Living Sounds Audio Discovery Warp-1 power amplifier

It takes a while for audio-related technologies to mature. Tubed amplifiers were invented by Lee de Forest in the nineteen-teens, but while there are still some adherents of early high-distortion triode designs, the age of mainstream high-fidelity amplification dawned with higher-power/lower-distortion amplifiers developed by Williamson and McIntosh followed by the Ultralinear take on the Williamson concept. That was 30+ years down the technology-evolution timeline after de Forest.

And when it comes to solid state amplifiers—the usual kind—does anyone prefer the state of the (germanium) art circa early 1960s to modern silicon class-AB designs? I doubt it.

Now, decades into its own development, class-D amplification seems to have sea legs, even in the audiophile world. Interesting fact: The class-D amplifier was invented and named in the 1950s by the man who had already invented pulse-code modulation for signal transmission, Englishman Alec Reeves. The first commercial class-D amp was a 2.5W kit from Sinclair Radionics of England, introduced in 1965 and followed the next year with a 20W second-generation model. Sinclair was eventually better known for pocket calculators.

The modern class-D amplifier, built into an integrated circuit, debuted in 1996 with the Tripath "Class-T" chips. Since then, there has been a steady march forward. Today, most "civilian" amplifiers in things like TV soundbars, "smart speakers," Bluetooth-connected portable speakers, non-fancy automobile sound systems, flat-screen TVs, and the like are commodity-priced class-D "amplifier bricks." They are small, efficient, cool-running, and cheap. Class-D amplifiers started to appear in audiophile-grade components about 10 years ago, although there were earlier, outlier examples. In the pro-audio world, they have been around a bit longer, often but not always inside powered monitor speakers. Class-D amplification is ubiquitous in the modern sound-reinforcement world, that is, for live-concert sound.

I have observed this evolution, and in fact have used a cheapo Tripath-based amplifier for 10+ years in a little garage sound system fed by my phone or iPod when I'm out there doing work. If I pried open the cases of the various TVs, Bluetooth speakers, and soundbars around the house, I'm sure I'd find class-D amp chips aplenty. But until very recently, I was not interested in a class-D amplifier to drive my listening-room speakers. Modern class-AB amps do that trick very well.

One of my audio-hobby buddies, Mike, is a fearless DIY builder of amplifiers and speakers. For several years, he has been acquiring the latest, greatest class-D "bricks"—self-contained amplifier circuit boards, sometimes including an input buffer stage—mating them to appropriate switch-mode power supplies, and installing them in professional-looking metal cases. Last fall, he was eager to show off his latest masterpiece, made with the new Purifi modules designed by Bruno Putzeys. We arranged to shoot out several of Mike's class-D amps plus a professional class-D audio amp I own that uses modules that were the newest thing about 10 years ago. Our friend Farrukh, who joins our semi-regular lunch-and-listening sessions, said he had a new class-D amp that utilized a commodity-priced chip from Texas Instruments that he wanted us to hear. He said this amp was a hot topic on interweb audio boards. Being a guy who often swaps components in and out of his system, he couldn't resist buying one to try out. He told me he was impressed.

On the day of our listening comparisons, I heard clearly what I hadn't liked about those earlier class-D amps. My older amp, and Mike's older builds based on prior generations of class-D modules, varied sonically in some respects, but they shared a "glaze" over the top end, which I find annoying. The best way I can describe it is as jagged treble, too harsh to be pleasing with most music. It's not what I'd call tizzy or splashy, but it's noticeable and not to my liking.

Two amps in the shootout did not exhibit this "glaze": Mike's amp made with the Purifi modules and the new amp that Farrukh brought: the Living Sounds Audio (LSA) Discovery Warp 1 ($1499). I knew right away that I wanted to live with this amplifier for a while.

Warp 1 backgrounder
The designer of the LSA Warp 1, 54-year-old, Virginia-based Viet Nguyen, works days for NASA, project-managing the next generation of weather satellites, which the space agency will build and put into space for NOAA, the government agency in charge of weather prediction and research. An electrical engineer by education and avocation, Nguyen undertook DIY'ing a pair of Bluetooth-connected speakers back in 2010—thus began an audio odyssey that led him to design horn speakers made of dual-layer foam-core board, then headphone amplifiers that he built and sold out of his home, and finally power amplifiers to drive his ever-more-ambitious speaker projects. In short, he DIY'd himself a second full-time gig.

