stumbling upon an amplifier that could outperform it, giving me a proper point of comparison.

You have to know, dear reader, that my audiophile journey developed rather rapidly. It all started less than few years ago, so I am not the most experienced person with a long list of amplifiers behind me. Truth be told, comparing my former Creek Evolution 50A solid-state amplifier with the beast I am going to review now is like comparing a photograph taken with my iPod Touch against one taken with the semi-professional Nikon DSLR camera I use—graininess, limited dynamic range, and poor saturation versus detail resolution, dynamic contrast, and vivid tone colours. Or, put another way, it is like comparing a printed reproduction with a real oil painting on canvas. Therefore, I do not want to enter into a detailed comparison here, where the differences are so substantial, and I cannot do so anyway because I sold the Creek a year ago after acquiring the LM-211IA.

At the moment I have no other amplifier at my disposal, so I cannot tell how it compares with other amplifiers on the market. Furthermore, I only have one pair of speakers, which means I cannot predict how it will behave with different reactive loads. Therefore, this review simply cannot be an examination of the component under test against several competitors, where virtues and deficiencies are assessed through direct comparison.

What I can do is provide some general information and describe my impressions of this amplifier, which serves as the link between my digital source—based on the SoTM sMS-200 network player feeding an AMR DP777 digital processor—and the Art of Sound back-loaded horn speakers BK108, fitted with Fostex FE 108-Sol full-range drivers.

Line Magnetic Audio

As an audiophile and beginner writer, it is part of my daily routine to check what other people have written. I consume a great deal of audio gear reviews, opinions, and reports, and by doing so the name Line Magnetic Audio naturally came into my view.

I first encountered some RMAF and Salon Son & Image (SSI) show reports from 2012, where it was mentioned that DeVore Fidelity presented its range of ape-named speakers partnered with Line Magnetic amplifiers. The overall impressions of this combination were rather positive. Later, I discovered even more intriguing developments happening here in Germany, where I reside.

It was at the 2012 Munich High End show that Keith Aschenbrenner from Auditorium 23 introduced his new line of speakers, which had been designed with Line Magnetic drivers instead of the older PHY-HP units. What followed was that the Auditorium 23 “PHY” speaker line was discontinued in favour of the new Hommage line, featuring Line Magnetic replicas of the famous Western Electric WE 755 8-inch full-range driver.

The replicas not only looked exactly the same, but according to Aschenbrenner they performed in the same league, being able to deliver the legendary Western Electric magic from the 1940s.

It turned out that here in Germany Line Magnetic Audio was represented by two of the most credible people in the high-end industry: Keith Aschenbrenner from Auditorium 23, distributing the speakers, and Claus Jäckle from AcousticPlan, offering the amplifiers and the rest of the electronics.

It became obvious that the founders of Line Magnetic Audio—the brothers Zheng Cai and Zheng Xi—were not joking, but were taking things very seriously by investing considerable resources into research and analysis of the materials used during the Western Electric production era.

Checking it out

As I have already mentioned, my former solid-state Creek Evolution 50A amplifier was a rather poor performer, especially when paired with my single-driver, crossover-less speakers, which are highly revealing. I was able to discern the graininess of the images, poor dynamic contrast, and the greyish monotony caused by a lack of tonal saturation.

It seemed likely that a tube amplifier would partner better with full-range horn speakers, and that is how the LM-211IA came into consideration. Although my preferences leaned more toward single-ended triode amplification, the most affordable SET amplifier available at the time—the LM-218IA (2800 EUR), a lighter version of the widely renowned LM-518IA 845-tube SET amplifier—was beyond my reach.

At the same time, the LM-211IA (1400 EUR), an EL34 push-pull amplifier featuring switchable triode and ultra-linear modes of operation and point-to-point wiring, strongly appealed to me. I realized that in this price range one simply cannot expect a hand-wired amplifier using quality components, housed in a solid and attractive chassis.

It is the most affordable model in the classic range lineup, followed by the LM-216IA (1600 EUR), a KT88-tube version with a similar topology and characteristics but higher power output. There is also a premium line of amplifiers consisting of exotic models such as the two-chassis LM-845 Premium integrated amplifier. This design separates the main amplifier, tubes, coupling driver transformers, and power supply into one chassis, while the output transformers and speaker output components are placed in another—a rather interesting concept, by the way.

