When the green light came on, I knew music was coming out of the radio. Then the pipes behind the fabric grille were warm and the radio filled the living room with sound. Warm, soft and comfortable sound.
My parents’ tube-based radio receiver was later replaced with a Japanese transistor receiver, which, even with two speakers and stereo sound, never played as full-bodied and beautiful as the old Philips.
Back then, vacuum tubes were a necessary component in radio receivers, amplifiers and TVs, but developments have given us transistors, integrated circuits and digital modules that are far more efficient. And more reliable.
Tube amplifiers may have gone out of style, but they have never disappeared, and well-known manufacturers such as McIntosh, Audio Research, Conrad Johnson, Jadis and Air Tight still make them.
There is something about pipes and the way they make music, which makes many people still swear by pipe amplifiers.
So do the Zheng brothers in Zhuhai, China, who are behind the speakers and amplifiers with the resounding name Line Magnetic Audio.
They make vacuum tubes according to old recipes, and make amplifiers from 3 W power, and upwards.
Like this one. An integrated amplifier with three analog line inputs, without turntable input, but with 48 W power per channel.
The amplifier uses only one tube per output, here it is 805 driven by a 300B tube, which provides a so-called single ended solution, in contrast to push-pull where two tubes per output are used to increase the effect.
Three pipes are located in front of the output stage (6SL7, 6SN7) and the user can adjust the bias current of the output pipes and hum damping with a small screwdriver.
But the coolest thing about the LM-805iA as the amplifier is called, is the ability to adjust negative feedback in four steps. Negative feedback is used to attenuate potential distortion in the output stage, and you hear the effect of it in the speakers when you select the amount of feedback.
I got the best balance with the feedback in step 2. In step 1, the sound image was moved far forward, while the bass became looser. Step 2 tightened up the soundscape, the bass and balance improved, while steps 3 and 4 muted the dynamic contrast more. Note that this will vary with the speakers you use, so the experience may vary with the speaker load.
Negative feedback can be adjusted in four steps, and has an audible effect on the sound. Photo: Lasse Svendsen
The integrated amplifier seems elaborate. Steel, aluminum and trustworthy switches and buttons, give a solid quality impression. Among the components of the LM-805iA, we find not only powerful transformers and tubes, but also Mundorf N-Cap capacitors, and an ALPS potentiometer.
The two 805 pipes, each powered by its own 300B pipe, supply 48 W per channel, in so-called class A operation. It is less efficient than the standard AB solution, but avoids switch distortion on the signal.
Line Magnetic also states respectable specifications, with a signal-to-noise ratio of 87 dB, bandwidth up to 50 kHz, and one percent distortion. Although the latter does not seem very impressive, it is about third harmonic distortion, to which the ears are not as sensitive.
Powerful and warm
The combination of tubes in a very linear connection, class A operation and relatively large bandwidth, gives the amplifier some appealing sonic qualities.
It fit like a glove with Klipsch Cornwall III, but also handled our reference monitors perfectly. The smaller Dynaudio Contour 20 are far from as efficient as the easily powered Klipsch speakers, but the tube amplifier did not let itself be affected by it.
Forget the numbers, the amplifier is perceived as far more powerful than the numbers suggest. It also has a good grip on the speakers when playing loud. Compared to e.g. McIntosh MA252 with 100 W power, there is nothing that reveals that the 805 has less power.
It creates a huge soundscape of Bob Dylan’s Oh Mercy. The bass response is astonishingly powerful, and the amplifier has steel control on the Klipsch’s large 15-inch basses. If you prefer to see the world through golden spectacle lenses, this may not be the amplifier. It does not clothe the sound in velor or smear it with honey, it does have a warm and full sound signature, but it is never side rumped or wrapped.
Woolly sound must be looked for elsewhere, because the sounds at Keith Jarrett’s Cologne concerto are well preserved, and the amplifier creates an outstanding depth and a sonorous sound image, on the 40-year-old recording.
Vowels are actually a bit slimmer rendered than I personally prefer it, but it suits the amplifier quite well. Because the relatively round bass mostly compensates for that, but it also gives the concert piano a slightly smaller soundtrack. Here, matching with speakers is important, to get optimal conditions for the many timbre the amplifier can reproduce.
A rehearsal with Dire Straits Love Over Gold from 1982, gave me a lot of joy, because the hot tube amplifier (the tubes get very hot, but it comes with a grid), gave the drums of Pick Withers phenomenal with weight. At Private Investigations, I thought the basses would come loose from the boxes, because the tube amplifier really gave the iron in the bass. But at the same time it had good control of the bass dynamics.
The dynamic contrast is sparkling, and the amplifier acts lightning fast on transients. The treble rolls off nicely and comfortably in the upper octaves, and despite the enormous power in the bass, it does not go all the way down to the basement in the bass here. But it is not important, because in contrast to any prejudices one may have against tube amplifiers, Line Magnetic mostly plays like a modern transistor amplifier.
Line Magnetic 805iA is a lead-heavy, glowing hot tube amplifier with few inputs, which must be heated before it performs at its best. But then it plays the braid of most of what we have heard in the price range. It has astonishingly explosive dynamics – especially in the bass – and just so much warmth in the sound, that the balance does not tip over into the parody. It kills some prejudices, and appears as an exciting alternative to the more established manufacturers’ amplifiers in the corresponding price range.