LSA Warp 1 Power Amplifier

Last month I received a note from my local power provider, Excel Energy, informing me that it would be installing a “smart meter” and placing me on a tiered pricing schedule. During “peak hours,” from 3pm to 7pm, my rate would go up substantially (like three times), while during “off-peak” hours it would dip slightly below current rates. I mentally shrugged my shoulders, concluding that for me the days of leaving a bunch of Class A power amps idling 24/7 were drawing to a close.

About a week later the LSA Warp 1 power amplifier arrived on my doorstep. Its specifications and early reviews held out the possibility that this might be a Class D power amplifier that could successfully replace an energy-guzzling traditional Class A power amp. Let’s see.

Technical Tour

The heart of the Warp 1 is a Texas Instruments TPA3255 “Purepath” Class D circuit. This primary part has been mated with a carefully cobbled layout. According to Underwood Hi-Fi, “the state-of-the-art layout was made using double planes stitched together with thousands of vias wherever an ultra-low impedance path was needed. Vias are traces that connect layers of a circuit board. They are made by drilling a hole and plating metal on the walls. For a two-layer board, vias connect the trace on the top to the bottom side.” The grounding scheme utilizes a star-hub methodology, and power input paths were designed to be as short as physically possible. Both help reduce potential noise issues.

The PCB boards themselves are 2mm thick FR4 with 2-ounce (70um thick) copper traces and an electroless nickel immersion gold finish. Output filter inductors are all high-current, low-distortion, shielded, CoilCraft flat-copper-wire SER that allow for maximum current flow with minimum distortion.

For the input buffer and preamplifier sections, a Texas Instruments OPA1642/1656 op-amp and OPA 1637 balanced drivers were employed, along with a “bootstrapped” input buffer. Combined with its 600W switching-mode power supply, the result is an extremely quiet power amplifier with a signal-to-noise ratio that achieves numbers consistent with the performance of the best DACs.

Setup and Ergonomics

The overall fit and finish of the Warp 1’s exterior is clean and workmanlike. Other than silver side columns and rounded corners, the Warp 1 is essentially a black-satin-finished rectangular box. While the overall look is more individualistic than a plain silver or black box, it certainly lacks the blingy features and details that have become standard fare for many high-end power amplifiers. I consider this a good thing because I’m not a blingy guy. For me, a power amplifier is an electronic device designed to perform a specific task, not a sculpture, painting, or fine art print. 

On the Warp’s front faceplate, you will find an illuminated on/off button and three small LEDs that only light up if the amplifier has an operational issue. The LSA Warp 1 has provisions for both balanced XLR/TRS and unbalanced RCA inputs. The rear panel has all the inputs spaced apart, so even a cable with the most hose-like-diameter hardware should fit. A pair of five-way speaker-cable binding posts, a small on/off switch, the IEC power-cable input connection, and a “reset” button (that I never had to use) complete the rear-panel geography.

Like most basic power amplifiers, the Warp 1’s exterior has no adjustments, but inside the chassis users have several choices for overall gain. The Texas Instruments OPA1656 operational amplifier’s buffer has a DIP switch, which can be set at 0dB, 6dB, 14dB, and 20dB. The TPA3255 amp has an intrinsic 22dB of gain, so the setting from the factory is 6dB for an overall 28dB gain. You also have the option of lowering the gain to only 22dB or raising it to 36dB! That should allow for a much wider range of input source levels and or speaker sensitivities. In my nearfield setup I found that I needed to lower the gain to 22dB, not due to noise but to allow my preamp or DAC volume controls to operate in their optimal regions.

Sound

During my many years of attending audio shows and visiting dealers and manufacturers, all too often I’ve entered a listening room and the first thing I heard was hum coming from somewhere in the system. For many audiophile’s systems, especially those that employ older tube electronics, hum or noise is a constant companion with the music. It is inevitable that signal will arrive with some noise, but the critical issue for me is whether that noise is audible and takes away from the musical experience. My two primary listening rooms both have a steady-state background noise levels of approximately 35dB, which means if there is any noise generated by the system, I will hear it. With its 120dB signal-to-noise specification (120dB at 57Vpp [50WRMS into 8 ohms] to be exact), the Warp 1 ranks as one of the quietest power amplifiers I’ve used in my systems. I can place my ear less than two inches away from the drivers of a pair of 93dB efficient Omega prototype single-driver loudspeakers and hear only the very faintest hiss. The same held true when I tethered the Warp 1 to a pair of Spatial X-2s—only the slightest hiss (you must strain to hear it) let me know whether the thing was on. Falcon and Sound Artist LS3/5A monitors were also virtually silent.

For any audiophile who has a passion for highly efficient loudspeakers, the LSA Warp 1 offers an alternative to flea-watt or single-ended-tube power amplifiers. Not only will you find the Warp 1 to be quieter than many power amplifiers, but its more flexible gain options will make it fit into a wider range of systems with varying gain requirements. Also, the Warp 1 generates far less heat than any tube or Class A solid-state amplifier, which makes it an ideal option for summer listening, when climate control can become problematic.

So how does it sound? To my ears, the Warp 1 is almost a straight wire with gain, meaning it displays almost nothing that I would characterize as “personality.” If you need an amplifier that “warms up” your system, the Warp 1 will not fill the bill. Unlike the Class A solid-state amps in my possession (a Nelson Pass design-based Chinese A-30 and a Pass 150.8), the Warp 1 does not add additional “grunt” or warmth to the lower midrange and upper bass. This doesn’t mean the Warp 1 is cold or sterile sounding. Even on aggressive or marginally passable recordings such as “Teenage Kicks” by the Undertones from the Teenage Kicks EP, the result was engaging and listenable. Sure, the electric guitars peaking around 3.5kHz can sound nasty, but through the Warp 1 the sound was still quite tolerable without any augmented electronic zazz or additional hash. Still, compared to the Class A amplifiers, the Warp 1 was simply not as warm or lush and did not have their seductively mellifluous midrange.

