Line Magnetic LM-518IA Integrated Amplifier
Here were showcasing the build quality and performance output of the popular Line Magnetic LM-518IA Integrated Amplifier. I wanted the opportunity to get elbow deep into this amplifier because I am quite skeptic of its offerings. The LM-518IA demands a fairly mid-high price for a 22W SET from China, yet the available technical information from the manufacturer and history is incredibly lacking on the unit. This is always a big flag to me. This will not be a subjective audio session review..I don’t understand those or why folks read them…this is a technical break down…so lets dig in!
Line Magnetic History:
Line Magnetic, from research was establish in Zhuhai, China in 2005 by brothers Zheng Cai and Zheng Xi. Their board product range includes reproductions of high-end West Electric topologies and proprietary designs. Their production line compasses DAC, tube CDPs amongst stand-by models designated to integrate one system brand synergy. The LM-518IA Integrated Amplifier is the mid-range SET amplifiers using LM’s purpose built 845 tubes, sitting below their KT-120 tubed 100W 501IA Integrated Amplifier.
...presumably the staff at Line Magnetic
The 845 designed by RCA and released in 1931 was primarily used in radio transmitters is a unique hi-fi tube. The 845 is a three-element direct heat tube using a thoriated tungsten filament working at parameters of 75W anode dissipation w/ 1250V, the filament requires a 10V 3.25A.
The LM-518IA is billed as a 22 Watt per channel Single-End Triode (SET) Class A Integrated Amplifier. The 518IA uses two 12AX7 (V6/7) voltage amplification tubes, two 6P3P (V3/4) driver tubes and two 845 (V1/2) output tubes along with a 5AR4(V5) rectifier tube. Also useful is the front meter display injunction with the V1/V2 bias adjustment, the front meter assists in obtaining the 70mA current. Along with the bias adjustment a Hum-Balance is equipped and easily adjustable with a small screw-driver. The control points consists a Alps attenuator and a multi-line in selector or main-in.
Tube complement:
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845 x2, 6L6 x2, 5AR4 x1, 12AX7 x2
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Output power:
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22W + 22W
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Distortion:
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1% (1kHz)
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S/N:
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87dB
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Input Impedance:
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100k
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Output impedance:
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4, 8, 16ohms
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Performance Reports:
Below are performance reports on the actual output of the LM-518IA using a 8 and 4 OHM Dummy loads...not some "self" emulated speaker simulator....none of my results are weighted or averaged, this is a what I consider a true representation. To keep the article un-bias I will not weigh in on a output conclusion here.
(8 OHM) LM-518IA
(4 OHM) LM-518IA
Build Quality:
The first few things I noted was the aesthetic impression and weight! The 518IA is incredibly heavy..always a good sign..like most amplifiers the weight is distorted through the rear chassis with the large power transformer centrally located, flanked by the two output transformers.
Chassis & Finish:
The finish of the 518IA is a gorgeous almost gloss heavy white powder coated over the irons that looks flawless and classy. The chassis has a brushed aluminum finish and front plate is a meter matching off-burnt orange metallic color. The brushed chassis cover is a very clean product used as a U-shaped chassis, I should note the corners and vents of the 518IA are very very sharp, sharp enough to cut skin or a careless child, none of the edges feature a smoothed over edge or even beveled. The rear plate has a very plastic/white metal feel that has a printed/painting white finish subject to easy mares. The bottom plate is painted top and bottom with 4 single screwed base feet featuring an brushed aluminum cap over plastic. The tube cage is also powder coated the same gloss-white finished as the iron covers, which banana-style pins to snap securely into the chassis. I really like this idea, yet it does have some significant wiggle room, is easy removed by a child and will not provide any protection I suspect in the case of a fall or blunt force as the grates are far to spaced out and thin.
Inputs/Outputs:
The 518IA has a series of three line-level inputs and one set of Pre-In level inputs. All the inputs are gold-plated Tiffany style metals. These seem incredibly robust and sturdy, one of my favorite hardware components of the 518IA.
In contrast the output terminals which consist of a two channel 16,8 and 4 ohm terminals. The 5-way binding posts feel exactly like the cheaper plastic bodied type available on eBay and surplus speaker suppliers. The caps are loosely constructed, non-locking do not contain a end retaining washer. The AC power inlet is a standard IEC plastic connector which feels firm and secured, the supplied power cord is clean, robust and heavy gauged.