A couple of years ago, on an online forum, he posted a design for a power amp using the commodity-priced Texas Instruments TPA3255 class-D amp chip (footnote 1) in a low-impedance, current-drive circuit backed up by an overspecified, high-current switching power supply with a solid state, electronically balanced buffer stage ahead of it. This caught the attention of Mark Schifter, who runs product development and manufacturing for Walter Liederman's mini-empire, Underwood HiFi (see Sidebar 1). The two connected, and Nguyen agreed to work with Underwood to commercialize his design.

Nguyen picks up the story: "Up to that point, I had never worked on things that were manufactured, just small runs of headphone amps I built by hand." Schifter connected Nguyen to an extensive network of engineers, parts suppliers, and contract manufacturers in China. "I learned how to be a project manager and make a product," Nguyen said. He has since designed several speakers and amplifiers for Liederman's LSA and Emerald Physics brands.

Warp 1 design
According to Nguyen, the strength of his design revolves around driving the TI amp in its comfort zone and using an overbuilt power supply to provide as much current as needed as quickly as any speaker will demand it. "These amplifiers are designed to work best with a balanced signal," he said—so the input driver board is a key part of the equation. He knew a power supply designer, and they worked together to come up with a 600W switch-mode supply that uses such "overbuilt" touches as "massive" pure-copper inductors from Coilcraft and special high-current wire (spec'd for up to 100 amps), designed to carry the battery power in high-performance drones. The goal, he explained, is "a low-impedance path for current from power supply to speakers." Low impedance means that the amp is fast and firm in its control of the speaker engines. "It should provide really slamming bass," Nguyen said. He noted that the damping factor is "around 500" although it's spec'd as ">300."

Nguyen says the input-buffer stage uses Texas Instruments OPA1637 "balanced drivers capable of low-distortion 52V [peak to peak] output swing with balanced inputs." He has designed the Warp 1's gain staging to never come close to the buffer's full output. That means tons of low-noise headroom.

Those over-specified coils are in the low-pass filter, which removes the class-D switching noise, which is centered at 400kHz. Removal of switching noise is the big challenge with class-D amps. The filter has to do the job thoroughly but not ring in such a way as to clash with parts of the audible frequency spectrum and create odd harmonics or other "glaze" sound components. To my ears, Nguyen's filter succeeds. Hopefully JA's measurements won't make me the fool!

Warp 1 details
Rated at 150Wpc into 8 ohms and 250Wpc into 4 ohms, the Warp 1 Underwood HiFi sent to me for review arrived double-boxed and securely packed, with a power cable and thin, laser-printed, stapled-together user manual. The amp doesn't weigh much and doesn't generate much heat. The TI amplifier modules are mounted on the bottom of the main circuit board, with a silicone heat-transfer pad between them and the metal bottom panel. In my time using the amp, the top and sides never went beyond room temperature and the bottom felt only slightly warm.

On the front panel is a pushbutton power switch, the outline of which glows blue when the amp is on and red when it's in standby mode. To the right are three LEDs indicating Power supply fault, amplifier fault, and "Over Temp"; the amp will shut down if this stays on too long. On the back panel is a reset button (required if the amp shuts down due to a fault), input connectors, speaker banana/screw-terminal binding posts, an IEC socket, and a master power switch, which cuts all power to all the innards. The input jacks are gold-plated RCA for single-ended and Neutrik combo connectors for balanced, so either XLR or pro-style ¼" TRS connectors may be used. The user manual notes that the amp is designed for balanced inputs by default, and balanced cables must be disconnected before single-ended sources are connected. The amp should be turned off before disconnecting and reconnecting input cables.

The sturdy metal case is free of sharp edges or other telltale signs of crude machining. It is held together with Allen screws. Inside are three circuit boards: the power supply, the input driver, and the power amplifier. All are securely attached to the chassis, and connecting wires are securely bundled with zip ties. Low-level signal wires are twisted pairs. Heavier-gauge, high-current wire is used to connect the power supply to the amplifier board and the amplifier output to the speaker terminals.

