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LSA VT-70 integrated amplifier | Stereophile.com

I like to think that my music taste is quite eclectic: jazz, pop, blues, Americana, metal, world music, ambient, prog rock, more. But opera music and classical singing? Thanks, I’ll pass.

There are exceptions. I find tear-jerking beauty in Alfredo Catalani’s “Ebben? Ne Andrò Lontana” La Wally, sung by Donij van Doorn or Wilhelmenia Wiggins Fernandez (footnote 1). The German songs by Kurt Weill, as performed by soprano Teresa Stratas, bring joy to mine heart but confusion in my misunderstood wife and children. Perhaps it’s because the often sarcastic, gruff songs about the trials and tribulations of the lumpen proletariat contrasts with the purity of Stratas’ classically trained voice. That collision is exactly what I love about it.

It must have been after a recent Stratas/Weill listening session that Roon Radio started playing songs that the algorithm assumed I would like. That’s how I came across a classic piece that touched me. The first surprise: this composition unknown to me was written by Antonio Vivaldi. I never liked Vivaldi, whose omnipresent Four Seasons always hit me like a fool. But the ethereal “Nisi Dominus, RV 608: Cum Dederit,” I must admit, is beautiful and moving.

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The second surprise was that, contrary to my assumptions, the vocals I heard in that piece were not sung by a lyrical alto or a mezzo-soprano. I had to dive into liner notes and a Wikipedia article to understand a reality my ears had rejected: the beautiful voice I heard belongs to a man, French countertenor Philippe Jaroussky, who has built quite a career with his translucent falsetto.

That experience reminded me that not everything is what it seems at first. A well-known composer can have more scope and depth than his most popular work shows. Vocals believed to be feminine can be produced by a person with a penis. And LSA’s VT-70, the low-power, tube-integrated amp I played all of the music mentioned above, turned out to be a sonic heavyweight, not the bantam class I expected.

Performance over price
LSA is a brand of Underwood HiFi, led by Walter Liederman, a 50-year audio industry veteran who also owns Core Power Technologies and Emerald Physics. He sells quality products directly to the consumer. Liederman scoffs at the “seven times the cost set by many manufacturers.” That number may be on the high side, but it’s true that given what you’re getting, Underwood’s prices approach Crazy Eddie’s territory (footnote 2).

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LSA, I’ve learned, stands for Living Sounds Audio. When I emailed to ask what VT-70 stands for, Underwood’s PR guy wrote back, “Isn’t it clear? :-> VT = Vacuum Tube. 70 = 70 watts (35 watts per channel).” well, excuse me me. But yes, I think that used to be obvious.

By the time the VT-70 arrived at my doorstep, the outer box had a cut on the bottom, but the inner box and precision-cut foam were intact and the product was free of damage. The seven tubes — four PSVANE EL34s in the back row, a pair of 12AU7s in addition to a single 12AX7 in the front — were factory installed and then wrapped in hollow foam rollers to protect them in transit, first from China to the warehouse in the USA and then from there to buyers’ homes. I removed the black metal tube cage and then the foam and gave the VT-70 a close inspection.

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It’s a nice product for ‘sho’. Tempting even. The top, sides and back of the solid metal chassis are finished in gloss black which wouldn’t look out of place on an expensive car, except my copy had a striped spot on the back of the transformer housing. It was small and invisible from its pristine front and sides. I admired the brushed aluminum fascia, whose standout feature is two VU meters. Frankly, I’ve never found VU meters particularly useful, but it’s fun to watch the needles do their jerky dance. Geek-approved! On the VT-70, the gauges serve another purpose, besides jerky dancing and indicating current power: they help preset the tubes, a topic I’ll get to shortly.

