Solid State Power Amp Reviews

For as long as I've known about high-end audio, I've put Dan D'Agostino, co-founder of Krell, on the same pedestal reserved for the likes of Frank McIntosh, Saul Marantz, Avery Fisher, H.H. Scott, and Sidney Harman. The reason is simple: Dan's the man whose achievements at Krell led me from the harsh sound of my first high-end amp into another dimension, one of truly musical sound reproduction.

I still recall the layout of the room where I first met D'Agostino—at an audio show, years before I began writing for Stereophile. I introduced myself in a trembling, fan-boy voice. (I did the same with John Atkinson.) Not many years later, when I found myself the owner of a Krell KSA-50S, its imaging blew me away. While the amp didn't entirely meet my needs, my Krell experience only deepened my appreciation for D'Agostino's work.

At the end of 2009, Dan and Krell's cofounder, Rondi D'Agostino, were forced out of the company by what Dan terms a "hostile takeover," but he wasted no time in founding Dan D'Agostino Master Systems. The company soon released a series of expensive Momentum amplifiers and preamplifiers, whose sound and distinctive "audiophile jewelry" enclosures further solidified his reputation as a cutting-edge designer (footnote 1). Now comes the less expensive but hardly plain-Jane Progression series.

The moment I heard the first pre-production pair of Progression monoblocks ($38,000/pair), driving Wilson Audio Alexx loudspeakers at Definitive Audio's 2016 Music Matters event, I wanted them to be the first amps I would review for Stereophile. Alas, when D'Agostino's longtime associate Bill McKiegan visited my home to install the first pair of Progression monoblocks manufactured in their initial, limited production run, technical problems intruded: First, a loose ribbon cable in one monoblock's chassis caused it to emit a loud noise. Although McKiegan easily reattached the cable—its new header and pin should prevent future problems—both monoblocks continued to emit an annoying hum that made listening a chore, and compromised all sound above the bass region. This second problem was traced to improper potting in the transformers, an error on the part of the transformer provider, and has since been addressed. Still, it took five months before a replacement pair of Progressions could be freed up for review.

Appearance and Design
The Progression's enclosure and chassis—in this case, the same thing—is machined from a solid billet of aluminum. Most visually striking are a large, round, copper-rimmed, green-lit power-output meter—it dominates the front panel—and, running along both edges of the top plate, the large holes that replace heatsink fins.

The handsomely designed user manual says that the meter is "driven by a high-speed ballistic circuit that enhances the meter's responsiveness" and allows it to cover the amp's entire output range. As I listened to high-resolution recordings while sitting 12' back from my speakers in my 20' by 16' by 9' listening room, the needle didn't rise very far, even when I raised the volume to the point of discomfort and every instrument in an orchestra or band was blaring simultaneously. Since I have no desire to stop working for Stereophile, I never tried to find out if my CDs would fall off their shelves before the needles pegged.

Secreted directly under the meter, on the bottom edge of the Progression, is a small, easily accessible On/Standby button. Assuming that these class-AB amps would consume little electricity when music wasn't playing, I left them on 24/7 to keep them ready for listening, instead of having to wait half an hour for them to reach optimal operating temperature. Even when I spent several hours listening nonstop to complex music with lots of dynamic peaks, the Progressions never got more than warm to the touch. On colder days, I still needed to heat the room.

On the Progression's rear panel are a 20-amp IEC inlet, a large main power toggle switch, a single balanced (XLR) input—there's no unbalanced input—and two speaker binding posts that are fairly easy to screw down tight. The large space between cable connections makes it easy to keep wires apart. There are also 12V on/off trigger input and output switches for use with other components (I never used them), and a toggle switch for adjusting the brightness of the power meter (Low/Off/On). I liked the green glow, and left the meter on.

D'Agostino believes that great sound reproduction requires power. Thus, the Progression's chassis contains a very large, 2.5kVA power supply claimed to deliver plenty of reserve power for peaks in loud rock and classical. D'Agostino says the amplifier "easily" delivers 2000W into 2 ohms. "The Progression . . . will play loud, but it is the control of the speaker drivers I was after," he wrote in the manual. (To learn more about the Progression and Dan D'Agostino, see "Dan D'Agostino's Progress to Progression" elsewhere in this issue.)

Listening
When the replacement Progressions arrived, Bill McKiegan returned to ensure that they were working properly. (They were driven directly from the analog outputs of my dCS Rossini DAC.) Normally, when company reps help install gear, Stereophile reviewers thank them for their time but keep their critical impressions to themselves. But I'm a Cancer—an emotional being. Thus, when we put on a familiar SACD of Iván Fischer conducting the Budapest Festival Orchestra in Mahler's Symphony 9 (Channel Classics CCS SA 36115), and the stone-cold Progressions delivered far more believable air and sense of hall boundaries than any other amps I've heard in my reference system, I found it difficult to mask my excitement.

At first, I began my tests with a wide assortment of familiar fare. Yes (check), that eccentric collection of percussion in Lou Harrison and John Cage's Double Music, with Angel Gil-Ordóñez conducting the Post-Classical Ensemble (24-bit/48kHz WAV file, Naxos 8559825), sounded as tight as could be. There was believable body to the sound, and maximum color differentiation between the composers' crazy collection of standard and repurposed percussion instruments. And, yes (check), the final track on Ludovic Morlot and the Seattle Symphony's excellent recording of Stravinsky's The Rite of Spring (SSM 24/96 WAV file, Seattle 1005) sounded equally outstanding. Not only did the Progression Monos nail the savagery of the high-driving piccolos and brutal bass without breaking a sweat, they also kept every instrument in control and balance while conveying a realistic, airy soundstage and thunderous percussion.

One other thing about the Progressions struck me from the get-go. Perhaps owing to their speed and reserve power, contrasts between soft and loud in hi-rez orchestral recordings were greater and more impactful than with any other pair of monoblocks I'd heard in my reference system.

Turning to Murray Perahia's performance, on piano, of Handel's Harpsichord Suite in E, HWV 430 (CD, Sony Classical 62785) left me marveling that, for the first time with any amp in my system, I could hear the resonant space around the piano, and sense the size of the space captured by Sony's engineers. I also noted that while the sound was just a touch on the warm side of neutral, the tonalities were beautiful, and the piano's bottom notes sounded more realistic than I'd ever heard them in my system.

Not only did the Progressions clearly convey Perahia's perfect, rapidly articulated runs in the suite's final, joy-filled Air with five variations, it also depicted those notes as connected in a continuous, supremely musical flow. As I've discovered in listening to this recording countless times at audio shows, some amps overemphasize the spaces between notes, making them sound a bit like machine-gun fire, while others blur the notes together. The Progression made Perahia's playing sound as musical and technically astounding as it would in real life.

"I love this recording as if new," I scribbled in my notes. "Everything sounds fabulous."

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Footnote 1: See Michael Fremer's reviews of the Momentum preamplifier and power amplifier here and here.