Here's something the user manual doesn't tell you: The driver board has DIP switches (one bank of switches for each channel), allowing the user to adjust its gain to best match the components feeding it (footnote 2). Nguyen says the class-D amps provide 22dB of gain. The driver board is factory-set for 6dB of gain, for 28dB total, "which is an average gain for most sources." Other switch combinations produce 0, 14, and 20dB gain, but Nguyen says "I would not ever use the 20dB setting, as that would easily clip the amp." Some preamps—for instance, my Benchmark LA4—produce high enough output to justify using the Warp 1 with 0dB gain from the driver board, which results in "lower noise performance." The 14dB setting may be appropriate "if all you have is a cellphone that can't even put out 1V RMS as a source," Nguyen said, but that setting usually provides too much gain and isn't generally recommended. I tried the amp with both 6dB and 0dB gain from the driver board. While I can't say I noticed a difference in its sound, I ended up preferring 0dB because I like to use my Benchmark LA4 with less attenuation (footnote 3).

Footnote 1: See

Footnote 2: There are two DIP switches, one for each channel, located on the top of the driver board; both sets of switches need to be the same. Since it's not in the manual, here are the settings for various gain levels: all switches OFF = 0dB; 1 and 4 ON (others OFF) = 6dB; 2 and 5 ON (others OFF) = 14dB; 3 and 6 ON (others OFF) = 20dB.

Footnote 3: Benchmark would approve: In an Application Note on their AHB2 amplifier, the intended partner for Tom's LA4 preamp, Benchmark writes, "Most power amplifiers have far too much gain, and this degrades noise performance of the overall system." The highest gain available from the AHB2 is 23dB. See notes/14680625-the-ahb2-a-radical-approach-to-audio-power-amplification.—Jim Austin

LSA Electronics
89 Kahana Makai Rd.
HI 96761
(770) 667-5633

cognoscente's picture

Thank you, good to know, so nice to read .this brief history about amp types.

I was never a believer in tube amps, they have limited listening hours and lack control and detail. And I was never a believer in class d amps, which sound too cold and artificial. I swear, swear, by toroidal transformer class a/b amplifiers.

Until I was able to buy a new Nad C298 class d amplifier as a real bargain. And this Nad is already a bargain compared to the Nad Master series or competing amplifiers from Primaire or T&A with the same Purifi Eigentakt module. Of from Purifi of couse. Anyway, the Nad C298 now replaces the power amp section of my Hegel H360, which only serves as a USB receiver, proprietary re-clocking and preamp. DA conversion is done via the HoloAudio Spring 3 3.

It was immediately clear, the Nad C298 sounds fresher, clearer, more detail, more crips and attack and with a tighter bass. You can better hear the piano strings vibrating, the fingers sliding over the strings. Then you would say it also must sounds more tangible, more "live" present (in-the-room), more real with all those extra details? But that's the funny thing about human hearing. So no. It sounds also clinical, the feeling, the emotion is gone. In other words, the music is gone. At the Nad, like all the sets of my audio friends, you listen "to a set" and not to "live" present music (in the room). Your ears tell you. I'm exaggerating to make my point, you have to sit down (and listen carefully) to hear the difference, but still, then the difference is obvious. As if the Hegel is squeezing detail to provide more power, to sound more muscular, more mature, more "live" present, while the Nad is doing the opposite, as if it squeezing the power in the bass to bring out more detail to the surface. To sound fresher, younger. I say my Hegel H360 sounds like a Ford GT while the Nad sounds like a Porsche 911. Which one is more fun to drive? It just depends on what you prefer. I can switch with both power amps available. Still, I almost always choose the Porsche. I'm more of an audiophile than a music lover after all. I want to hear everything. The art of omission! Not really I'm afraid.

Probably a (for me) priceless class a/b amplifier can offer the same freshness, clarity, detail with the same crips, attack and tight bass as this Nad while retaining the musicality, the emotion and live (in-the-room) feeling, perhaps but as said that is unattainable and that's why I don't even want to know. I'm happy with my Porsche. And Bugatti ... whatever

Kursun's picture

Would you believe toroidal transformers are actually inferior to EI transformers?

