LSA VT-70 integrated amplifier

I like to think that my musical tastes are pretty eclectic: jazz, pop, blues, Americana, metal, world music, ambient, prog rock, more. Operatic music and classical singing, though? Thanks, I'll pass.

There are exceptions. I find tear-tugging beauty in "Ebben? Ne Andrò Lontana" from Alfredo Catalani's La Wally, whether sung by Donij van Doorn or Wilhelmenia Wiggins Fernandez (footnote 1). The German Lieder of Kurt Weill, as interpreted by soprano Teresa Stratas, produce gladness in my heart but confusion in my uncomprehending wife and children. Maybe it's because the often sarcastic, gruff songs about the travails of the lumpenproletariat contrast with the purity of Stratas's classically trained voice. That clash is precisely what I love about it.

It must have been after a recent Stratas/Weill listening session that Roon Radio started playing songs the algorithm assumed I'd like. That's how I came across a classical piece that floored me. The first surprise: That unknown-to-me composition was written by Antonio Vivaldi. I've never liked Vivaldi, whose ubiquitous Four Seasons has always struck me as ignorable pap. But the ethereal "Nisi Dominus, RV 608: Cum Dederit," I had to admit, is magnificent and moving.

The second surprise was that, contrary to my assumptions, the vocals I heard in that piece were not sung by a lyric contralto or a mezzo-soprano. I had to delve into liner notes and a Wikipedia article to grasp a reality my ears had rejected: The lovely voice I heard belongs to a man, French countertenor Philippe Jaroussky, who has built quite a career on his pellucid falsetto.

That experience reminded me that not everything is what it seems at first. A well-known composer may have more range and depth than is clear from his most popular work. Vocals presumed to be female may be produced by a person with a penis. And LSA's VT-70, the lowish-power, tubed integrated amplifier through which I played all the music mentioned above, proved to be a sonic heavyweight, not the bantam-class contender I'd expected.


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

LSA, I 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 obvious? :-> VT = Vacuum Tube. 70 = 70 watts (35 watts per channel)." Well, pardon me. But yeah, I guess that was obvious.

By the time the VT-70 arrived on my doorstep, the outer box had a gash along the bottom, but the inner carton and the 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 flanking a single 12AX7 in the front—had been installed at the factory then sheathed in hollow foam rolls to protect them during transport, first from China to the US warehouse 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.


It's a winsome product fo' sho'. Seductive, even. The top, sides, and back of the sturdy metal chassis are finished in a gloss black that wouldn't look out of place on a pricey car, except that my specimen had a streaky blemish on the rear of the transformer housing. It was minor and invisible from the pristine front and sides. I admired the brushed-aluminum fascia, whose standout feature is two VU meters. Truth be told, I've never found VU meters particularly useful, but it's fun to watch the needles do their choppy dance. Geek-approved! On the VT-70, the meters serve another purpose, in addition to choppy dancing and indicating the current power output: They assist in biasing the tubes, a subject I'll return to shortly.

Except for those very visible tubes, the VT-70 has a best-of-the-'70s–solid state aesthetic. Yamaha, Luxman, Onkyo—that scene. Worthy of emulation, I'd say. I'm not fond of the raised metal border around the meters, but otherwise, the VT-70 is damn attractive. It closely resembles several Line Magnetic amplifiers, 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, formerly 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 and his team design and manufacture components for international clients, including LSA.


The back of the VT-70 is indistinguishable from that of the Line Magnetic LM-34IA, except for the minimal graphics. There's a standard IEC C15 power receptacle next to separate 4 and 8 ohm taps that let you match your speakers to the amplifier. (A third tap, labeled 0 ohms, caused my editor a moment's confusion. It is, of course, where the negative speaker cable is connected.) The company suggests that regardless of your speakers' specifications, you try both options and use the one that sounds best. Farther 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 (PDF-only) manual that this output "is not meant for the amplifier to be used as a preamplifier unless biamping with the LSA 70 and another power amplifier simultaneously."

On the front, from left to right, there's a springy power button accompanied by an amber LED; a ¼" headphone jack; a toggle switch that turns the backlight on and off; a meter switch you flick when it's time to bias the tubes; dual VU meters; an input selector (CD, AUX 1, AUX 2; there's no onboard phono stage); and a large volume knob with an embedded amber LED. The LED blinks for about 20 seconds on startup before the VT-70 will play music, but the manual advises a warm-up time of half an hour if you want the sonics to be top-notch. This is true for most tube amps I know.


You can operate the input selector with one finger by pushing against the small metal stalk that runs through it. For design consistency, I'd have appreciated a similar bar on the volume dial, but that's the tiniest of niggles. There's nothing wrong with using two fingers or the included remote control, a substantial metal affair that lets you control and mute the volume and nothing else. You'll have to score your own CR2032 battery.

