To investigate the Diablo separately which had already shown top synergy with its Pantheon stablemate over our darker heavier Pass amp, I harnessed to it the Apertura Audio Kalya. That €10'000/pr French 8-inch two-way monitor sports a complex xover with 6+12+24dB/octave stacked slopes, a fine ribbon tweeter and a downfiring port tuned to 35Hz all on a 20kg stand. With the Diablo 300, "the Kalya exhibited such righteous bass and did so with even fewer room mode excitations than the rear-ported Danish towers or our usual EnigmAcoustics Mythology M1 monitors that in our large 90m² space, I categorically had no use for the Zu Submission subwoofer. With obviously less cone surface for the bass than the Pantheon, the presentation wasn't as massive on LF displacement but on extension, left very little to the imagination. Right after crossing the bass bridge came admiration for the richly developed glowing nearly glossy tone. Instead of metallic overtones which some have come to expect from ribbons, the Kalya was slightly sweet instead. Massed violins on Claude Chalhoub's neo-classical albums were splendidly free of scratchy stridency to sing not saw even in angled spiccato mode. Baroque music including period ensembles were equally served without unduly playing up the brighter or more nasal timbres and metronomic gestalt which in the hands of lesser transducers can get trying. The color richness of an 8-inch midrange coupled to a masterfully implemented ribbon tweeter struck a truly gorgeous balance with only a pair of small-signal valves in sight."

"With ancillaries tuned for as vibrant and intense as the Fore Audio DAISy1 DAC and Diablo, this became the sound of sun-ripened tone fruit. Had I secretly worried that the Danish muscle amp with its low output impedance might overdamp and dry out gestalt, I did so without due cause. The presentation was buoyant and elastic, not sewing-machine mechanical and uptight. Classical listeners with regular concert experience would find the Kalya a very informed tour guide indeed. Its bandwidth proved fully equal to power piano salvos from Hiromi, Michel Camilo, Dorantes or Chano Domínguez. Whilst infrasonic ambient chicanery goes occasionally even lower, I felt far from shortchanged with Cheb i Sabbah, Mercan Dede, Bob Holroyd and assorted other ambient wizards. Sneaking the Zu sub in at 30Hz proved impossible without too much overlap above despite a 10Hz 4th-order low-pass. For success I would have needed a DSP-programmable interface to select a steeper filter slope. Again, for all reasonable purposes and the vast majority of material, I had no urge to bother pursuing that route."

The upshot from this encounter is plain. On woofer grip and control, the Diablo 300 is a Chevy Hemi-era muscle amp. It maximizes what a given bass alignment is truly capable of and tops off extension. That makes it ideal for the more compact speakers which buyers fancy for their lighter impact on décor yet worry about over low-down bandwidth. Quite unlike amplifiers which achieve such behaviour with copious negative feedback for extremely low output impedance but which sound overly dry and effectively overdamped as though constantly cramped, the Diablo's bass mastery was not accompanied by that dark shadow. As a true muscle amp, that's a major part of its appeal. But of course the Diablo is a lot more than just a very refined testosterone mule. It's an integrated amplifier optionally fitted with an ambitious DAC and/or phono stage.

For a familiar in-house speaker reference and to reduce variables, I leashed up the Albedo Audio Aptica 2-way towers. What their very effective transmission-line loading coaxes on extension from a compact Accuton ceramic mid/woofer is astonishing. Once again the Diablo 300 milked the last drop of reach from this bass alignment tuned with two Helmholtz resonators to eliminate primary organ-pipe resonances in a downward narrowing line. What's more, it also harnessed the Italian 1st-order design's innate softness and sweetness, putting a full-stop nyet behind claims that all hard-driver speakers sound hard. Wanting a premium sample of that driver breed in my hardware library, I'd specifically acquired these Italians because they're not brittle, lean and whitish as many especially earlier examples of their kind could be. The Diablo 300 did nothing to alter their signature behaviour. Gryphon's deserved reputation for intensely dynamic very vivid electronics interfaced perfectly. As with the Kalya standmounts, this overwrote popular expectations that powerful amplifiers are invariably less sophisticated—more brutish is the perception—than low-power variants based on the same circuit. Like with the Pantheon speakers, this was back at the art of making big/powerful devices behave as nimble and quick as small/low-power versions; with the vital add-on of dynamic headroom and scaling potential that's the reserve of power and size. Speed without attendant weight tends to get zippy. Weight without speed feels ponderous and too heavy. One might argue that the more bass mass a system delivers, the faster it must be to compensate. The Diablo 300 concurs as it does both to a high degree, upending the notion that these qualities must be mutually exclusive.

To explore its DAC section, I picked as comparator the €6'700 Fore Audio DAISy1. I'd earlier compared it to the Gryphon Kalliope and called it a 'baby Gryphon' for offering very much the same sonic virtues, just in slightly milder doses. Because a 7-metre USB cable wouldn't work—not that I own such a stutter snake to begin with—I had to relocate my iMac. It moved from its usual sidewall position to next to the amplifier to reach the Diablo's USB input.