Line Magnetic Audio LM-518IA integrated amplifier

When I began writing for Stereophile, I heard people whispering:

"Herb is one of those triode-horn guys."

Wrong. Most of my life, I've favored solid-state integrated amplifiers driving small, British-made speakers.

"I'm sure he hates digital."

Wrong again. I sold all my LPs some 12 years ago, and since then I've been filling my days with CDs and high-resolution downloads. (However, I am starting to collect vinyl again, because my vintage DNA still remembers how to worship at the Altar of Black Discs.)

"Reichert? He's a mono guy. He's not into imaging."

Way beyond wrong! In my view, hearing the tangible verity of a recording venue, and the precise locations in it of microphones and performers, are essential to any full comprehension of recorded music.

Of course, I am not free of audiophile prejudices. I am not attracted to giant robots (very large loudspeakers) or alien monoliths (big, heavy power amplifiers). Both tend to make me anxious. I also believe that, if an audio component is going to cost as much as a good car, it should image well enough to reveal to me its own blue-robed design wizard floating above it. Actually: I want to see that wizard, and his wand and pointy hat, even when the component costs only as much as an affordable integrated amplifier.

The highest-quality audio products are not designed using only a single audio technology, old or new, any more than they are created only by a particular ethnic group or only within a particular geopolitical sphere. Today's best hi-fi inventions are made everywhere on the globe, by brave, inspired, talented people whose creations aren't me-too products, but instead are unique components designed to fulfill the earnest dreams of devoted audio connoisseurs. The Line Magnetic LM-518IA integrated amplifier is such a product.

In 2005, two brothers established the Line Magnetic Audio Co. Ltd., to manufacture—in their own factory in Zhuhai, in China's Guangdong Province—distinct ranges of CD players, DACs, amplifiers, and loudspeakers. They were motivated by the excellent sound and build qualities and elegant appearance of vintage Western Electric movie theater electronics and loudspeakers.

The elder brother, Zheng Cai, is in charge of Line Magnetic's Classic models, which include high-quality reproductions of such vintage Western Electric gear as the renowned 91A and 86A 300B amplifiers, as well as other WE-inspired inventions of Cai's own design. His younger brother, Zheng Xi, is in charge of a team that creates Line Magnetic's Silver and Gold lines of more affordable audiophile products, including the LM-518IA ($4450), a single-ended-triode, line-level integrated amplifier, based on the 845 triode tube. The LM-518IA has been at the heart of my reference system for more than a year.

If you're not familiar with the Line Magnetic product range, I encourage you to take a moment and peruse the website of Tone Imports, Line Magnetic's US distributor. There you'll see that the LM-518IA is the middle model of a range of three 845-tube SET amps. The biggest, the LM-219IA—almost an alien monolith—costs $7495. It uses a single 300B triode tube per channel as a driver stage for its single 845 output tube per channel. The LM-518IA's diminutive sibling, the LM-218IA ($3495), is a smaller, lighter version of the '518 in hammertone silver, with no rectifier tube. Like the '518, the '218 has two 12AX7 tubes and a pair of triode-operated beam power tubes—6P3Ps are standard in the '518—to swing the high voltages needed to drive the grids of the fierce 845 output tubes. All three amps feature retro styling, and massive mains and output transformers.

For those of you unfamiliar with directly heated tubes, the 845 is a three-element tube that, unlike the ubiquitous, indirectly heated 12AX7 or EL34 tubes, does not employ a separate heater for the cathode to generate currents of electrons. Instead, directly heated triodes conduct large amounts of current in order to boil off high-energy electrons directly from their coiled-wire filaments. A directly heated tube has one of two filament types: dull emitters, which are nickel coated in oxide; or bright emitters of thoriated tungsten, as in the 845. Almost every guitar amp and audiophile tube amp made today uses indirectly heated coated-nickel dull emitters (footnote 1). To my ears, a properly designed amplifier using directly heated thoriated-tungsten tubes always sounds more vivid, elegant, direct, and brilliant than its indirectly heated dull-emitter counterpart—especially when excessive amounts of feedback aren't masking the tube's essential character.