Technical description

The LM-211IA is a three-stage Class AB push-pull integrated amplifier delivering 15 watts per channel in triode mode and 32 watts per channel in ultra-linear mode. The preamplifier stage consists of a pair of 12AX7 double triodes used for voltage amplification, while the driver stage is realized with a pair of 12AU7 double triodes for signal splitting and driving the output tubes.

The output stage consists of two pairs of EL34 pentodes in a push-pull configuration for power amplification. Wide-bandwidth EI output transformers are used to match the high impedance of the output stage to the low impedance of the speaker taps.

The power supply relies on a specially designed EI transformer combined with solid-state, choke-filtered rectification. Although the internal wiring is a point-to-point handmade construction, there are a few PCBs used for more complex functions, such as the triode/ultra-linear switch, which utilizes electrical relay switches for each channel, the soft-start and time-delay circuit, and the ALPS volume control servo automation.

The amplifier has a classic layout, with the tubes positioned at the front and the shielded transformers at the rear. This arrangement facilitates short signal paths and helps reduce the emission of hum and noise into the chassis. Nichicon and Realcap capacitors have been used.

User interface

The LM-211IA comes with a remote control for volume adjustment and mute functionality. On the front aluminum panel there are two knobs for volume and source selection, as well as a switch for choosing between triode and ultra-linear modes of operation.

There is also a status indicator light with two states: blinking and constant illumination. A blinking light indicates either the mute state or the time-delay function in progress, which is activated every time the amplifier is switched on to protect the tubes. It takes around 30 seconds for the cathodes of the output tubes to reach their optimal operating temperature, after which the amplifier is ready for use, indicated by the constant light of the indicator.

The sturdy power on/off switch is located on the left side. On the rear panel there are four pairs of gold-plated RCA inputs, three high-quality speaker terminals per channel with dedicated 4 and 8 ohm taps, and the power socket with the main fuse.

On the top plate there is an ampere meter displaying the bias current of the output tubes, as well as a pair of switches for selecting which of the four tubes’ bias current is being measured. There are also two pairs of potentiometers for adjusting the bias of the corresponding tubes using a screwdriver.

Listening Impressions

Within the limitations of its design—Class AB operation with the necessary negative feedback circuit and solid-state rectification—I would say that this amplifier has surpassed my expectations. It delivers a great deal of the midrange magic typically associated with DHT Class A amplifiers while, at the same time, having no obvious deficiencies at the frequency extremes.

The bass is authoritative and controlled, with a great sense of weight, while the highs are sparkling and precise, with a very fine grain structure. Giving one of my favourite guitar/vocalist combinations, Joe Pass and Ella Fitzgerald, a listen with their fourth and final release Easy Living, I must admit that I eventually gave up trying to concentrate on analyzing reproduction traits. The performance was so overwhelming that I surrendered to the sheer timbral richness of Pass’ D’Aquisto guitar and Ella’s emotionally mature voice.

Listening to another beautiful dialogue, this time between the voice of Eleonora Bianchini and the double bass of Enzo Pietropaoli In Sight, confirmed my impression that dynamic agility and soundstaging are among the main virtues of this amplifier.

Depending on the speaker taps used, these qualities can differ slightly. When connected to the 8-ohm taps, the Fostex FE 108-Sol speakers tend toward a leaner, more analytical presentation, showing greater micro-detail retrieval and more compact images.

Conversely, the 4-ohm taps deliver more energy and a larger soundstage, creating the impression that the amplifier has greater power reserves. Although the micro-details are not as sharply defined, there is a feeling of greater inertia and longer decay, making the presentation slightly more fluid and musical, but at the same time perhaps less natural.

Generally, full-range speakers are not particularly suited to reproducing complex music. This is simply because a single driver has to cover the entire frequency spectrum from top to bottom, requiring considerable cone movement that can push the driver toward non-linear behaviour and higher distortion levels.

Keeping this in mind, I refrain from judging whether the amplifier can keep pace with complex musical passages or not, because in this case the limiting factor might actually be the speakers. Personally, this does not bother me, because my musical preferences are governed to a large extent by the principle of simplicity, which I embrace in its full essence.

I would always prefer sparsely arranged chamber pieces over large orchestral works simply because fewer voices are easier to follow and create less clutter. The moments of silence within music, together with the natural decay of tones, are something to appreciate in the Stravinsky, Desyatnikov & Tchaikovsky album by the young but already world-renowned musicians Aylen Pritchin (violin) and Lukas Geniusas (piano).