This hobby of ours, hi-fi, is a hobby of prejudices!

Ortofan's picture

... record review, or little more than an advertisement for this product?

How did it perform/sound compared to the Benchmark amp?

The B&W 808 speakers have a minimum impedance of 4 ohms and can handle up to 200W on a continuous basis. The LSA can't sustain even 100W into a 4 ohm load without shutting down.

The LSA can't meet its rated power output, doesn't have a load-independent frequency response and has relatively high levels of IMD. The designer needs to go back to the drawing board.

If the amp contains special Coilcraft inductors that are supposed to remove/filter class-D switching noise from the audio output, then why did JA1 need to use an Audio Precision AUX-0025 passive low-pass filter between the test load and the analyzer. Either the filter built into the amp functions as claimed, or not.

As stated above, if you're in the market for a class-D power amp, then choose the NAD C 298, instead.

Kursun's picture

-"If the amp contains special Coilcraft inductors that are supposed to remove/filter class-D switching noise from the audio output, then why did JA1 need to use an Audio Precision AUX-0025 passive low-pass filter between the test load and the analyzer.

Filter was used during NAD C 298 tests too:
-"The C 298 has an output stage operating in class-D, so I inserted an Audio Precision auxiliary AUX-0025 passive low-pass filter between the test load and my Audio Precision SYS2722 system (see the January 2008 "As We See It"). This filter eliminates RF noise that could drive the SYS2722's input circuitry into slew-rate limiting, and I used it for all the tests other than frequency response."

Long-time listener's picture

"Class-D amplifiers started to appear in audiophile-grade components about 10 years ago..."

Interesting -- I recall auditioning a pair of Jeff Rowland digital monoblocks about 20 or more years ago.

Ortofan's picture

... TacT Millennium, introduced in 1998. That amp later became the Lyngdorf Millennium. It incorporated technology from Toccata Technology. Toccata Technology was eventually acquired by Texas Instruments.

Two members of the Toccata Technology team were Lars Risbo and Claus Neesgaard. They went on to work at TI.

Subsequently, Lars Risbo - along with Bruno Putzeys and Peter Lyngdorf - co-founded Purifi, of which Claus Neesgaard is a co-owner.

JRT's picture

If you want to try a TI TPA3255 based amplifier, consider trying the Fosi Audio V3 and 48VDC 5A switch mode power supply (avoid the 32VDC supply). At the online store at the Fosi Audio website, that bundle is priced at a penny under $110 and there is also a $10 off coupon, free shipping, and 24 month warranty. So it comes in at under $100 direct to your door.

That is a relatively recent addition to Fosi Audio's line, but has already received numerous favorable subjective reviews. And for objective measurements, Amir has posted a review, also very favorable, at his ASR discussion forum.

Here is a Google websearch on the subject:

Here is another Google websearch specific to the youtube website:

It is useful to consider amplifier output signal voltage. Loudspeaker sensitivity is most usually specified as a voltage sensitivity relative to 2.83 Vrms pink noise signal across the loudspeaker input terminals, with output measured as B-weighted SPL with the propagation distance normalized to 1 meter. Amplifiers most usually are designed ro provide a constant gain in voltage (not power) when operating below significant clipping, often represented as 1% THD+n, which can also be stated as -20dB THD+n.

With 48VDC 5A supply, Amir measured -74dB (.02%) THD+n at 141 Wrms into 4 Ohm load, corresponding to 23.75 Vrms across that load.
(141*4)^(1/2)= 23.75 Vrms
And relative to 2.83 Vrms that is
20*log(23.75/2.83)= +18.5dB

At 1% (-40dB) THD+n, 160 Wrms continuous into 4 Ohm, corresponding to 25.30 Vrms.
(160*4)^(1/2)= 25.30 Vrms
And relative to 2.83 Vrms that is
20*log(25.30/2.83)= +19.0dB

And for 20ms IAW CEA-2006/490A (suitable for headroom for brief crests in the music signal), at 1% THD+n, 190 Wrms into 4 Ohm, corresponding to 27.57 Vrms.
(190*4)^(1/2)= 27.57 Vrms
And relative to 2.83 Vrms that is
20*log(27.57/2.83)= +19.8dB

For $100 the Fosi Audio V3 might be sufficient in some applications, but don't expect Purifi modules at that price.


