Line Magnetic LM-845 Premium

Hardware Review

Line Magnetic LM-845 Premium
Friday, June 4, 2021
integrated tube amplifier
Jason Kennedy

I have reviewed a few integrated amplifiers in my time, many of them involving vacuum tubes (valves), but none has had the weight and physical presence of the Line Magnetic LM-845 Premium. For a start you have the main chassis with its plethora of tubes on the top and a dizzying array of knobs and meters on the front, this is bigger than the vast majority of integrated amplifiers, yet in Premium guise the LM-845 has a second chassis that looks a lot plainer but is as large and heavy as a decent power amp. This part of the combination contains output transformers alone which were separated to stop the amplifier as a whole becoming too heavy for mere mortals to lift, it weighs 20 kilos, the main chassis is twice as heavy.

Tube amps have always required the extra mass of output transformers (the rare OTL or output transformerless variant amps being the only exceptions) so it’s inevitable that when you take things to extremes mass and associated boxes start to build up. I’ve known enthusiasts to have at least this many boxes for a preamplifier in the past, but they were very enthusiastic, tubes seem to have that effect. And it’s understandable, a good glass powered amplifier has magical speed, dynamics and delicacy that make almost everything you play sound thrilling. And when you consider that tube electronics were used to make many of the finest sounding recordings around there is a good case for going down this route.

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Line Magnetic is a Chinese company with a large range of electronics the majority of which are tube based, some can be purchased direct from the factory online but this model is exclusive to official distributors. Which while it adds some cost does provide the benefit of demonstration, after sales service and warranty, you wouldn’t want to have to foot the return carriage bill and provide the mountain of paperwork required for an international return. And the price remains very competitive for an amplifier with this sort of spec, the headline being that it’s a single ended triode (SET) with 845 output tubes and 300B drivers, both highly regarded devices albeit the regard does depend on the manufacturing origins of the valves, the examples on this amp are made by Shuguang. The 845 is one of the most powerful triodes available today and it endows this amplifier with 30 Class A Watts per channel, which may not sound much to those familiar with transistor amp outputs but it’s pretty meaty for an SET where outputs in single figures are not uncommon.

The LM-845 Premium can be used as an integrated or a power amplifier, there are inputs and a front panel switch that turn it into the latter, but it’s well equipped for use alone with four line inputs one of which is on XLR connectors. It comes with a remote for volume and mute only and has an ALPS volume control alongside the central VU meter which shows output, I don’t think this got as far as the halfway point throughout my listening despite using speakers with a low ish sensitivity. Inside the box Line Magnetic have constructed the circuitry using point to point wiring rather than with printed circuit boards, which is the traditional way to build a tube amp but also the slowest and thus most expensive.

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The two smaller VU meters on the front are for setting bias on the 300B and 845 tubes, it’s easy to check and when I did they were all within spec so no tweaking was required, slot head adjusters can be accessed from the top if that is necessary. A more unusual feature is switchable negative feedback, traditionally this is the bete noire of SETs but does have its uses with less tube friendly speakers where it brings extra control to the bass. 

The output transformer chassis attaches to the main amplifier with a pair of chunky umbilical cables that have locking fixings at both ends, these are usefully long and let me put this chassis at the bottom of the next rack. It has speaker terminals for the 4, 8 and 16 Ohm taps on the transformers and these are worth experimenting with to establish which is the best match for your speakers. Most speakers are nominally 8 Ohm loads but this varies under dynamic conditions so the 4 Ohm option might well be better.

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Sound quality
The Line Magnetic arrived while I had a pair of Xavian Quarta Evo loudspeakers in the system, this is a large sealed box three-way with 87dB sensitivity so not particularly tube friendly. Nonetheless this pairing delivered fabulous voice projection and realism from Joni Mitchell’s A Case of You, a simple voice and guitar piece that doesn’t require much power. Trumpet player Matthew Halsall’s Salute to the Sun is still acoustic which plays to this amp’s strengths and the various instruments sounded sublime, the system bringing out the ethereal quality of the music while also placing the image well in front of the speakers. The double bass line is relaxed and timely with the LM845 providing sufficient power to keep things under control.