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Aside from those highly visible tubes, the VT-70 has a solid state 1970s aesthetic. Yamaha, Luxman, Onkyo—That scene. Worth following, I’d say. I’m not fond of the raised metal bezel around the gauges, but otherwise the VT-70 is damn attractive. It is very similar to several Line Magnetic amps, especially the LM-34IA, which has the same tube complement but lacks the meters. (Other Line Magnetic integrated amps have similar meters but use different tubes.) No wonder, the VT-70 is the work of Huang Jia Nuo, former chief engineer at Line Magnetic. Huang left that company three years ago and started his own business in Zhuhai, a city in Guangdong province. There he designs and produces components with his team for international customers, including LSA.

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The rear of the VT-70 is indistinguishable from that of the Line Magnetic LM-34IA, except for minimal graphics. There’s a standard IEC C15 power jack in addition to separate 4 and 8 ohm taps that allow you to match your speakers to the amplifier. (A third tap, labeled 0 ohms, caused a moment of confusion in my editor. It is, of course, where the negative speaker wire is connected.) Regardless of your speaker specs, the company suggests that you try both options and use one that sounds best. Further to the left are three sets of line-level RCA inputs and a pair of pre-out jacks: perfect for connecting one or two subwoofers. LSA says in the manual (PDF only) that this output is “not intended to be used as a preamplifier unless double-amping is done simultaneously with the LSA 70 and another power amp.”

On the front, from left to right, is a spring-loaded power button accompanied by an orange LED; a ¼” headphone jack; a toggle switch that turns the backlight on and off; a meter switch that you press when it’s time to affect the tubes; dual VU meters; an input selector (CD, AUX 1, AUX 2; there’s no built-in phono stage); and a large volume knob with a built-in orange LED. The LED will blink for about 20 seconds on power up before the VT-70 will play music, but the manual recommends a half hour warm-up if you want the sonics. most tube amps I know.

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You operate the input selector with one finger by pushing the metal stem that runs through it. For design consistency, I would have appreciated a similar bar on the volume knob, but that’s the minor glitch. There’s nothing wrong with using two fingers or the included remote, a hefty metal affair that lets you control volume and mute and nothing else. You will have to score your own CR2032 battery.

Keep your kittens safe
I didn’t open the amp, but I’m told that the guts combine circuit boards and point-to-point wiring. PCBs in tube amps always worry me a bit, because of the heat. Over time, heating and cooling the tubes can cause cracks in the thin traces of PCBs, necessitating a visit to the repair facility. But that’s mostly a theoretical concern, and it’s a problem that many carefully designed tube amps manage to avoid.

And since this is a tube amp, it isn’t quite a matter of plugging in and letting it rip; this will cause serious damage if the speaker terminals are not loaded. It’s best to make a connection that won’t slip. For this reason, I prefer locking banana plugs, like the ones that come standard on my Blue Jeans cables.

Before playing music through the VT-70, you need to preset the tubes. It’s a breeze. Turn on the amp, wait five minutes, turn the volume all the way down and set the meter switch on the front panel to “BIAS”. Locate the small, self-returning toggle switches on the left and right sides of the amp, next to the power tubes; they are marked V1 and V2 on either side of the left switch, V3 and V4 on the right. Pull the left switch towards you (position V1) to read the condition of the first tube. The left needle should jump to the center of the meter’s red zone and stay there. Now push the switch back to the V2 position, again paying attention to the needle. Then do the same with the switch and the meter on the right. If necessary, insert a small flat head screwdriver into the corresponding hole marked “BIAS ADJ” and gently turn the trim potentiometer until you have pushed the needle into position. The process took about a minute for all four tubes. LSA recommends a monthly bias check, but for the three months I had the amp in my system, the VT-70 was completely stable, no adjustments needed.


Footnote 1: Fernandez’s version is central to the 1981 French thriller diva, alongside a score of beautiful soundscapes by the Romanian film composer Vladimir Cosma. Strongly recommended.

Footnote 2: See youtube.com/watch?v=Ml6S2yiuSWE. Fair warning: In order to keep prices as low as possible, Underwood doesn’t offer a free 30-day home audition like most other online vendors do. Sure, try it at home, and if you don’t like it, send it back within 30 days, but you’ll have to pay a 15% restocking fee.

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