The most important thing to understand about the design of the LM-518IA is that it is not a KT120, EL34, EL84, KT88, or 6550 amp. Unlike those popular audio-tube types, the 845 was designed—by RCA, in the early 1930s—to be a sturdy source of power in commercial and military radio transmitters like the ones in your local AM station or B-17 bomber. Each 845 anode requires over 1000V DC and is capable of dissipating about 100W. Compared to some lazy, bourgeois EL34 amp, the LM-518IA is a fire-breathing fairytale beast: the sonic and aesthetic antidote to all those newfangled, cool-running, class-D solid-state amps. Run in pure class-A, the 845 tubes' filaments operate at 3140°F, and their glass surfaces emit literally skin-searing heat. Beware! Never touch the big tubes while they're lit, or for quite a while after they've been turned off—and never poke around inside an LM-518IA just after you've turned it off. The former will send you to the emergency room. The latter could send you to your grave—or, worse still, maybe even void your warranty!

The first time I lifted the 77-lb LM-518IA out of its box, I realized that it's a helluva lot of stereo amp for $4450. And when I removed its bottom plate, I couldn't stop staring at the expensive, German-made Neglex coupling capacitors, or counting the multitude of Japanese-made Rubycon electrolytic capacitors. Eventually, I noticed the LM's two substantial filter chokes, and the artfulness of its point-to-point wiring.

On the rear panel, for each of the two channels are four high-quality, gold-plated, five-way speaker terminals: one each for 0 (ground), 4, 8, and 16 ohms. The only preamp inputs are three pairs of gold-plated RCA jacks. A fourth pair of RCAs, labeled Pre In, lets the LM-518IA be used as a basic power amp.

On the LM-518IA's enameled top plate are screws for adjusting the bias and canceling any hum in each 845 tube. In the course of my yearlong possession of this amp, I have never had to use these: There has been no hum, no sputtering, no hissy crackling noise—just lots of warm air rising. Speaking of which, it's essential that you leave at least a foot of open space around and above the LM-518IA. And if you value the safety of curious pets or wayward children, use the tube cage (supplied).

On the front panel are a sturdy On/Off button, a meter to assist in biasing the 845 tubes, and two silver dials. The first of those is the volume control, its face containing a tiny orange LED that subtly flashes as the LM-518IA warms up, after which it glows steadily, serving to indicate the dial's position. The second dial selects among the three line-level inputs. The stainless-steel remote control sports only Volume and Mute buttons. The LM-518IA has no DAC, no phono stage, no Bluetooth receiver, no WiFi capabilities—and, to my extreme disappointment, no balance control or mono button.

It was never my intention to formally appraise the Line Magnetic LM-518IA. I borrowed it only to use it as a temporary reviewing tool: I needed a high-quality, reasonably priced integrated amplifier that was more contemporary and more available than my vintage Creek Audio 4330, and that could serve as a benchmark against which to assess other affordable (and mostly solid-state) integrateds. In this capacity, the LM-518IA has performed far beyond the original call to duty. I review it now only because I believe readers need to know: What is this brightly glowing, 22Wpc amplifier to which I keep alluding?

Footnote 1: All those dull tubes might actually be responsible for an expression—one that I've always hated—for something I've rarely experienced: tube sound. (For further reading on this, click here.)
Line Magnetic Audio Co. Ltd.
US distributor: Tone Imports

RobertSlavin's picture

This amplifier may sound very good but, personally, I wouldn't want glass tubes whose contents were 3140 degrees fahrenheit in my living room. It sounds too dangerous to me, setting aside how much heat they would generate.

Even if the amplifier had tube cages (it would have been nice to have seen them in this review), I suspect the cages themselves may get so hot to be dangerous to the touch.