Keep your kittens safe
I didn't open up the amplifier, but I'm told its innards combine printed circuit boards and point-to-point wiring. PCBs in tube amps always worry me a little, because of the heat. Over time, heating and cooling the tubes can cause cracks in PCBs' thin traces, necessitating a trip to the repair facility. But that's mostly a theoretical concern, and it's a problem that many tube amps manage to avoid with careful design.

And because this is a tube amp, it's not quite a matter of plugging it in and letting 'er rip; that will do serious damage if there's no load on the speaker terminals. It's best to make a connection that can't slip loose. I prefer locking banana plugs for this reason, like the ones that come standard on my Blue Jeans cables.

Before you play music through the VT-70, you'll have to bias the tubes. It's a cinch. Turn on the amp, wait five minutes, turn the volume down all the way, and flick the meter switch on the front panel to "BIAS." Locate the small, self-returning toggle switches on the top left and right sides of the amp, next to the power tubes; they're marked V1 and V2 on either side of the left switch, V3 and V4 on the right. Pull the left switch toward you (position V1) to get a reading on the state of the first tube. The left needle should jump to the middle of the meter's red zone and stay there. Now, push the switch to the rear, to the V2 position, and again watch the needle. Then do the same with the switch and the meter on the right. If necessary, insert a small slotted screwdriver in the corresponding hole marked "BIAS ADJ" and gently turn the trimpot until you've nudged the needle to the correct position. The process took about a minute for all four tubes. LSA recommends a monthly bias check, but during the three months I had the amplifier in my system, the VT-70 was completely stable, no adjustments needed.

Footnote 1: Fernandez's version is at the center of the 1981 French thriller Diva, alongside a score of gorgeous soundscapes by Romanian film composer Vladimir Cosma. Highly recommended.

Footnote 2: See Fair warning: In order to keep prices as low as possible, Underwood does not offer a free at-home 30-day audition, as most other online sellers 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.

LSA/Underwood HiFi
(770) 667-5633

Jack L's picture


Don't hold yr breath on Chinese-made tubes. Lower cost shorter life-span. No miracles !

Such 6-month short short warranty should have already hinted the consumers what would happen sooner or later.

FYI, the 50-plus-year-young Telefunken ECC83s & then-brand-new made-in-Geat-Brtain Mullard ECC82s used in my phono-preamp for some 7 years, operating quite many hours week-in week-out. They still make me good classical music - nooo problem.

Brandnames speak !

Listening is believing

Jack L

Bill Leebens's picture

Ir's worth noting that a great many audio products are only warranted for 90 days until the warranty is extended when the product is registered with the manufacturer.Those warranty terms don't apply to tubes included with a product---
that six month warranty on tubes is the de facto standard---Chinese, Czech, Russian, whatever. The longest warranty I know of for tubes included in a product is one year, and that was only for the small signal tubes. I've seen power output tubes with as little as 90 day warranty coverage.

Jack L's picture


Really? So please name a few brandname audio products in the marketplace today only provide "90 days" warranty.

I am all ears

Jack L

Jack L's picture


Guys, No politics in this open venue please.

As posted in Stereophile forums since day one a few years back, I am on 'quality" only.

While we are still on this tube amp, suppose you were the owner of this amp, just arrived & put on test run - it broke down in no time!
What woud you feel ? You would still love its design/quality control ?????

It could be built in the Silicon Valley, CA, or the Brazilian rain forests or whatever. It "happened" to be made-in-China ! This unfortunately reflects on the "ethnics" issue as seen by some politically knowledgeable readers here.

In fact, I fixed a few "high-end" tube power amps made-in-China, using bigboy tubes, e.g. 300B & 2A3 just within a few years & surely I know how good were those made-in-China were. Even after upgrading it with expensive audiophile-grade caps, interwiring etc etc as requested by their ownes, the upgraded sound quality did not impress me at all vs tube amps built in Japan/USA which I auditioned before.

I quote basing facts being an electrical engineering guy.

Listening is believing

Jack L

johnnythunder1's picture

Hungarian music (Bartok string quartets) on my French, Canadian, German, Italian and British system.

Jack L's picture


I love Chinese ethnic cuisines bigtime, not those cheapie 'alien' chinese food in foodcourt takeawys or in foodcups !! Like tubes, money talks !!!

Yes, I pretty like Brahms' music, particularly his Violin Concerto in D Major. Soooo romantic !!

His Hungarian Dance No. 5 is also my favourite, not the other Dances though.

Listenig is believing

Jack L

JaredBeebe's picture

I noticed the Crazy Eddie reference or Easter Egg, does this reference "The Mote in God's Eye" by Larry Niven and Jerry Pournelle?

RML's picture

Hi all - as a potential newbie to tube amplification, I'd appreciate any views on whether the knocks on the LSA VT-70 with respect to midrange vocals, etc. could be affected (or resolved) by using a tube set other than what is supplied?