Line Magnetic LM-88IA, LM-150IA, LM-845IA, LM-805IA and LM-845 Premium – part 1

A group review of five Line Magnetic amplifiers using KT-88 and KT-150 Push-Pull and 805 and 845 SET tube designs

Part 1 – Introduction
Part 2 – Review using Gustavson speakers
Part 3 – Review using Wilson speakers
Part 4 – Review using Duetta Signature speakers
Part 5 – LM-845 Premium and Conclusion

Review samples supplied by Frank Suijk of A Tube High Fidelity

Retail Prices in the Netherlands:

LM-88IA – 2.999 euro
LM-150IA – 4.999 euro
LM-845IA- 3.999 euro
LM-805IA- 4.999 euro
LM-845 Premium – 9.999 euro

When my good friend Jan Cramer aka Meneer Buis (Mr. Tube) tipped me about the Line Magnetic brand and I had a first look at their models, I got excited right away. These amplifiers have a very robust and solid look and a unique styling. These are amps with attitude, proud of what they are. Then, when I discovered that the brand employs a wide range of tube configurations, I got even more excited. Tubes in and of themselves do have certain sound characteristics but their implementation arguably has a larger share in the end result, meaning that you can’t really say much about the perceived differences between two different tube amps of two different brands as a consequence of the tubes that were used. When the same manufacturer is behind such products, however, then it becomes a much safer bet to say something relatively conclusive, for example about how KT88 compares to KT150 or how Push-Pull compares to SET. So, in order to make a nice showcase of the Line Magnetic brand and a good cross-section of their lineup, I set out to review a representative range of amplifiers using various tube types.

Removable protective cages make smart use of banana speaker connectors for a secure fixing yet easy removal.

BC Diffusion and A Tube High Fidelity

An internet search produced a couple of results from which it was not immediately clear which was the importer/distributor. One of the sites that I found suggests to be an importer but is not actually an official distributor or retailer. The other site that I found turned out to be the official distributor for Europe, BC Diffusion, where you can find the list of official dealers for Europe. I figured that BC was the company that I should contact for my review plan. Some time passed while I tended to other business, and when it was time to set the wheels in motion, I did another internet search and this time found 3 obvious results: the aforementioned importer which would later be identified as a parallel importer, the actual European importer BC Diffusion, and a brand new site called A Tube High Fidelity.

Following the information on the BC Diffusion site, A Tube High Fidelity turned out to the official dealer of Line Magnetic in the Netherlands so I opted to contact both A Tube High Fidelity and BC Diffusion and received a response the very same day from Frank Suijk, co-owner of A Tube High Fidelity. As it turned out, Frank had just recently settled in his new store in Almere and was now finalizing his website, showcasing the entire Line Magnetic lineup as well as various other electronics- and speaker brands. Frank was more than happy to jump on board and with help from BC Diffusion, provided five different Line Magnetic tube amps. Also see the separate A Tube High Fidelity Company Special.

Company History

Line Magnetic is established in Zhuhai, China, founded in 2005 by the Zheng brothers, both passionate audiophiles. The Line Magnetic Audio Company is a combination of Foshan Line magnetic audio studio and Zhuhai Line magnetic Audio Co., Ltd. The former is established in Zhuhai by elder brother Zheng Cai and the latter by younger brother Zheng Xi, in Zhuhai City.

This is how it started. In 1995 Mr. Zheng Cai, once the General manager and chief engineer at Cayin and later one of the shareholders, was in disagreement with the board when he suggested developing truly high-end amplifiers. After he left Cayin he worked for various other companies in the roles of engineer, researcher, developer, and co-founder, while gaining more and more understanding of Western high-end audio. For example, he was always interested in traditional Western Electric products and used to spend his spare time repairing and restoring products. This, together with his earlier experiences provided a solid foundation for starting the Line Magnetic Audio company.

Build quality is sublime – even the remote control is finished impeccably.

The unit is all metal, even the bottom plate. It seems that this sample has the wrong screws fitted or is missing rubber feet, probably an oversight.

Tube principles

Thanks to audio buddy Meneer Buis and his own quest on the road to tube nirvana that resulted in a steady stream of tube amplifiers reaching my listening room for evaluation, I’ve had my fair share of tube amp experience in a relatively short timeframe. During these comparisons, I noticed how a SET amp can sound incredibly pure but also very lively and dynamic, even more so than any solid state amp that I had used until that time. However, this would only be the case when the match with the speaker was ideal. Apogee magnetostatic speakers, for example, require too much power to work well with SET amps. Some Push-Pull designs, however, made the Duetta Signatures shine like never before. For those unfamiliar with these two principles, I will explain a little about PP and SET.

Push-Pull

In Push-Pull, there are two (or a multiple) output devices (be it transistors or tubes) that work together to amplify the sine wave. This can be done in Class AB but also in Class A. In Class AB this means that one output device takes care of the upper half of the sine wave, the positive side and the other takes care of the lower half, the negative side. This provides more power than using a single tube in class A but also introduces crossover distortion in the section where one device takes over from the other. Additionally, most people agree that while multiple output devices are often inherently more linear and have a higher factor (grip on the speaker), they will usually also sound less pure. The best Push-Pull designs in my experience so far use only two tubes per channel. When Push-Pull is used in Class A mode, each output device amplifies the entire sine wave but one of the devices does this in reverse phase. This is how Accuphase Class A transistor amps work, for example. The Push-Pull Line Magnetic amps work in Class AB.

