LSA VT-150 stereo tube amplifier; appraised!

The LSA VT-150 stereo tube amplifier from Underwood Hi-fi comes standard with KT-88 tubes but can be switched over to KT-150s. Howard Milstein takes a listen to the standard model!

In this review, we’ll be looking at the LSA (Living Sounds Audio) VT-150 stereo KT-88 tube power amp, which was kindly provided to me by Underwood Hi-Fi and proprietor Walter Liederman.

Walter, a veteran of high-end audio, runs and founded the company while this amplifier was designed by the ex-Chief Engineer of Line Magnetic in China. Their diverse products, which include power amplifiers, turntables, and phono stages, have attracted favorable reviews from customers for their physical and audible quality.  

Being LSA’s most powerful tube amplifier in their portfolio, (which includes a lineup of tubed and solid state integrated and power amplifiers,) it produces 80 watts per channel in its high bias mode and 60 watts in low bias, though it can be strapped to mono to produce 160 watts if need be. (LSA also offers solid state amplifiers of up to 600 watts/channel using the same modules as PS Audio’s M1200 mono amps—but in a stereo amp configuration)

The VT-150 amplifier has a front-panel volume control display for use in a bi-amp system to level-match one amplifier to another, as well as a front-mounted input switch that lets you switch between RCA and XLR inputs. By adding a phono stage to the RCA inputs and a DAC to the XLRs, the VT-150 can quickly be utilized as a 2-input integrated amplifier.

LSA VT-150 stereo tube amplifier

The standard amplifier is supplied with the now famous, (and arguably, best sounding) KT -88 vacuum tubes. However, it can be easily upgraded to the KT-150 tubes for those individuals who may need or demand more power for their system. The KT -150 tubes can deliver an additional 20 watts of output, but must be provided by the customer—( as Underwood HiFi does not carry the KT-150s.).

The amplifier’s bottom cover can be removed and jumpers replaced to supply the output tubes with the appropriate current to deliver the extra power. Keep in mind that running the KT88s at higher bias reduces tube life. However, with 60 Watts per channel, it offers more than enough power for all but the most insensitive loudspeakers, so you might as well carry on with the low-bias option and enjoy longer tube life.


Having had some good experiences as of late with several tube amplifiers, the long-time and old question of tubes vs solid state has been swirling around the audiophile circles for at least the past 50 years. I can remember the original Marantz 8b (1962) stirring the souls of the most adamant audio enthusiasts way back when.

Tube amplifiers in some ways…. can sound better to many audiophiles because of the euphonic distortions they add to the music, as well as plenty of other reasons.

These are subtle effects that are most noticeable to musicians and extremely devoted music fans and audiophiles; casual listeners (those who “listen” with their eyes open while doing something else) typically won’t notice; however, sometimes the difference is so pronounced that people’s wives will comment that “wow, that sounds much better” when people use tubes at home.

Although Tube amplifiers measure poorly in the lab specifically because of these added distortions, these malformations are often a part of what makes them sound great, if not better.

Professional studio microphones have included tube pre-preamplifiers inside the microphones themselves for decades and decades – even with an all-digital infrastructure currently encompassing the recording studio to the home. Their outputs have been digitized for recording, mixing, and distribution before being routed to tube preamplifiers. To be blunt, tubes are infectious simply because they can improve the sound of the music we produce, making it smoother, warmer, and more refined.

LSA VT-150 stereo tube amplifier back

Of course, these are all very broad generalizations, and this is just as much due to circuit designs used with tubes or transistors as the devices themselves. Although much of that distortion is second-order, (that’s why it’s called “harmonic” distortion), it is also the reason why they offer a quite musical-sounding experience.

Ironically, not only is tube amplifier distortion attractive, but it also gets louder as the volume rises, just like in a musical performance. More harmonic content emerges as instruments are played louder or as a percussion instrument or piano note is struck more forcefully. The proportion of harmonic content decreases once more as notes fade out.


The VT–150 is a profoundly good-looking amplifier thatcomes with KT88 tubes, while its front panel-mounted volume control also contains an advanced front-mounted RCA/XLR switch. Its displays power meters that can also bias 4 & 8-ohm outputs.

Adding to this it contains switchable voltage within its sturdy structure. The amplifier is quite heavy weighing in at approximately 75 pounds so make sure you are in good condition when lifting it onto your equipment rack!

At first, the VT-150 starts out quite ordinary sounding, indeed. Yes, it had good spatiality and layers of depth within the soundstage, but this varied in its initial auditioning. I was then switching back and forth between the VT-150 and the previously reviewed Allnic A-2000 20th anniversary amplifier which uses the aforementioned optional KT-150 tubes in its design. Being more powerful than the VT-150, my initial thoughts led me to believe that the Allnic amp was a slightly better performer, as its extra power with the speakers tested seemed to breathe more life into the music. That intrinsic tube ‘ambiance’ as well as a better bottom end brought me to that conclusion with the many recordings I was using.

I subsequently put the LSA to the side for a week or two and continued with the Allnic in my system. Now after a much longer auditioning time, the A-2000, while quite powerful for just about any loudspeaker, was showing a minuscule amount of ‘peakiness’ on strong transients and louder volume levels from some of my classical orchestral program sources.