While listening to the timbral diversity of traditional medieval instruments of Sicilian, Arabic, and Persian origin in Al Qantarah – Abballati, abballati! – Songs and Sounds in Medieval Sicily, it became obvious how extremely clean and believable the transients are rendered. This tells me that the amplifier preserves signal phase consistency remarkably well.

Tone colours are all there, and voices sound stunningly real. Even though a good Class A, zero-feedback amplifier could probably reveal even more nuances, the LM-211IA keeps very good pace in this regard.

With some studio recordings, however, it can sound slightly forward and hard on the ears, causing a certain degree of listening fatigue. This might also be related to the overall voicing of the system and the fact that the Fostex FE 108-Sol speakers have a slightly emphasized midrange.

Letting Toots Thielemans’ 1989 Footprints album flow makes this finest example of harmonica artistry shine. Dominated by Mulgrew Miller’s jazz mastery on piano, the soundstage is highly transparent, with plenty of air around the instruments and a clearly defined perception of depth in the front-to-back direction.

Playing Anette Maiburg’s Classica Española, the amplifier pushed my speakers to a level of performance that matched my preferences perfectly: a transparent, detailed, and immediate presentation, combining weight in the lower registers with a sparkling and airy top end in a very consistent and natural way.

I should not forget to mention that I am using this amplifier exclusively in triode mode, which, in my opinion, is far superior to ultra-linear operation. Despite the difference in power output, there is subjectively almost no difference in perceived loudness when switching between the two modes. This is probably due to the fact that in triode mode the level of transparency is higher, allowing lower sound pressure levels to create a similar impression of loudness.

Tube rolling

Already with its stock Chinese-made Shuguang tubes, the LM-211IA performed extremely well, but I was aware that good new old stock (NOS) tubes could potentially raise its performance even further. Therefore, I decided to begin by replacing the ECC83/12AX7 and ECC82/12AU7 tubes in the preamplifier stage, as it is generally known that these tubes are more likely to influence the sound than the EL34/6CA7 tubes in the output stage.

I was told that there are basically two main groups of NOS tubes worth considering. On the warm, vintage, and organic side are Mullard and Philips tubes. On the other side, associated with a more neutral, modern, and detailed sound, are Telefunken and Siemens.

It was difficult for me to decide which direction to take, so I reached out for advice from Ralph Wege, who is known as one of the NOS tube experts here in Germany. His company, Wege High Fidelity, has gained considerable credibility over the years.

He advised me to combine tubes from both groups in order to achieve a balanced and natural sound that would be neither overly warm nor excessively analytical. One option would be to choose a warm-sounding tube for the driver stage (ECC82) and a neutral one for voltage amplification (ECC83), or the other way around.

It happened that I stumbled upon a rare pair of NOS ECC83 Philips Miniwatt long-plate tubes from 1958, which I purchased. This predetermined my choice for the driver tubes: NOS ECC82 Siemens silver-plate tubes, which I acquired shortly afterwards.

Replacing the Chinese ECC82 tubes in the driver stage brought a noticeable improvement. The presentation became more articulate and detailed, and the transients—the tiny fragments of time in which a sound is born—gained a level of resolution that had been missing with the Chinese-made Shuguang tubes.

With the ECC83 Miniwatts, however, things were not as straightforward. Initially, they sounded rather rough, even harsh, and the presentation felt, I would say, somewhat retro. I was disappointed that after spending a small fortune on these tubes, they did not deliver what I had expected.

I contacted Mr. Wege again, and he explained that, being NOS tubes, the Miniwatts needed at least a few days of operation before opening up and reaching their best performance. Following his advice, I left them running for several hours a day, and already by the third day things had improved significantly.

After having them in the amplifier for a week, I had the impression that they were completely different tubes. This was an important lesson: one cannot judge the sound quality of a tube before giving it enough time to fully open up.

With the ECC83 Philips Miniwatts in the preamplifier stage, the sound became fuller and bolder. Instruments and voices gained more presence, and the bass became richer and deeper than before.

Despite all these positive qualities, probably because of their smoother and more liquid presentation, I had the suspicion that they might lack a little detail. After extensive listening and swapping tubes back and forth, I realized that what I had previously considered detail was actually a kind of graininess in the textures that the Chinese tubes tended to emphasize, as opposed to the more organic texture rendering of the NOS tubes.

As a conclusion, I would say that replacing the stock tubes with the aforementioned NOS selection brought a subtle but noticeable improvement, moving the presentation in the direction of a more organic and realistic sound.

Thank you for stopping by, and happy listening!