Solid State Power Amp Reviews

I've found that some audio amplifiers have sonic signatures so subtle that they emerge only over weeks of listening; yet other amps sound so distinctive—more vivid, more transparent, more dynamic—that their signatures are immediately apparent. Can those latter qualities really be inherent in the recording, or are they colorations produced in the amplifier?

I am finding hard to grasp that it is almost 50 years since I first went to a hi-fi show. That show, held at London's Olympia exhibition center, was notable both for Yamaha's launch of a loudspeaker with a speaker diaphragm shaped like a human ear, and for being the first time I saw the drop-dead gorgeous Transcriptors Hydraulic Reference turntable, which was later featured in the film A Clockwork Orange. The most recent show I attended was AXPONA, held last April in the Chicago suburb of Schaumburg. There I saw no ear-shaped drive-units, but the final room I visited featured sound that the 1969 me could have only fantasized about.

Amplifier designers have frequently looked for ways to marry the advantages of tubes to those of solid-state devices. Hybrid designs of various stripes have appeared over the years, most of them using tube input stages with transistor output stages, eliminating the major weaknesses of tube amplifiers: eg, they run hot, are unreliable in that tubes have a finite life, are more expensive than a similarly powerful solid-state design, and have power-hungry output tubes and output transformers.

If we had been asked some time ago to describe our "dream amplifier," chances are we would have described the Crown DC-300. Designed originally as an industrial device, it was made available as an audio amplifier rather as an afterthought. But if that roundabout approach is necessary to produce an audio amplifier like this, so be it.

Crown?

The Momentum M400 MxV Mono amplifier ($79,500/pair) is the latest iteration of Dan D'Agostino Master Audio Systems' debut amplifier of 2011, the Momentum Mono amplifier. Weighing 95lb, it is smaller and lighter than its entry-level sibling, the more powerful, 125lb Progression M550 Mono amplifier ($47,500/pair), and is veritably dwarfed by some other monoblocks, including the flagship D'Agostino Relentless Epic 1600 (570lb) and the Karan Acoustics POWERa mono (231lb), which I reviewed in May 2023. But if the M400 MxV's rock-solid look and feel and its exquisite aesthetics—a sleek amalgam of silver and copper fronted by a power meter that glows green and radiates Rolex quality—are any indication, a helluva lot is going on beneath its showy exterior.

What better way to celebrate the expiration of a noncompetition clause than to debut a product that has no competition? That's what Dan D'Agostino appears to have done with his Momentum monoblock amplifier ($55,000/pair)—his first new product since leaving Krell, the company he cofounded more than 30 years ago.