D'Agostino Progression M550
Stereophile|November 2021
MONOBLOCK POWER AMPLIFIER
JASON VICTOR SERINUS

We audiophiles so frequently get caught up in the pursuit of perfection that some have attempted to rebrand high-end audio as “perfectionist audio.” But is it even possible for a single piece of audio gear, let alone an entire audio system, to attain perfection when there’s no common agreement as to what “perfection” means? It’s easier to cue up a Nirvana track than to find the way to audio nirvana.

Nonetheless, the journey toward sonic perfection continues to grip many of us like a Siren who lures sailors to their death with the sweetness of her song. For some who listen closely and steer wisely, however, that death can be more akin to La petite mort than to a dead end.

I like to set sail with people whose sonic values, as manifest in the equipment they design, mirror my own. In the field of amplification, few American designers are more known for the pursuit of a certain vision of perfection than Dan D’Agostino. Over a 40+-year history in audio, which includes founding and serving as CEO and chief engineer of Krell Industries (1980–2009) before moving on to found Dan D’Agostino Master Audio Systems (aka D’Agostino) in mid-2010, Dan1 has envisioned, designed, and shepherded the development of a host of solid-state amplifiers and other products that have established a benchmark for melding power and speed with sonic beauty, tonal accuracy, and bass response.

“I want to make something that sounds musical—that satisfies and brings me closer to the musical event that’s being reproduced,” Dan said at the start of a phone chat that also included Senior Engineer Burhan Coskun, who did crucial work on D’Agostino’s latest designs. “I’ve always strived for this goal. The closer I get, the more engrossed I get in making it better.

“Where I am is way farther than I’ve ever been. With Krell, I never achieved sonically what I’ve achieved with Dan D’Agostino. Dan D’Agostino is much, much, much more musical and way closer to my sonic goal.

SPECIFICATIONS

Description Solid state class-AB mono power amplifier. Inputs: XLR. Outputs: Custom binding posts. Input impedance: 100k ohms. Output impedance: 0.1 ohms. Power: 550W into 8 ohms, 1100W into 4 ohm, 2200W into 2 ohms (all 27.4dBW). Frequency response: 1Hz–80kHz, –1dB; 20Hz–20kHz, ±0.01dB. S/N ratio: 105dB unweighted, 75dB A-weighted. Distortion: 0.15% @ 1kHz at 550W into 8 ohms. Power draw at idle: 80W.

Dimensions 17.875 (454mm) W × 9.0 (230 mm) H × 23 (584mm) D. Weight: 115lb (52.2kg).

Finish Silver or Black; custom finishes upon request.

Serial numbers of units reviewed PM0506P, PM0507P. Manufactured in the United States.

Price $44,950/pair. Approximate number of US dealers: 27. Warranty: Three years from date of retail purchase or four years from date of manufacture for original purchaser of a new product from an authorized dealer.

Manufacturer Dan D’Agostino Master Audio Systems, LLC. 5855 E Surrey Dr., Cave Creek, AZ 85337. (Tel): (480) 575-3069. Web: dandagostino.com.

“Our current designs have absolutely nothing in common with what I did at Krell. When I left that company, I wanted to do something in the completely opposite direction. I’m glad in a way that I was asked to leave, because [the move] provided me with the platform that I could use to do the designs I do today. I think that at Krell we got involved in a numbers game: We can do this better because it measures better, and it does this better. It was more about technology than listening. But at D’Agostino, we listen a lot. Listening is the most important thing, not how it measures.”

After Dan founded Dan D’Agostino Master Audio Systems, the Momentum monoblocks2 led the way in the first half of 2011. D’Agostino subsequently developed three tiers of products: Relentless, Momentum, and Progression. The monoblock amplifier line, topped by the 570lb Relentless monoblocks ($295,000/pair), until recently extended down through the 95lb Momentum M400 ($65,000/pair) to the 125lb Progressions ($38,000/pair)—my reference amplifiers since I reviewed them in October 2017. The Progressions are among the best sounding amps in their price range that have ever graced my system.