Voices are a clear strongpoint, Lester Bowie is expressive and sassy on Foolology (Conjure) and the band sounds juicy, ripe and deep in the groove. The imaging remains up front but the tonal balance is smooth and even. Moving onto Bowers & Wilkins 802 floorstanders which have an easier 90dB sensitivity combined with lower minimum impedance (making them harder speakers to drive overall), the limited grip in the bass is apparent but the pairing times well enough with Bob Marley’s Natural Mystic. Leading edges are less clearly defined than is the case with more powerful solid state amps however. Which is another way of saying that it has that lovely tube quality of fluidity and a near total absence of grain, you often hear about transistor amps claiming to have the qualities of a good valve design and this is the sort of quality they are trying to emulate. 

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When Oliver Nelson’s horn players harmonise on Blues and the Abstract Truth it’s all worth it, instruments are full of life and character, the piano big boned and chewy, the drums reverberant and the double bass bodacious. It’s the sort of sound that makes jazz come to life in the room. This sense of vitality is what makes single ended triodes so alluring, they may not have the power of push-pull pentodes or tetrodes but there is an immediacy that is totally captivating, it’s as if they are opening a window to the soul of the artist that other amps can’t find the handle for.

On less acoustic material like the Weather Station’s Free you get all of the scale in the recording alongside full heart on sleeve emotional exposure, the electric bass is round rather than firm with plenty of depth and speed and the guitar has just the right amount of edge. I love the way this amp delivers the electricity in the atmosphere of a good recording, Arab Strap’s New Birds delivers this palpably, producing a hair raising intimacy in its quietest passage that is very powerful indeed. Tortoise’s bass guitar powered Magnet Pulls Through has a fabulous depth of tone and lovely weight to the kick drum, it reels you in and won’t let go until the last note has faded away. On a less emotive level it’s nice to have a remote control that allows small changes of level, the one provided with the Line Magnetic is a nice piece of machined aluminium that works well.

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Adding a Line Magnetic LM512 CA preamplifier increases low level resolution quite clearly and makes a good case for itself, adding detail and improving the quality of timing quite markedly. It costs nearly as much as the LM845 Premium so nearly doubles the investment and if you don’t try it you won’t miss it, ignorance can be bliss. 

Finally I tried the LM845 Premium with PMC twenty5.26i floorstanders which are an easier load than the 802s but not exactly tube friendly. This combination timed beautifully, the amp being better able to control the bass and thus deliver nimbleness across the board. Once again voices are the strong point and quiet atmospherics, this time on Michael Chapman’s Aviator, are very poignant and inviting. You really get the message in the music with this amplifier, its transparency reveals the depth of reverb and the timbre of the instruments but what shines through is just how powerful the emotional message is. This is the heart of the matter, it’s what makes music worth investing time and money in, and this Line Magnetic is a powerful conduit.

Specifications: 

Type: Integrated triode stereo amplifier/power amplifier 
Analogue inputs: 3x RCA, XLR, pre input on RCA
Phono input: N/A
Digital inputs: N/A 
Analogue outputs: N/A 
Bluetooth: N/A
Headphone output: N/A
Speaker outputs: 4, 8 & 16 Ohm taps on 5-way binding posts
Power Output: 30W 
Dimensions (HxWxD): 
Control Chassis: 460 x 435 x 456mm
Output Chassis: 165 x 435 x 410mm
Weight: 40kg + 20kg
Warranty: 2 years (valves 6 months)

Price: 
£9,999
Manufacturer Details: 

Line Magnetic Audio Co. Ltd.
www.lm-audio.com

Distributor Details: 

VAL HiFi
T 0333 577 2005
www.valhifi.co.uk