This review page is supported in part by the sponsors whose ad banners are displayed below

Audiophilleo USB-to-S/PDIF (BNC) converter & NWO-M tube outputs
Though I've reviewed a number of class D amps, none have become a permanent fixture in my most serious system. Why not? My favorite kind of speakers thrive on a few watts where D class routinely starts out at 100wpc. The treble of past switching amps had lacked that truly teased-out tintinnabulation I enjoy particularly with the various FirstWatt class A amps. Though potent and highly damped, class D bass in the past had lacked textural sophistication and multi-hued tonal variations whilst overall textures felt a bit dry-cleaned too. To check status I'd now compare my best high-power amp (ModWright KWA100 SE) and my favorite low-power amp (FirstWatt SIT2) and combine those with my best source and best speakers. Enter APL Hifi's NWO-M. Its 20-paralleled 32-bit AKM 4399 chips and valve output stage would shake hands with my iMac via the Audiophilleo 2, then stream into ModWright's LS-100 preamp.

ModWright LS-100 with Psvane V-181T, 27" quad-core iMac with PureMusic 1.85 or Amarra 2.3 in memory play
Esoteric/APL Hifi UX1/NWO-M in fixed-gain mode

Next enter the Gladius from the small Cyprus company Aries Cerat. This speaker is a true 91dB sealed 3-way with Raal ribbon and modified 5" and 12" Fostex midrange and woofer. Its sophisticated outboard crossover presents a very linear impedance. The entire design is deliberately valve or low-power friendly since the company majors in tube electronics and hornspeakers. In my space the Gladius does superbly well on ten first-class transistor watts. I'd thus also have to use my Boenicke B10 speakers to represent the type of power-hungry load a prospective Eximus customer would most likely own. All cabling save for the Entreq USB was my customary Zu Event.


ModWright KWA100-SE vs. Eximus monos. To stay roughly on the same coin patch, the ModWright faced an Eximus pair. Because the ModWright preamp isn't dual-differential—neither is my Esoteric C-03 for that matter—I instinctively leashed up the same 6-meter single-ended properly shielded cable which always connects my source stack on the side wall to the amps on the front wall. Yet the bridged Koreans were unhappy. I got a loud mix of steady-state noise overlaid by what sounded similar to fluctuating power supply grunge. With my balanced cable they were dead quiet however. That's then how I ran the ModWright amp as well.


The literally first thing I noticed was how the ModWright's treble was the patently more dynamic and elucidated. This became particularly apparent on sharply struck triangles and ride cymbals. The presence of scintillating metal molecules spraying off vigorous sparks was far more acute and their dynamic cresting taller. The overtone content of the S1 seemed padded down by comparison. This translated as a small energetic damper on microdynamic fluctuations. It also showed up on subtler transients like the raspy friction of Anja Lechner's bow work on her cello. The Eximus duo meanwhile had the upper hand on bass weight. Lower left-handed fistfuls of ivories landed with more gravitas, massive drums with high reverb as on the evocative Tekbilek/Keane soundtrack to Kebelek energized more air. This combination of greater bass heaviness with reduced treble light and diminished upper harmonic energy led to a softer overall feel.


That feel then got transposed over an even more vacuous blackground. This acquired the appearance of high contrast with genteel attacks and somewhat damped internal motion. While the ModWright might have been the measurably noisier circuit on a scope, it projected the greater live vibe. Be it the darbuka and bendir trills, peppery oud accents or spitty overblown ney riffs on Yildirim Levent's Neverland Fusion crossover [Harmonia Mundi], the two-stage class A/B amp parlayed more of the energy and rhythmic tension which this gifted drummer sets up with his multi-layered grooves. The class D power houses toned down his artistic heat. The effect reminded me of massive isolation transformers in AC line filters. Their noise-killing attributes can slightly squelch the energetically lit-up velocity inside a tune. It's what I think of as musical charge which lives between/behind the notes.


Common hifi talk would call the ModWright faster, the Eximus more chilled or laid back. The effect on the vocal range was less apparent with mellower material where the singers didn't push - Miguel Poveda on Desglaç for example. On raunchy stuff filled with hoarseness, physical strain and great risk taking, the easy action of the Eximus became quite noticeable again. In some ways that related to greater stage distance. It too damps down incisive bite and harmonic vigor. If you favor a more farfield presentation not so much for its grander perspective but for this mellowing as then imposed by greater reverberant field interactions, you'll have an intuitive sympathy for the S1.


FirstWatt SIT2 vs. Eximus stereo. To be a tad closer to the notion of lower power, the Nelson Pass amp was compared to a stereo Eximus. By default the single-ended cable reappeared since the SIT2 has no XLR inputs. With the switching amp, purely steady-state noise reappeared as hiss on the tweeters. The S1 insisted on the balanced leash to be perfectly quiet. Naturally I obliged. For signal excellence I cued up a native 24/96 track from Les Yeux Noirs' Tiganeasca*. Here three singers perform a traditional Russian folk song. From the very first few bars the SIT2 showed the Eximus a clean set of very high heels. Harmonic density and image embodiment were simply on another plateau. The switching amp sounded not so much lean as hollow and lacking in oxygen. It felt stripped down as though working with a lower-order color palette. It lacked vital hues, vibrancy and grittiness.


Relative to spatial lock which requires a recreated acoustic to begin with, the Eximus came in a far second as well. It was paler, duller and dimensionally more homogenized. It had fewer ambient markers against which the performers could take up spatial context. Finally the SIT2's bass was of the singing variety with proper fades and buoyancy. The Eximus bass was more elephantine - powerful but somewhat rigid. I'd frankly not expected this delta of performance. To avoid serious bloodshed, the single-stage amp with the novel output device had to exit the scene. This led me to suspect that the bridged Eximus had rather more than just watts over its non-strapped self. But first I wanted far more power-hungry speakers. I wanted to deliberately cater to the monos' low output impedance and enormous power rating if the mild-mannered Gladius had not taxed them properly.
______________________________

Compare their "Dobri Dien Romale" to what Arbat does with it on Gypsy Songs. Les Yeux Noirs enjoy superior recording quality. Arbat's harmonized vocalizing with its warbling vibratos on peaks grabs you by the short hairs and squeezes. It's musical passion versus perfect measurements. This was a minor parallel to the performance difference between these amplifiers. In some important ways, the Eximus was too smooth and civilized for its own good. Unlike with tubes, this didn't seem to be primarily about THD distribution. Overdamping alone didn't seem to explain it either except perhaps for the bass quality.