I have a friend who regularly visits for a listening session, this time with the Warp 1 connected to a pair of Omega desktop prototypes (This design was going to be released, but a change in business plans postponed the Omega’s introduction, which is a shame, because it is a wonderful nearfield monitor, especially when paired with the Velodyne DD10+ and Sound Anchor FSTT-12 desktop stands [$350]). My friend owns a classic Spectral system (among a whole bunch of other stuff). After several minutes of listening, his first comment was: “This sounds as fast as my Spectral!” He played some challenging tracks, including “Naked” by Finneas, where he commented on the speed of the percussion’s snap. But unlike the Spectral gear I’ve heard in several different systems, which can occasionally sound hyper-detailed to the point of sterility, the Warp 1 manages to avoid that particular sonic characteristic. While the sound is well detailed and noticeably fast, it is more forgiving than a hyper-detailed power amplifier.

When a reviewer uses the term “more forgiving,” the readers’ assumption could be that it is also less revealing. The Warp 1 coupled to my reference loudspeakers, which currently include the forementioned Omega, Spatial, Audience 1+1 V4, and two LS3/5A versions, provided remarkably detailed insights into any recording. The Audience, Omega, and Spatial midrange/tweeter sections have no crossover circuits in front of them; they are all a direct connection from amplifier to speaker driver, so there is nothing to slow or alter the signal between the amplifier and the drivers themselves. This resulted in extremely accurate imaging specificity and three-dimensionality. The backwall reflections of University of Colorado’s Macky Auditorium on my own live concert recordings were clearly audible and precisely placed, as were the players’ positions on stage. The layering and depth cues were also well preserved, so on my recordings of Brahms Requiem the chorus was clearly behind the orchestra.

I used to own the Benchmark AHB2 power amplifier. While I no longer have it in my possession, I did log many hours of listening time with it in my systems. Harmonically and dynamically, the two power amplifiers are similar. The ABH2 was also equally quiet in terms of base-level noise, but it was not quite as revealing of subtle low-level details, nor was it as “fast” sounding as the Warp 1. While its soundstaging on the front two thirds was identical, the AHB2 truncated and homogenized the back ⅓ of the soundstage and did not delineate the space as well as the Warp 1. I also felt it was just easier to listen into the mix with the Warp 1. With the Benchmark I had to listen harder to hear all the subtle inner details.

Finding just the right amplifier to mate with an LS3/5A loudspeaker design can be challenging. Many audiophiles try tube-based power amplifiers, so they can luxuriate in the LS3/5A’s seductive midrange. But they find they must suffer through the downside of constricted dynamics, poorly controlled bass, and rolled-off upper frequencies. Coupling an LS3/5A to the Warp 1 proved to be an excellent compromise. While the midrange was a bit less liquid, the rest of the frequency range, especially the lower midrange and upper bass, were much more controlled, the treble range was more linear, and the dynamics were less constricted. Coupled to the Warp 1, the Falcon LS3/5A Gold Badge loudspeakers’ sonic presentation was more controlled and sounded more like the reference monitor it was intended to be.

Due in large part to its high damping factor (greater than 300), the Warp 1’s ability to produce well controlled bass was impressive. Especially on the LS3/5A loudspeakers, the Warp 1 delivered clean tight bass. Although I use subwoofers in all my systems, I have my systems set up so that the left and right speakers do not have any bass rolloff from a crossover but are instead allowed to roll off naturally. The Warp 1’s bass response made it easier to blend in a subwoofer and produce a more convincing result, since the upper bass emanating from the loudspeakers was more controlled with less bloom. 

Okay, no audio device is perfectly neutral, but many, including the Warp 1, can have such small amounts of harmonic coloration that they are essentially neutral. Any variations from neutrality that are heard are a result of other factors, such as the room or the transducers themselves. So, while I did not find the Warp 1 did anything to remedy any issues or improve the harmonic balance of any of the systems where it was employed, it also did not reduce fidelity in any way that I could discern.

Summary

At the opening of this review, I posed the question as to whether the LSA Warp 1 Class D amplifier could replace a solid-state Class A power amplifier. My conclusion is if you use a Class A amplifier partially because of its effect on the harmonic balance of your system, then no, the Warp 1 will not be an interchangeable substitute, because it has a different and, to my ear, more neutral, slightly less euphonic harmonic balance than a traditional Pass Class A design. But if you’ve ever wanted to hear what your system would sound like with an exceedingly noise-free power amplifier that produces a remarkably even-handed harmonic balance, then yes, the Warp 1 would be a viable power amplifier option.

Given its rather modest price of $1495, you might be tempted to write off the Warp 1 as just another me-too, mid-fi Class D power amplifier. That would be a mistake. I have, over the years, listened to plenty of Class D power amplifiers…so far, the Warp 1 is the best-sounding one I’ve reviewed. If you have loudspeakers that are at least reasonably efficient (or better), and you have no need to warm up their sonic personality, the Warp 1 power amplifier could be an excellent and exceedingly rational choice as your next reference power amplifier. 

Specs & Pricing

Type: Class D stereo amplifier
Output power: 150Wpc into 8 ohms, 250Wpc into 4 ohms
Inputs: Single-ended RCA, balanced XLR/TRS combination connectors
Input impedance: 47k ohms, RCA/47k ohms, balanced
Dimensions: 14″ x 3.5″ x 10″
Weight: 24 lbs.
Price: $1499 

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