Controls:
The two controls on the front of the 518IA are the volume and selector function. The volume knob is illuminated with a green indicator that flashes during the -soft start procedure. Both are bright aluminum finish that appear to be milled which is nice to see. However the selector positions exhibit some torque on the rotary controls gangs when turned and locked into a position, with only X1 set screw to retain the knob this extra torque appears to be contorting the internal selector switch, this particular unit auditioned has been service once already for this repair which required a new selector switch within several hundred hours of use only. A secondary set-screw should be utilized here. The power button is a typical push-button type with a aluminum cap and shaft, the action feels very solid and the hepatic feedback is good.
Internals:
Starting the core hardware, the tube sockets employed in the 518IA are all gold-pin ceramic sockets for the AX7, all are very secure, especially the front end 12AX sockets. The massive 845 sockets are also a ceramic base which offer a very heat hardened solid socket that should last ages.
As mentioned the motorized Alps volume potentiometer is the standard in high-grade audio logarithmic potentiometers which also offers the protection of potted enclosures. The bias IC circuit contains SMD controlled components and precisions Bourns trimmers which I personally use in our restorations here at Hallo-Fi All of the heavy wattage current limiting resistors are chassis mount type on their own separate chassis mounts which I like to see for 2W+ components due to the heat they exhibit.
The use of custom stand-alone PCB assemblies are evident through the construction which in some cases is better than eloquent point-to-point. Each of the large filtering capacitors (470MFD/450V) and full-wave bridge rectifier use a custom PCB for their associated networks. They appear to be properly screen-printed with good solid copper tracing and dual layer PCB’s which should stand up to the heat of unit quite well over time.
The compliment of capacitors was nice to see, the use of a high temp (105C) Nichicons and low impedance PW’s, again as we use here and Japanese Rubicons. I did see a review that quotes these as "German high-end Film capacitors"...That I think is purely marketing , I have found little info on German Neglex capacitors anywhere, all of the film construction I suspect to be Solen MKP capacitors or the like simply rebranded..but do not mis-read as I think the Solen polypropylene film capacitors offer a very high grade of reliability and performance for an affordable cost. The use of KOA MOX type resistors in the 1-5W are very dependable, robust resistors with and excellent track record, each leg is appropriately shielding thats exposed as well. (**EDITED to keep heads calm...)
All of the point-to-point busses, wiring and soldering appears well done and sturdy. No blobs or burnt wires, clean use of heat-shrinking and the topology was very well laid out and constructed, a good use of chassis space as well.
Conclusion
My time with the Line Magnetic LM-518IA has been very enjoyable. The unit appears to bias reliably and consistently. The tube compliment is sound and of true and tried designs out there. The soft-start circuit appears perfectly timed and active when tripped into protection. Overall I would mark the LM-518IA a reliable and dependable amplifier if well cared for. I would personally recommend checking the bias before each session and never operate around animals or children if their able to access the unit easily.
The internal build quality I think merits the start of the asking price, yes priced out separately the costs of core components is reliantly cheap, but the outputs are of very high quality, Alps and large microfarad capacitors can bump up construction costs substantially. The exterior I feel leaves a lot to be desired, from the sharp corners, poor controller design and cheap speaker terminals I expect a great deal more there for a 4500$ machine.
Edith Piaf's Non, je ne regrette rien and Nina Simone's Suzanne on a older British Stage 2 Micromega CDP
UPDATE:
Contrary to what I would like to present or typically do I would like to add a note on my listening impressions here. The LM518IA is destined to be heard by one of the DeVore Fidelity line ups as is highlighted in several online reviews, having done so on a pair of O/93's in Madison, Wisconsin and now at home with a very modest and simple pair of Full Range folded horn Bk12s with the 126EN Fostex driver playing Edith Piaf's Non, je ne regrette rien and Nina Simone's Suzanne via a older British Stage 2 Micromega CDP...this integrated amplifier is very impressive...The upper and mid range is well presented, neither sharp nor contrasting. Totally enveloping the idea of a Class SET and its expectations. The lower end and synergy between peak to peak differences is impeccably defined and robust when needed...something often lacking in my experience with SET's. Some may waver at the performance factors but the LM518IA should be paired a high efficient Full Range and a possible super driver or again the DeVore's.
References/Source
http://www.devorefidelity.com/
http://www.toneimports.com/
http://www.lm-audio.com/english/index.aspx