John Atkinson's picture
RobertSlavin wrote:
This amplifier may sound very good but, personally, I wouldn't want glass tubes whose contents were 3140 degrees fahrenheit in my living room.

When I tested the amplifier, it was sitting on my test bench just 2 feet away from me. I got a tan!

John Atkinson
Editor, Stereophile

Bogolu Haranath's picture

I thought you would be 'glowing' :-) ........

SET Man's picture


Beside making a nice space heater in winter and turn your room in to sauna in summer! A pair of 845 tubes are also make a great night light! Very pretty brightly warm glow.

On a serious note, I like 845 tubes. A well designed and executed one can sound amazing with power to drive more than horn speakers.

Metalhead's picture

I heard this at pitchperfect in LA with Devore speakers. Unlike Herb I have a small speaker=small sound bias. I fell in love with big horns and stats decades ago. Having said that it was a fantastic combo and I was certainly impressed with the demo. Enough so that I am going to to try to get chair time in front of it again and perhaps spring for it.

Heat is welcome here in Alaska so no worries on that front.

Wonderful review that captures what this integrated can do.

lo fi's picture

What a beautiful amp.

iosiP's picture

I currently read most ampilfier reviews in Stereophile (well, less the digital stuff) and most of the time I give more attention to JA's measurements. Now I've read many conclusions like (quoting from memory) "This amplifier behaves quite well for a low-powered SET design", "Yes, as it's a single-ended-triode design, its bent transfer function leads to a nonlinear signature dominated by second-harmonic distortion. And it's noisier than I like to see. But for such a design, it offers high power." and other similar qualifications.
Now do I have to remind you the underpowered Audio Note Jinro or the similarly grossly underpower Wavac SH-833?

So here comes my question: why would I opt for a tubed amplifier that sounds good "for it's class", i.e. with qualifications (or even does not deliver a shade of what it promises), generates heat, is a danger for kids and pets and uses... well, consumable output devices when the same amount of money can get me a decent - even class A - SS amp that would reproduce faitfully the signal that is fed in?

Milesian's picture

Having run the LM518-IA for close to a year in a house with three cats a dog and occasional grandchildren, I can attest that no creatures were harmed during the playing of my music. Nor was my listening room overbearingly hot during the sweltering Ontario Summer. Come on folks get serious, you do realize you can turn it off when you're not listening right? I'm more afraid of the electric stove and light bulbs in my house.

Marc210's picture

In the past, I've listened extensively to two tube amps, ARC Classic 30 and Yves Cochet ALP2, and many others briefly.
And it's no surprise I prefer ss even as pre and of course digital to analog.

james's picture

but the filaments get to 3140°F, not the glass itself. I could be wrong. I have one of these and it puts out some heat, but I don't feel it until I'm flipping a record.

I agree with Herb's review of this amp. It is fantastic

doak's picture


jmsent's picture

depends on the current in the filament. In this case about 3.25 amps. That's the same as a pair of KT 88's so the overall heat output of a push pull amp using those tubes would be about the same. The worst burn I've ever gotten from a tube was when I inadvertently grabbed onto a 6CW4 nuvistor in a tv tuner. Those tubes may be tiny, but they get hot as blazes because there's no surface area for heat dissipation.. At least the 845 has a huge glass envelope and has a filament with a large surface area.

james's picture

Hey, Line Magnetic...please make a phono stage to match the 518 and the gold series DAC!

MusicT's picture

Been running one of these for 18 months. I've not found the heat to be any issue at all - wondering if the reviewers are making good humor at the expense of accuracy. (i.e. I'm got a tan. ??) It does get warm but even in a small room, I've not found it bothersome.

Wonderful amp indeed. I picked this over PrimaLuna which I see you have rated as Class A in your annual roundup.

Patrick Raffin's picture

would you recommand an adress un Europe, in China, in America ?

piebia's picture

Dear All
I know that the new 508 has been released. did you have listened it?
How abaout the comparison with the 518 one matching with devore gibbon 3xl.

Thank you