Single Ended

Single-Ended means that there is only one power output device per channel, rather than 2 or multiples thereof as for Push-Pull. So, a Single Ended Triode amplifier uses only one Triode power tube per channel. Single Ended, by definition, is Class A.

Triode

A Triode is a tube type as well as a connection method. A Penthode tube, for example, can also be connected in Triode mode. Triode mode is only one of several different schemes that a tube can be connected up as. Penthode mode, for example, is more efficient but many people feel that the Triode mode is the purest mode for a tube.

Traditional triode tubes delivered only a couple of watts, necessitating the use of extremely sensitive speakers such as horn-loaded Lowther units. In their quest to combine purity with power, however, several tube companies have moved the goalposts. Vaic, now Ayon, for example, has created the 52B, capable of about 22 watts, doubled to 55 watts by using two of them in parallel. Do note this is not Push-Pull but actually PSET, Parallel SET, arguably a less pure implementation but achieving impressive results in my listening sessions nevertheless. The latest Ayon designs using 82B tubes, deliver a whopping 80 watts, which is incredible given their ancestry. Purists maintain that the original flee-power rated triodes sound best but these do severely limit speaker choice.

I’ve only touched the surface here, of course, there are exceptions and I’m sure that there are many more takes on the matter (so many people, so many opinions) but I hope to have supplied enough background info to help interpret the rest of this article.

Build Quality

Today, all the accomplishments are the result of a team of experienced audiophile engineers. But lest you think that this is yet another Chinese brand offering me-too products, I’ll be quick to add that these products have a unique styling and are not just finished to a high standard, or a relatively high standard given that they are of Chinese origin, nope, they are finished to an extremely high standard, period!

The LM-88IA has a bias meter on the top, the more expensive models have one or more meters on the front panel.

Honestly, handling these amps with their large heft, solid front panels, and piano lacquer finish feels more like using Accuphase or Luxman electronics than anything else. They’re heavy, too! Peeking at the insides through the ventilation holes in the bottom, there is point to point wiring for all the critical stages (tubes and transformers, for example) and where circuit boards are used, these are populated very neatly, with wires soldered to them in perfect alignment reminiscent of the stereotypical German precision. Line Magnetic does not supply a huge amount of technical information but do state that they employ Japanese ALPS potentiometers, American MIT and German Mcap and Mundorf coupling capacitors, Toroid Z11 Core transformers (of unknown origin) for the power supply and Japanese Audio Grade EI output transformers. It seems clear that the makers wanted to use the best materials and arrived at certain combinations, rather than simply using the same make for everything. Given their modest cost compared to German or American alternatives, they could be excused for taking a shortcut here or there, but this was clearly not on the agenda.

Tubes

The Line Magnetic-branded power tubes are made by Shuguang and these are used in all the amplifiers that I tested, except for the LM-88IA, which uses JJ KT-88 power tubes. In addition, the LM-845IA and LM845IA Premium use 310A tubes that are replicas of the original Western Electric designs, made by Line Magnetic.

Running in

The LM-805IA had already been used by Frank in his audio store and so this amp did not need any running in, only warming up. The other amps, however, were newly supplied by BC Diffusion. So, prior to my serious listening, I used each of them separately to play music for the majority of 2 days. Naturally, I also did some initial listening during this time. I found that all the amps sounded impressive from the first moment of switching on but also noticed a slight sharpness in the upper midrange/lower treble with certain music, especially with the LM-845IA, which mellowed out after a few hours and seemed to have completely settled down after a couple of listening sessions. The LM-805IA was definitely smoother from the very start and did not change its character much while running in or in successive comparisons thereafter. After the running in period, each amp was allowed to warm up for 30 minutes prior to starting the evaluations. For all amps, the same playlist was used, containing a mix of music genres ranging from electronic and techno to folk, soul and smooth jazz.

LM-805IA power tube socket. Note the conveniently placed Hum Balancer and Bias Adjust pots.

Fixed Bias

All the Line Magnetic amps use a fixed bias. This means that you adjust it yourself using a screwdriver and the visual indication of the built-in meters. There are ongoing discussions among audiophiles and manufacturers alike about the merits of fixed and automatic bias. Some maintain that fixed bias yields better results, others claim that when implemented properly there should not be a difference. Personally, I do not yet have a take on this. I have heard excellent amps using either method.

I followed the manufacturer’s recommendations and checked again every now and then and was glad to note that the amps retained their settings very tightly.

Integrated or Power Amp

All the Line Magnetic amps that I have for review are integrated amplifiers but they all also have inputs that bypass their built-in preamp sections, for use with an external preamp. LM refers to these as “pre-in” but they actually should be labeled “main-in”. Labeling aside, these inputs function as expected and so the amps could be assessed as a power amp as well as an integrated amp.

I will be reviewing all the Line Magnetic amps in my two systems: the main setup in the large room, using Wilson speakers and the secondary setup in the smaller room. In addition, the two push-pull designs will also be tested in audio buddy JW’s system, using Apogee Duetta Signatures.

Ok, I’m done rambling. Now the real fun can start!

Continue to part 2 – Line Magnetic with Gustavson speakers