That said, if you want to spend $1.1k on a two channel stereo class D amplifier, then I would suggest that there are other better alternatives than anything utilizing the TI TPA3255 chipset.

For example, investigate some offerings from Buckeye Amplifiers, all prices direct, with free shipping. Buckeye's "Purifi 1ET400A Amplifier, 2-channel" is $1095. And their "Purifi 1ET400A Amplifier, Monoblock" is priced at $750/each, $1.5k/pair.

The new (currently on backorder) Buckeye "Hypex NCx500 Amplifier, 2-channel" for $1095 with free shipping. That uses a new improved Hypex module in competition with the Purifi Eigentakt modules.

Buckeye's "Purifi 1ET7040SA Amplifier, Monoblock v2" is priced at $950/each, $1.9k/pair. That uses Purifi's newer improved higher current module, etc.

There are some very good amplifiers from NAD using the older Purifi 1ET400A modules, such as the C298 priced at $2.4k MSRP. Safe and Sound is currently advertising some factory refurbished units priced at $1.8k. But for only $100 more I would rather have the Buckeye monoblocks with the newer modules, higher current power supply, etc.

Ortofan's picture

... approvals from the relevant regulatory/safety agencies?
Photos of the amps do not appear to show the markings that would indicate those approvals.
Skipping that step is one way to reduce the cost of a product.

JRT's picture

Depending much on the device (consumer electronics are not medical devices or aircraft radios) the markings can be self-certifications of compliance to governmental regulations and/or industry standards, and do not necessarily require any validation with third party qualification testing or qualification testing by any regulatory agency.

That said, below is an image of the 48VDC 5A external switch mode power supply sold by Fosi Audio, and included in the $109.99 ($99.99 with $10 off coupon) Fosi Audio V3 48V bundle. Notice the CE Marking and FCC Marking. The amplifier itself is a low voltage device, does not directly connect to powerline voltages.

Ortofan's picture

... UL/CSA safety approvals for the amplifier unit itself?

afgverhart's picture

It is always interesting to read all these comment from people who - I think - have never heard this amplifier in real life. Well, I did, actually, I own one after having owned nCore 400 mono blocks as well as a Purifi Eval 1 design. The Warp does indeed not have this typical class D top end that other class D designs tend to have. And yes, I have heard them all, well most of them at least.

My Warp One has been driving Dynaudio Contour 3.4 LE, Dynaudio Confidence C2 Platinum, Focal Scala Utopia Evo and most recently Dynaudio Contour 60i comparing it with a NAD M22 and a Hattor nCore class D design. The Warp One was the best sounding amp, again. It sounds detailed (but not too), with black backgrounds, it separates instruments excellently and best of all: it sounded most natural. The Warp has a flow to it - some call it PRaT - that I have not heard better from any class D design. and the bass reproduction is sooo nice and layered. It’s addictive.

My advice: don’t have yourself fooled by the above comments or measurements, but just listen to it before forming an opinion on it.


Poor Audiophile's picture

"but just listen to it before forming an opinion on it."
That should always be the case IMHO.

JRT's picture

This Living Sounds Audio Discovery Warp-1 power amplifier has a reset switch on the rear panel.

When was the last time you had an amplifier in need of a reset?

What makes this amplifier vulnerable to a control failure in need of a reset? What is the behavior during that failure? What happens if the consumer fails to push the button?

Ortofan's picture

... circuit breaker, rather than having a fuse.

David Harper's picture

in need of a reset? My schiit Vidar amp when driving my magnepan LRS speakers often shuts down due to current/thermal overload. It's no big deal I just turn it off and on again, turn the volume down a bit, and it's good to go.

Delius T's picture

So, he is out of jail?

Mark Schifter of AV123 Indicted by Grand Jury on Five Counts