From past experiences, I attributed this to the KT-150 vacuum tubes, but as of this moment, I am still not sure if this was the reason I was experiencing this occasional yet subtle occurrence. I must admit, however, that after returning to the LSA-VT-150 with continued further listening, I am pretty much convinced that I prefer the KT88 vacuum tubes in the VT-150 design; having a slightly more vibrant, rich midrange and a more subtle and layered top end (similar to the EL-34 tube)– which can be best for most musical genres employed. Eventually, I started thinking to myself at its retail price of $2299, vs. the Allnic, currently selling at approximately $7950, this is one of the few tube amplifiers I have heard that can take on much more expensive solid state as well as tube units in the current high-end marketplace.

The build quality of the VT-150 is excellent while the unit was as quiet as a church mouse. It had an extremely subtle yet very wide stage width from the loudspeakers that I was using. I must not forget to mention its depth perspective, assuming the speakers and room are up to the task, which was quite deep and very stratified in my tuned listening room.

This layering of massed violins was exquisitely portrayed at stage left and there was a lack of any type of over-accentuated brightness or steeliness on orchestral strings. Piano notes rang true with a distinct, ‘twang’, as the keyboard hit the strings with exceptional detail and transparency on the grand piano. This was evident with exceptionally recorded solo piano works by Murray Perahia as well as extremely well-engineered piano concertos, here featuring the late Paul Bradura Skoda.

Other notably profound recordings that the LSA VT-150 presented exceedingly well-included music by The Oslo Philharmonic soloists in an extremely well-balanced recording of Mozart’s flute and harp concerto, and Fasil Says, magnificently recorded box set of the complete Mozart Piano Sonatas. You will be quite overwhelmed by the quality of sound the VTA -150 displayed with this latter box set by Mr. Say,–yes, it is that good!

Of course, it was the midrange that topped everything with the LSA amplifier. It was singularly smooth, elegant, full-bodied, ethereal, and amazingly distinctive from octave to octave. The amplifier had all the subtlety your loudspeakers will allow you to exhibit with an open, airy, and creamy midrange response. The overall sound, in its own way, was quite equal to some of the best solid-state amplifiers one could muster up. Not missing a beat, the mid/treble was silky sweet, yet distinctive when called for and not what you would expect from an amplifier at this price point.

The VT-150 is dynamic enough to play hard rock or classical music at any volume you require while also providing excellent linearity at lower volumes. This VT-150 amplifier can generate a huge sound field in all three dimensions in addition to having an even, yet regulated extension at both ends of the frequency scale. Undoubtedly, there is a lot of that “vacuum tube enchantment” going on here.”

I have been using the Q Acoustics Concept 500 for some months now as one of my reference loudspeakers in its price category. There is no doubt that it allowed all the beauty of this loudspeaker to shine through to its ultimate heights!


While the bass response was maybe a ‘touch’ light-footed as compared to say, the hybrid PS Audio M1200 monoblocks, or my Pass Labs XA -30.8, the VT-150 still exhibited a nicely weighted and tremendously rousing bass response and was surely able to hold its own on almost every recording that was tried. You feel the impact while at no time ever missing the underlying fundamentals on deep bass notes. I listened to other pop and jazz performances as part of my exploration of this amp and I personally was never in need of a fuller or deeper amount of bass!

Quite basically, this amp just lets the music play the full audio spectrum supremely as a whole while exhibiting an airy subtleness on woodwinds, bassoons, and flutes that arguably, only the best tube amplifiers can convey. And the bass is there, believe me- you will never miss a beat! 


One can’t help but think that the LSA VT-150 tube amplifier virtually offers up everything a true audiophile and music lover could ever want. This feeling of having a great sounding amplifier and/or an alternative to your favorite solid-state amplifier will surely entice most of you to want to explore the enormous integrity of this tube amplifier– without having to take out a bank loan to purchase one!

There can be no doubt that at the suggested price of the VT-150, you will be getting musical satisfaction that will never urge you to start auditioning tubed power amps at nearly twice its price or more. This product offers true value and exquisitely musical sound quality that most enthusiasts will find hard to ignore. Try to get an Audition of the LSA VT-150 in your system and see what I mean. The LSA VT-150 is an excellent amplifier and a true bargain to boot! It is a definitive BEST BUY, five-star performer!

The system used for evaluation: Loudspeakers: ~ Harbeth Compact 7ES-3 XD loudspeaker ~ Q Acoustics Concept 500 loudspeaker ~ Digital: Mojo Audio ‘Mystique’ X DAC ~ Innuos Zenith Mk.3 server/streamer ~ Audio Note (UK) CD3.1x/2 player/DAC Analog: Audio Technica LP-7/ZYX Bloom 3 mc cartridge Amplification:~Pass Labs XP-12 preamp, Pass Labs XA30.8 power amp ~PS Audio M1200 monoblocks,~ Allnic Audio A-2000 25th Anniversary SE amplifier ~ Cables/ Conditioners: ArgentPur AG 12 loudspeaker cables~ Inakustik AC-3500p power station &, AC-2404 reference Air Power Cord ~ Audience Studio 1 interconnects and speaker cables~ Wireworld Gold Starlight 8 – 75 OHM DIGITAL CABLE / Audio Art 1 e” AC Power Cord

LSA -VT 150 Power Amp: $2995, Introductory pricing: $2299.00″

Underwood Hi-Fi  89 Kahana Makai Road Lahaina, HI 96761 USA

“Order at or call Walter Liederman direct at (770) 667-5633.”



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