Now the company has replaced the original Progression monos with the fully balanced, 115lb Progression M550 monoblocks ($44,950/pair). The class-AB M550, which requires a 20A power cable, has a new input-stage transistor structure that is claimed to handle a lot more current and provide six times more power, greater thermal stability during power delivery, “perfect” gain matching between the improved high-signal N and P–channel tran sistors, and an improved high-frequency response that melds lower saturation voltage with higher gain. There’s also an upgraded output stage that includes 48 power transistors and a 2000VA power supply transformer with nearly 100,000 microfarads of power supply storage capacitance. Together with a new and far more efficient heatsink design borrowed from the Relentless, these changes enable the Progression M550’s transistors to handle a lot more current flow and run hotter than previous devices used by D’Agostino. “We’re pushing a lot harder on all the circuits, but our safe operating area has actually gotten bigger,” Dan said.

According to Coskun, technological advances in the Progression M550s have made possible what amounts to a “new amplifier” with a higher bias setting. The M550s can remain in class-A for up to the first 100W of their output. When used in a moderately sized room—mine is 16' × 20' with ceilings that flatten out at 9'—the Progression M550s can deliver 550Wpc into 8 ohms, 1100Wpc into 4 ohms, and a whopping 2200Wpc into 2 ohms. Operating in classA avoids the switching distortion that is an inevitable result of operating in class-B at higher power levels. Yet, because the M550 is a class-AB design, it consumes only 80W at idle.3 They’re not the Relentless monsters, which start at 1500Wpc into 8 ohms and keep doubling down from there, but they are still a significant advance for products presented by a man who has been pursuing what he refers to as “audio pleasure” for his entire career.

“In all my products, I like to put enough class-A in [the output stage] so that at low, low levels, the amplifier maintains its sweet presentation and sounds more musical,” Dan explained. “I’m certainly not advocating pure class-A operation, which is very inefficient. The techniques I’ve developed do not necessitate the use of pure class-A circuitry, because I get a very musical sound without being in class-A all the time and using a tremendous amount of energy and huge heatsinks. Our designs give you the best of high-powered delivery when needed, as well as the sonic accuracy that class-A bias delivers.”

Dan told me that if he’d listened to the new Progression M550s when he designed the original Momentum monoblocks 10 or 11 years ago, he would have declared the Progression M550s better. Nonetheless, in the current lineup, price reflects sound quality. “All three amps are very musical,” he insisted, “but they’re all absolutely different designs that we borrow from [as we upgrade]. If part of a circuit works really well, we will incorporate it into an existing or future design to see if we can improve it.

“The Momentum 400 is definitely another step toward ultimate musicality—it has a mammoth soundstage, sits on a warm palette, and has more harmonic texture to it. We’re not upgrading the Relentless; we’re kind of in stasis mode because we don’t know how to improve it. The Relentless is a completely different-sounding amplifier with a different presentation. It’s big and musical with a really solid platform, but it seems as ultradelicate as listening to a small 10W amplifier on a small speaker. The unfortunate thing is that the Relentless is very heavy. It takes a crew to get them in your house. And they’re very expensive as amplifiers go.

“We keep looking at the M400 to see how we can improve it, because it’s my baby; it’s my Phoenix of an amplifier that brought me back as a company. But I don’t think you’ll see anything migrating from the new Progression M550 into the Momentum, because we borrowed from the Momentum to develop the Progression M550, and we borrowed from the Relentless to make the M400. I guess the same thing happens with automakers.”

Several times during our chat, Dan was effusive in his praise for Coskun, his chief engineer. “Now that I have Burhan, who is so astute with circuits, I conceptualize what I want to do,” he said. “Then I draw up a circuit and ask him what he thinks. We decide what looks good and where we might try to change it before we make one. After we get it where we like it, we simulate it to make sure it does what it’s supposed to do. Then we build the board, and then we listen to it. That’s exactly what we did with our new Relentless preamplifier, which will perhaps ship in September. It makes an extraordinary difference to have someone who understands circuitry working with you. I had 11 engineers at Krell, but none was as keen on circuits as Burhan.”

What about the conundrum of D’Agostino products that many, including myself, believe sound great yet which do not yield stellar measurements on Technical Editor John Atkinson’s equipment? While the D’Agostino website claims that the Progression’s “distortion, signal/noise ratio, channel separation, and bandwidth measurements have all improved,” that doesn’t guarantee that JA1 will find the M550’s measurements even close to superb.

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